Ruthenium Cumulenylidene Complexes Bearing ... · PDF fileHeteroscorpionate Ligands...

Ruthenium Cumulenylidene Complexes Bearing

Heteroscorpionate Ligands

Rutheniumkumulenylidenkomplexe mit Heteroskorpionatliganden

Der Naturwissenschaftlichen Fakultät

!der Friedrich-Alexander-Universität Erlangen-Nürnberg

zur !

Erlangung des Doktorgrades Dr. rer. nat.

vorgelegt von

Frank Strinitz

aus Nürnberg

Als Dissertation genehmigt von der Naturwissen-

schaftlichen Fakultät der Friedrich-Alexander-Universität

Erlangen-Nürnberg

Tag der mündlichen Prüfung: 02.12.2014

Vorsitzender des Promotionsorgans: Prof. Dr. Jörn Wilms

Gutachter: Prof. Dr. Nicolai Burzlaff

Prof. Dr. Rik Tykwinski

Die vorliegende Arbeit entstand in der Zeit von November 2011 bis August 2014 im

Department für Chemie und Pharmazie (Lehrstuhl für Anorganische und Metallorganische

Chemie) der Friedrich-Alexander-Universität Erlangen-Nürnberg unter der Anleitung von

Prof. Dr. Nicolai Burzlaff.

Teile dieser Dissertation wurden bereits veröffentlicht:

„Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands“, Türkoglu,

G.; Tampier, S.; Strinitz, F.; Heinemann, F. W.; Hübner, E.; Burzlaff, N., Organometallics

2012, 31 (6), 2166-2174.

„Allenylidene Complexes Based on Pentacenequinone“, Strinitz, F.; Waterloo, A.; Tucher, J.;

Hübner, E.; Tykwinski, R. R.; Burzlaff, N., Eur. J. Inorg. Chem. 2013, 5181-5186.

„Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands“,

Strinitz, F.; Tucher, J.; Januszewski, J. A.; Waterloo, A. R.; Stegner, P.; Förtsch, S.; Hübner,

E.; Tykwinski, R. R.; Burzlaff, N., Organometallics 2014, 33, 5129-5144.

Die schönsten Theorien werden durch die verdammten Versuche über den Haufen geworfen,

es ist gar keine Freude mehr Chemiker zu sein.

-J. V. LIEBIG-

I

!Table of contents

!! !

Table of Contents

1! Introduction ......................................................................................................................................1!

2! State of Knowledge ...........................................................................................................................3!2.1! Carbonyl Complexes ..................................................................................................................... 4!2.2! Carbene Complexes ...................................................................................................................... 8!2.3! Vinylidene Complexes ................................................................................................................. 11!2.4! Allenylidene Complexes .............................................................................................................. 15!2.4.1! Neutral 16 Valence Electron Complexes ...................................................................................18!2.4.2! Cationic 18 Valence Electron Complexes ..................................................................................21!2.4.3! Neutral 18 Valence Electron Complexes ...................................................................................27!2.4.4! Reactions Involving Ruthenium Allenylidene Complexes as Precatalysts ................................28!2.5! Heteroscorpionate Chemistry .................................................................................................... 29!

3! Objective and Aims ........................................................................................................................35!

4! Results and Discussion ...................................................................................................................37!4.1! Manganese Based Photo-CORMs .............................................................................................. 38!4.2! Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands ............... 44!4.3! Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands ..................... 52!4.4! Carbon-rich Ruthenium Allenylidene Complexes ................................................................... 58!4.4.1! Sterically Demanding Diphenyl Allenylidene Complexes ........................................................59!4.4.2! Fluorene Based Allenylidene Complexes ..................................................................................66!4.4.3! Anthraquinone Based Allenylidene Complexes ........................................................................74!4.4.4! Pentacenequinone Based Allenylidene Complexes ...................................................................86!4.4.5! Vinylidene Complex Bearing a Malonodinitrile Substituted Pentacenequinone .......................97!4.4.6! Benzotetraphenone Based Allenylidene Complexes ...............................................................101!4.4.7! Larger Quinoidal Polyaromatic Compounds ...........................................................................110!4.4.8! Carbon-Rich Allenylidene Complexes Based on [RuCl2(PPh3)3] ............................................115!4.5! Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides .............. 119!4.5.1! Polyaromatic Ruthenium Vinylidene Complexes ....................................................................120!4.5.2! Pyrene Based Allenylidene Complexes ...................................................................................127!4.5.3! Carbon-Rich Ruthenium Allenylidene Complexes Bearing the PTA Ligand .........................135!4.6! Arenium Cation or Radical Cation Pathway: Mechanistic Analysis and Experimental

Proof of the Scholl Reaction of Pyrenophenone .............................................................................. 143!

5! Summary and Outlook ................................................................................................................147!

II

!Table of contents

!! !

6! Zusammenfassung und Ausblick ................................................................................................153!

7! Experimental Section ...................................................................................................................161!7.1! General Remarks ...................................................................................................................... 162!Working Techniques ............................................................................................................................162!7.1.1! Chemicals ! .................................................................................................................................162!7.1.2! Instrumentation ........................................................................................................................163!7.1.3! CO-Release Studies ..................................................................................................................164!7.1.4! Cyclic Voltammetry .................................................................................................................164!7.2! Synthesis of Compounds ........................................................................................................... 165!7.2.1! Manganese Based Photo-CORMs ............................................................................................165!7.2.1.1! [Mn(bpzp)(CO)3] (4) .............................................................................................................165!7.2.1.2! [Mn(HIm)3(CO)3]Br (6) ........................................................................................................165!7.2.2! Ruthenium Carbonyl Complexes Bearing Heteroscorpionate Ligands ...................................166!7.2.2.1! [Ru(bdmpza)H(CO)2] (11A/B) .............................................................................................166!7.2.2.2! [Ru(bdmpza)(CO)(μ2-CO)]2 (12) ..........................................................................................167!7.2.2.3! [Ru(bpza)Cl(CO)2] (13) ........................................................................................................168!7.2.3! Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands .......................169!7.2.3.1! [Ru(bdmpza)Cl(IBQ)(PPh3)] or [Ru(bdmpza)Cl(ISQ)(PPh3)] (16) ......................................169!7.2.4! Carbon-Rich Ruthenium Allenylidene Complexes ..................................................................170!7.2.4.1! [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A/19B) ......................................................170!7.2.4.2! [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) ...............................................................171!7.2.4.3! 10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23) ............................................173!7.2.4.4! 10-Ethynyl-10-hydroxyanthracen-9-one (24) .......................................................................174!7.2.4.5! [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B) ...............................................................175!7.2.4.6! [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B) .............................................................176!7.2.4.7! [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31) .......................................................................178!7.2.4.8! 7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35) .............................................179!7.2.4.9! 7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36) .........................................................................180!7.2.4.10! [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B) .............................................................181!7.2.4.11! Bisanthenequinone (39) ......................................................................................................183!7.2.4.12! [RuCl2(═C═C═(FN))(PPh3)2] (45) .....................................................................................184!7.2.4.13! [RuCl2(═C═C═(AO))(PPh3)2] (46) ....................................................................................185!7.2.4.14! [RuCl2(═C═C═(PCO))(PPh3)2] (47) ..................................................................................187!7.2.5! Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides ...................189!7.2.5.1! [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48) ..........................................189!

III

!Table of contents

!! !

7.2.5.2! [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) ..........................................................................190!7.2.5.3! 1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51) .........................................................................191!7.2.5.4! [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B) ........................................................192!7.2.5.5! [Ru(bdmpza)Cl(PTA)(PPh3)] (55) ........................................................................................193!7.2.5.6! [Ru(bdmpza)Cl(PTA)2] (56) .................................................................................................194!7.2.5.7! [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B) ...............................................................195!7.2.5.8! [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B) ........................................................196!7.2.6! Intramolecular Scholl Reaction of Pyrenophenone ..................................................................198!7.2.6.1! 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63); 11H-Indeno[2,1-a]pyren-11-one (64) .198!

8! Appendix .......................................................................................................................................201!8.1! Details of the Structure Determinations ................................................................................. 202!8.2! Cyclic Voltammetry .................................................................................................................. 211!8.3! Myoglobin Assay of CORMs .................................................................................................... 214!8.4! List of Abbreviations and Symbols .......................................................................................... 216!8.5! List of Compounds .................................................................................................................... 219!

9! Bibliography .................................................................................................................................221!

10! Danksagung ................................................................................................................................241!

1

1 INTRODUCTION

2

!Introduction

!! !

In 1975 G. VIEHE et al. introduced the cumulogy principle as heuristicly important for the

discovery of new substance classes.[1] They described on a series of organic molecules how

the structure and reactivity correlates between common molecules and their cumulogous

derivatives.

Scheme 1. Cumulogy principle by G. VIEHE et al.[1]

The principle was explained for several examples in organic chemistry as insertion of C2

fragments to obtain elongated molecules with comparable characteristics to the parent

compound (Scheme 1). In the first report regarding this topic carbon dioxide was compared to

tricarbon dioxide, which is surprisingly stable (Scheme 1-a) and the previously reported

allenetetraamine to methanetetraamine (Scheme 1-b). The “vinylogy“ and „ethynylogy“

principles describe in a similar way the insertion of CH═CH and C≡C units between a few

pairs of conjugated carbon atoms. A more complex approach towards an analogy principle is

the carbo-mer principle which implies the insertion of Csp–Csp units into at least all symmetry-

related bonds of a Lewis structure.[2-3]

While commonly applied in organic chemistry, the cumulogy principle can be extended to

organometallic coordination chemistry. In their first report on allenylidene complexes in 1976

E. O. FISCHER et al. discussed the allenylidene moiety as cumulogous carbene ligand (Figure

1).[4] But also the metallacumulenes with even numbers of carbon atoms are accessible with

the vinylidene complexes being the smallest of this series.

Figure 1. Principle of uneven and even metallacumulenes.

O C O O C C C O

C C C(H3C)2N

(H3C)2N N(CH3)2

N(CH3)2

C(H3C)2N N(CH3)2

(H3C)2N N(CH3)2

a)

b)

[MLn] (C)n CR

R[MLn] (C)n C C

R

R

n = 0, 2, 4, etc.

3

2 STATE OF KNOWLEDGE

4

!State of Knowledge

!! !

In the following chapter a brief overview over the most common carbon based ligands namely

carbonyl, carbene, vinylidene and allenylidene ligands will be given with focus on their

syntheses, properties and possible applications.

2.1 Carbonyl Complexes

In the early 19th century J. V. LIEBIG synthesized a compound he named “Kohlenoxidkalium”

which may be translated as “potassium carbon oxide” and was initially expected to be the

carbonyl complex with the formula KCO.[5-6] In 1885 R. NIETSKI and T. BENCKISER identified

this compound as potassium salt of hexahydroxybenzene due to its similar reactivity after

hydrolysis.[7] But it was not until the sixties of the last century that the final verdict was

spoken on this compound. E. WEISS et al. revealed with an X-ray crystal structure analysis the

formation of potassium acetylenediolate KOC≡COK which can undergo hydrolysis or

thermolysis to form potassium hexahydroxybenzene.[8-9] The first real transition metal

carbonyl complex that survived later investigations was reported in 1868 by M. P.

SCHÜTZENBERGER as he published dicarbonyl dichloroplatinum [Pt(CO)2Cl2] along with

[Pt2(CO)Cl4] and [Pt2(CO)3Cl4].[10-11]

However, carbonyl chemistry first arouse significant interest with the development of the

Mond Process in 1890 which allowed purification of nickel via the volatile [Ni(CO)4].[12-13]

Starting from this observation the synthesis of homoleptic complexes i.e. carbonyl complexes

only with carbonyl ligands and heteroleptic complexes with additional ligands were

extensively studied.

Especially, for the neutral binary metal carbonyls a strong influence of the group in the

periodic table can be observed. To achieve the formal 18 valence electrons (VEs) group 7 and

9 metal carbonyls are forced to dimerize or to form even larger clusters (Table 1). Common

features are the high hydrophobicity, which leads to good solubility in organic solvents like

acetone or hexanes. Depending on their geometry a variety of air-stable or pyrophoric

complexes are reported. Moreover, the volatility of complexes like [Ni(CO)4] or [Fe(CO)5]

leads to high toxicity. The variety of transition metal complexes is extensively discussed in

literature and will not be further discussed within this thesis.[14-15]

5

!State of Knowledge

!! !

Group

5 6 7 8 9 10

[V(CO)6] [Cr(CO)6] [Mn2(CO)10]

[Fe(CO)5]

[Fe2(CO)9]

[Fe3(CO)12]

[Co2(CO)8]

[Co4(CO)12]

[Co6(CO)16]

[Ni(CO)4]

[Mo(CO)6] [Tc2(CO)10]

[Tc3(CO)12]

[Ru(CO)5]

[Ru3(CO)12]

[Ru6(CO)18]

[Rh2(CO)8]

[Rh4(CO)12]

[Rh6(CO)16]

[W(CO)6] [Re2(CO)10] [Os(CO)5]

[Os3(CO)12]

[Ir4(CO)12]

[Ir6(CO)16]

Table 1. Neutral binary carbonyl complexes of the transition metals.[16]

The Dewar-Chatt-Duncanson Bonding Model is employed to describe the bond properties

between metal atoms of the d-block and carbon monoxide, which describes the bonding as

donor-acceptor-interaction with a σ donor (forward donation) and π acceptor (back

donation).[16]

The mainly carbon centered 5σ orbital of the carbonyl ligand interacts as highest occupied

molecular orbital (HOMO) under formation of a σ bond with an empty d or p orbital of the

metal center and transferring electron density towards the center (Figure 2-a).[16] To maintain

the principle of electroneutrality a π backbond is formed from the highest occupied atomic

orbital (HOAO) of the metal atom and the 2π* orbital (LUMO) of the carbonyl ligand (Figure

2-b). Thus the π backbond shifts electron density into the antibonding 2π* orbital in the

carbonyl ligand (Figure 2-c), which leads to a lower bond strength and in consequence to a

lower CO force constant in comparison to gaseous carbon monoxide (kCO = 18.6 × 102

Nm–1).[17] This holds true for most known metal carbonyls indicating that the π backbond is

the dominating part of the M-CO bonding energy. Nevertheless, for positively charged metal

carbonyl complexes larger CO force constants can be observed, which backs the conclusion

that the π backbond is in these cases inferior to the σ forward bond.[16]

6

!State of Knowledge

!! !

Figure 2. Bonding in carbonyl complexes.[16]

These sensitive parameters make carbonyl complex precursors useful for modern

organometallic chemistry as they lead to complexes with easily comparable parameters that

support conclusions on the bond strength of carbonyls and thus the carbonyl vibrations.

CO Releasing Molecules (CORMs)

In recent years, the therapeutic potential of carbon monoxide has attracted a lot of attention

despite the general high toxicity to humans due to interaction of this odorless and colorless

gas with heme proteins. The biological importance of the closely related isoelectronic

nitrogen monoxide has been underlined already in 1992 by Science as “The Molecule of the

Year”.[18] R. TENHUNEN and R. SCHMID identified in 1968 that heme oxygenase (HO)

enzymes are ubiquitous in nature and evolutionary conserved.[19] HO catalyzes the heme

oxidation at the α position of the protoporphyrin ring leading to the formation of biliverdin

and an endogenous production of one equivalent CO at a rate of a few milliliters per day

(Scheme 2).[20]

Scheme 2. Heme degradation catalyzed by heme oxygenase and the resulting oxidation product biliverdin.[20]

O C M O C M MO C

a) b) c)

N

NN

N

MeCH2

Me

COOHHOOC

Me

CH2

Fe

Me

HN

NNH

NH

MeCH2

Me

COOHHOOC

Me

CH2 Me

OO

heme oxygenase- CO, Fe2+

7

!State of Knowledge

!! !

Furthermore, it participates in the reaction as both prosthetic group and substrate, while O2

and NADPH are required as cofactors.[21] In the next step the biliverdin reductase reduces the

intermediary species to bilirubin.[19] This endogenously produced CO acts as a small-molecule

messenger (gasotransmitter), like hydrogen sulfide or nitric oxide.[22-24] In most cases the

interaction of CO is focused on heme-containing metalloproteins. Vasodilation can be

induced by binding of CO to soluble guanylate cyclase (sGC) and to heme groups inside the

network of large conductance Ca2+-activated potassium channels (BKCa).[25] Some other

pharmacological activities include anti-inflammatory, anti-hypertensive and anti-ischemic

effects.[26-28]

The difficulties in handling and dosing a highly toxic gas like carbon monoxide lead to the

development of solid storage forms like Carbon Monoxide Releasing Molecules (CORMs),

which allow the generation of CO at constant low concentrations in proximity to the

pharmacological target.[29-31] The first generation of CORMs consists of CORM-1

(dimanganese decacarbonyl, Mn2(CO)10) and CORM-2 (tricarbonyldichloro-ruthenium(II)

dimer, [RuCl2(CO)3]2) (Figure 3), which are only soluble in organic solvents but show carbon

monoxide release in biological environments under appropriate conditions.[32]

Figure 3. CORM-1 (dimanganese decacarbonyl) and CORM-2 (tricarbonyldichloro-ruthenium(II) dimer).[32]

For CORM-1, an external light trigger is required to induce CO-release while for CORM-2,

the presence of myoglobin (Mb) leads to ligand dissociation and formation of MbCO. To

overcome the poor solubility in aqueous media, CORM-3 (tricarbonylchloro(glycinato)-

ruthenium(II)) was designed by R. MOTTERLINI et al. and is so far the most commonly

employed CORM in biological studies.[27] More recently, CORM-F7 (η5-4-(4-chloro-2-

pyrone)tricarbonyliron(0)) and CORM-F10 (carbonyl pyrone molybdenum complex) have

also received considerable attention.[33-35] In these complexes, the CO-release is triggered by

ligand exchange in aqueous media. As an alternative, the functionalization of CORM-1 to

yield manganese-based PhotoCORMs has received a lot of attention, lately. For example,

[Mn(CO)3(tpm)]+ releases CO upon activation with UV light, leading to a cytotoxic activity

RuCC

C

ClRuCl

Cl CC

Cl

CC Mn Mn C

CC

CC

C

C

C

C

O O

O O

O

OO

O

OO

OO

O

O

OO

8

!State of Knowledge

!! !

against cancer cells, but remaining inactive even after prolonged exposure in the dark.[36]

Additionally, bioconjugates of this lead compound led to improved drug delivery. Therefore,

peptides and SiO2 particles as well as carbon nanomaterials functionalized with azide moieties

were connected via Click Chemistry with the alkyne substituted [Mn(CO)3(tpm)]+

fragment.[37-39] Nevertheless, due to a Tolman cone angle close to 180° for Tp

(Tp = hydridotris(pyrazol-1-yl)borate), the exchange of more than one carbonyl during

synthesis is hindered in the case of tricarbonyl Tp complexes.[40-41] As an alternative ligand

system, less bulky heteroscorpionate ligands have been established such as Hbpza

(bis(pyrazolyl)acetic acid), in which one pyrazole has been substituted by a carboxylate

group.[42-43] From a synthetic point of view, the closely related class of bis(pyrazolyl)methane-

carboxylates (bpmc) has been explored, too.[44]

2.2 Carbene Complexes

In comparison to the aforementioned carbonyl complexes a transition metal carbene complex

is an organometallic compound featuring a divalent organic ligand that is most commonly

described as metal carbon double bond. The classical carbene complex synthesized by E. O.

FISCHER et al. in 1964 was the starting point for the following metathesis catalysts.[45] The

conversion of W(CO)6 with phenyllithium and subsequent methylation with diazomethane

yielded the first tungsten methoxymethylcarbene complex (Scheme 3).

Scheme 3. Synthesis of the classical Fischer Carbene Complex.[45]

WOCOC CO

CO

CO

CO

1. PhLi

(OC)5W CPh

OMe4N+

2. Me4N+

1. H+

2. CH2N2 or [(CH3)3OBF4]

(OC)5W CPh

OMe(OC)5W C

Ph

OMe4N+

(OC)5W CPh

OMe

(OC)5W CPh

OMe

9

!State of Knowledge

!! !

The class of Fischer Carbene Complexes is composed of middle to late transition metals in

low oxidation states with the carbene ligand stabilized by heteroatoms with a positive

mesomeric effect like oxygen. These electron rich complexes are usually bearing additional

carbonyl ligands to transfer electron density via π backbonding towards the LUMO of the

carbonyl.[46]

The bond between the metal fragment and the carbene ligand is based on a σ-bond between

the double occupied sp2 hybridized orbital of the singlet carbene and an empty d-orbital of the

metal center (Figure 4-a). Additional stabilization results from a π backbond from a double

occupied d-orbital into the unoccupied pz-carbene orbital (Figure 4-b). Further stabilization of

this unoccupied orbital can be achieved via conjugation with the free electron pair of the

neighboring heteroatom (Figure 4-c).[46]

Figure 4. Bonding in Fischer Carbene Complexes.

The use of electron donating heteroatoms and carbonyl ligands as electron density acceptors

leads to a less pronounced metal to carbene backbonding. As consequence of this reduced

bond order between ligand and center a higher bond order between carbon and neighboring

heteroatom can be observed. This electron distribution explains the reactivity of Fischer

Carbene Complexes, which are classified by their electrophilicity on the Cα carbon atom.

On the contrary the nucleophilic carbene complexes developed by R. R. SCHROCK were first

published in 1974. The attempt to coordinate five neopentyl ligands to a tantalum center led

to the intermolecular deprotonation of one Cα carbon atom forming the carbene complex.[47]

M COR

R´

M COR

R´C

R´

O R

a) b) c)

10

!State of Knowledge

!! !

Scheme 4. Synthesis of the tantalum based Schrock Carbene Complex.[47]

The class of Schrock Carbenes is composed of early transition metals in high oxidation states

bearing stabilizing π-donor ligands to overcome the reduced electron density at the center.

These changes result in the characteristic triplet state of the carbene ligand (Figure 5-a).

Overall these modifications lead to a significantly enhanced π backbond between the metal

center and the carbene ligand. On the one hand this behavior explains the strong double bond

character and on the other hand the nucleophilicity of the system (Figure 5-b).

Figure 5. Bonding in Schrock Carbene Complexes.

Based on these results, R. R. SCHROCK[48] and R. GRUBBS[49] developed their famous

metathesis catalysts which were awarded with the Nobel Price in 2005 and included Y.

CHAUVIN for the suggested mechanism.[50-52]

Figure 6. Structure of the first generation Grubbs Catalyst and the Schrock Catalyst.[48-49]

The two classic metathesis catalysts by R. GRUBBS and R. SCHROCK are depicted in Figure 6.

Today a wide variety of catalyst systems are known that can be employed depending on the

` Kenntnisstand

3

Aufgrund der zuvor bereits erwähnten Verwendung von Carbonylen als S-Akzeptoren

kommt es zu einer vergleichsweise geringen Ausprägung der Metall-Carben-

Rückbindung. Dies bedeutet eine Verringerung der Bindungsordnung zwischen Ligand

und Zentrum, führt jedoch gleichzeitig zu einer Erhöhung der Bindungsordnung zwi-

schen Kohlenstoff und benachbartem Heteroatom (Abb. 5). Die Reaktivität der Fi-

scher-Carbene ist vor allem durch ihre Elektrophilie geprägt.

Abb. 5: Elektronische Struktur der Fischer-Carbenen.

Schrock et al. hingegen synthetisierten 1974 den ersten nukleophilen Carbenkomplex

durch Deprotonierung eines D-Kohlenstoffatoms an einem Tantalalkylkomplex.[4] Bei

dem Versuch fünf Neopentylliganden an einem Tantalzentrum zu koordinieren, kam es

zu dieser „unerwarteten“ Reaktion. Die Zugabe von Neopentyllithium führte zur Koor-

dination eines vierten Liganden, der fünfte jedoch fungierte als Base und führte zur

Bildung des Tantal-Alkyliden-Komplexes (Abb. 6).

Abb. 6: Synthese des Tantal-basierten Schrock-Carbens.[4]

Bei Schrock-Carbenen handelt es sich im Allgemeinen um Komplexe früher Über-

gangsmetalle in hoher Oxidationsstufe, die durch S-Donorliganden stabilisiert werden.

Ein weiterer charakteristischer Unterschied ist der Triplettzustand des Carbens (Abb.

7-I). Insgesamt führen diese Unterschiede vor allem zu einer signifikant stärkeren S-

Rückbindung zwischen Metallzentrum und Carben, was sich einerseits durch einen

deutlichen Doppelbindungscharakter äußert, andererseits die Nukleophilie des Sys-

tems erklärt (Abb. 7-II).

MLn CR

R´M C

R

R´+

a)

MLn CR

R´b)

P(Cy)3

Ru

P(Cy)3

Cl

Cl

Grubbs I Catalyst

O MoN

O Ph

CF3CF3

F3CF3C

Schrock Catalyst

Ph

11

!State of Knowledge

!! !

desired substrate. This topic has been intensively reviewed within the last years. This also

explains the importance of the metathesis reaction especially for pharmaceutical applications

and green chemistry.

Due to the simplicity of the mechanism behind the catalytic olefinic metathesis, which was

once described by R. SAALFRANK as consolidated enough to fit on a beer coaster, a brief

description will be given (Scheme 5).[53] Starting from the carbene catalyst a formal [2+2]

cycloaddition of an alkene leads to a metallacyclobutane intermediate. This compound can

either undergo cycloreversion to the starting compounds or proceed towards a new carbene

complex and alkene. The entire reaction is per se reversible but driving forces behind the

conversion like reduced ring strain, increase in entropy and removal of gaseous compounds

(in the depicted case ethylene) direct the equilibrium towards the product.[52]

Scheme 5. Basic mechanism of metathesis reactions as described by Y. Chauvin.[52]

2.3 Vinylidene Complexes

Vinylidene H2C═C: is the simplest unsaturated carbene and is tautomeric to acetylene

HC≡CH.[54] The organic chemistry of unsaturated carbenes has been summarized by P.

STANG.[55-56] Regarding vinylidenes from an organometallic point of view, the first synthesis

of a molybdenum based vinylidene complex was reported by M. SARAN and R. KING in

1972.[57] The reaction of a 1-chloro-2,2-dicyanovinylmolybdenum complex with PPh3 leads to

[M] CH

H

[M]C C

C

C CH

HR1

H

HH

HH

HR1

CC

HH

H H

[M]

R1 H

CC

HH

H R2

[M]CC

CH

H

HR2

HR1

C CR2

HR1

H

12

!State of Knowledge

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carbonyl-free vinylidene complex under migration of the chloride anion towards the

molybdenum center (Scheme 6).

Scheme 6. Synthesis of the first vinylidene complex based on molybdenum.[57]

In analogy to carbene complexes vinylidene complexes can be described as extended

cumulene. The bonding in vinylidene complexes takes place in a similar fashion as it consists

of a σ bond and a π backbond, which results in an electrophile Cα atom and a nucleophilic Cβ

position. The preparation of vinylidene complexes is quite versatile although four major

synthetic routes have been established. The direct transformation of 1-alkynes via a 1,2-

hydrogen shift, the addition of electrophiles to metal alkyne complexes, the deprotonation of

carbyne complexes and the formal dehydration of acyl complexes will be briefly discussed.

1,2-Hydrogen Shift

The 1,2-hydrogen shift is due to its simplicity a useful access into vinylidene complex

chemistry (Scheme 7-a). After side-on coordination of the alkyne the rearrangement precedes

by an η2- to η1-alkyne slippage. The relative stability of the vinylidene complex in

comparison to the intermediary alkyne complex increases with electron density on the

ruthenium center. This allows for several ruthenium systems depending on the ligands

employed the isolation and characterization of the vinylidene complex as well as the alkyne

complex. First reports on the formation of Cp based ruthenium vinylidene complexes were

published in 1989 by R. BULLOCK.[58] M. BRUCE et al. reported extensively on the

transformation of [RuCp*Cl(PPh3)2] with a series of 1-alkynes to neutral vinylidene

complexes (Scheme 7-b).[59-60] The initial reaction step was the displacement of one PPh3

ligand followed by the 1,2-H shift described above. Similar results were obtained by N.

BURZLAFF et al. with the bdmpza (bis-(3,5-dimethylpyrazol-1-yl)acetato) based complex

[Ru(bdmpza)Cl(PPh3)2] that also allows the formation of neutral vinylidene complexes.[61]

Due to the N,N,O binding motif the formation of two structural isomers can be observed with

OCOC

Mo COCl

NC CN

PPh3,Δn-octane Ph3P

Ph3PMo ClC

CNNC

13

!State of Knowledge

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the vinylidene unit being either positioned trans to the pyrazole unit or the carboxylate anchor

and the PPh3 ligand remaining trans to the pyrazole moiety.

Scheme 7. a) Mechanism of the 1,2-hydrogen shift; b) synthesis of a ruthenium based Cp* vinylidene complex.[58]

Metal Acetylides

Scheme 8. Preparation of ruthenium vinylidene complexes via electrophile addition.[62-65]

benzene, ΔRu

PPh3ClPh3P

HC CR RuCl

Ph3P CC

H

R

LnM

H

R

CH

CMLn RMLn C C

H

R

1,2-H-shifta)

b)

R = Me, Et, Pr, tBu

[Ru] C C R

[Ru] C CR

H

H+ NaOMe

H C C R[Ru] Cl +

[Ru] C CR

X

X2

[Ru] C CR

N NAr

ArN2+

C7H7+

[Ru] C CR

[Ru] = Ru(PPh3)2(η5-C5H5)R = Me, tBu, Ph, etc.R´= Me, iPr, CH2Ph, etc.Ar = Ph, Xyl, etc.X = Cl, Br, I

- Cl–

14

!State of Knowledge

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The coordination of an acetylide anion to a metal center results in a transfer of electron

density to Cα and in consequence in a shift of nucleophilicity from Cα to Cβ. The addition of

electrophiles to the electron rich Cβ has been described extensively and is the best entry into

vinylidene complex chemistry, if no proton on Cβ is required. A large amount of substituted

vinylidene complexes is achievable by switching electrophiles. Known in literature are

reversible protonation, alkylation, halogenation, diazotization and insertion of further

functional groups (Scheme 8).[62-65]

Deprotonation of Carbyne Complexes

Deprotonation of carbyne complexes bearing protons at the Cβ atom allows the isolation of an

anionic vinylidene complex. A. ORPEN et al. reported for the system [MoCp(CCHtBu)-

(P(OMe)3)2] the deprotonation with n-BuLi which led to the anionic molybdenum complex

which can either be described with the charge located on the ligand or the metal center

describing a vinylidene complex (Scheme 9).[66] This route to vinylidene complexes is usually

limited to the earlier transition metals.[67-70]

Scheme 9. Synthesis of a molybdenum vinylidene complex starting from a carbyne complex.[66]

Acyl Complexes

A fourth pathway towards vinylidene complexes starts from acyl complexes and was first

described by B. BOLAND-LUSSIER and R. HUGHES.[71] J. GLADYSZ et al. reported a similar

approach starting from a rhenium based acyl complex which required a stepwise addition of

(CF3SO2)2O and KOtBu followed by (CF3SO2)2O (Scheme 10). Further cycles of base and

acid addition allowed the reversible reaction between vinylidene and acetylide complex.[72-73]

Mo(MeO)3P(MeO)3P C

Mo(MeO)3P(MeO)3P C

n-BuLiTHF Mo

(MeO)3P(MeO)3P C

CHtBuCH2tBu CHtBuLi Li

15

!State of Knowledge

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Scheme 10. Dehydroxylation of an acyl complex to the corresponding vinylidene or acetylide complex.[72-73]

2.4 Allenylidene Complexes

The first reports on allenylidene complexes were published in 1976 independently by H.

BERKE and E. O. FISCHER et al.[4, 74] Previously only the free labile allenylidene (:C═C═CH2)

could be trapped in a matrix.[75] Similar to the vinylidene complexes several routes are known

to allenylidene complexes, which have been extensively reviewed.[76-82] Hence, only the most

common routes will be discussed within this work. For group 6 metals the method employed

by E. O. FISCHER et al. starts from an alkenylalkoxycarbene complex. The stepwise

conversion with a Lewis acid and THF as base led under 1,2-elimination of ethanol to the

allenylidene complex (Scheme 11).[4]

ON Re PPh3

1. 0.5 eq. (CF3SO2)2O2. KOtBu3. 0.5 eq. (CF3SO2)2O

CO

R

ON Re PPh3CC

HR

ON Re PPh3CC

tBuOKCF3SO3H

R

R = H, Me, Ph

16

!State of Knowledge

!! !

Scheme 11. Synthesis of the first allenylidene complex by E. O. FISCHER et al.[4]

This route allows the formation of mono-heteroatom substituted allenylidene complexes but a

different approach is required for di-heteroatom substitution patterns. H. FISCHER et al.

established a route starting from [(CO)5M(THF)] (M = Cr, W), which yields upon addition of

deprotonated 3,3,3-tris(dimethylamino)prop-1-yne the intermediary metalate (Scheme 12).[83]

The abstraction of one amino group with BF3 etherate directly afforded the corresponding

neutral allenylidene complex. This route has also been employed on the synthesis of the

cumulogous pentatetraenylidene complex.[83]

Scheme 12. Synthesis of di-heteroatom substituted allenylidene complexes via alkynyl metalates.[83]

The current popularity of ruthenium allenylidene complexes can also be attributed to the

discovery of J. SELEGUE in 1982, that the direct conversion of [RuCpCl(PMe3)2] with 1,1-

diphenylprop-2-yn-1-ol led to a cationic allenylidene complex (Scheme 13).[84] This method is

based on the spontaneous dehydration of propargyl alcohols after η2-coordination of the

alkyne to 16 VE complexes that form intermediary hydroxyl vinylidene complexes.[84]

(CO)5M COC2H5

HCN(CH3)2

Ph (CO)5M C C CN(CH3)2

Ph1. EX3/CH2Cl22. THF- C2H5OH

M = Cr, EX3 = BF3M = W, EX3 = Al(C2H5)3

C C C(NMe2)3[(CO)5M(THF)] C CM(CO)5 C(NMe2)3

[(CO)5M] C C CNMe2

NMe2BF3 OEt2.

+

M = W, Cr

17

!State of Knowledge

!! !

Scheme 13. Synthesis of the first allenylidene complex based on a propargyl alcohol by J. SELEGUE and the mechanism of the dehydration.[84]

This method has proven to be suitable for a wide variety of ruthenium systems although

certain limitations are known. For a successful transformation i) the metal precursor needs to

form a coordinatively unsaturated 16 VE complex that allows η2-coordination of the alkyne.

The next limitation ii) is oftentimes the reluctance of the 3-hydroxyvinylidene to undergo

dehydration (Scheme 14-a). This behavior is especially distinctive when electron-rich metal

fragments are used. Depending on the used propargyl alcohol also iii) the competitive

formation of alkenylvinylidene complexes can occur, if the Cδ is carrying protons and thus

allows an 3,4-elimination of water with respect to the ruthenium center.[85-88] In some cases the

high stability of 3-hydroxyvinylidenes requires the treatment with acidic Al2O3 to complete

the conversion towards the allenylidene complex.[89-90] Calculations on the half-sandwich

system [RuCp(PH3)2]+ have emphasized the importance of protic solvents (e.g. MeOH) for the

transformation of the propargyl alcohol to the allenylidene complex (Scheme 14-b).[91]

RuMe3P PMe3

+ C CH CPh

OHPh

RuMe3P

Me3P CC

CPh

Ph

RuMe3P PMe3

RuMe3P

Me3P CCH

Cl

- Cl-

C CH CPh

OHPh

- H2O

- H2O, Cl-

Ph PhOH

18

!State of Knowledge

!! !

Scheme 14. a) Synthesis of allenylidene and alkenylvinylidene complexes via 3-hydroxyvinylidene intermediate; b) Mechanism of methanol catalyzed allenylidene formation.

The different ruthenium allenylidene complexes can be divided into three different groups,

namely neutral 16 VE complexes, cationic 18 VE complexes and neutral 18 VE complexes.

2.4.1 Neutral 16 Valence Electron Complexes

Starting from [RuCl2(PPh3)3] and [RuCl2(PPh3)4] A. HILL and P. NOLAN independently

explored the reaction with the propargyl alcohol 1,1-diphenylprop-2-yn-1-ol which led to the

complex [RuCl2(═C═C═CPh2)(PPh3)2] or upon addition of PCy3 to the complex to

[RuCl2(═C═C═CPh2)(PCy3)2],[92-95] which is closely related to Grubbs first generation catalyst

[RuCl2(═CHPh)(PCy3)2]. Nevertheless, the synthesis of [RuCl2(═C═C═CPh2)(PPh3)2] has

shown to be strongly temperature dependent as high temperatures allow the selective

formation of this 16 VE complex. Lower temperatures and the addition of NaPF6 led to the

additional formation of two 18 VE complexes that can be explained as dimeric forms of the

parent 16 VE complex. To compensate the lack in electron density either strongly donating

solvents are reported in the crystal structures of the complexes ([RuCl2(═C═C═CPh2)-

C CH COH

R2

R1

[M] C CH

COH

R1 R2

R2 = CHR3R4

- H2O[M] C C

H

C CR3

R4R1

[M] C C CR2

R1

[Ru] C CC O

HOH

Me

HHH

C C[Ru] CO

HH

HHO

Me

H[Ru] C C C

HH

OH

HOMe

H

- H2O

19

!State of Knowledge

!! !

(PPh3)2(solvent)] (solvent = H2O, MeOH, EtOH) or the formation of a symmetric or

asymmetric unit can be observed (Scheme 15).[96]

Scheme 15. Synthesis of monomeric, neutral dimeric and cationic dimeric diphenyl allenylidene complexes based on [RuCl2(PPh3)3].[96]

For the dimeric species two AB quartet patterns can be observed in the 31P NMR spectrum,

which can be assigned to the two different dimers (Scheme 15). Based on spectroscopic

analysis, one of the dimers contains two bridging and two terminal chlorido ligands, leading

to a neutral 18 VE complex. The second dimer is a monocationic complex that contains three

bridging chlorido ligands. The positive charge is compensated by a chloride anion that is

released during dimerization but can also be exchanged by addition of NaPF6 allowing to shift

the equilibrium towards the cationic dimer.

The monomeric allenylidene complex [RuCl2(═C═C═CPh2)(PPh3)2] can also be used as a

precursor for the selective formation of 18 VE complexes. Addition of dppe (1,2-

bis(diphenylphosphino)ethane) and KPF6 leads to the cationic complex [RuCl(═C═C═CPh2)-

(dppe)2]PF6 while the addition of carbon monoxide leads to the formation of

[RuCl2(═C═C═CPh2)(CO)(PPh3)2].[93]

The chemistry of the tricyclohexylphosphine-based complex [RuCl2(═C═C═CPh2)(PCy3)2] is

even more versatile as it allows a series of conversions. Reaction with the potassium salt of

[RuCl2(PPh3)3]HC C C(Ph)2OH

toluene, Δ, 4 hRu

Cl

ClPh3P

PPh3C C C

Ph

Ph

HC C C(Ph)2OHTHF25 °C2h

Ru C C CPh2Cl

ClCl

PPh3

Ph3P

RuCCPh2CPPh3

Ph3P

Cl

ClRuRu

Cl

Cl

CC

CPh2Ph3P

PPh3PPh3

Ph3P

CC

Ph2C

X

for X = ClTHF

Δ

NaPF6

X = Cl, PF6

20

!State of Knowledge

!! !

the hydridotris(1-pyrazolyl)borate ligand leads to the formation of the neutral 18 VE complex

[Ru(HB(pz)3)Cl(═C═C═CPh2)(PPh3)].[93] Addition of the dimeric [Ru2Cl4(η6-MeC6H4iPr)2]

leads to the formation of the dimer [Ru2Cl4(═C═C═CPh2)(PCy3)(η6-MeC6H4iPr)] which in

this case shows two bridging chlorido ligands with two terminal chlorido ligands, thus

resulting in a neutral complex (Scheme 16).[92] In comparison the conversion of the

allenylidene complex with the N-heterocyclic carbene ligand 1,3-bis((2,6-di-isopropyl-

phenyl)imidazol-2-ylidene) (IPr) leads to the 16 VE complex [RuCl2(═C═C═CPh2)-

(PCy3)(IPr)], which undergoes rearrangement to the indenylidene complex [RuCl2(3-

phenylindenylid-1-ene)(PCy3)(IPr)].[94]

Several of the aforementioned complexes have been tested as precatalysts in metathesis

reactions and this topic will be discussed later within this work (2.4.4, page 28).

Scheme 16. Synthesis of [Ru2Cl4(═C═C═CPh2)(PCy3)(η-MeC6H4iPr)], [RuCl2(═C═C═CPh2)(PCy3)(IPr)] and

[RuCl2(3-phenylindenylid-1-ene)(PCy3)(IPr)] starting from[RuCl2(═C═C═CPh2)(PCy3)2].[92, 94]

RuCl

ClCy3P

PCy3C C CPh2

ClRu Ru

ClCl

Cl

PCy3C

CCPh2

IPr

[Ru2Cl4(MeC6H4iPr)2]

RuCl

ClCy3P

IPrC C CPh2 Ru

Cl

ClCy3P

IPrC

Ph

NNIPr =

21

!State of Knowledge

!! !

2.4.2 Cationic 18 Valence Electron Complexes

The group of cationic 18 VE ruthenium allenylidene complexes can be divided into the group

of complexes based on ligands with heteroatoms coordinating in κ1- to κ4-mode and the group

of η5- and η6-arene complexes. As mentioned previously for the 16 VE complexes many of

the complexes based on κ1-coordinating ligands like PPh3 and PCy3 tend to form 18 VE

complexes via addition of Lewis bases.[93, 96] Ruthenium allenylidene complexes bearing κ2-

coordinating ligands are usually based on the diphosphine ligands dppm (1,2-

bis(diphenylphosphino)methane) and dppe (1,2-bis(diphenylphosphino)ethane). Starting from

cis-[RuCl2(dppm)2] a variety of cationic ruthenium allenylidene complexes of the general

formula trans-[RuCl(═C═C═CHR)(dppm)2]PF6 has been synthesized.[82] Especially

remarkable is the stabilization of monosubstituted allenylidene complexes starting from

secondary propargyl alcohols as usually the formation of α,β-unsaturated and polyenyl

carbenes via reactive γ-monosubstituted allenylidenes occurs (Scheme 17).[97-99] It is assumed

that the system [RuCl(dppm)2]+ shows larger electron releasing properties than comparable

cationic arene based systems and thus a decrease of the electron deficiency of the

[Ru═C═C═CHR]+ moiety and especially of the Cα carbon atom occurs.

Scheme 17. Synthesis of stable monosubstituted allenylidene complexes bearing dppm ligands.[82]

Following this initial work, based on the dppm ligand, the complexes based on the dppe

system led to even more stable systems as indicated by the in situ generation of

[RuCl(dppe)2]PF6 from cis-[RuCl2(dppe)2] upon addition of NaPF6.[100-101] This system has

proven to be quite versatile and allows on the one hand systems similar to the dppm based

allenylidene complexes bearing a chlorido ligand trans to the allenylidene unit.[102] On the

other hand, highly unsaturated alkynyl allenylidene ruthenium complexes are achievable

(Scheme 18),[102] which are especially interesting due to their potential to create a C–C bond,

RuPh2P

Ph2P Cl

Cl

PPh2

PPh2

Ru

Ph2P PPh2

PPh2Ph2P

Cl C C CR

HPF6

C CH CHR(OH)NaPF6

R = Ph, p-PhCl, p-PhF, p-PhOMe

22

!State of Knowledge

!! !

by carbon-rich ligand coupling.[103-105] In addition, their dual alkynyl donor and allenylidene

acceptor functionalities raise interest in building linear conjugated organometallics.[102]

Scheme 18. Synthesis of highly unsaturated alkynyl allenylidene complexes via deprotonation of allenylidene complexes based on trans-[RuCl(═C═CHR)dppe2]PF6.[102]

It is noteworthy that these mixed alkynyl allenylidene complexes are stable towards the

addition of methanol at Cα and Cγ in contrast to other systems.[106-107] The steric hindrance and

the strong electron donating capabilities of the dppe ligands reduce the reactivity allowing

only stronger nucleophiles like sodium methoxide to react selectively with the Cγ carbon atom

resulting in ruthenium diacetylide complexes.[102, 108-109] Starting from the mixed alkynyl

allenylidene complex trans-[Ph2C═C═C═(dppe)2Ru—C≡C―CHPh]PF6, the oxidation with

Ce(IV) ammonium nitrate allows the isolation of the first real bis(allenylidene) metal

complex (Scheme 19). The previously reported bis(allenylidene) complex trans-[(dppm)2Ru-

(═C═C═C(OMe)(CH═CPh2))2]2+ shows due to the presence of a donor group on the

unsaturated chain an elevated bis(alkynyl) character and can better be described as trans-

(dppm)2Ru[—C≡C—C(═OMe)(C═CPh2)]22+.[110-112] Especially interesting is the behavior

upon one electron reduction due to the formation of a stable radical complex with an electron

pair delocalized identically on both sides of the alkynyl allenylidene complex. This

observation shows the possibility of these carbon-rich systems to mediate conductivity

between metal centers.[110]

Ru

Ph2P PPh2

PPh2Ph2P

Cl C CH

R

PF6

Ru

Ph2P PPh2

PPh2Ph2P

C C C

PF6

CR1

R2CR

HC C CR1R2OH,NaPF6, Et3N

CH2Cl2

R = H; R1 = R2 = PhR = nBu; R1 = R2 = PhR = Ph; R1 = R2 = Phetc.

23

!State of Knowledge

!! !

Scheme 19. Reduction of trans-[Ph2C═C═C═(dppe)2Ru—C≡C―CHPh]PF6 with ammonium cerium(IV) nitrate to trans-[Ph2C═C═C═(dppe)2Ru═C═C═CPh2][B(C6F5)4]2.[110]

While carbon-rich ruthenium allenylidene complexes are no rarity, systems based on

polyaromatic ligands are rare. One interesting spacer is the dipropargyl alcohol 10,10′-

diethynyl-10H,10′H-[9,9′]bianthracenylidene-10,10′-diol that features the interesting

nonplanar bianthracenylidene moiety. Bis(allenylidene) ruthenium(II) complexes based on

this system can be obtained by reaction with two equivalents [RuCl(dppe)2]OTf. The addition

of one equivalent affords the expected monoallenylidene derivative and the electrochemical

and spectroelectrochemical properties were measured in detail (Scheme 20).[113] Both

techniques highlighted the presence of electronic communication between the metal centers

through the multiconjugated organic chains and allow allenylidene-centered reversible

reductions, which are not interrupted on passing from mononuclear allenylidene complexes to

dinuclear bisallenylidene complexes. This synthesis also allows the stepwise formation of

heterobimetallic allenylidene complexes via stepwise reaction of the propargyl alcohol with

selected ruthenium and rhenium precursors.

Ru

Ph2P PPh2

PPh2Ph2P

C C C

PF6

CPh

PhCC

Ph

PhH Ru

Ph2P PPh2

PPh2Ph2P

C C C

X2

CPh

PhCC

Ph

Ph1. CeIV, CH2Cl22. KB(C6F5)4X = B(C6F5)4

24

!State of Knowledge

!! !

Scheme 20. Synthesis of monoallenylidene and homobimetallic bisallenylidene complexes based on the bianthracenylidene linker.[113]

The dppe ligand system also allows the formation of further dinuclear allenylidene complexes

based on homocoupling reactions of ruthenium diyne complexes and heterocoupling reactions

between diyne complexes with allenylidene complexes.[102, 108, 114-116] Even larger trinuclear

complexes are accessible from aromatic spacers bearing three propargyl alcohols as

substitutes.[117]

HO

OH

CH

CH

Ru

Ph2P PPh2

PPh2Ph2P

C C CClOH

CH

Ru

Ph2P PPh2

PPh2Ph2P

C C CCl C C C Ru

Ph2P PPh2

PPh2Ph2P

Cl

(OTf)2

OTf

+ 1 eq. [RuCl(dppe)2]OTf

+ 2 eq. [RuCl(dppe)2]OTf

25

!State of Knowledge

!! !

The group of κ3 coordinated cationic ruthenium allenylidene complexes consists mainly of

N,N,N and S,S,S ligands, which are either facial or meridional coordinating. Cationic 18 VE

ruthenium allenylidene complexes are known for systems based on 1,4,7-trithia-

cyclononane,[93] trimethyl-1,4,7-triazacyclononane,[118] hydridotris(pyrazolyl)-borates,[119-121]

2,6-bis(oxazolyn-2"-yl)pyridines[122] and bis(pyrazol-1-yl)pyridines[123] but are mostly limited

to the diphenyl allenylidene complexes.

The ligand system with the next higher coordination, the κ4-N,N,N,N-makrocycle 1,5,9,13-

tetramethyl-1,5,9,13-tetraazacyclohexadecane (16-TMC), employed by C.-M. CHE et al.

selectively forms the trans positioned allenylidene complexes bearing heteroatom donor units

in the allenylidene residues.[124-125] The use of the dipyridyl allenylidene unit as a “molecular

clip” allows the coordination of zinc or ruthenium ions to form either homo- or hetero-

bimetallic allenylidene complexes (Scheme 21). DFT and TD-DFT calculations and

experimental data showed delocalization along the [Ru═C═C═C(2-py)2Ru] moiety in the

MLCT giving rise to NIR absorptions. This behavior highlights the potential application of

allenylidene ligands as molecular bridges to allow electronic communication between remote

functional groups.

Scheme 21. Synthesis of a heterobimetallic ruthenium zinc allenylidene complex and a homobimetallic ruthenium allenylidene complex based on 16-TMC.[125]

Important for this group of heteroatom based bimetallic complexes is the trans-arrangement

of the chlorido and allenylidene ligand due to the competitive behavior of both towards the

NN

N N

Me Me

Me

Ru

Me

Cl C CN

N

NN

N N

Me Me

Me

Ru

Me

ClN

NZn

Cl

Cl

NN

N N

Me Me

Me

Ru

Me

Cl C C CN

NRu(acac)2

C C C

C

+ ZnCl2

+ cis-[Ru(acac)2-(CH3CN)2]

26

!State of Knowledge

!! !

binding site. The irreversible formation of the allenylidene unit outcompetes the reversible κ1

coordination of the N-donor. Similar results were obtained with the trans-[RuCl(dppe)2]

system.[126-128]

The group of cationic half-sandwich complexes does not only include the classical η5-

cyclopentadienyl, η5-indenyl and η6-arene ruthenium complexes but also tethered type ligands

in which an ancillary κ1-coordinating donor atom is introduced leading to η5: κ1(L)- or

η6: κ1(L)-coordination. Most commonly η5 half-sandwich complexes bearing two phosphine

ligands and one allenylidene moiety are reported following a similar procedure to the classical

approach by J. SELEGUE (Scheme 13) leading to a general structure [Ru(η5-Ring)-

(═C═C═CR1R2)(L1)(L2)][X] with X– = BF4–, BPh4

–, PF6– and L1, L2 = PPh3, PMe3, PiPr3,

dppe.[89-90, 129-138]

Recently, several remarkable examples by E. NAKAMURA et al. based on a ruthenium(II)

fullerene-cyclopentadienyl complex bearing allenylidene ligands have been isolated (Figure

7).[139]

Figure 7. Ruthenium allenylidene complexes bearing a fullerene-cyclopentadienyl ligand.[139]

The focus of these complexes lies on the interaction of the physical and chemical properties

of the allenylidene and fullerene moieties. On the one hand the bulkiness of the C60Me5 ligand

leads to regio- and stereoselectivity for nucleophilic additions. On the other hand the intense

absorptions of the aforementioned complexes in the visible and NIR region are of particular

interest for their potential use in photophysical applications.[139-144]

MeMe

MeMe

Me

RuPh2P

PPh2Me

CC

C R1

R2 PF6

R1 = R2 = PhR1 = H, R2 = Ph R1 = H, R2 = 4-OMeC6H4R1 = H, R2 = FcR1 = H, R2 = 4-NMe2C6H4

27

!State of Knowledge

!! !

2.4.3 Neutral 18 Valence Electron Complexes

The third large group of ruthenium allenylidene complexes can be categorized as neutral

18 VE ruthenium allenylidene complexes. As mentioned above, several of these can be

stabilized via Lewis acid and base interactions to form the more stable 18 VE adducts.

Nevertheless, also genuine neutral 18 VE allenylidene complexes have been reported which

are commonly based on anionic η5 or κ3 coordinating ligands. Although, mainly cationic

allenylidene complexes based on Cp and Cp* are known, the allyl complexes [(η5-

C5H5)Ru(η3-2-MeC3H4)(PPh3)] or [(η5-C5Me5)Ru(η3-2-MeC3H4)(PPh3)] allow also the

formation of the corresponding neutral allenylidene complex following the method described

by J. SELEGUE (Scheme 22).[145] In comparison to [Ru(Cp)Cl(PPh3)2] the lack of the chlorido

ligand in the reactant makes the chloride abstraction impossible. Addition of hydrochloric

acid to the intermediary 16 VE complex leads to the coordination of a chlorido ligand and

formation of the neutral 18 VE complex.

Scheme 22. Synthesis of a neutral 18 VE ruthenium allenylidene complex based on Cp.[145]

A further example for neutral allenylidene complexes is based on the κ3 facial coordinating

hydridotris(pyrazol-1-yl)borate (Tp)[146] ligand developed by S. TROFIMENKO which has been

widely used in ruthenium chemistry.[147-154] The follow-up chemistry often shows parallels to

the related Cp complexes due to the close relation of half-sandwich complexes and the

facially coordinated Tp analogs.[155-156] The corresponding ruthenium allenylidene complex is

readily formed by reaction of [Ru(Tp)Cl(COD)] with different propargyl alcohols and

phosphine ligands yielding allenylidene complexes of the general formula [Ru(Tp)Cl-

(═C═C═CR2)(L)] (L = PPh3, PCy3, PiPr3, PPh2iPr) (Scheme 23).[93, 157] The reactivity of many

allenylidene complexes, especially if they are cationic, concentrates on the addition of

nucleophiles either to the Cα or Cγ carbon atom. Electron-rich allenylidene complexes, like

the neutral Tp based systems, are capable of adding electrophiles at the Cβ carbon atom

thereby forming vinylcarbyne complexes.[109, 158-160]

RuPPh3

RuPPh3Cl C

CCPh

Ph

1.2. Al2O3 acidic

HC C C(Ph)2OH, HCl

28

!State of Knowledge

!! !

Scheme 23. Synthesis of diphenyl and diferrocenyl (Fc) allenylidene complexes starting from [Ru(Tp)Cl(COD)].[157]

The Tp ligand and its complex chemistry is quite versatile, whereas a major drawback is the

inherent lability of the borohydride bridge, which upon contact with water easily hydrolyses.

Closely related to the Tp system is the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand

that features two pyrazole units and an acetate moiety leading to the κ3 coordinating N,N,O

motif. In the following chapter, a summary will be given on heteroscorpionate ligands and

their use in bioinorganic, and especially organometallic ruthenium chemistry.

2.4.4 Reactions Involving Ruthenium Allenylidene Complexes as Precatalysts

In the chapter 2.2 the importance of metathesis reactions has already been briefly introduced.

The great functional group tolerance of well-defined ruthenium carbene complexes

[LnRu]═CHR (i.e. Grubbs type catalysts) has led to a breakthrough in alkene metathesis

chemistry within the last decades.[50, 161] Although the carbene-based catalyst are versatile and

a powerful synthetic tool in organic and polymer chemistry the requirement of more

accessible and active complexes leads to the development of new precatalysts. Especially

easy to prepare and handle ruthenium allenylidene complexes are a valid alternative and

several reviews concerning the properties of ruthenium allenylidene catalysts have been

published.[77, 162-163]

The first example of RCM (ring closing metathesis) using an allenylidene complex was

reported in 1998 by A. FÜRSTNER et al. and P. DIXNEUF et al. (Scheme 24).[164-166] They

employed [RuCl(═C═C═CR2)(η6-p-cymene)(PR3)][X] as precatalyst for the conversion of

N

NN

N N

N

Ru

B

ClR3P C

CC

H

R2

R1

N

NN

N N

N

Ru

BH

Cl

HC C C(R1R2)OHPR3

PR3 = PPh2iPr, R1 = R2 = Ph

PR3 = PPh2iPr, R1 = R2 = Fc

PR3 = PPh3, R1 = R2 = PhPR3 = P iPr3, R1 = R2 = Ph

29

!State of Knowledge

!! !

N,N-diallyltosylamide into N-tosyldihydropyrrole. Three general trends could be observed:

i) The activity of the catalyst increases with the electron richness off the phosphine

ligand in the series PPh3 < PiPr3 < PCy3 the.

ii) The employed counter anion has a drastic impact on the reactivity which increases

with the sequence BF4– < BPh4

– ≈ PF6– < TfO–.

iii) While several substituted diarylallenylidene complexes have been tested the most

potent was the simple diphenylallenylidene which showed values comparable to

[RuCl2(═CHPh)(PCy3)2].[164-166]

Scheme 24. Conversion of N,N-diallyltosylamide into N-tosyldihydropyrrole catalyzed by the precatalyst [RuCl(═C═C═CR2)(η6-p-cymene)(PR3)][X]. [164-166]

A common rearrangement for diphenylallenylidene complexes is the formation of an

indenylidene system that leads to a stronger repulsive interaction between the indenylidene

group and the arene ligand resulting in a dissociation of the later. The generated vacant sites

are required for substrate binding and the utility of isolated indenylidene complexes has been

reported in detail by P. DIXNEUF et al.[158, 167] Due to the rigid structure of the fluorenyl unit no

rearrangement into carbene complexes is possible thus, leading to a different mechanism that

has not yet been fully understood.[163, 166]

2.5 Heteroscorpionate Chemistry

The aforementioned bdmpza ligand has been first reported by A. OTERO et al. in 1999 and can

be synthesized starting from bis(3,5-dimethylpyrazol-1-yl)methane.[43] Deprotonation with

n-butyllithium followed by reaction with carbon dioxide leads to the lithium compound

[Li(H2O)(bdmpza)4].[43] A more versatile one-pot synthesis has been introduced by N.

BURZLAFF et al. starting from either 3,5-dimethylpyrazole or unsubstituted pyrazole.[42] The

reaction with dichloroacetic or dibromoacetic acid under basic conditions in the presence of a

phase transfer catalyst allows after acidic workup the direct isolation of the protonated ligands

Hbdmpza or Hbpza (bis(pyrazol-1-yl)acetic acid). In comparison to bpza the methyl

NTs

NTs[RuCl(=C=C=CR2)-

(η6-p-cymene)(PR3)][X]- C2H4

30

!State of Knowledge

!! !

substituents of the bdmpza ligand increase the solubility in common organic solvents and

furthermore the steric hindrance. This leads in comparison to the air-stable complex

[Ru(bpza)Cl(PPh3)2] to an oxygen sensitive complex [Ru(bdmpza)Cl(PPh3)2] (Figure 8). The

methyl substituents and the corresponding steric hindrance causes a smaller angle between the

nitrogen donor atoms and the ruthenium center as observed in the crystal structure and thus

leads to a labilization of the phosphine ligands.[168] This is remarkable as the closely related Tp

complex [Ru(Tp)Cl(PPh3)2] and the Cp complex [Ru(Cp)Cl(PPh3)2] are air stable compounds

which indicates that the steric hindrance of the bdmpza ligand strongly increases the tendency

to release one phosphine ligand.[169-171]

Figure 8. Ruthenium based triphenylphosphine complexes bearing the Tp scorpionate ligand ([Ru(Tp)Cl(PPh3)2], left) and the heteroscorpionate ligands bdmpza ([Ru(bdmpza)Cl(PPh3)2], middle) and the ligand bpza

([Ru(bpza)Cl(PPh3)2], right).[168-169]

The class of pyrazole based N,N,O heteroscorpionates contains mainly acetic acid based

systems, although more flexible ligands based on propionic acid have been introduced by E.

DÍEZ-BARRA et al. as sodium salt of 3,3-bis(pyrazol-1-yl)propionate (Na[bpzp]) and 3,3-

bis(3,5-dimethylpyrazol-1-yl)propionate (Na[bdmpzp]).[172] The free acids and coordination

properties have been explored by N. BURZLAFF et al.[173] Synthesis of these elongated N,N,O

ligands involves a double Michael Addition of the pyrazole precursor to methyl propiolate.

Depending on the aqueous workup this either affords the free acid or the corresponding

sodium salt (Scheme 25). The coordination behavior of these two ligands has been explored

with manganese carbonyl complexes as the CO vibrations can be monitored by IR

spectroscopy and thus allows probing the electron donating and accepting properties of the

ligands. Addition of [MnBr(CO)5] to the in-situ formed potassium salt (K[bdmpzp]) leads to

the formation of the corresponding manganese(I) carbonyl complex fac-

[Mn(bdmpzp)(CO)3].[173] Closely related are the complexes fac-[Re(bdmpza)O3] and fac-

[Tc(bpza)O3] which attracted attention for their possible application regarding radio-

NN N

N

Me

Me

Me

MeRu

OO

Cl PPh3Ph3P

NN N

N

Ru

OO

Cl PPh3Ph3P

N

NN

N N

N

Ru

BH

PPh3Ph3P Cl

31

!State of Knowledge

!! !

pharmaceutical purposes.[174-175] In comparison to the previously reported complexes fac-

[Mn(bdmpza)(CO)3] and fac-[Re(bdmpza)(CO)3] the elongated propionate based complex

show only slight deviations in their chemical properties as for example the carbonyl ligand

trans to the carboxylate anchor shows a longer distance to the manganese center and the

coordination geometry around the manganese center is closer to perfect octahedral geometry

due to the decreased strain.[173] For further work on the chemistry of N,N,N, N,N,S, N,N,O and

N,N,Cp scorpionate ligands several reviews are available.[44, 176-180]

Scheme 25. Synthesis of the propionic acid based ligands Hbpzp and Hbdmpzp via methyl propiolate; formation of the manganese (I) and rhenium (I) carbonyl complexes [Mn(bdmpzp)(CO)3] and [Re(bdmpzp)(CO)3].[172-173]

The aforementioned system [Ru(bdmpza)Cl(PPh3)2] has proven to show rich follow-up

chemistry due to the labile triphenylphosphine and chlorido ligands. Moreover, the complex

has been used as a model for the active site of 2-oxoglutarate dependent iron enzymes, which

are often difficult to investigate due to their paramagnetic ferrous high-spin constitution. In

comparison, the ruthenium based system with its low-spin state allows NMR characterization

of the complexes. Conversion of [Ru(bdmpza)Cl(PPh3)2] with acetate or benzoate allows the

formation of the κ2 coordinated neutral ruthenium complexes [Ru(bdmpza)(O2CMe)(PPh3)]

and [Ru(bdmpza)(O2CPh)(PPh3)] (Scheme 26).[181] In similar fashion the reaction of

[Ru(bdmpza)Cl(PPh3)2] with thallium 2-oxocarboxylates Tl[O2CC(O)R] (R = Ph,

CH2CH2CO2H) produces κ2O1,O2-2-oxocarboxylato complexes which can also be synthesized

via the intermediary acetato or benzoato complexes due to the higher acidity of the

oxocarboxylic acid. This is especially relevant for the catalytic cycle of the 2-oxoglutarate

dependent enzymes, which has been postulated to show the exchange of a carboxylato ligand

by a 2-oxocarboxylato ligand as a regenerative step.[182-183] The hemilabile behavior of the

κ1O1,O1´ ligands allows the isolation of the water and acetonitrile adducts [Ru(bdmpza)-

(O2CMe)(H2O)(PPh3)] and [Ru(bdmpza)(O2CPh)(MeCN)(PPh3)] which are promising

candidates for further reactions.[181]

NN N

N

Me

Me

Me

MeMO

CO COCO

NNH

R

R

1. NaH2.3. H+/H2O

CO2CH3 ONN N

N

R

R

R

R

COOH1. KOtBu2. [MnBr(CO5)]

R = H, Me M = Mn, Re

32

!State of Knowledge

!! !

Scheme 26. Formation of carboxylato and 2-oxocarboxylato ruthenium(II) complexes.[181]

The reaction of [Ru(bdmpza)Cl(PPh3)2] with pyridine, acetonitrile, carbon monoxide and

sulfur dioxide has also been reported and has shown that the N,N,O ligand bdmpza leads to a

preferred arrangement around the ruthenium center with the remaining triphenylphosphine

ligand positioned trans to a pyrazole unit. The chlorido ligand is positioned trans to the

acetate anchor in the aforementioned cases and leaves the newly introduced ligand in trans

position to the remaining pyrazole unit. This behavior has been observed for the complexes

[Ru(bdmpza)Cl(CO)(PPh3)],[61] [Ru(bdmpza)Cl(SO2)(PPh3)],[184] [Ru(bdmpza)Cl(pyridine)-

(PPh3)][185] and [Ru(bdmpza)Cl(MeCN)(PPh3)] (Scheme 27).[185]

Scheme 27. Exchange reactions of the triphenylphosphine ligand in the [Ru(bdmpza)Cl(PPh3)2] system (py = pyridine, MeCN = acetonitrile).[61, 184-185]

The compound [Ru(bdmpza)Cl(PPh3)2] has also shown a versatile organometallic chemistry

ranging from classical carbene and Fischer-type oxocarbene complexes to vinylidene and

NN N

N

Me

Me

Me

MeRu

OO

Cl PPh3Ph3P

NN N

N

Me

Me

Me

MeRu

OO

O OPh3P

NN N

N

Me

Me

Me

MeRu

OO

O OPh3P

R1

OR4

O

HOO

R3O

OO

R2Tl

+ Tl[O2CR1]- TlCl, - PPh3

- TlCl - HO2CR1

R1 = Me, PhR2 = Ph, CH2CH2CO2HR3 = Me, EtR4 = Ph, CH2CH2CO2H, Me, Et

NN N

N

Me

Me

Me

MeRu

OO

Cl PPh3Ph3P

+ L- PPh3

NN N

N

Me

Me

Me

MeRu

OO

Cl LPh3P

L = CO, SO2, py, MeCN

33

!State of Knowledge

!! !

allenylidene complexes. The reaction of the bisphosphine ruthenium complex with a series of

terminal alkynes led via 1,2-H shift of the intermediary η2 coordinated alkyne to the

vinylidene complexes with the vinylidene ligand positioned trans to the pyrazole or

carboxylate unit. The relation of the two formed isomers is attributed to the sterical hindrance

of the respective alkyne complex during the η2 coordination preferring the arrangement trans

to the pyrazole moiety for larger substituents. Up to now, the phenyl, tolyl, propyl and butyl

substituted vinylidene complexes of the general formula [Ru(bdmpza)Cl(═C═CHR)(PPh3)]

have been reported (Scheme 28).[61, 186]

Scheme 28. Synthesis of bdmpza based ruthenium vinylidene complexes with the cumulenylidene ligand positioned either trans to a pyrazole or the carboxylate unit (R = phenyl, tolyl, propyl, butyl).[186]

Due to the sensibility of the vinylidene complexes towards oxidation, a separation of the two

occurring structural isomers cannot be achieved. Hence, the reactivity of the ruthenium

precursor with propargyl alcohols was explored leading to the diphenyl and ditolyl substituted

allenylidene complexes of the general formula [Ru(bdmpza)Cl(═C═C═CR2)(PPh3)]

(R = phenyl, tolyl) which are stable towards air and humidity (Scheme 29). Separation via

column chromatography allows the isolation of both structural isomers, which show different

chemical and physical properties. Studies on the reactivity of these allenylidene complexes in

metathesis reactions were disappointing as no catalytic activity could be observed, which is

attributed to the stability of the 18 VE complex that does not undergo ligand dissociation to

the reactive 16 VE species.

NN N

N

Me

Me

Me

MeRu

OO

Cl PPh3Ph3P

- PPh3

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

H RC H

R

+C CH R+

34

!State of Knowledge

!! !

Scheme 29. Synthesis of bdmpza based ruthenium allenylidene complexes with the cumulenylidene ligand positioned either trans to a pyrazole or the carboxylate unit (R = phenyl, tolyl).[186]

As mentioned in chapter 2.4.3 for the Tp based allenylidene complexes, the addition of

nucleophiles usually occur either in α or γ position. For weak nucleophiles, like ammonia, the

addition to the γ position on the complex [Cr(═C═C═C(OMe)NMe2)(CO)5] has been

reported.[187] The rearrangement of the Cγ ammonia adduct to the α-aminocarbene is known

for the complex [Re(═C═C═CPh2)(CO)2(triphos)][OTf] (triphos = 1,1,1-tris(diphenyl-

phosphinomethyl)ethane).[188] In the case of the reaction of [Ru(bdmpza)Cl-

(═C═C═C(tolyl)2)(PPh3)] with methylamine, the product can be obtained as aminocarbene

complex indicating the higher reactivity of the α carbon atom which is in good agreement

with DFT calculations (Scheme 30).[189]

Scheme 30. Addition of methylamine to the complex [Ru(bdmpza)Cl(═C═C═C(tolyl)2)(PPh3)] yielding the corresponding aminocarbene complex.[189]

NN N

N

Me

Me

Me

MeRu

OO

Cl PPh3Ph3P- PPh3

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

C

+C CH CR2OH+

CCR

R

R R

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CC

Tol

Tol

+ NH2Me

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PNHMe

HCC Tol

Tol

35

3 OBJECTIVE AND AIMS

36

!Objective and aims

!! !

During the last years a rich variety of heteroscorpionate complexes based on transition metals

has been reported by the BURZLAFF group and other working groups and extensively reviewed

by A. OTERO.[44, 173, 176, 180, 184-185, 189-190] In the field of manganese(I) carbonyl complexes bearing

heteroscorpionate ligands I. HEGELMANN and L. PETERS of the BURZLAFF group synthesized

several complexes of the general formula [Mn(L1-3)(CO)3] with the heteroscorpionate ligands

bis(3,5-dimethylpyrazol-1-yl)acetate (L1 = bdmpza), bis(pyrazolyl)acetate (L2 = bpza) and

3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (L3 = bdmpzp).[42, 173] Given the interest in

medicinal applications of heteroscorpionate complexes, the carbon monoxide release

properties of these and closely related manganese(I) carbonyl complexes should be

investigated as first project within this thesis. Closely related is a topic previously

investigated by S. TAMPIER and G. TÜRKOGLU concerning ruthenium carbonyl complexes

with heteroscorpionate ligands. A single crystal X-ray structure determination of the dinuclear

complex [Ru(bdmpza)(CO)(μ2-CO)]2 was obtained by serendipity and in consequence the

rational synthesis of this compound should be explored within this work.

Especially the complex [Ru(bdmpza)Cl(PPh3)2] has shown a versatile organometallic

chemistry including ligand exchange reactions leading to the 2-oxocarboxylato complex

[Ru(bdmpza)(O2C(CO)Me)(PPh3)].[185] As these can be classified as bioinorganic model

complexes for iron enzymes, the topic of aminophenol ligands and their non-innocent

behavior should be explored starting from previous results of M. KECK.

Moreover, a major part of this thesis should be the synthesis and characterization of carbon-

rich cumulenylidene complexes, i.e. ruthenium allenylidene and vinylidene complexes. The

starting point was previous work by H. KOPF on the synthesis of neutral bdmpza based

ruthenium complexes with the general formula [Ru(bdmpza)Cl(L)(PPh3)].[61, 186, 189] Thus

within this work several new carbon-rich propargyl alcohols should be synthesized and the

reaction to the corresponding ruthenium allenylidene complex should be performed. The

properties of the resulting allenylidene complexes should be characterized with a focus on

cyclic voltammetry and absorption spectroscopy. As a side project the formation of water-

soluble carbon-rich allenylidene complexes should be explored for possible applications in

non-covalent functionalization of carbon allotropes.

37

4 RESULTS AND DISCUSSION

38

!Results and Discussion

!! !

4.1 Manganese Based Photo-CORMs

Recently, P. KURZ and coworker compared the CO-release properties of [Mn(bdmpza)(CO)3]

(1) (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate), that was published by the BURZLAFF

group some years ago, to that of a related tris(pyrazol-1-yl)methane (tpm) complex.[42, 191]

Given the interest in medicinal applications of heteroscorpionate complexes, it was decided to

explore the carbon monoxide release properties of such heteroscorpionate manganese(I)

carbonyl complexes further. During the last decade, the BURZLAFF group has reported on the

synthesis of various manganese(I) complexes based on heteroscorpionate ligands. Up to date,

the complexes [Mn(bdmpza)(CO)3] (1), [Mn(bpza)(CO)3] (2) (bpza = bis(pyrazol-1-

yl)acetate), and [Mn(bdmpzp)(CO)3] (3) (bdmpzp = 3,3-bis(3,5-dimethylpyrazol-1-yl)-

propionate) have been described.[42, 173] Due to the rising interest in CORMs, especially with

Alfama´s lead compound fac-[Mo(CO)3(histidinate)]Na (ALF-186),[192] which also features a

κ3 coordinated N,N,O motif, we decided to synthesize the missing link, a manganese(I)

complex bearing a 3,3-bis(pyrazol-1-yl)propionic acid (Hbpzp) and to study the complexes

towards their CO-release properties (Scheme 31).

Scheme 31. Synthesis of heteroscorpionate complexes [Mn(bdmpza)(CO)3] (1), [Mn(bpza)(CO)3] (2), [Mn(bdmpzp)(CO)3] (3) and [Mn(bpzp)(CO)3] (4).[42, 173]

The ligands and complexes were synthesized according to reported procedures.[42, 173]

Deprotonation of the free acids (e.g. Hbpzp) with potassium tert-butylate lead to the

potassium carboxylates (e.g. K[bpzp]). Reaction of [MnBr(CO)5] with these carboxylates

resulted in the formation of tricarbonyl complexes [Mn(heteroscorpionate)(CO)3] (1-4). The

new complex [Mn(bpzp)(CO)3] (4) could be filtered off after spontaneous precipitation from

the reaction mixture. Complex 4 is stable towards oxygen as a solid but decomposes in

solution within some hours, as described previously for complexes 1-3.[42, 173] In comparison to

NN N

N

R

R

R

RMn

OO

OC COCO

NN N

N

R

R

R

RMnOC COCO

OO

or

R = Me (1), H (2) R = Me (3), H (4)

[MnBr(CO)5] potassium carboxylateof the scorpionate+

39


!! !

the dimethylpyrazole based complex [Mn(bdmpzp)(CO)3] (3), its solubility in most solvents

is lower. The two pyrazolyl groups of 4 give rise to only one set of signals in the 1H NMR

spectrum in accordance with the expected Cs structure. Due to poor solubility, no carbonyl

signals could be detected in the 13C NMR spectrum. Nevertheless, the IR spectrum shows

three carbonyl signals (A’, A’’ and A’) at 2026, 1932 and 1915 cm–1, as expected for a facial

coordinated tricarbonyl complex with Cs symmetry.

Furthermore, the complex [MnBr(CO)3(Hpz)2] (5) was included in this study representing a

simplified analogue of complexes 2 and 4 and that - from a synthetic point of view - is a lot

simpler to prepare (Scheme 32). Moreover, it was tried to synthesize the analogous

imidazole based manganese(I) complex but the reaction of one equivalent [MnBr(CO)5] with

two equivalents of imidazole in CH2Cl2 over 5 h only led to the formation of the cationic

manganese complex [Mn(CO)3(HIm)3]Br (6) (Scheme 32).

Scheme 32. Synthesis of manganese based complexes [MnBr(CO)3(HPz)2] (5) and [Mn(CO)3(HIm)3]Br (6).[193]

The high symmetry (C3v) of complex 6 is emphasized by the 1H NMR and 13C NMR spectra.

Both spectra show only one set of signals for all relevant positions including the amine

protons at 12.97 ppm in the 1H NMR spectrum and the carbonyl ligands at 220.3 ppm in the 13C NMR spectrum. ESI-MS experiments showed that the cation can be detected at

m/z = 343.05 which is the characteristic [M]+ signal for the complex after loss of the counter

ion.

The 13C NMR and IR data of the carbonyl ligands in complexes 1-6 is listed in Table 2. The

characteristic facial coordinating motif of the heteroscorpionate N,N,O ligands leads to the

formation of complexes with Cs symmetry as has been shown previously.[42-43, 173] This reduced

symmetry compared to the C3v symmetrical tpm M(CO)3 based complexes gives rise to three

IR absorption bands (A’, A’’ and A’) for the CO vibrations. Due to its higher C3v symmetry,

complex 6 exhibits only two characteristic CO vibrations in the IR spectrum.

MnOC

OC N

Br

N

CO

MnOC

N N

CO

N

CO

HN

NH

NH

NH

NH

[MnBr(CO)5]2 HPz 3 HIm

5 6

Br

40


!! !

Ligand Complex δ (CO) [ppm] ṽ (CO)(KBr) [cm–1]

bdmpza 1 219.8 2038, 1954, 1931

bpza 2 219.3 2039, 1956, 1917

bdmpzp 3 222.0 2030, 1925, 1899

bpzp 4 / 2028, 1947, 1929

2 × Hpz, 1 × Br– 5 222.8 2035, 1940, 1918

3 × HIm 6 220.3 2024, 1907

Table 2. Overview of relevant 13C NMR and IR spectroscopic data of compounds 1-6.

CO release properties

In order to study the properties of the new compounds as photoactivatable CO releasing

molecules (Photo-CORMs), the manganese complexes 1-6 were investigated using the

UV/Vis based myoglobin assay. Complex 1 has been reported previously to show Photo-

CORM activity,[191] but due to a slightly different assay, it was decided to reassess the values

to facilitate comparison with compounds 2-6. Prior to measuring the release upon UV

excitation, the stability of each compound was tested in the dark. Complexes 1-3 were stable

and did not show any decomposition during 6 h. Nevertheless, complexes 4-6 showed

CO release upon dissolution in aqueous media in the dark. Similar behavior has previously

been reported for the precursor [Mn(CO)5]Cl, which forms the aqua complex

[Mn(CO)3(H2O)3]+.[194] Complex 4 exhibited slow release within a timeframe of 24 h yielding

1.42 ± 0.04 eq. of carbon monoxide with an average half life of 217 min (Chapter 8.3, Figure

64). For bis(imidazol-2-yl)propionate (bip) based complexes, a betain-like structure has been

reported with a κ2 coordination of the bis(imidazo-2-yl)methane moiety and a dissociated

propionate anchor.[195] A similar dissociation of the carboxylate donor might explain the low

stability of 4 in solution, but up to now it was not possible to isolate such an intermediate. The

pyrazole-based compound 5 shows faster decomposition in the dark, releasing 1.14 ± 0.09 eq.

CO with t1/2 = 124 min (Chapter 8.3, Figure 65). In contrast, the cationic imidazole complex 6

shows the fastest CO release in the dark with a t1/2 = 73 min and the release of 2 eq. CO

41


!! !

(1.94 ± 0.39) (Chapter 8.3, Figure 66). Nevertheless, it was decided to take a look at the effect

of photoactivation of 5 and 6 with UV light to see if complete CO release can be achieved.

Figure 9. Fitted average CO release of 6 (squares) and 5 (dots) measured via myoglobin assay.

For complex 5, a strong acceleration of the CO release was achieved via UV excitation

(365 nm), lowering the release time to t1/2 = (6.40 ± 0.14) min and yielding an increased

amount of equivalents CO (2.17 ± 0.09 eq.) (Figure 9). In comparison, 6 shows an even

higher activity under these conditions, releasing about 2.5 equivalents of carbon monoxide in

20 min (t1/2 = 5.56 min, 2.60 ± 0.35 eq.). Due to the different coordination sphere of the

manganese(I) center with two pyrazole or three imidazole ligands, a direct comparison is

difficult. However, removal of the ligand backbone from either tris(imidazol-2-yl)phosphanes

or bis(pyrazol-1-yl)acetate leads to manganese tricarbonyl complexes that are not stable under

the conditions of the myoglobin assay.[196]

In the next step, the Photo-CORM properties of the compounds, which showed no CO release

in the dark were evaluated. For 1, a t1/2 = 6.73 min with a release of 2.38 ± 0.11 eq. of carbon

monoxide was observed upon photoactivation at 365 nm, which is in good accordance with

the literature value of 2.5 eq. (Figure 10).[191] Compound 2 lacks the methyl substituents as in

complex 1 and shows slower CO release. With 2.15 ± 0.11 eq. and t1/2 = 11.35 min, the

complex seems to be more stable than the methyl substituted one, which is in agreement with

previous observations regarding these ligands.[168] In a similar context, the ruthenium based

system [Ru(bpza)Cl(PPh3)2] is quite stable towards oxygen, whereas the bulkier methyl-

0 5 10 15 20 25 300.0

0.5

1.0

1.5

2.0

2.5

3.0

eq. (CO)

t [min]

42


!! !

substituted [Ru(bdmpza)Cl(PPh3)2] is highly oxidation sensitive and decomposes within hours

in the presence of oxygen.[168]

Figure 10. Fitted average CO release of 1 (squares), 2 (dots) and 3 (triangles) measured via myoglobin assay.

Extending the acetate anchor to a propionate leads to complex 3, which has the fastest

CO release kinetics of the compounds presented within this work. Full release of 2 eq. CO has

been observed after less than 15 min with t1/2 = 3.77 min (2.06 ± 0.09 eq.). This might be due

to the propionate based ligand that allows more dynamic behavior in the resulting complexes.

The less rigid coordination seems to facilitate the dissociation of carbonyl ligands compared

to the acetate based ones. The difference in CO-release rate between 3 and 4 seems to be

strongly influenced by the methyl substituents. Obviously, in this case, the methyl groups

stabilize the complex, hinder the mobility of the carboxylate anchor and prevent solvent-

controlled dissociation of CO molecules for 3. The proton-substituted complex 4 is however,

not stable in solution and solvent-controlled dissociation of the carbonyl ligands occurs in the

dark.

In Table 3, the properties of several literature known Photo-CORMs are collected.

Comparison with the heteroscorpionate complexes shows that on average, only two of the

three CO ligands per complex are released. The half life of the complexes presented in this

work is shorter than most of the compounds described so far in the literature, but varies

significantly with the ligand system.

0 5 10 15 20 25 300.0

0.5

1.0

1.5

2.0

2.5

eq. (CO)

t [min]

43


!! !

Complex t1/2 [min] eq. (CO) Reference

1 [Mn(bdmpza)(CO)3] 7 2.38 [a]

2 [Mn(bpza)(CO)3] 11 2.15 [a]

3 [Mn(bdmpzp)(CO)3] 4 2.06 [a]

[Mn(tpm)(CO)3]PF6 20 1.96 [36]

fac-[Mn(his)(CO)3] 93 1.26 [197]

[Mn2(CO)10] (CORM-1) not determined 0.68 [32]

Table 3. Photoinduced CO release upon UV excitation for manganese(I) carbonyl complexes, with half-lifes and number of CO molecules released per complex determined with the myoglobin assay; [a] reported in this work.

44


!! !

4.2 Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato

Ligands

Parts of this chapter have been published:

Türkoglu, G.; Tampier, S.; Strinitz, F.; Heinemann, F. W.; Hübner, E.; Burzlaff, N.,

Organometallics 2012, 31, 2166-2174.

Bis(pyrazol-1-yl)acetic acids have proven to be a versatile N,N,O heteroscorpionate ligand

closely related to the well known hydridotris(pyrazol-1-yl)borate (Tp) ligand as mentioned in

the introduction. Several ruthenium(II) complexes like [Ru(bdmpza)Cl(PPh3)2] and recently

[Ru(2,2-bdmpzp)Cl(PPh3)2] (2,2-bdmpzp = 2,2-bis(3,5-dimethylpyrazol-1-yl)propionic acid)

have been reported by N. BURZLAFF et al. and other groups.[61, 168, 181, 184-185, 189-190, 198-201] Some of

these ruthenium(II) complexes are good structural models for iron oxygenases that exhibit a

facial 2-His-1-carboxylate triad as a ferrous iron binding motif.[181, 190] The uncatalyzed

reaction of organic compounds with atmospheric dioxygen is thermodynamically feasible but

is a spin-forbidden process. In nature, iron oxygenases make use of their high-spin ferrous

centers to overcome this spin mismatch.[202-206] Thus, an analogous enzyme activation of

dioxygen with ruthenium(II) complexes is not favorable due to their low-spin character.

However, the necessity of a high-spin center becomes irrelevant in so-called peroxide shunt

type reactions. Oxidizing agents such as peroxides and iodosylbenzene are used to directly

generate high-valent and reactive RuIV═O or RuVI(═O)2 species which are able to catalytically

epoxidize alkenes, oxidize sulfides, or hydroxylate alkanes.[207-214] C.-M. CHE and co-workers,

for instance, reported on cationic ruthenium(IV) complexes such as [Ru(Me3tacn)(3,3′-Me2-

bpy)(O)]2+ and [Ru(terpy)(tmeda)(O)]2+ that can be used to epoxidize alkenes

stoichiometrically (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane, 3,3′-Me2bpy = 3,3′-

dimethyl-2,2′-bipyridine, terpy = 2,2′:6′,2′′-terpyridine, tmeda = N,N,N′,N′-tetramethyl-

ethylenediamine).[215-218] Furthermore, the complex [Ru(Me3tacn)(OH2)(O2CCF3)](O2CCF3)2

was shown to be an effective catalyst for homogeneous oxidation of alkenes by tert-butyl

hydroperoxide (TBHP) as an oxidant.[219] Thus, in previous experiments some of the

ruthenium bdmpza complexes mentioned above, such as [Ru(bdmpza)Cl(PPh3)2] and

[Ru(bdmpza)(OAc)(PPh3)], were tested for their catalytic activity in similar alkene

45


!! !

epoxidations.[220] Unfortunately, rather poor catalytic activity with only 2−3 turnovers was

observed, due to large quantities of O═PPh3 byproduct, which inhibit the catalytic

epoxidation. Thus, it was decided to focus on phosphine-free complexes for further studies. S.

TAMPIER and G. TÜRKOGLU synthesized [Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl-

(CO)2] (10) starting from [RuCl2(CO)2]n[221] that has been reported by J. VOS et al. as quite

useful and easily accessible precursor for phosphine free ruthenium chemistry.[222-223] Addition

of the respective potassium salt of the heteroscorpionate ligand leads to formation of the

mononuclear ruthenium complex (Scheme 33).

Scheme 33. Synthesis of dicarbonyl complexes [Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl(CO)2] (10).

In addition the formation of the dinuclear byproduct [Ru(bdmpza)(CO)(μ2-CO)]2 was

observed in the FAB+ mass spectrum as indicated by the molecular ion peak (m/z 810, 4%). Thus, it was not surprising that, in attempts to crystallize complex 9, crystals of this

byproduct [Ru(bdmpza)(CO)(μ2-CO)]2 (12) suitable for an single-crystal X-ray structure

determination were isolated by S. TAMPIER.[222] The structure determination revealed its

molecular structure as a dinuclear μ2-CO complex as reported in his dissertation.[222]

There are several procedures described in the literature for the synthesis of the analogous

cyclopentadienyl compound [Ru(η5-C5H5)(CO)(μ2-CO)]2. Thus, attempts were undertaken to

rationally synthesize this compound. E. O. FISCHER et al. synthesized [Ru(η5-C5H5)(CO)(μ2-

CO)]2 via reaction of the ruthenium(II) precursor [Ru(CO)2I2][224] with an excess of sodium

cyclopentadienide, Na[C5H5].[225] Attempts to adopt this procedure by using potassium bis(3,5-

dimethylpyrazol-1-yl)acetate instead of Na[C5H5] failed because of the insolubility of

K[bdmpza] in the aliphatic solvent. In further attempts an oxidative addition of bis(3,5-

dimethylpyrazol-1-yl)acetic acid to [Ru3(CO)12] was tested. This should result in the hydrido

complex [Ru(bdmpza)H(CO)2] (11), which might then be oxidized by oxygen and dimerize to

[Ru(bdmpza)(CO)(μ2-CO)]2 (12) as reported for [Ru(η5-C5H5)(CO)(μ2-CO)]2.[226-227] Indeed,

NN N

N

Ru

OO

OC ClCO

Me

Me

Me

Me

R

NN N

N

Me

Me

Me

Me

CO2HR

R = H (7)R = Me (8)

R = H (9)R = Me (10)

1. KOtBu2. [RuCl2(CO)2]n

46


!! !

the 1H NMR spectrum of the resulting product indicated formation of two hydrido complexes

by two singlet signals at −13.32 and −10.10 ppm (in CDCl3) (Scheme 34). These signals have

been assigned to two structural isomers, the symmetrical hydrido complex [Ru(bdmpza)-

H(CO)2] (11A) and the unsymmetrical hydrido complex [Ru(bdmpza)H(CO)2] (11B). In the

Cs symmetric isomer 11A the hydrido ligand resides trans to the carboxylate and only one set

of signals is observed for the two 3,5-dimethylpyrazole donors in the 1H NMR spectrum,

whereas the C1 symmetric, chiral, but racemic complex [Ru(bdmpza)H(CO)2] (11B) shows

two sets of signals in the 1H NMR spectrum, instead.

Scheme 34. Synthesis of complexes [Ru(bdmpza)H(CO)2] (11A,B) and [Ru(bdmpza)(CO)(μ2-CO)]2 (12).

The solubility of the hydrido complex [Ru(bdmpza)H(CO)2] (11A,B) is rather poor in most

solvents apart from CHCl3 and CH2Cl2. Unfortunately, the complex decomposes quickly in

CDCl3 by formation of the chlorido complex, a reactivity that was reported for other hydrido

complexes such as [Ru(η5-C5H5)H(CO)(PPh3)].[225] In CD2Cl2 the stability of the complex is

slightly better. Thus, only 1H NMR data could be obtained so far. Nevertheless, ESI-MS data

and elemental analysis prove the formation of 11A,B. Surprisingly, so far it was not possible

to isolate 12 from solutions of the hydrido complex [Ru(bdmpza)H(CO)2] (11A,B), that had

been exposed to air. Obviously, the hydrido complex 11A,B seems to be quite unreactive

regarding oxygen. Even heating under reflux in nonpolar solvents such as n-heptane and

NN N

N

Ru

OO

OC HCO

Me

Me

Me

Me

Hbdmpza[Ru3(CO)12]

HOAc

[Ru(OAc)(CO)2]n

toluene, Δ

THF, Δ- HOAc

Hbdmpza

NN N

N

Ru

OO

OC COH

Me

Me

Me

Me

+

O

NN

NNOO

NN

N

O

Ru

OC

RuCO

CO

OC

Me

Me

Me

Me

Me

Me

Me

Me N

11A 11B

12

47


!! !

applying aerobic conditions did not yield complex 12 but mostly unreacted 11A,B. Thus,

another attempt was undertaken by reacting the acetate polymer catena-[Ru(OAc)(CO)2]n

with Hbdmpza. The polymer catena-[Ru(OAc)(CO)2] is readily available but is also easily

accessible by reacting [Ru3(CO)12] with acetic acid.[228] It has been successfully applied in the

syntheses of various dinuclear ruthenium(I) complexes before.[229-230] Reaction in THF at

reflux for 24 h replaced the acetate of catena-[Ru(OAc)(CO)2]n by bis(3,5-dimethylpyrazol-1-

yl)acetic acid and resulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2 (12) in a yield of

30%. The constitution of the molecule is confirmed by elemental analysis as well as by ESI-

MS data in acetonitrile, which show a 100% peak at m/z 405.02 (100) assigned to a

[Ru(bdmpza)(CO)2]+ fragment and a small (4%) molecular ion peak at m/z 810.05. Due to the

low solubility of 12 in all common deuterated solvents, only 1H NMR data could be obtained

so far. As expected for the C2h-symmetric molecule depicted in Scheme 34, only one set of

signals is observed, with the methyl singlet signals at 2.35 (Me3) and 2.62 ppm (Me5). The

pyrazole CH proton is found at 6.04 ppm and the methine proton at 6.31 ppm. In theory at

least three isomeric forms of complex 12 might be possible: (I) terminal trans-CO/μ2-CO

bridged, (II) terminal cis-CO/μ2-CO bridged, (III) nonbridged. Apparently, according to the

NMR data only one of these possible isomeric forms seems to be present in solution. This is

in contrast to [Ru(η5-C5H5)(CO)(μ2-CO)]2, where an equilibrium of various isomeric forms

was reported.[231-234] The bdmpza ligand exhibits its typical IR vibrations at 1673 cm–1 (as-

CO2–) and 1559 cm–1

(C═N) as expected for κ3 coordination. The IR spectrum in solution

(CHCl3) is almost identical with that obtained in a KBr matrix. IR vibrations (CHCl3) at

1978 cm–1 (terminal CO) and 1761 cm–1 (μ2-CO) agree well with those reported for μ2-CO

isomers of [Ru(η5-C5H5)(CO)(μ2-CO)]2 (ν(CO) (CHCl3) 2009 cm–1 (terminal CO) and

1768 cm–1 (μ2-CO); ν(CO) (MeCN) 1995 cm–1 (terminal CO) and 1775 cm–1 (μ2-CO)).[233]

Thus, owing to the observed very strong μ2-CO vibration one μ2-CO isomer seems to

dominate in the solid state as well as in solution. Nevertheless, a very weak shoulder around

2010 cm–1 and a weak signal at 1950 cm–1 might indicate traces of a nonbridged species.

Similar results could be obtained with the sterically less demanding bpza ligand, as the

bridged complex could be synthesized.[235] However, the complex [Ru(bpza)Cl(CO)2] (13)

was still missing. 13 can be easily synthesized in analogy to [Ru(bdmpza)Cl(CO)2] (9) by

adding the potassium salt of the bpza ligand and heating under reflux (Scheme 35).

48


!! !

Scheme 35. Synthesis of dicarbonyl complex [Ru(bpza)Cl(CO)2] (13).

The complex [Ru(bdmpza)Cl(CO)2] (9) shows high solubility in CH2Cl2 and CHCl3, in

comparison [Ru(bpza)Cl(CO)2] (13) remains completely insoluble and can only be

characterized as DMSO or methanol solution. 13 shows in the 1H NMR spectrum six protons

for the two pyrazolyl units indicating that the chlorido ligand is positioned trans to a pyrazole

moiety and thus an asymmetric bpza ligand without a mirror plane is isolated. The 13C NMR

spectrum confirms the presence of two asymmetric carbonyl ligands at 194.8 and 193.9 ppm

that are positioned trans to the second pyrazole moiety and the acetate anchor. The complex

shows two intense absorptions at 2081 and 2014 cm–1 in the IR absorption spectrum in a

similar region to 9 (2074 cm–1, 2005 cm–1).[236] Two additional very weak absorptions at 1768

and 1760 cm–1 indicate that traces of the dimeric complex could be present however, attempts

of removal via recrystallization from DMSO did not lead to disappearance. The complex

could further be characterized via ESI-MS experiments showing the presence of the sodium

adduct of 13 as 100% peak at m/z 406.91 (100) assigned to a [Ru(bpza)Cl(CO)2 + Na]+

cluster. Crystals suitable for a single crystal X-ray structure determination were obtained by

dissolving 13 in boiling methanol and afterwards vapor diffusion of Et2O into the methanolic

solution at room temperature. [Ru(bpza)Cl(CO)2] (13) crystallizes as two independent

molecules in the space group C2/c and shows co-crystallization of methanol and Et2O. The

complex shows the arrangement deduced from the NMR data and shows the chlorido ligand

trans to a pyrazole moiety leading to two non-equivalent carbonyl ligands trans to the

remaining pyrazole unit and trans to the carboxylate anchor (Figure 11).

NN N

N

Ru

OO

OC ClCO

NN N

N

CO2H 1. KOtBu2. [RuCl2(CO)2]n

13

THF

49


!! !

Figure 11. Preliminary molecular structure of [Ru(bpza)Cl(CO)2] (13). Hydrogen atoms and solvent molecules have been omitted for clarity.

To elucidate the spectroscopic properties and the binding situation in [Ru(bdmpza)(CO)(μ2-

CO)]2 (12) further, DFT calculations were performed by E. HÜBNER starting from the X-ray

structure determination data. The resulting geometry of the DFT calculations was almost

identical with the geometry of the X-ray structure determination. The spin density of the two

electrons forming the Ru−Ru bond is mainly located at the metal centers and the bridging

carbonyl ligands (Figure 12). Surprisingly, the spin density plot does not resemble the contour

plots of two dz2 orbitals but the contour plots of dxy, dxz or dyz orbitals. This implies that the

Ru−Ru bond is better described as a π bond than as a σ bond. In order to verify the IR signals

of 12, DFT calculations were performed. It is well-known for the chosen B3LYP/6-31G*

DFT functional and basis set, that calculated vibrational frequencies are typically

overestimated in comparison to experimental data. These errors arise from the neglect of

anharmonicity effects, incomplete incorporation of electron correlation, and the use of finite

basis sets in the theoretical treatment.[237] In order to achieve a correlation with observed

spectra, a scaling factor of approximately 0.96 has to be applied.[237] Depending on the

examined vibration, this factor differs slightly even in the same molecule and is usually

greater for lower energies.[238]

O4C41

N21 N11

N22 N12

RuC31

ClO3

O1

O2

50


!! !

Figure 12. Spin density plot regarding the electrons forming the Ru−Ru bond.

We were especially interested in the two carbonyl vibrations, which were predicted (unscaled)

at 2078 cm−1 (terminal CO) and at 1851 cm−1 (μ2-CO). This leads to expected vibrations at

1995 and 1777 cm−1. Both values agree well with the experimental data. In further agreement

with the experimental data, the trans geometry of the bridged isomer of 12 was found to be

the lowest in energy. The energy difference between the bridged and nonbridged species

(Figure 13) was found to be rather small, with ΔE = 22 kJ/mol in comparison to an energy

difference of ΔE = 45 kJ/mol between the cis and trans geometries. The low energy

difference toward the unbridged isomer implies a rather high possibility of finding the

nonbridged isomer in solution, which may agree with the data of the IR spectra discussed

above. The strong asymmetric IR vibrations of the nonbridged CO were predicted (unscaled)

at 2075 and 2047 cm−1, which should result in vibrations around 1992 and 1965 cm−1.

polymer catena-[Ru(OAc)(CO)2]n with Hbdmpza. The poly-mer catena-[Ru(OAc)(CO)2]n is readily available but is alsoeasily accessible by reacting [Ru3(CO)12] with acetic acid.54 Ithas been successfully applied in the syntheses of variousdinuclear ruthenium(I) complexes before.42,49 Reaction in THFat reflux for 24 h replaced the acetate of catena-[Ru(OAc)-(CO)2]n by bis(3,5-dimethylpyrazol-1-yl)acetic acid andresulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2(6) in a yield of 30%. The constitution of the molecule isconfirmed by elemental analysis as well as by ESI MS data inacetonitrile, which show a 100% peak at m/z 405.02 (100)assigned to a [Ru(bdmpza)(CO)2]

+ fragment and a small (4%)molecular ion peak at m/z 810.05. Due to the low solubility of6 in all common deuterated solvents, only 1H NMR data couldbe obtained so far. As expected for the C2h-symmetric moleculedepicted in Figure 3, only one set of signals is observed, withthe methyl singlet signals observed at 2.35 (Me3) and 2.62(Me5) ppm. The pyrazole CH proton is found at 6.04 ppm andthe methine proton at 6.31 ppm. In theory at least threeisomeric forms of complex 6 might be possible: (I) terminaltrans-CO/μ2-CO bridged, (II) terminal cis-CO/μ2-CO bridged,(III) nonbridged. Apparently, according to the NMR data onlyone of these possible isomeric forms seems to be present insolution. This is in contrast to the case for [Ru(η5-C5H5)(CO)(μ2-CO)]2, where an equilibrium of variousisomeric forms was reported.50,55 The bdmpza ligand exhibitsits typical IR vibrations at 1673 cm−1 (as-CO2

−) and 1559 cm−1

(CN) as expected for κ3 coordination. The IR spectrum insolution (CHCl3 solvent) is almost identical with that obtainedin a KBr matrix. IR vibrations (CHCl3) at 1978 cm

−1 (terminalCO) and 1761 cm−1 (μ2-CO) agree well with those reportedfor μ2-CO isomers of [Ru(η5-C5H5)(CO)(μ2-CO)]2 (ν(CO)(CHCl3 solvent) 2009 cm−1 (terminal CO) and 1768 cm−1

(μ2-CO); ν(CO) (MeCN solvent) 1995 cm−1 (terminal CO)and 1775 cm−1 (μ2-CO)).

55b Thus, owing to the observed verystrong μ2-CO vibration one μ2-CO isomer seems to dominatein the solid state as well as in solution. Nevertheless, a veryweak shoulder around 2010 cm−1 and a weak signal at 1950cm−1 might indicate traces of a nonbridged species. Due to thesteric hindrance of the bdmpza ligands and in accord with DFTcalculations (see below), the μ2-CO isomer cis-[Ru(bdmpza)-(CO)(μ2-CO)]2 (isomer II) with cis geometry of the terminalCO ligands seems to be thermodynamically disfavored. Thus,in accordance with the solid-state structure (Figure 3) trans-[Ru(bdmpza)(CO)(μ2-CO)]2 (6) (isomer I) is the mainisomeric form. To elucidate the spectroscopic properties andthe binding situation in [Ru(bdmpza)(CO)(μ2-CO)]2 (6)further, DFT calculations were performed for 6 starting fromthe X-ray structure determination data. The resulting geometryof the DFT calculations was almost identical with the geometryof the X-ray structure determination. The spin density of thetwo electrons forming the Ru−Ru bond is mainly located at themetal centers and the bridging carbonyl ligands (Figure 4).Surprisingly, the spin density plot does not resemble thecontour plots of two dz2 orbitals but the contour plots of dxy,dxz, or dyz orbitals. This implies that the Ru−Ru bond is betterdescribed as a π bond than as a σ bond. In order to verify the IRsignals of 6, DFT calculations on 6 were performed. It is well-known for the chosen B3LYP/6-31G* DFT functional andbasis set that calculated vibrational frequencies are typicallyoverestimated in comparison to experimental data. These errorsarise from the neglect of anharmonicity effects, incompleteincorporation of electron correlation, and the use of finite basis

sets in the theoretical treatment.56 In order to achieve acorrelation with observed spectra, a scaling factor ofapproximately 0.96 has to be applied.56 Depending on theexamined vibration, this factor differs slightly even in the samemolecule and is usually greater for lower energies.57 We wereespecially interested in the two carbonyl vibrations, which werepredicted (unscaled) at 2078 cm−1 (terminal CO) and at 1851cm−1 (μ2-CO). This leads to expected vibrations at 1995 and1777 cm−1. Both values agree well with the experimental data.In further agreement with the experimental data, the transgeometry of the bridged isomer of 6 was found to be the lowestin energy. The energy difference between the bridged andnonbridged (Figure 5) species was found to be rather small,

with ΔE = 22 kJ/mol in comparison to an energy difference ofΔE = 45 kJ/mol between the cis and trans geometries. The lowenergy difference toward the unbridged isomer implies a ratherhigh possibility of finding the nonbridged isomer in solution,which may agree with the data of the IR spectra discussedabove. The strong asymmetric IR vibrations of the nonbridgedCO were predicted (unscaled) at 2075 and 2047 cm−1, whichshould result in vibrations around 1992 and 1965 cm−1.Experiments regarding the oxidation of cyclohexene

mediated by complexes 3 and 4 were carried out inunstabilized, HPLC grade CH2Cl2 under a dinitrogen


Figure 5. Calculated geometry of a nonbridged isomer of 6.

Organometallics Article

dx.doi.org/10.1021/om2009155 | Organometallics 2012, 31, 2166−21742170

51


!! !


Preliminary studies by G. TÜRKOGLU revealed the promising potential of

[Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl(CO)2] (10) as epoxidation catalysts, with a

TON for complex 9 up to 20.[223] Even higher TON values might be accessible by

optimization of the reaction conditions or by applying soluble iodosylbenzene derivatives as

oxidant.

Currently the complex [Ru(bpza)Cl(CO)2] (13) is tested in cooperation with the group of S.

MÉNAGE as center for an artificial oxygenase. Therefore, complex 13 was incorporated into an

enzyme pocket and the isolated hybrid was employed in the oxidation of styrene yielding

styrene glycol, which is not accessible by the complex or protein itself. Currently, the single

crystal X-ray structure determination of the hybrid is solved and refined and the parameters of

the catalysis are tuned for a greener reaction.

polymer catena-[Ru(OAc)(CO)2]n with Hbdmpza. The poly-mer catena-[Ru(OAc)(CO)2]n is readily available but is alsoeasily accessible by reacting [Ru3(CO)12] with acetic acid.54 Ithas been successfully applied in the syntheses of variousdinuclear ruthenium(I) complexes before.42,49 Reaction in THFat reflux for 24 h replaced the acetate of catena-[Ru(OAc)-(CO)2]n by bis(3,5-dimethylpyrazol-1-yl)acetic acid andresulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2(6) in a yield of 30%. The constitution of the molecule isconfirmed by elemental analysis as well as by ESI MS data inacetonitrile, which show a 100% peak at m/z 405.02 (100)assigned to a [Ru(bdmpza)(CO)2]

+ fragment and a small (4%)molecular ion peak at m/z 810.05. Due to the low solubility of6 in all common deuterated solvents, only 1H NMR data couldbe obtained so far. As expected for the C2h-symmetric moleculedepicted in Figure 3, only one set of signals is observed, withthe methyl singlet signals observed at 2.35 (Me3) and 2.62(Me5) ppm. The pyrazole CH proton is found at 6.04 ppm andthe methine proton at 6.31 ppm. In theory at least threeisomeric forms of complex 6 might be possible: (I) terminaltrans-CO/μ2-CO bridged, (II) terminal cis-CO/μ2-CO bridged,(III) nonbridged. Apparently, according to the NMR data onlyone of these possible isomeric forms seems to be present insolution. This is in contrast to the case for [Ru(η5-C5H5)(CO)(μ2-CO)]2, where an equilibrium of variousisomeric forms was reported.50,55 The bdmpza ligand exhibitsits typical IR vibrations at 1673 cm−1 (as-CO2

−) and 1559 cm−1

(CN) as expected for κ3 coordination. The IR spectrum insolution (CHCl3 solvent) is almost identical with that obtainedin a KBr matrix. IR vibrations (CHCl3) at 1978 cm

−1 (terminalCO) and 1761 cm−1 (μ2-CO) agree well with those reportedfor μ2-CO isomers of [Ru(η5-C5H5)(CO)(μ2-CO)]2 (ν(CO)(CHCl3 solvent) 2009 cm−1 (terminal CO) and 1768 cm−1

(μ2-CO); ν(CO) (MeCN solvent) 1995 cm−1 (terminal CO)and 1775 cm−1 (μ2-CO)).

55b Thus, owing to the observed verystrong μ2-CO vibration one μ2-CO isomer seems to dominatein the solid state as well as in solution. Nevertheless, a veryweak shoulder around 2010 cm−1 and a weak signal at 1950cm−1 might indicate traces of a nonbridged species. Due to thesteric hindrance of the bdmpza ligands and in accord with DFTcalculations (see below), the μ2-CO isomer cis-[Ru(bdmpza)-(CO)(μ2-CO)]2 (isomer II) with cis geometry of the terminalCO ligands seems to be thermodynamically disfavored. Thus,in accordance with the solid-state structure (Figure 3) trans-[Ru(bdmpza)(CO)(μ2-CO)]2 (6) (isomer I) is the mainisomeric form. To elucidate the spectroscopic properties andthe binding situation in [Ru(bdmpza)(CO)(μ2-CO)]2 (6)further, DFT calculations were performed for 6 starting fromthe X-ray structure determination data. The resulting geometryof the DFT calculations was almost identical with the geometryof the X-ray structure determination. The spin density of thetwo electrons forming the Ru−Ru bond is mainly located at themetal centers and the bridging carbonyl ligands (Figure 4).Surprisingly, the spin density plot does not resemble thecontour plots of two dz2 orbitals but the contour plots of dxy,dxz, or dyz orbitals. This implies that the Ru−Ru bond is betterdescribed as a π bond than as a σ bond. In order to verify the IRsignals of 6, DFT calculations on 6 were performed. It is well-known for the chosen B3LYP/6-31G* DFT functional andbasis set that calculated vibrational frequencies are typicallyoverestimated in comparison to experimental data. These errorsarise from the neglect of anharmonicity effects, incompleteincorporation of electron correlation, and the use of finite basis

sets in the theoretical treatment.56 In order to achieve acorrelation with observed spectra, a scaling factor ofapproximately 0.96 has to be applied.56 Depending on theexamined vibration, this factor differs slightly even in the samemolecule and is usually greater for lower energies.57 We wereespecially interested in the two carbonyl vibrations, which werepredicted (unscaled) at 2078 cm−1 (terminal CO) and at 1851cm−1 (μ2-CO). This leads to expected vibrations at 1995 and1777 cm−1. Both values agree well with the experimental data.In further agreement with the experimental data, the transgeometry of the bridged isomer of 6 was found to be the lowestin energy. The energy difference between the bridged andnonbridged (Figure 5) species was found to be rather small,

with ΔE = 22 kJ/mol in comparison to an energy difference ofΔE = 45 kJ/mol between the cis and trans geometries. The lowenergy difference toward the unbridged isomer implies a ratherhigh possibility of finding the nonbridged isomer in solution,which may agree with the data of the IR spectra discussedabove. The strong asymmetric IR vibrations of the nonbridgedCO were predicted (unscaled) at 2075 and 2047 cm−1, whichshould result in vibrations around 1992 and 1965 cm−1.Experiments regarding the oxidation of cyclohexene

mediated by complexes 3 and 4 were carried out inunstabilized, HPLC grade CH2Cl2 under a dinitrogen



Organometallics Article

dx.doi.org/10.1021/om2009155 | Organometallics 2012, 31, 2166−21742170

52


!! !

4.3 Ruthenium Heteroscorpionate Complexes with Aminophenol Based

Ligands

The oxidative ring cleavage of substituted aromatic compounds such as catechols and

o-aminophenols is most commonly performed by mononuclear non-heme iron

dioxygenases.[239-241] Some play important roles in human metabolism, for example in

tryptophan degradation. 3-Hydroxyanthranilate (HAA) is O2-mediated cleaved by the HAA-

3,4-dioxygenase (HAD) and reacts to quinolinate (Scheme 36).[242-243]

Scheme 36. Catalyzed reaction from 3-hydroxyanthranilate (HAA) to quinolinate.[242, 244]

In 2012 A. FIEDLER et al. reported the first synthetic intermediate of this enzyme in form of

the Fe2+–ISQ (ISQ = iminobenzosemiquinonate) complex.[244] Reaction of the Tp based iron

complex [(Ph2Tp)Fe(OBz)] with the sterically demanding aminophenol ligand 2-amino-4,6-di-

tert-butylphenol (tBuAPH2; 2-amino-4,6-di-tert-butylphenolate = tBuAPH–) yields the κ2

coordinated complex [(Ph2Tp)Fe(2+)(tBuAPH)] which mimics the enzyme-substrate complex.[244]

Reaction of this complex with 2,4,6-tri-tert-butylphenoxy radical (TBBP

•) leads to an iron(II)

complex bound to an ISQ radical.[244] The resulting Fe2+–SQ (SQ = semiquinone) complex is

often invoked as intermediate for the mechanism of catechol dioxygenases although all other

relevant models feature [Fe3+–catecholate]+ units.[245-247] Further one-electron oxidation using

Ag[SbF6] allows isolation of a cationic complex that shows an oxidation state that can be

attributed to a [Fe3+–ISQ–]+ or [Fe2+–IBQ]+ complex (IBQ = iminobenzoquinonate).[244]

Recently T. PAINE et al. reported the first functional model for 2-aminophenol dioxygenases,

namely APD (2-aminophenol-1,6-dioxygenase) and HAD.[248] The non-heme complex [(6-

Me3-TPA)Fe2+(4-tBuHAP)](ClO4) (6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine, tBuHAP = 2-amino-4-tert-butylphenol), which is readily available from a one-pot synthesis

shows reactivity with dioxygen and formation of 4-tert-butyl-2-picolinic acid through C–C

bond cleavage of 2-amino-4-tert-butylphenol.[248]

N

NH2OH-O2C

CO2H-O2C

NH2

COOHCHO

-O2CO2

HAD

non-enzymatic

- H2O

53


!! !

Due to the high sensibility of Fe2+ based heteroscorpionate complexes bearing aminophenol

ligands it was decided to start from the commonly used precursor [Ru(bdmpza)Cl(PPh3)2]

(14). M. KECK synthesized during his master thesis a dark blue complex bearing the tBuAPH2

ligand. Due to the lack of a single crystal X-ray structure determination it was supposed from

analytical data that the complex should be of the general formula [Ru(bdmpza)-

(tBuISQ)(PPh3)]Cl (Scheme 37). Strong antiferromagnetic spin-spin coupling might lead in this

case to diamagnetic coupling in NMR spectroscopy allowing the observation of the imino

proton at 14.19 ppm in the 1H NMR spectrum. It was discussed that two theoretical binding

modes for the tBuAPH– could occur with the imino and hydroxo functionality positioned trans

to the carboxylate anchor and one pyrazole unit and vice versa.

Scheme 37. Synthesis of [Ru(bdmpza)(tBuISQ)(PPh3)]Cl (15A, 15B) by M. KECK and its supposed structures a) and b).

The high solubility of complex 15 in polar and nonpolar solvents led to difficulties in

obtaining crystals suitable for a single crystal X-ray structure determination. Nevertheless,

dissolving complex 15 in a hot mixture of CH2Cl2 and n-hexane, layered with pure n-hexane

led to the formation of crystals.

The result of a single crystal X-ray structure determination shows that the predicted binding

mode is not in agreement with the observed structure (Figure 14). Instead of a κ2 coordinated tBuISQ ligand a κ1 coordination of a possibly neutral tBuIBQ or monoanionic tBuISQ occurs,

which is unprecedented in literature. The APH2 based ligand coordinates with the imino

moiety trans to a pyrazole unit of the bdmpza ligand. A PPh3 and a chlorido ligand occupy the

two remaining coordination sites and the absence of counter ions indicates the formation of a

neutral complex.

NN N

N

Ru

OO

Ph3P PPh3Cl

Me

Me

Me

Me

KtBuAPH

NN N

N

Ru

OO

PPh3

Me

Me

Me

Me

NHO

tBu

tBu

NN N

N

Ru

OO

PPh3

Me

Me

Me

Me

OHN

tBu

tBu

a) b)

- Cl-

54


!! !

Figure 14. Molecular structure of [Ru(bdmpza)Cl(tBuISQ/tBuIBQ)(PPh3)] (15). Thermal ellipsoids are drawn at the 50% probability level. Most hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1495(17), Ru–N(21) = 2.098(2), Ru–O(1) = 2.1037(14), Ru–P(1) = 2.3318(6), Ru–Cl(1) = 2.3956(6), Ru–N(61) = 1.962(2), N(61)–C(61) = 1.310(3); N(11)–Ru–N(21) = 85.29(7), O(1)–Ru–N(21) = 85.72(7), O(1)–Ru–N(11) = 85.57(6), O(1)–Ru–P(1) = 85.76(4), P(1)–Ru–Cl(1) = 99.45(2), P(1)–Ru–N(61) = 87.43(5), O(1)–Ru–N(61) = 97.17(7), N(11)–Ru–P(1) = 170.81(5), N(21)–Ru–Cl(1) = 92.35(5), Cl(1)–Ru–N(61) = 84.39(6), Ru–N(61)–C(61) = 138.72(17).

For “non-innocent” APH2 ligands several oxidation states are known which in conclusion

allow the interaction with the metal center in form of redox chemistry.[249] Starting from the

deprotonated tBuAP2– the first one electron oxidation leads to the aforementioned anionic tBuISQ radical, which in the next oxidation step forms the tBuIBQ compound (Scheme 38).[249]

Scheme 38. Forms of the tert-butyl substituted aminophenol ligand seperated by one-electron redox steps.[249]

Cl1

N21N11

N12 N22

Ru

H61

C1

O62

N61

P1

C62

C61

O1

C66

C63

O2

C65

C64

ab

c

tBu

tBu

O

NH

tBu

tBu

O

NH

tBu

tBu

O-

NH-

- e-

+ e-- e-

+ e-

tBuAP2- tBuISQ tBuIBQ

55


!! !

Bond length [Å] 15 16 [Ru(acac)2(ISQ)] [RuCl(terpy)(ISQ)]+

Ru–N(61) 1.962(2) 1.962(5) 1.906(3) 1.942(8)

N(61)–C(61) 1.310(3) 1.293(8) 1.340(4) 1.312(12)

C(61)–C(62) 1.498(3) 1.485(9) 1.439(4) 1.433(13)

C(62)–O(62) 1.231(2) 1.221(9) 1.291(4) 1.270(11)

C(62)–C(63) 1.470(3) 1.441(11) 1.424(5) 1.416(13)

C(63)–C(64) 1.350(3) 1.280(11) 1.363(6) 1.322(13)

C(64)–C(65) 1.449(3) 1.425(11) 1.409(7) 1.446(15)

C(65)–C(66) 1.347(3) 1.351(10) 1.345(6) 1.377(14)

C(66)–C(61) 1.432(3) 1.406(9) 1.411(5) 1.433(13)

Table 4. Selected bond lengths of the ruthenium iminoquinone complexes 15, 16, [Ru(acac)2(ISQ)][250] and [RuCl(terpy)(ISQ)]ClO4.[251]

Bond length [Å] 15 16 [Ru(bdmpza)Cl(PPh3)2] [Ru(bdmpza)Cl2(PPh3)]

Ru–N(11) 2.1495(17) 2.133(5) 2.199(4) 2.184(3)

Ru–N(21) 2.098(2) 2.102(5) 2.173(4) 2.109(3)

Ru–O(1) 2.1037(14) 2.088(4) 2.133(3) 2.045(3)

Ru–Cl(1)/Cl(2) 2.3956(6) 2.3835(17) 2.4157(17) 2.346(2) / 2.3581(19)

Ru–P1/P2 2.3318(6) 2.3300(18) 2.3555(17) / 2.3688(18) 2.3715(18)

Table 5. Selected bond lengths of the ruthenium iminoquinone complexes 15 and 16 and closely related heteroscorpionate complexes [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)Cl2(PPh3)].[168]

In comparison with literature known [Ru3+–ISQ] complexes the bond lengths of the ISQ

ligands are in good agreement, although the alternation between located double and single

bonds is more pronounced for complex 15 (Table 4).[250-251] In addition the oxygen–carbon

bond is shortened due to the lack of interaction with the ruthenium center. To further

understand the oxidation state of the metal center, a look at the heteroscorpionate ligand is

useful. The closely related compounds [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)-

Cl2(PPh3)] show ruthenium(II) and ruthenium(III) centers, respectively, which in comparison

to complex 15, highlight the proposed ruthenium(III) structure (Table 5).[168] Especially the

bond Ru–N(11) which is positioned trans to a PPh3 ligand and thus not directly influenced by

ligand exchange shows similar values for 15 and the ruthenium(III) complex. This

56


!! !

emphasizes the assumption of a [Ru3+–ISQ] compound, although they do not allow a final

decision between an ISQ or IBQ ligand. Questionable remains the reaction pathway as the

metal and the ligand both undergo one-electron oxidation in absence of an oxidant. Possibly

contamination with oxygen might play a key role and lead to the low reported yields.

Hence it was decided to synthesize the analogous complex based on unsubstituted

2-aminophenol (APH2) similar to [Ru(acac)2(ISQ)][250] and [RuCl(terpy)(ISQ)]ClO4.[251]

Deprotonation of APH2 with potassium tert-butylate followed by addition of [Ru(bdmpza)Cl-

(PPh3)2] (14) at room temperature led to the formation of a dark solution (Scheme 39). After

two chromatography steps the complex was obtained as a dark blue solid in extremely low

yields.

Scheme 39. Synthesis of ISQ or IBQ complex [Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16).

In accordance with the expected structure ESI-MS experiments showed the presence of the

molecular ion (m/z 753.12 (5%) M+) and the closely related sodium adduct (m/z 742.15

(100%) [M – Cl + Na]+). The 13C NMR and 1H NMR spectrum show the pattern of an

asymmetric [Ru(bdmpza)] fragment with four independent signals for the methyl substituents.

The imino proton results in a signal at 14.77 ppm in the 1H NMR spectrum. The carbonyl

moiety of the ISQ/IBQ ligand gives rise to a signal at 171.3 ppm in the 13C NMR spectrum

indicating a similar binding motif as 15 with an uncoordinated keto moiety. The lower

solubility of 16 in nonpolar solvents in comparison to 15 allows crystallization from CH2Cl2

solution layered with n-hexane.

The result of a single crystal X-ray structure determination shows that the previously

observed κ1 binding motif also occurs for the sterically less demanding ISQ/IBQ ligand. The

arrangement around the ruthenium center is similar to 15 with the imino moiety of the

ISQ/IBQ ligand positioned trans to one pyrazole donor forcing the PPh3 ligand in trans

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

HO NH2

THF

16 (IBQ)

1. KOtBu2. 14

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

16 (ISQ)

or

57


!! !

position of the second pyrazole donor and the remaining chlorido ligand trans to the

carboxylate anchor (Figure 15).

Figure 15. Molecular structure of [Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16). Thermal ellipsoids are drawn at the 50% probability level. Most hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(21) = 2.102(5), Ru–N(11) = 2.133(5), Ru–O(1) = 2.088(4), Ru–P(1) = 2.3300(18), Ru–Cl(1) = 2.3835(17), Ru–N(61) = 1.962(5), N(61)–C(61) = 1.293(8); N(11)–Ru–N(21) = 84.9(2), O(1)–Ru–N(21) = 86.4(2), O(1)–Ru–N(11) = 85.96(18), O(1)–Ru–P(1) = 85.26(12), P(1)–Ru–Cl(1) = 99.56(6), P(1)–Ru–N(61) = 88.53(16), O(1)–Ru–N(61) = 97.9(2), N(11)–Ru–P(1) = 170.61(14), N(21)–Ru–Cl(1) = 91.18(18), Cl(1)–Ru–N(61) = 84.06(16), Ru–N(61)–C(61) = 137.9(5).

The bond lengths in the ISQ/IBQ ligand of complex 16 are listed in Table 4 and are in good

agreement with the closely related complex 15 and especially the two unsubstituted ISQ/IBQ

complexes by G. LAHIRI et al.[250-251] However, especially the double bond character of C(63)–

C(64) is more pronounced with a bond length of 1.280(11) Å for 16 compared to 1.350(3) Å

for [Ru(bdmpza)Cl(tBuISQ/tBuIBQ)(PPh3)] (15). The comparison with the ruthenium(II) and

ruthenium(III) complexes [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)Cl2(PPh3)] (Table 5)

indicates that the complex can best be described as [Ru3+–ISQ] due to the shortened

ruthenium nitrogen bonds between the bdmpza ligand and the ruthenium center indicating a

ruthenium(III) center (2.133(5) Å and 2.102(5) Å for 16 in comparison to 2.184(3) Å and

2.109(3) Å for [Ru(bdmpza)Cl2(PPh3)]), although a [Ru2+–IBQ] system can not be ruled out.

Cl

O62

H61

N11

C62N61

N21Ru

N12

C61

N22

C63

P1C64

C66C65O1

O2

a b

c

58


!! !

4.4 Carbon-rich Ruthenium Allenylidene Complexes

Parts of this chapter have been published:

Strinitz, F.; Waterloo, A.; Tucher, J.; Hübner, E.; Tykwinski, R. R.; Burzlaff, N., Eur. J.

Inorg. Chem. 2013, 5181-5186.

Starting from the previous results of the BURZLAFF group concerning the formation of

carbene, vinylidene and allenylidene complexes and their reaction behavior it was decided to

investigate the possible substitution patterns of the propargyl alcohols employed.[61, 189]

As mentioned in chapter 2.5 only two structural isomers can be observed for

[Ru(bdmpza)Cl(PPh3)2] (14) based cumulenylidene complexes. For easy nomenclature the

isomer with the cumulenylidene moiety trans to the pyrazole unit is indicated with “A” and

the isomer with the cumulenylidene moiety trans to the carboxylate anchor with “B”. In a

similar way the bdmpza ligand is numbered for NMR and single crystal X-ray structure

determination purposes. The numbering is dependent on the position of the PPh3 ligand and

follows the depicted scheme (Scheme 40).

Scheme 40. Numbering scheme used for cumulenylidene complexes.

NN N

N

Me5´

Me3´

Me5

Me3Ru

OO

ClPh3P R

H4´ H4

59


!! !

4.4.1 Sterically Demanding Diphenyl Allenylidene Complexes

Typically the straight forward synthesis of ruthenium allenylidene complexes following

Selegue´s route starts from substituted propargyl alcohols leading to the dissociation of water

from the intermediary hydroxyvinylidene complexes. Depending on the used metal fragment,

the dissociation of water requires the addition of catalytical amounts of acid, which allows the

isolation of the labile vinylidene species. Nevertheless, for the facially coordinating bdmpza

ligand, it has been observed that the intermediary vinylidene complexes can be detected via 1H NMR due to the characteristic vinylidene proton but the complex cannot be isolated and

reacts directly to the allenylidene complex.[61] P. DIXNEUF et al. have previously shown that a

reversible addition of sodium methoxide to the cationic allenylidene complex trans-[(dppm)2-

ClRu(═C═C═CPh2]PF6 yields the corresponding neutral alkynyl complex trans-[(dppm)2Cl-

Ru(–C≡C–CPh2(OMe)].[252] In an attempt to synthesize an isolable vinylidene complex based

on [Ru(bdmpza)Cl(PPh3)2] (14) it was decided to start from the 3,5-di-tert-butyl substituted

methoxy ether of the conventional used diphenyl propargyl alcohol. This compound has

recently been shown to be an effective building block for forming stabilized organic

cumulenes with up to ten carbon atoms.[253] Furthermore, the presence of the ether group

might enhance the formation of the vinylidene complex due to the reduced leaving potential

of the methanol unit in comparison to the free hydroxyl group.

The synthesis of the intended neutral vinylidene complex started from [Ru(bdmpza)Cl(PPh3)2]

(14) and excess propargyl alcohol 1,1-bis-(1,3-di-tert-butylphenyl)-1-methoxy-2-propyne in

THF (Scheme 41). Initially, no apparent color change was observed. After 3 d, however, a

strong purple color was visible and the formation of the allenylidene complex

[Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A, 19B) was completed by heating for 4 h

under reflux. Due to the facial coordinating motif of the bdmpza ligand, the formation of two

structural isomers was observed, as has been reported previously.[61] The relatively high

stability (no degradation over days was observed) allowed the separation via column

chromatography under aerobic conditions affording a purple (19A) and a red isomer (19B). 13C NMR spectra revealed for 19B characteristic signals for a ruthenium allenylidene complex

at 314.7 ppm (d, 2JCP = 18.3 Hz, Cα), 234.6 ppm (Cβ) and 152.4 ppm (Cγ) for the allenylidene

unit, as well as a singlet in the 31P NMR spectrum at 34.5 ppm.

60


!! !

Scheme 41. Synthesis of ruthenium vinylidene intermediate [Ru(bdmpza)Cl(═C═CH(COMe(PhtBu2)(PPh3)] (17), carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A, 18B) and allenylidene complex [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A, 19B).

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

CtBu

tBu tBu

tBu

tBu

tBu

tButBu

19A 19B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

OMe

H

tBu

tBu tBu

tBu+

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P C H

C

tBu

tBu

tBu

tBuOMe

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P C

+

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P C

17

18A

18B

14

O

O

61


!! !

For compound 19A the 13C NMR spectrum revealed strong contamination with the carbonyl

complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A, carbonyl trans to pyrazole), which can be formed

by oxygen induced bond cleavage of the vinylidene intermediate as has been shown

previously for [Ru(bdmpza)Cl(═C═CHPh)(PPh3)].[61] Unfortunately, all attempts to avoid

formation of 18A during synthesis or separation of 19A via column chromatography provided

only impure product. Nevertheless, the assignment of the two structural isomers A and B to

the respective symmetry and positions was accomplished based on comparisons to previously

reported two-dimensional NMR experiments (ROESY) and APT 13C NMR measurements.[61]

Namely, type B complexes show cross-peaks between the methyl substituents in the 3- and 3´

positions with the aryl protons of the allenylidene moiety in the ROESY spectrum, which

indicate an arrangement trans to the carboxylate anchor.[61]

Cyclic voltammetric analyses were performed on the precursor [Ru(bdmpza)Cl(PPh3)2] (1)

and on the resulting allenylidene complex 19B. The exhibited electrochemical properties are

summarized in Chapter 8.2. The reversibility of the redox processes shows strong dependence

on the solvent used, as voltammograms recorded in acetonitrile lead to irreversible oxidations

and reductions indicating side reactions of the allenylidene complexes with acetonitrile. The

voltammograms recorded in dichloromethane with nBu4NPF6 (0.1 M) as electrolyte and

referenced to the ferrocene/ferrocenium couple as internal standard at a scan rate of 100 mV/s

feature exclusively reversible and quasi-reversible processes. For the used precursor

[Ru(bdmpza)Cl(PPh3)2] (14) one reversible oxidation at 394 mV can be observed, which is

attributed to the Ru(II)/Ru(III) couple. For the ferrocene/ferrocenium couple literature reports

a peak separation of 78 mV (83 mV in our setup) in dichloromethane,[254] which is a good

indication that the peak separation of 73 mV and the peak current ratio ipa/ipc = 0.80 for 14

confirm a reversible one-electron oxidation. For the first ruthenium allenylidene complex

[Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19B) two quasi-reversible redox processes can

be observed. The oxidation of the ruthenium center happens at a lower potential of 265 mV

compared to 14, indicating a possible electron releasing effect of the used allenylidene ligand

in comparison to the PPh3 ligand. The reduced peak current ratio indicates however, that the

reversibility is lowered in comparison to 14. A second redox process at –1631 mV can be

attributed to the quasi-reversible reduction (ipa/ipc = 0.67) of the allenylidene moiety as

reported previously for the systems [Cl(dppe)2Ru(═C═C═CPh2)]PF6 (–1.03 V) and [Cl(16-

TMC)Ru(═C═C═CPh2)]PF6 (–1.27 V).[124, 255] In comparison it is obvious that the two redox

62


!! !

couples of the neutral bdmpza allenylidene complex 19B are more cathodic in comparison to

the aforementioned cationic allenylidene complexes (Δ = 0.60 V/0.36 V).

The intense color of the allenylidene complexes can best be characterized via UV/Vis

absorption spectroscopy. Hence the comparison with the previously reported bdmpza based

allenylidene complexes [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] and [Ru(bdmpza)Cl-

(═C═C═C(tol)2)(PPh3)] is a good starting point. For type B isomers absorption maxima of

495 and 507 nm have been reported for solutions in CH2Cl2.[61] The closely related complex

[Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19B) shows a maximum at 506 nm with a molar

extinction coefficient of approximately 13000 L mol–1cm–1 (Figure 16). This transition was

assigned to a metal-to-ligand charge-transfer (MLCT) for the diphenyl and ditolyl substituted

allenylidene complexes in literature.[61] However, newer calculations performed for complexes

within this work indicate, that this transition corresponds to a metal-perturbed π-π*

transition.[256] A further transition that can be observed in the NIR region at 1024 nm with an

extremely low extinction coefficient indicating a forbidden transition, which might belong to

the MLCT in which the HOMO–1, HOMO and LUMO have been involved for the

pentacenequinone based allenylidene complexes (Figure 17).[256] Due to lack of a single

crystal X-ray structure determination no TD-DFT calculations were performed on this

complex and no definite answer can be given on this topic.

63


!! !

Figure 16. Absorption spectrum of 19B in CH2Cl2.

Figure 17. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 19B.

400 600 800 1000 1200 1400 1600

0

5000

10000

15000

20000ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

800 1000 1200 1400 16000

50

100

150

200

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

64


!! !

Figure 18. Molecular structure of [Ru(bdmpza)Cl(CO)(PPh3)] (18B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.156(3), Ru–N(21) = 2.082(3), Ru–O(1) = 2.119(2), Ru–P(1) = 2.3360(10), Ru–Cl(1) = 2.3880(11), Ru–C(3) = 1.923(5), C(3)–O(3) = 1.009(5); N(11)–Ru–N(21) = 82.68(11), O(1)–Ru–N(11) = 85.60(10), O(1)–Ru–N(21) = 87.15(10), O(1)–Ru–P(1) = 86.27(7), P(1)–Ru–Cl(1) = 90.05(4), P(1)–Ru–C(3) = 95.27(11), O(1)–Ru–C(3) = 177.34(13), N(21)–Ru–P(1) = 97.08(8), N(11)–Ru–Cl(1) = 89.87(8), Cl(1)–Ru–C(3) = 87.26(11), Ru–C(3)–O(3) = 176.0(4).

Attempts to obtain crystals of 19B suitable for X-ray diffraction by layering a solution in

dichloromethane with n-hexane leads, within several weeks, to bond cleavage of the

allenylidene unit with conservation of the relative geometry, providing complex 18B as

illustrated in Figure 18. In comparison to the previously reported carbonyl complex 18A, the

carbonyl ligand in 18B is in trans position to the carboxylate. Thus, the chlorido and

triphenylphosphine ligands are in trans position to the pyrazole units. This observation is

unexpected since the direct carbonylation of [Ru(bdmpza)Cl(PPh3)2] (14) and decomposition

of the resulting vinylidene complexes leads exclusively to the carbonyl complex 18A with the

carbonyl trans to a pyrazole.[61] The ruthenium(II) center is facially coordinated by the

bdmpza ligand resulting in a slightly distorted octahedral geometry caused by the rather rigid

and strained coordination geometry of the heteroscorpionate ligand. The Ru–C(3)

(1.923(5) Å) bond is slightly elongated and C(3)–O(3) (1.009(5) Å) contracted in comparison

to the other structural isomer 18A (Ru–C(3) = 1.831(5) Å, C(3)–O(3) = 1.151(6) Å) as a

O2

O1

C2

Cl1P1

C1

Ru1

N12

N11

N22

N21

C3

O3

ab

c

65


!! !

result from the trans-orientation of the carboxylate group. This is in contrast to the pyrazolyl

donor, which is a σ and π donor as well as a π acceptor and shows no trans influence, as

previously discussed and supported by DFT calculations for the dissociation energies of

N,N,O ligands.[173] This observation suggests that the steric demand of the four tert-butyl

groups reduces the stability in comparison to the analogous unsubstituted diphenyl

allenylidene complex, i.e., substituted with only two phenyl rings.

66


!! !

4.4.2 Fluorene Based Allenylidene Complexes

Closely related to the diphenyl allenylidene complexes are systems bearing a fluorene group

on Cγ. Fluorene based allenylidene complexes have previously shown to inhibit the

rearrangement of the allenylidene moiety into the corresponding indenylidene complex.[167]

NMR spectroscopic experiments have shown that [(η6-p-cymene)RuCl(═C═C═(FN))(PCy3)]-

OTf (FN = fluorenyl) reacts upon addition of HOTf to the alkenylcarbyne, but no further

transformation could be observed.[167] Furthermore polyfluorenes are organic electro-

luminescent materials that have been applied to devices in photonics and optoelectronics.[257-

259] Following the route described above, addition of excess amounts of 9-ethynylfluoren-9-ol

to [Ru(bdmpza)Cl(PPh3)2] (14) led to the formation of a deep purple solution (Scheme 42).

The increased stability of the obtained structural isomers allowed separation via column

chromatography under aerobic conditions yielding a purple (20A, allenylidene trans to

pyrazole) and a red isomer (20B, allenylidene trans to carboxylate).

Scheme 42. Synthesis of bdmpza based ruthenium allenylidene complexes [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (FN = fluorenyl) (20A, 20B).

For 20A the characteristic signals for the allenylidene chain are observed in the 13C NMR

spectrum at 300.6 (d, 2JC,P = 27.6 Hz, Cα), 236.4 (d, 3JC,P = 4.6 Hz, Cβ) and 141.0 ppm (Cγ)

with doublets for Cα and Cβ caused by coupling with the phosphorus atom of the

triphenylphosphine ligand. Furthermore, the IR spectrum shows an intense band at 1910 cm–1

in the IR spectrum corresponding to the cumulenylidene ligand. The 31P NMR spectrum

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

20A 20B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

+

OH

H+ THF

14

67


!! !

consists of one singlet at 34.6 ppm and ESI-MS experiments showed the presence of the

protonated monocationic species (m/z 825.16 (100%) MH+). Similar spectroscopic values are

obtained for the second isomer 20B with signals at 314.4 (d, 2JC,P = 19.3 Hz, Cα), 256.2 (Cβ)

and 141.6 ppm (Cγ) in the 13C NMR spectrum (P–C coupling observable for Cα), while the 31P NMR spectrum shows one singlet at 30.9 ppm, which is shifted upfield in comparison to

20A. The IR spectrum shows the cumulenic stretch at 1903 cm–1 a slightly lower value than

that for 20A and the ESI-MS experiments reveal the main observable signal that is consistent

with the protonated monocationic species (m/z 825.16 (100%) MH+). The assignment of the

geometries was in accordance to the previous synthesized bdmpza based allenylidene

complexes and could be verified by single crystal X-ray structure determinations of both

isomers. Crystals were obtained from solutions in CH2Cl2 layered with n-hexane. 20A and

20B represent the first single-crystal X-ray structure determinations of fluorene based

allenylidene complexes.[107, 166-167, 252, 260-261] Complex 20A crystallizes as an racemic mixture

(space group Pbca) as [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] × H2O with one water molecule

bound via a hydrogen bond to the carbonyl moiety of the carboxylate unit (Figure 19). The

molecular structure exhibits a slightly distorted octahedral geometry at the Ru(II) center with

the allenylidene positioned trans to a pyrazole donor, the triphenylphosphine trans to the

second pyrazole donor and the chlorido ligand trans to the carboxylate anchor. In comparison

to the diphenyl allenylidene complex [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)], the bdmpza

ligand of 20A shows only slight deviations.[61] The Ru–C(61) bond is with 1.865(3) Å similar

to the analogous [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] (1.886(5) Å)[61] and the octahedral Tp

ruthenium allenylidene complex [Ru(κ3-HB(pz)3)(═C═C═CPh2)(PPh3)2]PF6 (1.889(3) Å)[121]

but considerably longer than in pentacoordinated 16 VE ruthenium allenylidene complexes

like [RuCl2(═C═C═CPh2)(PCy3)2] (1.794(11) Å).[95] The allenylidene chain deviates slightly

from the linear geometry (∠Ru–C(61)–C(62) = 175.1(3)°, ∠C(61)–C(62)–C(63) = 172.7(3)°)

with the fluorenyl moiety remaining in plane with the C═C═C moiety.

68


!! !

Figure 19. Molecular structure of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and one water molecule have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.172(2), Ru–N(21) = 2.231(2), Ru–O(1) = 2.094(2), Ru–P(1) = 2.3121(9), Ru–Cl(1) = 2.3552(9), C(63)–C(67) = 1.472(4), C(63)–C(64) = 1.470(4), C(64)–C(65) = 1.406(4), C(65)–C(66) = 1.466(5), C(66)–C(67) = 1.407(4), Ru–C(61) = 1.865(3), C(61)–C(62) = 1.247(4), C(62)–C(63) = 1.352(4); N(11)–Ru–N(21) = 83.05(9), O(1)–Ru–N(11) = 86.32(9), O(1)–Ru–N(21) = 82.43(9), O(1)–Ru–P(1) = 92.72(6), P(1)–Ru–Cl(1) = 92.09(3), P(1)–Ru–C(61) = 85.66(9), O(1)–Ru–C(61) = 92.39(11), N(21)–Ru–P(1) = 99.15(7), N(11)–Ru–Cl(1) = 89.19(7), Cl(1)–Ru–C(61) = 96.26(9), Ru–C(61)–C(62) = 175.1(3), C(61)–C(62)–C(63) = 172.7(3).

As has been described for the structural related butatriene 4-(9H-fluoren-9-ylidene)-2-

methylbuta-2,3-dienal (COH(CH3)C═C═C═(FN)),[262] the bond lengths of the five-membered

ring of the fluorenyl unit of 20A show less bond length alternation than the parent

fluorenone,[263] which indicates a strong delocalization of the electron density from the

allenylidene moiety to the fluorenyl unit. Also noticeable are strong solid-state π-π stacking

interactions between two neighboring fluorenyl units (Figure 20), with an interplanar distance

of 3.45 Å as calculated from the least-squares plane generated from the carbon atoms of one

fluorenyl moiety to the plane of its neighbor.

Cl1

N21N11

N22N12

Ru1

C1

P1C61C62

O1

C2

C64C63

O2

C65 C67C66

abc

69


!! !

Bond length [Å] 20A 20B Fluorene COH(CH3)C═C═C═(FN)

C63–C64 1.470(4) 1.469(7) 1.486 1.469

C64–C65 1.406(4) 1.408(7) 1.390 1.390

C65–C66 1.466(5) 1.463(8) 1.475 1.471

C66–C67 1.407(4) 1.407(7) 1.390 1.404

C67–C63 1.472(4) 1.466(7) 1.486 1.465

Table 6. Selected bond lengths of the five membered rings of the ruthenium allenylidene complexes 20A and 20B, fluorene and the structural related butatrien COH(CH3)C═C═C═(FN).[262-263]

Figure 20. π–π stacking interactions between two molecules of 20A a) top view and b) side view.

a) b)

70


!! !

Figure 21. Molecular structure of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules CH2Cl2 have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.146(4), Ru–N(21) = 2.081(4), Ru–O(1) = 2.144(3), Ru–P(1) = 2.3552(12), Ru–Cl(1) = 2.4077(11), C(63)–C(67) = 1.466(7), C(63)–C(64) = 1.469(7), C(64)–C(65) = 1.408(7), C(65)–C(66) = 1.463(8), C(66)–C(67) = 1.407(7), Ru–C(61) = 1.855(5), C(61)–C(62) = 1.247(7), C(62)–C(63) = 1.363(7); N(11)–Ru–N(21) = 83.54(15), O(1)–Ru–N(11) = 85.55(13), O(1)–Ru–N(21) = 86.49(13), O(1)–Ru–P(1) = 85.75(9), P(1)–Ru–Cl(1) = 88.10(4), P(1)–Ru–C(61) = 95.27(15), O(1)–Ru–C(61) = 178.55(16), N(21)–Ru–P(1) = 98.00(11), N(11)–Ru–Cl(1) = 90.02(11), Cl(1)–Ru–C(61) = 89.85(14), Ru–C(61)–C(62) = 175.7(4), C(61)–C(62)–C(63) = 177.2(5).

The second structural isomer 20B shows solid-state characteristics similar to that of 20A,

including a distorted octahedral geometry (Figure 21). Compound 20B crystallizes in space

group P–1 as a racemic mixture. The chlorido and PPh3 ligand are now positioned trans to

pyrazole donors, placing the allenylidene unit trans to the carboxylate anchor. Therefore, the

respective bond lengths differ slightly in comparison to isomer 20A. For example, there is

shortening of the Ru–C(61) bond to 1.855(5) Å and a similar contraction of the Ru–N(11)

bond, which can be explained by the reduced trans influence in this structural isomer because

of the π accepting pyrazole and allenylidene ligand are no longer positioned trans to each

other. Additionally, the allenylidene chain is slightly less distorted from linearity than in 20A

(∠Ru–C(61)–C(62) = 175.7(4)°, ∠C(61)–C(62)–C(63) = 177.2(5)°). This can be explained by

the different packing motif in the solid state. The change in the relative positions around the

ruthenium center also leads to reduced distances between the fluorenyl moiety and one phenyl

ring of the triphenylphosphine ligand of the complex. This close proximity of the phenyl rings

N21

C65

C64

N22

P1C63

C66

C62C61

C67

C1

Ru1

O1

C2

O2 N12

N11

Cl1

ab

c

71


!! !

appears to hinder the π-π stacking interaction between two neighboring fluorenyl units in the

solid state, which also seems to result in the smaller angles in ∠Ru–Cα–Cβ and ∠Cα–Cβ–Cγ of

20A.

The fluorene based allenylidene complexes [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A, 20B)

show a reversible oxidation at 389 mV/371 mV indicating a positive shift in peak potential in

comparison to 19B (Chapter 8.2). Interesting is the appearance of two redox processes at

negative voltages. While the process at –1273 mV (20A, 20B) is again attributed to the

reduction of the allenylidene moiety and appears more anodic in comparison to 19B, a second

quasi-reversible/reversible process appears at –1932 mV (20A) and –1937 mV (20B), that we

assign to the reduction of the fluorenyl moiety. Although the position of the allenylidene

moiety trans to the pyrazole or carboxylate moiety strongly influences the physical and

chemical properties of the complex no obvious differences in electrochemical properties

could be observed for these two structural isomers.

The UV/Vis absorption spectra of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A, 20B) recorded

in CH2Cl2 show several intense absorptions (Figure 22). The strong absorptions below 400 nm

can be attributed to ligand centered π–π* transitions involving the bdmpza and PPh3 ligand.

As mentioned previously the strong absorption at 546 nm (20A) or 517 nm (20B) with molar

extinction coefficients around 15000 L mol–1 cm–1 correspond to a metal-perturbed π-π*

transition of the allenylidene moiety. Again weak transitions can be observed in the NIR

region for both complexes with a signal at 1053 nm with a shoulder at 919 nm for 20B

(Figure 23). For 20A, two distinct signals at 1201 nm and 944 nm can be observed. These

transitions can be assigned to HOMO → LUMO and HOMO–2 → LUMO excitations, which

are MLCT transitions (Table 7).

Observed values Calculated values

Compound Wavelength [nm]

Absorption coefficient [M–1 cm–1]

Wavelength [nm]

Transition dipole moment [debye]

Transition

20A 1053

919

226

175

906

813

0.12

0.54

HOMO ! LUMO

HOMO–2 ! LUMO

Table 7. Calculated and measured transitions for 20A in the NIR region.

72


!! !

Figure 22. Absorption spectrum of 20A (black) and 20B (grey) in CH2Cl2.

Figure 23. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 20A (black) and 20B (grey); signal caused by CH2Cl2 is indicated by *.

400 600 800 1000 1200 1400 1600

0

5000

10000

15000

20000

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

800 1000 1200 1400 16000

100

200

ε'[L'm

ol-1'cm

-1]

W ave leng th'[nm]

*

73


!! !

To further understand the absorption spectra TD-DFT calculations (time-dependent DFT)

have been performed by E. HÜBNER for complex 20A that explain the absorptions at the edge

of the NIR region. Especially, the HOMO → LUMO and HOMO–2 → LUMO transitions

with low transition dipole moments of 0.12 and 0.54 debye seem to correspond to forbidden

MLCT transitions. The calculated geometries emphasize that the LUMO is delocalized over

the ruthenium center as well as the entire allenylidene moiety and the fluorenyl unit, whereas

the HOMO and HOMO–2 are mainly located on the ruthenium center and Cα and Cβ (Figure

24). Furthermore, the calculated absorptions are in good agreement with the measured values

(Table 7).

LUMO HOMO

HOMO–1 HOMO–2

Figure 24. Orbital diagrams of the LUMO (–2.9 eV), HOMO (–5.2 eV), HOMO–1 (–5.3 eV) and HOMO–2 (–5.4 eV) of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A).

74


!! !

4.4.3 Anthraquinone Based Allenylidene Complexes

Although heteroatom substituted allenylidene complexes based on 4,5-diazafluorene[126-127]

and cyclopentadithiophene[128] have been reported, little is known about allenylidene

complexes with larger polyaromatic substituents. To date, only few complexes are discussed

in literature, such as, for example, trans, trans-[(dppe)2RuCl(C═C═C(bianth)C═C═C)ClRu-

(dppe)2](OTf)2 that is based on the extended conjugated system [9,9′]bianthracenylidene-

10,10′-dione are discussed in literature.[113] Notably in this system, the close proximity of the

protons of two anthrone units of the bianthrone moiety results significant strain and a non-

planar organic spacer. For further studies on the π-π stacking interactions between

polyaromatic allenylidene units and electron transfer properties between the ruthenium(II)

center and the organic substituents it was decided to look into anthraquinone based

allenylidene complexes.

The use of anthraquinone derivatives is manifold ranging from the anthraquinone oxidation

process for hydrogen peroxide production to dye precursors.[264-265] A recent highlight was the

construction of a metal-free organic-inorganic aqueous flow battery by B. HUSKINSON and M.

MARSHAK et al.[266] 9,10-Anthraquinone-2,7-disulphonic acid (AQDS) undergoes rapid and

reversible two-electron two-proton reduction in sulfuric acid. Combination of the couple

quinone/hydroquinone with the couple Br2/Br– with glassy carbon electrodes allows the

formation of promising flow batteries for electrical energy storage at greatly reduced cost.[266]

O. WENGER et al. recently published a bpy (bpy = 2,2´-bipyridine) based ruthenium complex

bearing an anthraquinone moiety in its periphery.[267] The thermodynamics and kinetics of the

intramolecular electron transfer between the [Ru(bpy)3]2+ core and the anthraquinone unit

linked via one up to three xylene linkers in the complex [Ru(bpy)2(bpy–xyn–AQ)]2+ (xy = p-

xylene, n = 0-3) was investigated. It was shown that electron transfer between the ruthenium

core and the anthraquinone unit can be triggered by photoexcitation leading to the charge

separated state. The solvent influence on the electron transfer indicates a finite proton density

transfer rather than a full PCET (proton coupled electron transfer).[267] This redox behavior

shows similarities to the electron transfer cascade in photosynthetic reaction centers of

bacteria.[268]

For the formation of the first anthraquinone based allenylidene complex the anthraquinone

(AQ) based 10-ethynyl-10-hydroxyanthracen-9-one (24) is promising. The required precursor

75


!! !

24 is known to the literature, however, an appealing high yield synthesis is missing.[269-271] The

classic approach to 24 begins with the formation of a lithium acetylide, via reaction of

gaseous acetylene with lithium in liquid ammonia followed, by the addition of anthraquinone

leading to the monosubstituted propargyl alcohol 24. This synthesis can be mimicked by the

addition of the commercially available suspension of sodium acetylide in xylenes to

anthraquinone. These procedures, however, offer low yields of 24, and they are also

unattractive because of difficult purification due to the low solubility of 24. In analogy to the

pentacenequinone based synthesis of the monopropargyl alcohol the addition of trimethylsilyl

(TMS) acetylene followed by the desilylation allows the high yield synthesis of ketone 24

(Scheme 43).[256, 272] In the first step of the reaction, a substoichiometric amount of n-BuLi is

added to trimethylsilylacetylene in dry THF. In the following, step the lithium acetylide was

added dropwise to an excess amount of anthraquinone (21) in THF to avoid the formation of

the bis-adduct 9,10-bis((trimethylsilyl)ethynyl)-9,10-dihydroanthracene-9,10-diol (22). After

aqueous workup, the unreacted anthraquinone can be removed via column chromatography on

silica with CH2Cl2 as eluent yielding the ketone 23. The desymmetrization of anthraquinone

via acetylide addition leads to the appearance of four aromatic signals in the 1H NMR

spectrum of 23 at 8.17, 8.08, 7.71 and 7.51 ppm, with second-order coupling patterns

characteristic of an ortho-substituted arene. Furthermore, singlets for the alcohol and TMS

groups are observed at 3.16 and 0.16 ppm, respectively. The 13C NMR spectrum shows the

moiety at 183.1 ppm and the three characteristic signals for a propargyl alcohol groups at

106.7, 91.5 and 66.4 ppm. The removal of the TMS group from 23 to give 24 leads to no

change in the coupling pattern of the aryl protons in the 1H NMR spectrum, while the

appearance of an additional signal corresponding to the alkyne proton at 2.71 ppm can be

observed concurrent with the loss of the singlet of the TMS group. The solubility of 24 is

significantly decreased, however, and a 13C NMR spectrum can only be recorded in DMSO-d6

and shows the terminal alkyne carbon appearing at 76.1 ppm and the keto moiety at

182.4 ppm.

76


!! !

Scheme 43. Synthesis of the TMS protected ketone 23, the deprotected propargyl alcohol 24 and the undesired bisadduct 22.

Similar to the method described for the fluorenyl based systems, the preparation of the

corresponding ruthenium allenylidene complex (25A, 25B) was carried out by using an

excess amount of propargyl alcohol 24 (Scheme 44). The formation of the intense purple

color and the appearance of a peak at 1880 cm–1 in the IR spectrum, characteristic for

allenylidene complexes, confirmed the successful conversion of the anthraquinone based.

Separation of the two structural isomers was achieved following the procedure described

above.

O

O O

O

OH

HO

OH

OH

TMS

TMS

H

TMS

1. n-BuLi / TMS-acetylene (< 1.0 eq.)2. H2O

THF

KOHMeOH, H2O

21 23

24

22

77


!! !

Scheme 44. Synthesis of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (AO = anthrone) (25A, 25B).

For the first isomer 25A the allenylidene carbon atoms Cα (292.1 ppm, d, 2JC,P = 26.8 Hz), Cβ

(251.0 ppm, d, 3JC,P = 5.0 Hz) and Cγ (141.4 ppm, d, 4JC,P = 3.0 Hz) appear as doublets in the 13C NMR spectrum including long-range 4JC,P coupling between the triphenylphosphine ligand

and Cγ. A singlet is found in the 31P NMR spectrum at 30.1 ppm resulting from the

triphenylphosphine ligand, which also supports the suggested structure. ESI-MS experiments

again show the major observable signal resulting from the protonated monocationic species

(m/z 863.14 (100%) MH+). For the structural isomer 25B with the allenylidene unit positioned

trans to the carboxylate, the 13C NMR spectrum shows a downfield shift for Cα (309.6 ppm, d, 2JC,P = 19.8 Hz) and Cβ (277.0 ppm) relative to 25A. The third allenylidene carbon Cγ appears

almost unchanged at 140.5 ppm, and a signal at 29.1 ppm in the 31P NMR spectrum confirms

the triphenylphosphine ligand. The change in coordination geometry gives rise to an increase

of 16 cm–1 (1896 cm–1) in the cumulene vibration compared to 25A. For the other ruthenium

allenylidene complexes reported within this work, no clear trend for the allenylidene

absorptions in the IR spectrum could be observed regarding A and B type isomers. However,

in this case the difference might be explainable by a reduced linearity of the allenylidene

moiety as described in the following part. ESI-MS experiments showed that the change in

coordination in this complex strongly influence the stability of 25B although the

monocationic complex can be observed the intensity is low (m/z 863.14 (4%) MH+). The

major signals result from the dissociation of the chlorido ligand followed by decarboxylation

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

25A25B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

++ THF

OH

O

H

O

O

14

78


!! !

of the bdmpza ligand (m/z 783.18 (88%) [M – Cl – CO2]+) and can be followed by addition of

one solvent molecule (m/z 824.21 (100%) [M – Cl – CO2 + MeCN]+).

Figure 25. Molecular structure of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and solvent molecules have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.138(3), Ru–N(21) = 2.193(3), Ru–O(1) = 2.077(2), Ru–P(1) = 2.3325(8), Ru–Cl(1) = 2.3761(8), Ru–C(31) = 1.868(3), C(31)–C(32) = 1.243(5), C(32)–C(33) = 1.362(5); N(11)–Ru–N(21) = 83.07(10), O(1)–Ru–N(11) = 87.20(9), O(1)–Ru–N(21) = 84.01(10), O(1)–Ru–P(1) = 83.87(6), P(1)–Ru–Cl(1) = 100.47(3), P(1)–Ru–C(31) = 86.76(10), O(1)–Ru–C(31) = 97.22(12), N(11)–Ru–P(1) = 170.16(8), N(21)–Ru–Cl(1) = 85.76(8), Cl(1)–Ru–C(31) = 92.65(10), Ru–C(31)–C(32) = 177.0(3), C(31)–C(32)–C(33) = 175.2(4).

The assignment of the relative geometry could be verified for both complexes from X-ray

crystal structure analysis that were performed on crystals obtained from solutions in CH2Cl2

layered with n-hexane (Figure 25). Complex 25A (allenylidene trans to pyrazole) crystallizes

as racemic mixture [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] × CH2Cl2 in space group P–1 with

one solvent molecule disordered and parted over three positions. The distorted octahedral

geometry is affected by the strained bdmpza ligand that shows values comparable to the

fluorenyl allenylidene complex 20A discussed above. The change from the central 5-

membered ring in the fluorenyl moiety to the 6-membered ring in the anthraquinone based

Cl1

N21 N11

N22

Ru1

N12

C31P1C32

C1

C33

O1

C2

C36

O3

O2

ab

c

79


!! !

system in complex 25A leads to increased steric repulsion between the anthrone moiety and

the triphenylphosphine ligand. This results in a smaller bond angle ∠O(1)–Ru–P(1) (83.9°)

compared to 92.7° in 20A and considerable greater angle ∠P(1)–Ru–Cl(1) (100.5°) in

comparison to 92.1° (20A). The allenylidene unit itself shows rather unremarkable values of

d(Ru–C(31)) = 1.868(3) Å, ∠Ru–C(31)–C(32) = 177.0(3)°, and ∠C(31)–C(32)–

C(33) = 175.2(4)°.

Figure 26. π–π stacking interactions between two molecules of 25A a) top view and b) side view.

Similar to complex 20A, π-π stacking interactions between two anthrone units are observed

with approximately two thirds of the anthrone area affected resulting in a mean interplanar

distance of 3.37 Å (Figure 26), as calculated between the least-squares plane generated from

the carbon atoms of one anthrone moiety to the plane of its neighbor. For comparison, it is

noted that anthraquinone shows a similar slipped stack arrangement in the solid state, with a

mean interplanar distance of 3.48 Å.[273]

For the second structural isomer 25B (allenylidene trans to carboxylate) crystals of

[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (Figure 27) in space group P–1 were obtained. Similar

to the structures discussed above the positioning of the π donor and acceptor pyrazole trans to

the chlorido ligand and the allenylidene trans to the carboxylate anchor leads to a loss of the

trans-influence for both ligands. This change in the coordination sphere results in a shortened

Ru–N(21) bond with 2.0740(18) Å and a similar Ru–C(61) bond with 1.862(2) Å. The bond

angles of the allenylidene chain are with ∠Ru–C(61)–C(62) = 174.4(2)° and ∠C(31)–C(32)–

C(33) = 169.8(3)° slightly reduced compared to 25A in contrast to the fluorenyl system

(20A/20B).

a) b)

80


!! !

Figure 27. Molecular structure of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1355(19), Ru–N(21) = 2.0740(18), Ru–O(1) = 2.1367(15), Ru–P(1) = 2.3546(6), Ru–Cl(1) = 2.4100(6), Ru–C(61) = 1.862(2), C(61)–C(62) = 1.232(3), C(62)–C(63) = 1.354(3); N(11)–Ru–N(21) = 83.87(7), O(1)–Ru–N(11) = 85.11(7), O(1)–Ru–N(21) = 86.94(7), O(1)–Ru–P(1) = 85.94(5), P(1)–Ru–Cl(1) = 87.68(2), P(1)–Ru–C(61) = 95.87(7), O(1)–Ru–C(61) = 178.13(8), N(11)–Ru–P(1) = 170.75(5), N(21)–Ru–Cl(1) = 174.12(5), Cl(1)–Ru–C(61) = 87.84(7), Ru–C(61)–C(62) = 174.4(2), C(61)–C(62)–C(63) = 169.8(3).

The explanation for this bent allenylidene unit can be deduced from the solid state packing

motif of two neighboring complexes. The space filling model clarifies that only a small

overlap of two anthrone units is observed due to the presence of one phenyl ring (dark grey)

of the triphenylphosphine ligand on top of the anthrone moiety, which thus blocks the π-π

interactions as observed for 25A and forcing the neighboring allenylidene chain into a slightly

bent structure in the solid state (Figure 28).

Cl1

N11

N12

O3

O2

O1

C67

C2

Ru1

C63

C61C62

C1

P1

N22

N21

a

b

c

81


!! !

Figure 28. Space-filling model of complex 25B; phenyl ring highlighted in dark grey, anthrone moiety highlighted in light grey.

For the anthraquinone based allenylidene complexes [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)]

(25A, 25B) the influence of the anthrone unit is clearly visible and the difference between

both structural isomers is obvious (Chapter 8.2). Three reversible redox processes can be

observed and can be attributed to the Ru(II)/Ru(III) couple (466 mV/641 mV), the

allenylidene moiety (–1013 mV/–870 mV) and the anthrone moiety (–1479 mV/–1315 mV).

Apparently, the facile reduction of the anthrone unit leads to a positive shift for all three redox

processes and this effect is especially prominent in the B-type isomer with the allenylidene

moiety trans to the pyrazole unit.

The UV/Vis absorption spectra of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A, 25B)

recorded in CH2Cl2 show several intense absorptions (Figure 29). The strong absorptions

below 400 nm can again be attributed to ligand centered π–π* transitions involving the

bdmpza and PPh3 ligand. As mentioned previously the strong absorption at 578 nm (25A) or

550 nm (25B) with molar extinction coefficients around 14000 L mol–1 cm–1 correspond to a

metal-perturbed π-π* transition of the allenylidene moiety and are bathochromic shifted in

comparison to 20A/B. Again weak transitions can be observed in the NIR region for both

complexes with two signals at 1331 and 939 nm for 25B (Figure 30). For 25A one broad

signal at 1131 nm can be detected. These transitions can be assigned to HOMO → LUMO

and HOMO–1 → LUMO excitations, which are MLCT transitions (Table 8).

82


!! !


Figure 30. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 25A (black) and 25B (grey); signal caused by CH2Cl2 is indicated by *.

400 600 800 1000 1200 1400 1600

0

5000

10000

15000

20000

25000

30000

ε)[L)m

ol/1)cm

/1]

W ave leng th)[nm]

800 1000 1200 1400 16000

50

100

150

200

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

*

83


!! !




Wavelength [nm]


Transition

25A 1131 184 997

879

0.85

0.25

HOMO ! LUMO

HOMO–1 ! LUMO

25B

1331

939

155

204

1204

905

0.68

0.24

HOMO ! LUMO

HOMO–1 ! LUMO

Table 8. Calculated and measured transitions for 25A and 25B in the NIR region.

For further understanding the absorption spectra TD-DFT calculations have again been

performed by E. HÜBNER for complexes 25A and 25B, which explain the absorptions at the

edge of the NIR region. Especially, the HOMO → LUMO and HOMO–1 → LUMO

transitions with low transition dipole moments between 0.24 and 0.85 debye seem to

correspond to forbidden MLCT transitions for both structural isomers (Table 8). The

calculated geometries emphasize that the LUMO is delocalized over the ruthenium center as

well as the entire allenylidene moiety and the anthrone unit for both complexes (Figure 31

and Figure 32). The B type isomer seems to show a stronger involvement of the anthrone unit

to the calculated orbital in comparison to the A type complex. The HOMO and HOMO–1 are

mainly located on the ruthenium center, Cα and Cβ for both isomers. The comparison of the

calculated absorptions with the measured values (Table 8) confirm the assumption of the

MLCT between the calculated orbitals.

84


!! !

LUMO HOMO

HOMO–1 HOMO–2

Figure 31. Orbital diagrams of the LUMO (–3.2 eV), HOMO (–5.3 eV), HOMO–1 (–5.5 eV) and HOMO–2 (–5.7 eV) of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A).

85


!! !

LUMO HOMO

HOMO–1 HOMO–2

Figure 32. Orbital diagrams of the LUMO (–3.2 eV), HOMO (–5.2 eV), HOMO–1 (–5.5 eV) and HOMO–2 (–5.8 eV) of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B).

86


!! !

4.4.4 Pentacenequinone Based Allenylidene Complexes

Functionalized acenes have proven to be good candidates for small-molecule semiconductor

applications and have been widely explored over the past decade.[274-276] In comparison to

field-effect transistors (FETs) based on single-crystal, polycrystalline or amorphous silicon,

those based on acene molecules allow the realization of large-area, mechanically flexible, and

low-cost devices.[277] Likewise, the direct precursors to pentacenes, namely pentacene-

quinones, are potentially useful organic semiconductors in their own right.[278] To date, the

functionalization of the framework of pentacenes and pentacenequinones has focused on

organic substituents and is accomplished mainly by appending alkyl, aryl, and alkyne residues

to the framework to influence the HOMO–LUMO gap and packing motif in the crystalline

state. [274-276, 279] The organometallic chemistry of pentacenes has been little explored,[280] and

organometallic derivatives of pentacenequinone were unknown.

As a starting point for the pentacenone component, the known 13-hydroxy-13-

[(triisopropylsilyl)ethynyl]pentacen-6-one (27)[272] was converted in cooperation with the

group of R. TYKWINSKI into the propargyl alcohol 13-ethynyl-13-hydroxypentacen-6-one (28)

by desilylation with TBAF (tetra-n-butylammonium fluoride) in THF (Scheme 45).[272]

Scheme 45. Synthesis of the TIPS (triisopropylsilyl) protected alcohol 27 and deprotection of the propargyl alcohol 28 (reaction conditions: I) 1. n-BuLi, TIPS-acetylene, THF, 2. H2O; II) TBAF, THF).

A similar approach as for the previously described complexes was used to obtain the

corresponding heteroscorpionate allenylidene bdmpza complexes 29A and 29B. To the

precursor [Ru(bdmpza)Cl(PPh3)2] (14), 1.5 equiv. of 13-ethynyl-13-hydroxypentacen-6-one

O O OHO

TIPS

OHO

H

I) II)

27 2826

87


!! !

(28) was added in THF. This led to the formation of a deep-blue solution after 4 d of stirring

at room temperature (Scheme 46).

Scheme 46. Synthesis of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (PCO = pentacenone) (29A, 29B).

As a result of the facial κ3 coordination of the bdmpza ligand the two expected structural

isomers were formed, namely 29A and 29B. The neutral 18 VE allenylidene complexes 29A and 29B are rather stable towards oxygen and water. Therefore, the complexes were purified

by column chromatography under aerobic conditions, although a clean separation of the two

isomers was hindered in comparison to all previously describe bdmpza based allenylidene

complexes.[61] However, it was possible to isolate trace amounts of the major isomer 29A

from a mixture of 29A and 29B by column chromatography on silica gel

(CH2Cl2/acetone/n-hexane, 1:1:1, v/v/v). Surprisingly, all attempts to obtain pure 29B by

chromatographic separation resulted in samples that contained traces of isomer 29A.

Nevertheless, crystals suitable for an X-ray structure determination of 29B were obtained by

slow diffusion of n-hexane into a solution of the complex 29B in CH2Cl2 (Figure 33).

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

29A 29B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

+

+THF

28

O

O

OH

O

H

88


!! !

Figure 33. Molecular structure of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.0881(16), Ru–N(21) = 2.1394(17), Ru–O(1) = 2.1458(14), Ru–P(1) = 2.3435(5), Ru–Cl(1) = 2.3884(5), Ru–C(101) = 1.861(2), C(101)–C(102) = 1.263(3), C(102)–C(103) = 1.363(3); N(11)–Ru–N(21) = 83.59(7), O(1)–Ru–N(11) = 85.01(6), O(1)–Ru–N(21) = 86.76(6), O(1)–Ru–P(1) = 86.23(4), P(1)–Ru–Cl(1) = 89.036(18), P(1)–Ru–C(101) = 97.39(6), O(1)–Ru–C(101) = 173.68(7), N(11)–Ru–P(1) = 99.60(5), N(21)–Ru–Cl(1) = 87.14(5), Cl(1)–Ru–C(101) = 95.20(6), Ru–C(101)–C(102) = 167.78(17), C(101)–C(102)–C(103) = 163.2(2).

The ruthenium complex 29B exhibits an octahedral geometry that is slightly distorted due to

the facial coordinating N,N,O ligand with the allenylidene unit positioned trans to the

carboxylate and the PPh3 as well as the chlorido ligand trans to the pyrazole donors. In

comparison with other ruthenium allenylidene complexes, the Ru–C3 chain is extremely bent

with angles ∠Ru–C(101)–C(102) = 167.78(17)° and ∠C(101)–C(102)–C(103) = 163.2(2)°

(Table 9). These distorted angles might be caused by crystal packing effects and are

unprecedented for mononuclear ruthenium allenylidene complexes.[281] The distortion of the

sp carbon chain can be explained by strong π–π stacking interactions in the solid state that

Cl1 N21N22

C103

C102

C106

C101

O3

Ru1

C1O1

C2

O2

P1

N12N11

a

bc

89


!! !

force the allenylidene unit into this bent structure. In the crystal structure, two pentacenone

units are stacked with less than half a phenyl ring slippage and a mean interplanar distance of

3.63 Å (Figure 34).

Figure 34. π–π stacking interactions between two molecules of 29B from a) side view and b) top view.

This is in good agreement with the distance reported for 27 (3.60 Å), but is longer than in

pentacenequinone (ca. 3.4 Å).[282-283] These favorable π-stacking interactions could lead to

aggregation in solution, which would explain the difficult separation of the isomers by

column chromatography. In addition, the pentacenone units are arranged parallel throughout

the crystal lattice with a diagonal distance of around 3.9/4.0 Å between two neighboring

pentacenone units, giving a structure resembling a staircase. TD-DFT calculations by E.

HÜBNER on a single molecule and neglecting π interactions led to an almost linear

90


!! !

allenylidene moiety (Table 9). This supports the assumption that the considerable deviations

in the solid state are a result of strong π–π stacking interactions. Cyclic voltammetric (CV)

analysis of complex 29B revealed several ligand based and one ruthenium based redox

transitions (see Chapter 8.2). The Ru(II)/Ru(III) couple is totally irreversible and appears at

+0.92 V. A weak reversible oxidation is observed at +0.12 V and derives most likely from the

pentacenone unit. Two reversible peaks at –0.48 and –0.88 V indicate facile reduction of the

pentacenone and allenylidene moieties. The latter peak at –0.88 V agrees well with values of

other ruthenium allenylidene complexes reported in the literature.[125] Further reversible

reductions are observed at –1.40 and –1.83 V. In summary, these data seem to indicate that

29B has potential electron-acceptor properties.

The UV/Vis spectrum of 29B recorded in CH2Cl2 is depicted in Figure 35 and a magnification

of the relevant parts of the NIR region is given in Figure 36. The strong absorption bands

(55000 L mol–1 cm–1 for 29B) below 400 nm have been assigned to ligand-centered (LC) π–

π* transitions involving the PPh3 and bdmpza ligands. An additional metal-perturbed π–π*

transition can be observed at 605 nm (ε ≈ 14000 L mol–1 cm–1), and the broad transitions at

lower wavelengths (830–1400 nm) can be attributed to HOMO–1→LUMO and

HOMO→LUMO excitations, which are MLCT transitions.

Figure 35. Absorption spectrum of 29B in CH2Cl2.

400 600 800 1000 1200 14000

10000

20000

30000

40000

50000

60000

ε)[L)m

ol/1)cm

/1]

W ave leng th)[nm]

91


!! !

Figure 36. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 29B.

To further understand the UV/Vis data, DFT calculations were performed on 29B by E.

HÜBNER. TD-DFT calculations of the excited states revealed two absorption bands located at

the edge of the NIR region (830–1400 nm, 370 L mol–1 cm–1). The two bands were assigned to

metal-to-ligand charge-transfer transitions. The absorption band at lower wavelength for the

first excited state was calculated to be at 1114 nm (i.e., 1.11 eV) and correlates mainly to a

HOMO→LUMO transition. The second absorption band was calculated to be at 857 nm (i.e.,

1.45 eV) and correlates to a HOMO–1→LUMO transition. Both occupied orbitals are mainly

located on the ruthenium center in the d orbitals with some of the electron density extending

towards the adjacent chlorido ligand as well as the oxygen atom of the carboxylate group of

the bdmpza ligand. The lowest unoccupied orbital is delocalized mainly throughout the

pentacenone ligand (Figure 37). The high degree of delocalization might explain the long-

wave absorption bands because, as a consequence, the LUMO is expected to have a rather

low energy, leading to a small energy difference between the occupied and unoccupied

orbitals. For both transitions, the dipole moment was calculated to be rather small (0.65 and

0.17 debye), which indicates forbidden transitions. The HOMO→LUMO gap, calculated as

the difference between the calculated orbital energies of the ground state (DFT) of 29B, is

2.0 eV, and this correlates reasonably well with the long-wavelength absorption bands found

experimentally. The longest wavelength absorption bands obtained by the more accurate TD-

900 1000 1100 1200 1300 14000

50

100

150

200

250

300

350

400

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

*

92


!! !

DFT (1.1 to 1.4 eV), however, match the experimental CV data better, revealing a HOMO–

LUMO gap of around 1.4 eV, which agrees as well as the UV/Vis data (0.9 to 1.5 eV).

LUMO HOMO

HOMO–1

Figure 37. Orbital diagrams of the HOMO–1 (–5.4 eV), HOMO (–5.1 eV), and LUMO (–3.06 eV) of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B).

93


!! !

Experimental Calculated

Distances [Å] 29A 29B 29A 29B

Ru–Cα 1.859(3) 1.861(2) 1.868 1.875

Cα–Cβ 1.244(5) 1.263(3) 1.263 1.265

Cβ–Cγ 1.365(5) 1.363(3) 1.359 1.359

Angles [°]

Ru–Cα–Cβ 172.8(3) 167.78(17) 174.41 174.51

Cα–Cβ–Cγ 179.0(4) 163.2(2) 176.40 175.75

Table 9. Selected distances and angles for complexes 29A and 29B determined from the X-ray crystal structure and theoretical calculations (LACVP*/B3LYP).

The same TD-DFT calculations were performed for complex 29A. For the three calculated

occupied orbitals HOMO–2, HOMO–1 and HOMO the orbitals are again mainly located on

the ruthenium center in the d orbitals with some of the electron density extending towards the

adjacent chlorido ligand as well as the oxygen atom of the carboxylate group of the bdmpza

ligand (Figure 38).

The LUMO is delocalized mainly throughout the pentacenone ligand. However, the change in

geometry from the allenylidene unit positioned trans to the carboxylate unit (29B) to trans to

the pyrazole unit (29A) seems to reduce the delocalization of the HOMO within the

pentacenone unit (Figure 38).

94


!! !

LUMO HOMO

HOMO–1 HOMO–2

Figure 38. Orbital diagrams of the LUMO (–3.0 eV), HOMO (–5.2 eV), HOMO–1 (–5.3 eV) and HOMO–2 (–5.5 eV) of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A).

In comparison the second structural isomer (29A) shows the expected behavior for a bdmpza

based allenylidene complex in crystalline state. The arrangement with the allenylidene unit

positioned trans to a pyrazole unit forces the chlorido ligand trans to the carboxylate anchor.

The allenylidene chain exhibits common angles with ∠Ru–C(61)–C(62) = 172.8(3)° and

∠C(61)–C(62)–C(63) = 179.0(4)°. This indicates that in the solid state less repulsion occurs,

compared to complex 29B, thus, allowing the allenylidene moiety to maintain its preferred

geometry.

95


!! !

Figure 39. Molecular structure of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.142(3), Ru–N(21) = 2.196(3), Ru–O(1) = 2.079(2), Ru–P(1) = 2.3325(10), Ru–Cl(1) = 2.3770(9), Ru–C(61) = 1.859(3), C(61)–C(62) = 1.244(5), C(62)–C(63) = 1.365(5); N(11)–Ru–N(21) = 83.03(10), O(1)–Ru–N(11) = 87.15(10), O(1)–Ru–N(21) = 83.38(10), O(1)–Ru–P(1) = 83.79(7), P(1)–Ru–Cl(1) = 99.43(3), P(1)–Ru–C(61) = 89.24(11), O(1)–Ru–C(61) = 95.41(13), N(11)–Ru–P(1) = 170.45(8), N(21)–Ru–Cl(1) = 88.72(7), Cl(1)–Ru–C(61) = 92.13(11), Ru–C(61)–C(62) = 172.8(3), C(61)–C(62)–C(63) = 179.0(4).

The packing motif in the solid state resembles for 29A more or less the packing motif of the

anthraquinone based complex (25A) although due to the extended ring system only partial

overlap of four phenyl rings can be observed (Figure 40). This can be attributed to the fifth

phenyl ring being slightly forced out of the planar system due to repulsive interactions with

the PPh3 ligand. For a possible application of pentacene or pentacenequinone based

compounds in, for example, field effect transistors, efficient overlap of the planar π-systems is

crucial in order to allow for charge transport along this axis.[274]

Cl1

O3C74

C63

N11

C62C61

Ru1

N21

N12N22

P1

C1

O1

C2O2

a

bc

96


!! !

Figure 40. π–π stacking interactions between two molecules of 29A from a) top view and b) side view.

The arrangement observed for 29A and 29B in the crystalline state renders the complexes

promising candidates for metal-tuned FETs or “organic” metal-semiconductor field-effect

transistors (OMESFETs), whereas the electron-accepting ability and low-energy absorption

characteristics might be tuned for use in solar cells. Both aspects present an appealing starting

point for new kinds of functionalized organic semiconductors.

a) b)

97


!! !

4.4.5 Vinylidene Complex Bearing a Malonodinitrile Substituted Pentacenequinone

A common way to modulate the electron-accepting properties of quinones is the formation of

the corresponding tetracyano-p-quinodimethane (In the case of unsubstituted quinone:

7,7,8,8-tetracyano-p-quinodimethane (TCNQ)) by reacting the quinone with malonodinitrile

in the presence of titanium(IV) chloride.[284-285] Especially TCAQ (11,11,12,12-tetracyano-

9,10-anthraquinodimethane) has played an important role in the area of organic electron

acceptors and its properties have been extensively reviewed.[286] The major drawback of most

TCNQ based polyaromatic systems is the stabilization of the resulting radical anion resulting

from the reduction of the electron acceptor. M. HANACK et al. synthesized a series of

symmetrical acene based TCNQ derivatives like TCPQ (15,15,16,16-tetracyano-6,13-

pentacenequinodimethane) that however, were poorer electron acceptors as indicated by the

more negative reduction potentials observed in CV analysis.[285] Unsymmetrical acenes

bearing acetylene moieties on one side and malonodinitrile units one the opposing side are

currently a project investigated by A. WATERLOO in the group of R. TYKWINSKI. Starting from

the previously used 13-ethynyl-13-hydroxypentacen-6-one (28), the reaction with

malonodinitrile in the presence of TiCl4 leads to the isolation of 2-(13-(dicyanomethyl)-13-

ethynylpentacen-6(13H)-ylidene)malononitrile (30) as the reaction with the hydroxyl moiety

could not be avoided. In cooperation, it was decided to investigate the reaction of this

acetylene derivative with the [Ru(bdmpza)Cl(PPh3)2] (14) precursor to explore the effects of

the electron withdrawing groups. Reacting [Ru(bdmpza)Cl(PPh3)2] (14) with 30 in THF led

within minutes to a dark blue solution very similar to 29A/29B, nevertheless the solution

obtained is highly sensitive towards oxygen as it turns from blue to brownish green within

hours (Scheme 47). From this lack of stability it was expected that the formed complex 31

might be the corresponding vinylidene complex (For the sake of simplicity the pentacene-

quinone derivative of the vinylidene complex 31 is referred to as PCN).

98


!! !

Scheme 47. Synthesis of [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (PCN = pentacenone based tetracyano derivative) (31).

Due to the poor stability under aerobic conditions, the isolation of complex 31 via column

chromatography was performed under nitrogen atmosphere with CH2Cl2/acetone (1:1, v/v,

silica). It was concluded that compound 31 has the vinylidene moiety positioned trans to a

pyrazole unit as no second structural isomer could be observed. In the 1H NMR spectrum the

bdmpza ligand can be assigned by its characteristic four methyl signals at 2.51, 2.15, 1.94 and

1.91 ppm. One of the pyrazole protons in 4 position is shifted upfield to 4.98 ppm while the

second one shows a more common value with 5.93 ppm. Furthermore, the vinylidene proton

shows an extremely low value for an aromatic vinylidene complex of 3.82 ppm, which might

result from the strong electron withdrawing groups of the substituent.[61] The aliphatic proton

at 3.47 ppm and several aromatic protons between 8.68 and 7.65 ppm characterize the PCN

moiety. Moreover, only one set of signals of the PCN moiety can be observed indicating free

rotation around the Cβ–Cγ bond. The 13C NMR spectrum confirms the aforementioned

assumption that the vinylidene ligand is positioned trans to a pyrazole moiety as a long range

P–C coupling can be observed for one 4 position pyrazole carbon atom at 106.6 ppm

(4JC,P = 2.9 Hz).[186] Additionally, the presence of Cα gives rise to a doublet downfield shifted

to 365.1 ppm (2JC,P = 39.1 Hz) clearly providing evidence for a vinylidene complex.

Furthermore, a set of four signals of the cyano substituents at 119.1, 113.4, 110.6 and

110.1 ppm confirm the obtained complex 31. In addition the pentacenequinone backbone

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

CNNC

CNCN

31

H

NC CN

CNCN

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3+ THF

30

99


!! !

leads to several aromatic signals between 134.6 and 126.9 ppm. The 31P NMR spectrum

supports the assumption that only one structural isomer has been formed as one strongly

downfield shifted singlet at 44.6 ppm can be observed. The IR spectrum confirms the

presence of two weak nitrile vibrations at 2198 and 2126 cm–1 arising from the two different

sets of nitrile moieties. Finally ESI-MS experiments allowed the detection of the protonated

complex 31 (m/z 1077.21 (15%) MH+) and its sodium adduct (m/z 1099.20 (100%)

[M + Na]+).

The intense blue color of complex 31 seems to indicate an allenylidene complex, thus UV/Vis

absorption spectroscopy was performed to compare the spectrum to the closely related

ruthenium allenylidene complexes 29A and 29B based on pentacenequinone. The signals

below 450 nm resemble the typical pattern for ruthenium bdmpza based complexes. However,

a very broad absorption with maxima at 578 and 692 nm and high molar extinction

coefficients between 6000 and 8000 L mol–1 cm–1 can be observed (Figure 41), although these

extinction coefficients are high, in comparison to the allenylidene complexes reported

previously, the values are moderate. A possible explanation would be that the electron

withdrawing nitrile substituents lead to a strong bathochromic shift and the absorptions

observed are similar to the allenylidene complexes metal-perturbed π–π* transitions, but in

this case of the vinylidene unit. A further feature of 31 is an intense absorption in the NIR

region between 1000 and 1087 nm with an molar extinction coefficient around 800 L

mol–1 cm–1 that could not yet be attributed to a certain transition due to the lack of a single

crystal X-ray structure determination and thereafter TD-DFT calculations (Figure 42).

Nevertheless, a HOMO–LUMO transition seems logical in analogy to values reported in this

work for the allenylidene complexes.

100


!! !

Figure 41. Absorption spectrum of 31 in CH2Cl2.

Figure 42. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 31; signal caused by CH2Cl2 is indicated by *.

400 600 800 1000 1200 1400 16000

5000

10000

15000

20000

25000

30000

35000ε)[L)m

ol/1)cm

/1]

W ave leng th)[nm]

800 1000 1200 1400 16000

200

400

600

800

1000

ε'[L'm

ol-1'cm

-1]

W ave leng th'[nm]

*

101


!! !

4.4.6 Benzotetraphenone Based Allenylidene Complexes

In the next step the focus was more on the packing motif in the solid state. For theoretical

device formation a 3D electronic communication in the solid state is required. This can be

achieved either by intramolecular transport within a polymer or intermolecular via close

distance interactions by π-π stacking interactions.[272, 287] Based on the previous results, it was

assumed that the allenylidene substituent is too close to the PPh3 and the bdmpza ligand to

show extended intermolecular stacking interactions. Hence it was decided to look into related

carbon-rich compounds that show substitution patterns extending the size of the polyaromatic

system in the opposing direction to the allenylidene chain. For comparable size, 7H-

benzo[no]tetraphen-7-one (10,11-BzBT, 34) consisting of five six-membered rings was

chosen. Due to the so called 1,7 interaction the molecule is greatly distorted from a planar

geometry, even in comparison to the closely related 7H-benzo[hi]chrysene-7-one (8,9-BzBT,

32) and 13H-dibenz[a,de]anthracen-13-one (5,6-BzBT, 33) (Figure 43).[288]

Figure 43. 7H-benzo[hi]chrysene-7-one (8,9-BzBT, 32), 13H-dibenz[a,de]anthracen-13-one (5,6-BzBT, 33) and structures of 7H-benzo[no]tetraphen-7-one (10,11-BzBT, 34) (steric repulsion indicated with *).[288]

Starting from compound 34 is most promising as two of the phenyl rings are facing away

from the keto moiety and in consequence from the future allenylidene unit. Thus it was

decided to investigate the follow up chemistry of 10,11-BzBT as up to now only the nitration

of the aromatic backbone, the dimerization of two units and the reduction of the keto moiety

is know to literature.[289-291]

O O O

32 33 34* *

* *

102


!! !

Scheme 48. Synthesis of the TMS-ethynyl alcohol 35 and the deprotected propargyl alcohol 36 (reaction conditions: I) 1. n-BuLi, TMS-acetylene, THF, 2. H2O; II) KOH, MeOH, H2O).

Starting from 7H-benzo[no]tetraphen-7-one (34) (Scheme 48), the addition of excess amounts

of lithiated TMS-acetylene leads to the quantitative formation of the corresponding propargyl

alcohol indicated by the characteristic singlets of the alcohol proton at 2.59 ppm and the TMS

group at 0.23 ppm in the 1H NMR spectrum. In the 13C NMR spectrum of compound 35, the

two relevant alkyne signals appear at 107.6 and 93.2 ppm, while that of the tetrahedral carbon

is observed at 69.9 ppm. The product gives a signal in negative mode of ESI-MS analysis that

can be attributed to a chloride adduct of 35 (m/z 413.11 (18%) [M + Cl]–). Deprotection of the

alkyne is achieved in methanol with potassium hydroxide. 7-Ethynyl-7H-benzo[no]tetraphen-

7-ol (36) shows the additional signal of alkyne proton at 2.91 ppm in the 1H NMR spectrum,

while the singlet of the TMS group is lost. In the 13C NMR spectrum, the loss of the methyl

resonance from the TMS group and the shift of the terminal alkyne carbon to 76.4 ppm

support the successful transformation from 35 to 36.

O

34 35 36

OH OH

TMS H

I) II)

103


!! !

Scheme 49. Synthesis of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A, 37B).

The preparation of the corresponding benzotetraphene (BT) based ruthenium allenylidene

complexes 37A/37B was carried out by combinig equimolar amounts of propargyl alcohol 36

and [Ru(bdmpza)Cl(PPh3)2] (14) (Scheme 49). The reaction mixture turns to deep blue,

similar to the reaction to give pentacenequinone based allenylidene complexes 29A/29B

indicating in both cases a strong influence of the size of the aromatic group on the color of the

allenylidene complex. The separation of the two structural isomers can be achieved by

column chromatography as described for the anthraquinone based allenylidene complexes

25A/25B. For the major isomer 37A, Cα shows a characteristic signal in the 13C NMR

spectrum at 273.6 ppm with a coupling constant of 2JC,P = 19.2 Hz. For Cβ (221.1 ppm, d, 3JC,P = 3.5 Hz) and Cγ (139.8 ppm, d, 4JC,P = 1.7 Hz) the signals are also shifted upfield in

comparison to the fluorenone, anthraquinone and pentacenequinone based systems. The

allenylidene stretch appears in the IR spectrum at 1903 cm–1. A singlet in the 31P NMR

spectrum of 37A is found at 35.2 ppm for the PPh3 ligand, supporting assignment of the

allenylidene trans to a pyrazole moiety. ESI-MS experiments confirm the formation of the

complex through detection of the molecular ion (m/z 934.18 (100%) [M]+) and similar to 24B

the decarboxylation followed by chloride dissociation can be observed (m/z 855.22 (23%)

[M – CO2 – Cl]+). For isomer 37B similar upfield shifted signals for Cα (289.5 ppm, d, 2JC,P = 18.4 Hz), Cβ (237.2 ppm) and Cγ (138.0) can be observed. The IR spectrum reveals an

allenylidene stretch in a similar region at 1907 cm–1. The PPh3 ligand shows a singlet in

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

37A

37B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

+

+ THF

36

14

OH

H

104


!! !

31P NMR spectrum of 37B confirming the assignment that the allenylidene is positioned trans

to the carboxylate anchor. These values are overall in good agreement with the previously

observed NMR chemical shifts for type B isomers in comparison to type A isomers.[61]

ESI-MS experiments again show the appearance of a signal that is characteristic for the

ionized complex (m/z 934.18 (100%) [M]+). Layering a solution of 37A in CH2Cl2 with

n-hexane gave crystals of complex 37A suitable for a single crystal X-ray structure

determination. The compound crystallizes as racemic mixture in the space group P–1 with

two disordered molecules CH2Cl2 in the asymmetric unit. A graphical presentation of the

compound is illustrated in Figure 44. As mentioned previously for type A isomers the typical

strained coordination of the bdmpza ligand is observed and the allenylidene unit is

coordinated trans to a pyrazole group, which leaves the PPh3 ligand trans to the second

pyrazole and the chlorido ligand trans to the carboxylate anchor.

105


!! !

Figure 44. Molecular structure of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.159(5), Ru–N(21) = 2.199(5), Ru–O(1) = 2.091(4), Ru–P(1) = 2.2936(17), Ru–Cl(1) = 2.3803(16), Ru–C(61) = 1.878(6), C(61)–C(62) = 1.239(8), C(62)–C(63) = 1.374(8); N(11)–Ru–N(21) = 85.5(2), O(1)–Ru–N(11) = 86.85(19), O(1)–Ru–N(21) = 85.14(19), O(1)–Ru–P(1) = 86.09(13), P(1)–Ru–Cl(1) = 95.91(6), P(1)–Ru–C(61) = 89.08(17), O(1)–Ru–C(61) = 95.5(2), N(11)–Ru–P(1) = 172.60(14), N(21)–Ru–Cl(1) = 89.08(15), Cl(1)–Ru–C(61) = 90.02(17), Ru–C(61)–C(62) = 174.1(5), C(61)–C(62)–C(63) = 176.0(6).

The main feature of the structure of 37A is the nearly linear allenylidene moiety with ∠Ru–

C(61)–C(C62) = 174.1(5) and ∠C(61)–C(62)–C(63) = 176.0°(6). The benzotetraphene group

is non-planar, due to hydrogen-hydrogen repulsion that forces the phenalene and naphthalene

portions out of planarity. For rational description of the distortion between the two units the

twisting angle around the pseudo bond C(72)–C(74) is defined. The torsion angle ∠C(75)–

C(74)–C(72)–C(71) = 32.58° is similar to the angle observed for the parent ketone (33.4°).[288]

Also the distance C(71)–C(75) = 3.006 Å for 37A is close to the precursor which shows a

distance of 2.993 Å.[288] The combination of reduced planarity and of an extended π-system

facing away from the ruthenium center allows the formation of a stepwise arrangement within

the crystal lattice. While the pentacenequinone based systems did not show any extended

stacking motifs, several π–π stacking interactions can be observed for complex 37A (Figure

45). The mean distance between two neighboring phenalene units accounts to 3.39 Å, which

Cl1

N21N11

N22N12

RuC61

C62P1

C63

C71C72

O1

C73

C74

O2

C75

ab

c

106


!! !

indicates attractive interactions. For comparison the interplanar distance in the parent 10,11-

BzBT (34) has been reported with 3.582 Å for the face to face stacked ketone.[288] For the

naphthalene unit three short contact interactions between 3.25 and 3.62 Å to the neighboring

phenalene unit can be observed. This slip-stacked arrangement leads to a staircase type

arrangement in the crystal that might allow charge transport between the polyaromatic

systems.

Figure 45. π–π stacking interactions between two molecules of 37A from a) side view and b) top view.

For the second structural isomer 37B only a single crystal X-ray structure determination of

poor quality could be obtained due to a strongly disordered crystal. Nevertheless, qualitative

interpretation of the structure reveals that due to steric hindrance of the remaining ligands no

π–π stacking interactions can be observed for this isomer.

The voltammograms of the benzotetraphene based allenylidene complexes

[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A, 37B) show mainly similarities to the fluorene

based allenylidene complexes 20A and 20B, although the potentials again show dependence

on the structural isomer (Chapter 8.2). The reversible redox process involving the Ru(II)

center appears at 87 mV (37A) or 118 mV (37B) indicating a more cathodic process due

electron releasing properties of the benzotetraphene unit. The first redox process at negative

voltage can best be described as quasi-reversible for the reduction involving the allenylidene

moiety (–1228 mV (37A); –1168 mV (37B)) due to the lower peak current ratios. The second

process for the reduction of the benzotetraphene unit itself (–1914 mV (37A); –1859 mV

(37B)) is fully reversible.

a) b)

107


!! !

The UV/Vis spectra of the benzotetraphene based systems 37A/B recorded in CH2Cl2 share

several common features for ruthenium allenylidene complexes as previously reported (Figure

46).[61, 125, 127, 256] The strong absorptions at wavelengths less than ~450 nm have been assigned

to ligand centered (LC) π–π* transitions involving the PPh3 and bdmpza ligands. An

additional metal perturbed π–π* transition can be observed at 654 nm for 37B with a molar

extinction coefficient around 15000 L mol–1 cm–1. In comparison to the complex of type B a

further increase in absorption energy can be observed for the complex bearing the

allenylidene unit positioned trans to the pyrazole moiety (708 nm for 37A) with a comparable

extinction coefficient. Again, absorption bands are observed in the NIR region (Figure 47),

thus E. HÜBNER performed TD-DFT calculations of the excited states on the basis of crystal

structures of 37A. The results of the calculations of the excited states revealed two absorption

bands at 1058 nm (1.17 eV) and 905 nm (1.37 eV) that can be assigned to MLCTs which are

in good agreement with the experimental values (1097 nm, 989 nm) (Table 10). The first

absorption correlates mainly to the HOMO → LUMO transition with the second one

assignable to the HOMO–1 → LUMO transition. The HOMO and HOMO–1 orbital may be

described as ruthenium d orbitals with a small contribution of the chlorido ligand and the

carboxylate anchor of the bdmpza ligand (Figure 48). For the HOMO orbital electron density

can be observed to extend towards the allenylidene chain. For the LUMO a high degree of

delocalization along the allenylidene unit into the phenalene moiety of the benzotetraphene

unit can be observed. Overall, this results in a rather low energy LUMO leading to a small

energy difference between the occupied and unoccupied orbitals and thus long-wave

absorptions can be observed. The two small transition dipole moments that are calculated

(1.54 and 0.51 debye) indicate forbidden transitions, which correlate well with the low

absorption coefficients that were observed experimentally (764 and 708 L mol–1 cm–1).

Furthermore, the HOMO–LUMO gap calculated as the difference between the calculated

orbital energies of the ground state (DFT) of 37A correlates less with the experimental CV

data (calcd.: 2.0 eV, observed 1.36 eV).

108


!! !


Figure 47. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for of 37A (black) and 37B (grey); signal caused by CH2Cl2 is indicated by *.

400 600 800 1000 1200 1400 16000

5000

10000

15000

20000

25000

30000ε)[L)m

ol/1)cm

/1]

W ave leng th)[nm]

800 1000 1200 1400 16000

200

400

600

800

*

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

109


!! !

LUMO HOMO

HOMO–1 HOMO–2

Figure 48. Orbital diagrams of the LUMO (–2.9 eV), HOMO (–4.9 eV), HOMO–1 (–5.1 eV) and HOMO–2 (–5.3 eV) of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A).




Wavelength [nm]


Transition

37A 1097

989

764

708

1058

905

1.54

0.51

HOMO ! LUMO

HOMO–1 ! LUMO

Table 10. Calculated and measured transitions for 37A in the NIR region.

110


!! !

4.4.7 Larger Quinoidal Polyaromatic Compounds

Based on the previous results even larger graphene like systems were considered as suitable

precursors in which an extension of the substituent along the direction of the allenylidene

chain would lead to 3D stacking patterns. Derived from anthraquinone and pentacenequinone,

several dimerized and fused systems are viable (Figure 49), although no synthetic route for

peripentacenequinone has been described, so far.[292]

Figure 49. Structures of the acenequinones (bisanthracenquinone/bianthrone (38), bispentacenequinone (40)) and fused acenequinones (bisanthenequinone (39), „fused bispentacenequinone“ (41), peripentacenequinone

(42)).[292]

O

O

O

O

O

O

O

OO

O

38 39

40 41

42

111


!! !

From the structures shown in Figure 49, bisanthenequinone is a promising candidate due to its

planarity and its considerable larger π system compared to the previously used systems. The

bisanthenequinone structure is the lead structure for many naturally occurring pigments like

hypericin controlling biophysical processes like phototoxicity and antiseptic actions.[293-294]

The first synthesis of 39 was described by R. SCHOLL in 1910 via oxidation of meso-

benzdianthrone with potassium dichromate in concentrated sulfuric acid.[295] Given the recent

interest in carbon-rich chemistry several groups have used bisanthenequinone based systems.

H. BOCK et al. used this as building block to create soluble and liquid-crystalline ovalenes,[296]

which are of great interest for devices like field effect transistors and solar cells.[297-302] Closely

related are dicyano ovalene diimides reported by J. WU et al. that allow solution processing of

OFET devices, which show high electron mobility under aerobic conditions.[303] Further

compounds by J. WU et al. focused on the reactivity of the meso positions and allowed the

formation of NIR dyes that undergo several reversible redox processes.[304] Similar results

were obtained for the parent bisanthene core that without meso-substituents rapidly

decomposes.[305]

Based on these promising results it was decided to focus on the synthesis of an allenylidene

complex bearing a bisanthenequinone unit. Starting from commercially available bianthrone

(38) required as first step a photocyclization reaction previously described by S. ARABEI and

coworker.[306] Illumination was performed with a mercury vapor lamp and a solution of 38 in

benzene, which reacted via intermediary helianthrone (43) in one step cleanly to

bisanthenequinone (39, Scheme 50). Experiments showed that the cyclization can either be

performed under an argon atmosphere or without inert gas, although the yields are higher in

the presence of oxygen. The presence of oxygen leads to an orange product in comparison to

a brownish product after inert gas conditions, although the spectroscopic datas are equivalent.

112


!! !

Scheme 50. Photocyclization reaction for the synthesis of bisanthenequinone (39).[306]

The poor solubility of bisanthenequinone (39) leads to precipitation from benzene and after

removal of unconverted bianthrone the IR spectrum shows a shift for the two characteristic

quinone signals. For 38 these two signals appear at 1667 and 1594 cm–1 and are shifted for 39

to lower wavenumbers at 1659 and 1582 cm–1. For further characterization, it was decided to

measure a 1H NMR spectrum in deuterated concentrated sulfuric acid as no other solvent

allows dissolution of 39. The signals confirm the high symmetry of the bisanthenequinone

unit as only three signals can be observed. Two well resolved doublets at 8.63 and 8.22 ppm

and a further signal that appears as triplet at 7.26 ppm are in agreement with the reported

structure.

In the following step, the conversion of the quinone moiety into a propargyl alcohol by

nucleophilic addition of acetylene precursors was attempted. As promising candidates sodium

acetylide, ethynylmagnesium bromide and lithiated trimethylsilyl acetylide were added in

equimolar amounts to 39 to form the monoaddition product (Scheme 51) in analogy to the

anthraquinone and pentacenequinone systems.

O

O

O

O38 39

O

O43

hν hν

113


!! !

Scheme 51. Attempted syntheses of a bisanthenone propargyl alcohol (44).

Nevertheless, all described attempts failed to produce a propargyl alcohol. Due to the poor

solubility of the resulting compounds, a positive identification of the obtained compounds is

questionable. In comparison to the literature known bisanthenequinone derivatives that bear

bulky or electron withdrawing groups on the reactive zigzag edges 44 lacks stabilization.[307]

This might cause decomposition of 44 after formation. Another explanation might be a report

by J. WU et al. indicating that lithiated species can be added to the bisanthenequinone

backbone and not directly to the quinone moiety allowing the formation of a mixture of

substances.[304] Based on these results, two routes seem promising. On the one hand, the

symmetrical functionalization, known in literature to obtain 7,14-bis(triisopropylsilylethynyl)-

phenanthro[1,10,9,8-opqra]perylene and after deprotection the formation of bimetallic

allenylidene complexes.[305] On the other hand functionalization of the armchair area of the

bisanthenequinone unit, which shows diene character, might be an opportunity.[303] Diels-

Alder reaction with 1,4-naphthaquinone can introduce quinoidal systems that in a next step

could be converted into a suitable precursor with strongly enhanced solubility in comparison

to the unsubstituted bisanthenequinone system (Scheme 52).[308]

O

O39

O44

OH

R

1.2. H2O

R R´

R = H, R´ = NaR = H, R´ = MgBrR = TMS, R´ = Li

114


!! !

Scheme 52. Functionalization of the bay region of soluble bisanthene derivatives by J. WU et al.[308]

tButBu

tButBu

tButBu

tButBu

O

O

O

O

+ benzeneΔ

115


!! !

4.4.8 Carbon-Rich Allenylidene Complexes Based on [RuCl2(PPh3)3]

It has been reported previously that [RuCl2(PPh3)3] is a versatile starting compound for quite

stable 16 VE ruthenium allenylidene complexes like [RuCl2(═C═C═CPh2)(PPh3)2].[93] This

complexes can be further stabilized as 18 VE complexes via coordination of solvents to form

systems such as [RuCl2(═C═C═CPh2)(PPh3)2(solvent)] (solvent = H2O, MeOH, EtOH).[96] A

controlled dimerization to less reactive 18 VE bimetallic allenylidene complexes [(Ph3P)4(μ-

Cl)3Ru2(═C═C═CAr2)2]PF6 has been reported.[309] Therefore, the corresponding fluorenone

based allenylidene complex [RuCl2(═C═C═(FN))(PPh3)2] (45) was targeted by applying the

conditions for the analogous diphenyl allenylidene complex. Heating [RuCl2(PPh3)3] with

9-ethynylfluoren-9-ol in THF for 2 h under reflux led to the formation of a deep red solution

(Scheme 53).

Scheme 53. Synthesis of [RuCl2(═C═C═(FN))(PPh3)2] (45).

The progress of the reaction could be monitored via IR spectroscopy by the disappearance of

the alkyne peak and appearance of the resulting allenylidene peak at 1922 cm–1. After

recrystallization from CH2Cl2/n-hexane, the compound was further characterized via its

characteristic 13C NMR spectrum showing the Cα at 313.8 and Cβ at 239.1 ppm. Both signals

are shifted downfield in comparison to the analogous diphenyl allenylidene complex. The

high symmetry of complex 45 leads to only one singlet for two triphenylphosphine ligands in

the 31P NMR spectrum at 29.1 ppm. ESI-MS experiments verified the proposed structure as a

monocationic species (m/z 849.12 (100%), [M – Cl]+) that fits complex 45 after loss of one

chlorido ligand. The compound is easily obtained and long storage under anaerobic conditions

is possible. Solutions of 45 in chlorinated solvents like CHCl3 and CH2Cl2 tend to form

dimeric complexes as indicated by the formation of four doublets in 31P NMR spectrum. It is

literature known that, if no strongly coordinating solvents like alcohols or pyridine are present

the stabilization of the 16 VE complex can occur via dimerization processes.[93] For the

Ru

Ph3P Cl

PPh3Cl

C C C[RuCl2(PPh3)3]OH

+ Δ

THF

45

H

116


!! !

[RuCl2(PPh3)3] based complexes two different structures are possible with one cationic (45A)

and one neutral 18 VE complex (45B) (Scheme 54). In accordance to the previously reported

dimers the two doublets at 47.8 (d, 2JP,P = 35.6 Hz) and 47.1 ppm (d, 2JP,P = 37.3 Hz) can be

assigned to the neutral allenylidene complex that consists of two µ2 bridged chlorido ligands

and two terminal chlorido ligands with the allenylidene units positioned trans to each other.

In consequence the two remaining doublets at 37.3 (d, 2JP,P = 26.7 Hz) and 34.8 ppm (d, 2JP,P = 26.7 Hz) are caused by the cationic form that contains a Ru2Cl3-cluster as a central

feature with two ruthenium(II) centers bridged by three chlorido ligands resulting in a

monocationic complex. The positive charge is compensated by a chloride counter anion that

has been displaced from the monomeric ruthenium allenylidene complex.

Scheme 54. Dimerized neutral ruthenium allenylidene complex 45A and mono cationic allenylidene complex 45B.

For comparison of the ligand influence on the stability of the 16 VE complex the

anthraquinone based precursor 10-ethynyl-10-hydroxyanthracen-9-one (23) was applied to

form the corresponding complex based on [RuCl2(PPh3)3] ([RuCl2(═C═C═(AO))(PPh3)2]

(46)) in analogy to the synthesis described above for 45. The complex 46 was obtained as a

purple powder due to the influence of the enlarged aromatic system (Scheme 55).

Ru C C C

C C C Ru Cl

Cl

Cl

Cl

PPh3

Ph3PPPh3

Ph3P

Ru C C C

C C C Ru Cl

Cl

Cl

PPh3Ph3P

Ph3P PPh3

Cl

45A

45B

117


!! !

Scheme 55. Synthesis of [RuCl2(═C═C═(AO))(PPh3)2] (46).

The characteristic Cα (321.0 ppm) and Cβ (271.9 ppm) appear downfield shifted compared to

the analogous diphenyl ([RuCl2(═C═C═CPh2)(PPh3)2]) and fluorenyl ([RuCl2(═C═C═(FN))-

(PPh3)2] (45)) substituted allenylidene complexes.[93] This indicates the ability of the enlarged

aromatic system and the keto moiety to withdraw electron density from the allenylidene

chain. The IR signal of the allenylidene is shifted towards lower wavenumbers and appears at

1904 cm–1. The monomeric structure could be confirmed by the 31P NMR spectrum showing a

singlet at 25.1 ppm, characteristic for a symmetrical trans arrangement of the two PPh3

ligands. Similar to the fluorenyl based system the formation of two different dimers can be

observed in 31P NMR spectroscopy experiments and the assignment is in agreement with the

detailed reports by A. HILL et al regarding ([RuCl2(═C═C═CPh2)(PPh3)2].[93] For the neutral

dimer 46A signals at 48.3 (d, 2JP,P = 35.6 Hz) and 46.8 ppm (d, 2JP,P = 37.9 Hz) can be

observed. The cationic system 46B gives rise to two doublets at 36.3 (d, 2JP,P = 26.7 Hz) and

33.2 ppm (d, 2JP,P = 26.7 Hz).

Finally, following again the procedure of Selegue, the pentacenequinone based propargyl

alcohol 28 was combined with [RuCl2(PPh3)3] in THF under reflux, which led to the

formation! of a deep-blue solution. Removal of the solvent and several cycles of

recrystallization from CH2Cl2/n-pentane gave! the coordinatively unsaturated 16 valence

electron complex 47 (Scheme 56).

Ru

Ph3P Cl

PPh3Cl

C C C[RuCl2(PPh3)3] +Δ

THF

46

O

O

OH

23

H

118


!! !

Scheme 56. Synthesis of [RuCl2(═C═C═(PCO))(PPh3)2] (47).

As discussed above for [RuCl2(═C═C═(FN))(PPh3)2] (45) and [RuCl2(═C═C═(AO))(PPh3)2]

(46), the dimerization of the resulting 16 VE allenylidene complex 47 occurs, depending on

the temperature and solvent. After purification by several cycles of recrystallization, two AB

quartet patterns can again be observed in the 31P NMR spectrum, which can be assigned to the

two different dimer structures (Scheme 57). Based on spectroscopic analysis, one of the

dimers contains two bridging and two terminal chlorido ligands, leading to a neutral 18 VE

complex (47A). The second dimer, on the other hand, is the monocationic complex that

contains three bridging chlorido ligands (47B). The positive charge is again compensated by a

chloride anion that is released during dimerization.

Scheme 57. Dimerized neutral ruthenium allenylidene complex 47A and mono cationic allenylidene complex

47B.

Ru

Ph3P Cl

PPh3Cl

C C C[RuCl2(PPh3)3] +Δ

THF

47

OOHO

28

H

Ru C C (PCO)

(PCO) C C Ru Cl

Cl

Cl

Cl

PPh3

Ph3PPPh3

Ph3PRu C C (PCO)

(PCO) C C Ru Cl

Cl

Cl

PPh3Ph3P

Ph3P PPh3

Cl

47A 47B

119


!! !

4.5 Ruthenium Heteroscorpionate Cumulenylidene Complexes as

Molecular Slides

Carbon nanotubes (CNTs)[310-312] are a key material in the nanotechnological progress[313] due

to their physical properties (electrical, optical, mechanical, etc.) and their nanometer scale

size.[314] The potential applications are ranging from electronics,[315] sensing[316] and energy

conversion[317-321] to biological functions.[322] The first discovered CNTs were multiwalled

carbon nanotubes (MWCNTs) consisting of several layers of tubes.[323] However, the leading

nanotubular structures in terms of possible applications are singlewalled carbon nanotubes

(SWCNTs), which can be described as small graphene like sheets that have been rolled up to

cylinders.[314] However, strong intermolecular bundling in SWCNTs leads to difficulties in

exfoliation of single strands and dispersing them afterwards in solution, especially in aqueous

media. The common ways are the covalent functionalization, i.e. functionalization of the open

edges or sidewall and the noncovalent interactions of aromatic molecules or macromolecules

with the sidewall. The advantage of noncovalent functionalization is the preservation of the

pristine sp2 hybrid state and the inherent electron transport properties.[324]

A wide variety of metallophthalocyanines and their CNT donor-acceptor systems are known

to literature and have been extensively reviewed.[314] Only few metal complex based systems

focusing on classical complex chemistry are known.[325-326] A first example was reported from

S. WONG and coworker, who described the addition of Wilkinson´s catalyst to oxidized

CNTs.[327] On the one hand, this increased the solubility in a variety of organic solvents and

exfoliation of larger nanotube bundles. On the other hand, the CNT worked as reusable

catalyst support for homogenous hydrogenation of cyclohexene, demonstrating the conserved

activity of the catalyst.[327] To name an example for the phthalocyanine based systems a

pyrene conjugate by D. GULDI et al. can be named.[328] The pyrene anchor allows the

noncovalent functionalization of CNTs and spectroscopic and photoelectrochemical

techniques were used to characterize the resulting adducts. Integration into photoactive

electrodes allowed the detection of stable and reproducible photocurrents.[328] A further

interesting approach is the reversible solubilization performed by A. IKEDA et al. based on a

[Cu(bpy-R2)2]2+ derivative bearing two cholesteryl groups.[329] The square planar copper(II)

complex allows π-π stacking interactions with the CNTs and leads to solutions of the

aggregated compound. Upon reduction with ascorbic acid, the coordination geometry of the

120


!! !

copper(I) center changes to tetrahedral and leads to precipitation of the CNTs. Reoxidation

with oxygen leads to the former geometry and again a stable solution is formed. This behavior

was tested in several cycles and allows the purification of metallic and semiconducting CNTs

via modulation of the redox state of the copper center.[329]

Recently, A. MARTI et al. reported a series of cationic ruthenium(II) bpy complexes that are

able to solubilize CNTs in aqueous media via noncovalent interactions.[330] The complexes

[Ru(bpy)2L1]2+, [Ru(bpy)2L2]2+ and [Ru(bpy)2L3Ru(bpy)2]4+ allow π-π stacking interactions

with the CNTs and allow high individualization in water (Figure 50).

Figure 50. Ligands L1 (dppz = dipyrido[3,2-a:2´.3´-c]-phenazine), L2 (dppn = benzo[i]dipyrido-[3,2-a:2´.3´-c]phenazine) and L3 (tpphz = tetrapyrido[3,2-a:2´.3´-c:3´´,2´-h:2´´´,3´´´-j]phenazine) used by A. MARTI et al.[330]

4.5.1 Polyaromatic Ruthenium Vinylidene Complexes

Given the interest of the BURZLAFF group in carbon-rich cumulenylidene ruthenium

complexes it was decided to synthesize a series of complexes that could be suitable for

noncovalent functionalization of carbon nanotubes. Due to the simplicity of synthesis the first

focus was on ruthenium vinylidene complexes bearing the bdmpza ligand. From previous

work it was known that for acetylene compounds with small substituents a mixture of A and

B type isomers is formed (see Scheme 28). Due to the sensibility of vinylidene complexes

towards oxygen the separation was avoided, as column chromatography was not favorable.

Thus two important questions are, if larger polyaromatic substituents stabilize the vinylidene

complexes and if the steric demand leads to selective formation of A type isomers.

With the phenylacetylene based vinylidene complex already known to literature the next

larger 2-ethynyl-6-methoxynaphthalene was picked as suitable precursor. Reaction of excess

amounts of the ethynyl substituted naphthalene with [Ru(bdmpza)Cl(PPh3)2] (14) in THF at

N

N N

N N

N N

N N

N N

N

N

N

L1 L2 L3

121


!! !

room temperature afforded an orange solution. Reducing of the solvent and cooling in the

freezer led to crystallization of the complex [Ru(bdmpza)Cl(═C═CH(6-methoxy-

naphthalene))(PPh3)] (48) (Scheme 58).

Scheme 58. Synthesis of the vinylidene complex [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48).

The 1H and 13C NMR spectrum exhibit only one set of signals characteristic for an A type

isomer indicating the influence of the steric demand of the substituent on the coordination

pattern. The 1H NMR spectrum of 48 shows the characteristic Hß, gained by the 1,2-H shift, at

5.11 ppm with a 4JH,P coupling constant of 4.7 Hz due to the PPh3 ligand. Furthermore, the

four methyl groups of the bdmpza ligands appear at 1.87, 2.39, 2.46 and 2.53 ppm and the

methoxy group at 3.88 ppm. The complete absence of further signals in the aliphatic region

proves the clean formation of one isomer. In the 13C NMR spectrum, the Cα signal is found at

363.2 ppm as a doublet with the coupling constant 2JC,P = 24.8 Hz and the Cß signal appears at

109.0 ppm as a doublet with the coupling constant 3JC,P = 3.0 Hz. The singlet at 37.3 ppm in

the 31P NMR spectrum confirms the assignment to an A type isomer in comparison to the

literature value of 37.5 ppm for the A type isomer of the complex [Ru(bdmpza)Cl-

(═C═CHPh)(PPh3)] (B type: 32.3 ppm).[61] The absence of vibrations between 2200 and

1800 cm–1 in the IR spectrum that would indicate alkyne moieties and the detection of the

potassium adduct of complex 48 (m/z 867.12 (100%) [M + K]+) in ESI-MS experiments

confirm the structure.

Based on this promising result, it was decided to synthesize a pyrene (Pyr) based vinylidene

complex for possible applications as noncovalent linker to CNTs. Pyrene derivatives linked

via a variety of spacer groups are widely spread in literature for CNT exfoliation and further

applications.[331-342] In organometallic chemistry one example of pyrene substituted complexes

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

H+

48

THF OMe

OMe

122


!! !

is reported by R. WINTER et al., demonstrating the non-innocent behavior of a ruthenium

vinylpyrenyl complex [(Pyr)CH═CH)Ru(CO)Cl(PPh3)3] allowing the large π ligand to

heavily participate in electron-transfer processes.[343] The first example of a pyrene based

vinylidene complex [Ru(κ1-OAc)(κ2-OAc)(═C═CH(Pyr))(PPh3)2] has been reported by J.

LYNAM et al. in 2012 in a study that emphasized the similar donor/acceptor properties of

vinylidene and isocyanide ligands.[344]

The synthesis of the corresponding bdmpza based ruthenium complex was achieved similar to

48. [Ru(bdmpza)Cl(PPh3)2] (14) and 2.2 equivalents of 1-ethynylpyrene were stirred in THF

at room temperature and after reducing the solvent and storing in the freezer the crystalline

complex [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) was obtained (Scheme 59).

Scheme 59. Synthesis of the vinylidene complex [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49).

Again only one set of signals characteristic for an A type isomer could be observed. The 1H NMR spectrum indicates that the larger pyrene substituent leads to a deshielding of Hß and

thus to an increased chemical shift with 5.78 ppm and a coupling constant of 4JH,P = 4.7 Hz.

The larger polyaromatic substituent shows less influence on the bdmpza ligand as the four

methyl substituents of 49 appear with 1.88, 2.39, 2.49 and 2.55 ppm in a similar region

compared to 48. In the 13C NMR spectrum, Cα and Cß give rise to doublets at 359.1

(2JC,P = 23.1 Hz) at 111.8 ppm (3JC,P = 2.6 Hz). The deshielding influence apparently only

influences Cß significantly as the Cα position appears further upfield shifted. In addition all 16

carbon atoms of the pyrene unit could be detected and the C–H multiplicities were assigned

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

H+

49

THF

123


!! !

via APT 13C NMR experiments. Further prove for the molecular structure is provided by the

singlet at 37.1 ppm in the 31P NMR spectrum and the detection of the molecular ion in ESI-

MS experiments (m/z 872.16 (100%) M+).

Finally, the geometry of complex 49 could be unambiguously characterized by a single

crystal X-ray structure determination. Crystals suitable for analysis were obtained from a

concentrated solution in CH2Cl2 layered with n-pentane stored in a Schlenk flask under argon

atmosphere with a septum allowing slow evaporation. The complex crystallizes as racemic

mixture in space group P–1 with one molecule CH2Cl2 and a strongly disordered molecule n-

pentane in the asymmetric unit (Figure 51).

Figure 51. Molecular structure of [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms (except the vinylidene proton) and solvent molecules have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.162(5), Ru–N(21) = 2.216(10), Ru–O(1) = 2.091(4), Ru–P = 2.322(4), Ru–Cl = 2.388(4), Ru–C(71) = 1.781(9), C(71)–C(72) = 1.315(10), C(72)–C(73) = 1.482(8); N(11)–Ru–N(21) = 81.3(2), O(1)–Ru–N(11) = 86.8(2), O(1)–Ru–N(21) = 83.7(2), O(1)–Ru–P = 87.05(17), P–Ru–Cl = 96.16(14), P–Ru–C(71) = 87.5(2), O(1)–Ru–C(71) = 97.5(3), N(11)–Ru–P = 173.61(13), N(21)–Ru–Cl = 86.2(2), Cl–Ru–C(71) = 92.3(2), Ru–C(71)–C(72) = 173.7(5), C(71)–C(72)–C(73) = 123.8(6).

Complex 49 shows the typical strained octahedral coordination of the bdmpza ligand with the

vinylidene ligand positioned trans to one pyrazole moiety. The angles and distances for the

O2O1

H72P

N22N12

C72

C71

Ru

N11N21

C73

Cl

a

b

c

124


!! !

bdmpza ligand are in good agreement with the previously reported bdmpza based vinylidene

complex [Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] (Tol = tolyl).[61] The vinylidene moiety

exhibits an angle ∠Ru–C(71)–C(72) = 173.7(5)° with bond lengths dRu–C(71) = 1.781(9) Å

and dC(71)–C(72) = 1.315(10) Å that are similar to the tolyl complex and the pyrene based

vinylidene complex [Ru(κ1-OAc)(κ2-OAc)(═C═CH(Pyr)(PPh3)2] (Table 11).[61, 344]

Complex Ru–Cα / [Å] Cα–Cß / [Å] ∠Ru–Cα–Cß / [°]

[Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)]

(49)

1.781(9) 1.315(10) 173.7(5)

[Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] 1.821(13) 1.347(18) 176.7(11)

[Ru(κ1-OAc)(κ2-OAc)(═C═CH(Pyr))-

(PPh3)2]

1.7863(16) 1.325(2) 174.72(14)

Table 11. Overview of characteristic bond lengths and angles of ruthenium vinylidene complexes [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49), [Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] and [Ru(κ1-OAc)(κ2-OAc)-(═C═CH(Pyr))(PPh3)2].[61, 344]

The torsion angle ∠C(61)–C(62)–C(63)–C(64) is a good indicator for possible conjugation

between the metal center and the pyrenyl unit. Complex 49 shows an angle of approximately

36°. This is quite large in comparison to the tolyl based complex [Ru(bdmpza)Cl-

(═C═CH(Tol))(PPh3)], which has a torsion angle of –18°. The rotation around the C(62)–

C(63) axis should not be hindered and in solution a planar arrangement might be achievable.

125


!! !

Figure 52. Absorption spectrum of 49 in CH2Cl2.

Figure 53. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 49; signal caused by CH2Cl2 is indicated by *.

400 600 800 1000 1200 1400 1600

0

5000

10000

15000

20000

25000

30000ε)[L)m

ol/1)cm

/1]

W ave leng th)[nm]

800 1000 1200 1400 16000

50

100

150

200

250

ε([L(m

ol.1(cm

.1]

W ave leng th([nm]

126


!! !

The absorption spectrum of complex 49 measured in CH2Cl2 shows the expected pattern for a

ruthenium vinylidene complex based on bdmpza (Figure 52). Two intense absorptions at 406

and 389 nm with high molar extinction coefficients (~21000 L mol–1 cm–1) can be attributed to

a metal-perturbed π–π* transition of the vinylidene moiety and ligand centered π–π*

transitions of the bdmpza and PPh3 ligand. In addition, a further weak absorption can be

observed in the NIR region at 921 nm (~200 L mol–1 cm–1) as reported for the vinylidene

complex [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31) (Figure 53).

Complexes 48 and 49 are remarkably stable in the presence of oxygen. This is noteworthy

since for possible applications like exfoliation and non-covalent functionalization of CNTs,

higher stability is required to simplify procedures.

127


!! !

4.5.2 Pyrene Based Allenylidene Complexes

As described in the previous chapters, ruthenium allenylidene complexes have proven to be

good candidates for remarkably stable organometallic compounds. A common disadvantage is

however, that the Cγ position needs to be stabilized with aryl substituents as protons or alkyl

substituents might lead to decomposition or rearrangement into vinylvinylidene

complexes.[157] Hence, pyrenophenone (50) was picked as conveniently available compound,

as it can be easily obtained by a Friedel-Crafts Acylation of pyrene with benzoyl chloride

(Scheme 60).[345-346] This compound has recently been employed as starting material for

several ethenes showing aggregation-enhanced excimer emission and electroluminescence.[346]

Furthermore, it is reported that 50 can undergo a Scholl Reaction creating an additional five-

or six-membered ring (Scheme 60, compound 52), depending on the publication.[291, 345, 347]

Therefore, it was decided to a) synthesize from pyrenophenone (50) the corresponding

propargyl alcohol 51 and convert the alcohol into the bdmpza based allenylidene complex and

b) explore the Scholl reaction and if possible synthesize a second propargyl alcohol 53 with

extended π system.

128


!! !

Scheme 60. Synthetic overview of propargyl alcohols 53 and 51 that should be available starting from pyrenophenone (50).[291, 345, 347]

Pyrenophenone (50) was synthesized according to literature via a Friedel-Crafts Acylation of

pyrene.[346] Since the synthesis of the compounds 52 and 53 was not as straight forward as

expected these compounds will be discussed in detail in chapter 4.6.

Crystals of pyrenophenone (50) suitable for a single crystal X-ray structure determination

could be obtained from slow evaporation of a solution of 50 in a mixture of CH2Cl2 and n-

hexane. The ketone crystallizes in space group P–1 and confirms the previously reported

connectivity of the pyrenyl residue (Figure 54). The keto moiety shows a bond length dC(1)–

O(1) = 1.2227(15) Å and the three surrounding angles are close to 120°, which is in good

agreement with free rotation around the single bonds.

O

OH

H

OO

or

or

OH OH

H

H

50

51

52

53

129


!! !

Figure 54. Molecular structure of pyrenophenone (50). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): C(1)–O(1) = 1.2227(15), C(1)–C(2) = 1.4989(17), C(1)–C(21) = 1.4964(18), C(2)–C(3) = 1.3960(18), C(3)–C(4) = 1.3836(19), C(21)–C(26) = 1.3943(19), C(25)–C(26) = 1.393(2); O(1)–C(1)–C(2) = 119.81(11), O(1)–C(1)–C(21) = 120.15(11), C(2)–C(1)–C(21) = 120.04(11).

a)

b)

Figure 55. π–π stacking interactions between two molecules of 50 from a) top view and b) side view.

In the solid state, strong π–π stacking interactions between two neighboring pyrene units can

be observed (Figure 55). The pyrene units overlap with approximately 75% of their surface

O1C22

C1

C23C21

C2

C3

C15

C4

C14

C5

C16

C24

C13

C6

C26

C17

C12

C7

C8C25

C11

C9

C10

130


!! !

area and an average distance of 3.46 Å can be observed. The plane of the phenyl moiety is

66.2° rotated against the plane formed by the pyrene and blocks further stacking interactions.

Reacting pyrenophenone (50) with ethynylmagnesium bromide in THF leads to the formation

of the brownish propargyl alcohol 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51), which can be

isolated after aqueous workup (Scheme 61).

Scheme 61. Synthesis of propargyl alcohol 51 starting from pyrenophenone (50).

The addition of the acetylene unit leads to the characteristic acetylene proton at 2.98 ppm and

the alcohol proton at 3.86 ppm in the 1H NMR spectrum. In the 13C NMR spectrum the

corresponding signals for the acetylene unit appear at 86.7 and 76.8 ppm and the sp3 carbon

atom results in a signal at 74.7 ppm. Further proof for the structure are ESI-MS experiments

that show the sodium adduct (m/z 355.11 (30%) [M + Na]+) and the IR spectrum that shows a

characteristic alkyne absorption at 2114 cm–1.

In the next step the corresponding pyrenophenone based allenylidene complex was

synthesized by addition of propargyl alcohol 51 to the complex [Ru(bdmpza)Cl(PPh3)2] (14)

in THF and stirring for 4 d at room temperature until a deep red color could be observed

(Scheme 62). The separation of the resulting allenylidene complexes

[Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A/54B) was achieved via column

chromatography with CH2Cl2/acetone = 1:1 yielding a purple isomer 54A (allenylidene trans

to pyrazole) and a red isomer 54B (allenylidene trans to carboxylate). Complex 54A shows

the Cα carbon atom as doublet at 304.6 ppm (2JC,P = 26.3 Hz) in the 13C NMR spectrum and

the Cβ gives rise to a singlet at 231.2 ppm in the expected region. The PPh3 ligand leads as

expected to a singlet in the 31P NMR spectrum at 32.2 ppm. Further proof for the allenylidene

moiety is the appearance of a characteristic absorption in the IR spectrum at 1918 cm–1 and

O

OH

H

5051

H MgBr+

1. THF2. H2O

131


!! !

the observation of a weak signal during ESI-MS experiments (m/z 960.19 (0.2%) [M]+). The

second structural isomer 54B shows downfield shifted values for Cα and Cβ with a doublet at

315.6 (2JC,P = 19.8 Hz) and a singlet at 241.9 ppm in the 13C NMR spectrum. Further evidence

for the allenylidene complex is the singlet in the 31P NMR spectrum at 32.2 ppm. However,

this signal has the identical value as structural isomer 54A and is usually the easiest indicator

for the geometry and allows in this case no statement. In the IR spectrum the typical

absorption appears at 1916 cm–1 and ESI-MS experiments allowed the observation of the

molecular ion (m/z 960.19 (14%) [M]+).

Scheme 62. Synthesis of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A, 54B).

Layering a solution of 54B in CH2Cl2 with n-hexane gave crystals suitable for a single crystal

X-ray structure determination. The compound crystallizes as racemic mixture in the space

group P–1. A molecular presentation of the compound is illustrated in Figure 56. As

mentioned previously for type B isomers the typical strained coordination of the bdmpza can

be observed and the allenylidene unit is coordinated trans to a pyrazole leaving the PPh3

ligand trans to the second pyrazole and the chlorido ligand trans to the carboxylate anchor.

Furthermore, this structure determination proves that the assignment to the A and B type

isomers is correct. The characteristic allenylidene angles are with ∠Ru–C(61)–

C(62) = 172.1(2) and ∠C(61)–C(62)–C(63) = 165.7°(3) strongly bent and show values similar

to the pentacenequinone based allenylidene complex 29B. In the case of complex 54B the π–

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

54A

54B

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

+14THF

51

OH

H

132


!! !

π stacking interactions between the neighboring pyrenyl moieties is reduced as the pyrenyl

units are showing less than half a pyrene overlap. However, π–π stacking interactions

between the pyrenyl moiety and one pyrazolyl unit can be observed, which seems to be

responsible for a larger distortion of the bdmpza ligand, the reduced linearity of the

allenylidene unit and the reduced planarity of the pyrenyl moiety.

Figure 56. Molecular structure of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1458(19), Ru–N(21) = 2.086(2), Ru–O(1) = 2.1477(16), Ru–P(1) = 2.3521(6), Ru–Cl(1) = 2.3999(7), Ru–C(61) = 1.850(2), C(61)–C(62) = 1.250(4), C(62)–C(63) = 1.366(4); N(11)–Ru–N(21) = 84.67(8), O(1)–Ru–N(11) = 84.85(7), O(1)–Ru–N(21) = 87.18(7), O(1)–Ru–P(1) = 86.81(5), P(1)–Ru–Cl(1) = 87.93(2), P(1)–Ru–C(61) = 95.68(7), O(1)–Ru–C(61) = 176.51(9), N(11)–Ru–P(1) = 171.03(6), N(21)–Ru–Cl(1) = 173.29(5), Cl(1)–Ru–C(61) = 91.96(8), Ru–C(61)–C(62) = 172.1(2), C(61)–C(62)–C(63) = 165.7(3).

The reduced planarity is apparent for C(72), the carbon atom that connects the pyrenyl unit to

Cγ, as it deviates from the plane calculated for all pyrenyl carbon atoms by 0.16 Å. The mean

distance between the pyrazolyl moiety and the plane calculated for the pyrenyl moiety is

3.48 Å, indicating the strong interactions possible for the pyrene unit. The arrangement

Cl1

O2

N11

N12

O1

Ru

C61P1

C62

N22

N21

C63

C72

133


!! !

suggests that the pyrenyl moiety should allow further π–π stacking interactions with carbon

allotropes in solution. However, the solubility is limited to polar solvents like acetone,

CH2Cl2, CHCl3 and mixtures containing aforementioned solvents and nonpolar solvents like

n-hexane and n-pentane as apparently the pyrenyl unit reduces the polarity of the complex in

comparison to the quinone based allenylidene complexes.

Cyclic voltammetric analyses were again performed on the pyrenophenone based allenylidene

complexes 54A and 54B (Chapter 8.2). Both compounds show a behavior similar to the

benzotetraphene based allenylidene complexes [Ru(bdmpza)Cl(═C═C═C(BT))(PPh3)] (37A,

37B). The oxidation process involving the ruthenium(II) center appears at 252 mV (54A) or

320 mV (54B). For 54A this process is reversible, however, for 54B this process is

irreversible and followed by a second oxidation process at higher potential that shows no

backward peak. The reduction processes are all best described as irreversible as the forward

scan shows signals similar to the previously reported allenylidene complexes within this

work. The backward scan however, shows extremely weak current intensities with larger peak

separations.

The UV/Vis spectra of the pyrenophenone based complexes 54A and 54B recorded in CH2Cl2

share several common features with the other ruthenium allenylidene complexes bearing the

bdmpza ligand (Figure 57). The strong absorptions at wavelengths less than ~300 nm have

been assigned to ligand-centered (LC) π–π* transitions involving the PPh3 and bdmpza

ligands. However, the intense absorption around 330 nm (54A: 336 nm, 29000 L mol–1 cm–1;

54B: 335 nm, 27000 L mol–1 cm–1) seems to correspond to the parent pyrenophenone moiety

50. An additional metal-perturbed π–π* transition can be observed at 543 nm for 54A with a

molar extinction coefficient around 24000 L mol–1 cm–1. This extinction coefficient is

noticeably larger in comparison to the allenylidene complexes discussed so far, although the

absorption maximum is close to the diphenyl based allenylidene complex

[Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] (519 nm, 17000 L mol–1 cm–1).[61] In comparison to the

complex of type A, complex 54B shows with an absorption at 523 nm a decrease in

absorption energy and the extinction coefficient (19000 L mol–1 cm–1) is in the common range

if compared to 37A. Again absorption bands are observed in the NIR region around 1050 nm

(45A) and 900 nm (45B) that can be attributed to HOMO–LUMO transitions and can best be

described as MLCTs (Figure 58).

134


!! !

Figure 57. Absorption spectrum of 54A (black) and 54B (grey) in CH2Cl2; signal caused by switching lamp is indicated by *.

Figure 58. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for of 54A (black) and 54B (grey); signal caused by CH2Cl2 is indicated by *.

300 400 500 600 700

0

10000

20000

30000

40000)ε)[L

)mol

/1)cm

/1]

W ave leng th)[nm]

*

800 900 1000 1100 1200 13000

20

40

60

80

100

120

140

160

180

200

*

**ε*[L

*mol

01*cm

01]

W ave leng th*[nm]

*

135


!! !

4.5.3 Carbon-Rich Ruthenium Allenylidene Complexes Bearing the PTA Ligand

For possible applications of the carbon-rich allenylidene complexes, e.g. in the exfoliation of

carbon allotropes, solubility in aqueous media or at least in alcohols is required. Hence, it was

decided to adapt the ligand sphere of the ruthenium precursor to allow the formation of water-

soluble allenylidene complexes.

Two types of water-soluble phosphines are commonly used in organometallic chemistry. On

the one hand, sulfonated derivatives of the classical triphenylphosphine ligand like the

triphenylphosphine-3,3′,3′′-trisulfonic acid trisodium salt (TPPTS) and on the other hand the

adamantane derived 1,3,5-triaza-7-phosphaadamantane (PTA). For ruthenium allenylidene

complexes, especially the PTA ligand has proven successful, as the cyclopentadienyl and

hydridotrispyrazolyl based complexes [Ru(Cp)(═C═C═CPh2)(PTA)(PPh3)](CF3SO3)[348] and

[Ru(Tp)(═C═C═CPh2)(PTA)(PPh3)]PF6[261] have been reported. Precursors for these

complexes are the chlorido complexes [Ru(Cp)Cl(PTA)(PPh3)][349] and [Ru(Tp)Cl-

(PTA)(PPh3)].[350] Reaction of the latter with propargyl alcohols led to the formation of

cationic allenylidene complexes due to chloride abstraction. As for the bdmpza based

ruthenium triphenylphosphine complex [Ru(bdmpza)Cl(PPh3)2] (14) usually one phosphine

ligand can be replaced easily, it was decided to synthesize the PTA analogues

[Ru(bdmpza)Cl(PTA)(PPh3)] (55) and [Ru(bdmpza)Cl(PTA)2] (56), each (Scheme 63).

136


!! !

Scheme 63. Synthesis of [Ru(bdmpza)Cl(PTA)(PPh3)] (55) and [Ru(bdmpza)Cl(PTA)2] (56).

The reaction of [Ru(bdmpza)Cl(PPh3)2] (14) with one equivalent PTA in THF under reflux

allows the almost quantitative exchange of one PPh3 ligand. Complex 55 shows in the IR

spectrum the characteristic carboxylate absorption at 1661 cm–1 in CH2Cl2. The 1H NMR

spectrum shows two multiplets around 7.66 and 7.26 ppm that can be assigned to the PPh3

ligand and the PTA ligand leads to four quartets showing an AB pattern in the aliphatic region

at 4.37, 4.23, 3.89 and 3.78 ppm. The bdmpza ligand exhibits two asymmetric protons in the

4- and 4´ position indicating the expected asymmetric structure. The 13C NMR spectrum

repeats the conclusions drawn from the proton NMR spectrum as the characteristic doublets

from the PTA ligand at 73.1 (3JC,P = 5.8 Hz) and 52.4 ppm (1JC,P = 14.8 Hz) can be observed as

well as four asymmetric methyl substituents at 16.7, 14.0, 11.5 and 11.5 ppm. Further

evidence is the coupling pattern in the 31P NMR spectrum showing one doublet of the PPh3

ligand at 41.2 ppm (2JP,P = 43.5 Hz) and one doublet of the PTA ligand at –27.5 ppm

(2JP,P = 43.5 Hz) caused by the two different phosphine ligands. Additional ESI-MS

experiments show the presence of the molecular ion as major observable compound (m/z

803.17 (100%) M+). Complex 55 is nicely soluble in polar solvents like chlorinated solvents,

THF and alcohols, but unfortunately insoluble in water.

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P PPh3

NN N

N

Me

Me

Me

MeRu

OO

Cl

NN

N

P

NN

N

P

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P

NN

N

P+ 1.0 eq. PTA

+ 2.2 eq. PTA

- PPh3

- 2 PPh3

55

56

137


!! !

Figure 59. Molecular structure of [Ru(bdmpza)Cl(PTA)(PPh3)] (55). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.184(3), Ru–N(21) = 2.184(3), Ru–O(1) = 2.112(2), Ru–P(1) = 2.2621(10), Ru–P(2) = 2.3027(10), Ru–Cl(1) = 2.4048(9); N(11)–Ru–N(21) = 79.22(11), O(1)–Ru–N(11) = 87.42(10), O(1)–Ru–N(21) = 86.97(10), O(1)–Ru–P(1) = 86.90(7), P(1)–Ru–Cl(1) = 93.08(4), P(1)–Ru–P(2) = 91.86(4), N(11)–Ru–P(1) = 170.19(8), N(21)–Ru–Cl(1) = 88.84(8).

Crystals of 55 suitable for single crystal X-ray structure determination could be obtained from

a concentrated solution in CH2Cl2 layered with n-hexane (Figure 59). The complex

crystallizes as enantiomeric mixture in space group Pbca with one co-crystalized CH2Cl2 per

asymmetric unit. As expected the PPh3 and PTA ligand are similar to the parent ruthenium

complex [Ru(bdmpza)Cl(PPh3)2] (14) positioned trans to the pyrazolyl moieties, thus the

chlorido ligand is positioned trans to the carboxylate anchor. The smaller Tolman cone angle

and the resulting reduced steric demand of the PTA ligand in comparison to the PPh3 ligand

leads to a Ru–P(1) bond length of 2. 2621(10) Å and a longer Ru–P(2) bond length of

2.3027(10) Å. The reduced repulsion between the two phosphine ligands is also responsible

for a smaller angle ∠O(1)–Ru–P(1) = 86.90(7)° in comparison to the larger PPh3 ligand with

the angle ∠O(1)–Ru–P(2) = 93.20(7)°. The angle between both phosphine ligands is in

consequence reduced from 94.12(6)° for [Ru(bdmpza)Cl(PPh3)2] (14) to 91.86(4)° for

Cl1

N11 N21

N22N12

Ru

P2

P1

O1

O2

a

b

c

138


!! !

complex 55.[61] However, the rigid structure of the bdmpza ligand leads to an almost

symmetrical coordination of the bdmpza ligand with identical ruthenium–nitrogen bond

lengths of 2.184(3) Å for Ru–N(11) and Ru–N(12).

In analogy the synthesis of [Ru(bdmpza)Cl(PTA)2] (56) was attempted starting from

[Ru(bdmpza)Cl(PPh3)2] (14) with two equivalents PTA either in THF or toluene under reflux.

The reaction formed a mixture of 56 and [Ru(bdmpza)Cl(PTA)(PPh3)] (55). Employing 2.2

equivalents of PTA and longer reaction times in THF under reflux led to a full conversion to

56. However, it was not possible to purify complex 56 convincingly as the excess amounts of

PTA could not be removed. Complex 56 shows high solubility in water as expected from the

similar cyclopentadienyl ruthenium complex [Ru(Cp)Cl(PTA)2].[351] The 1H NMR spectrum

shows a triplet at 4.17 and a multiplet around 4.01 ppm that can be assigned to the two

coordinated PTA ligands. The signals of the bdmpza ligand seem to indicate that the reduced

steric demand of the PTA ligand might allow a dynamic exchange between the two PTA

ligands and the chlorido ligand as for the protons in position 4 of the pyrazole moiety only

one signal at 5.79 ppm can be observed but the four methyl substituents lead to one singlet

consisting of two methyl substituents at 1.80 ppm and two further singlets at 2.12 and

2.21 ppm representing one methyl group each. The 13C NMR spectrum shows a symmetrical

complex as only one set of signals can be observed as the Me3 and Me3´ substituents give one

signal at 13.6 ppm and in consequence the Me5 and Me5´ substituents lead to one signal at

11.6 ppm. In the 31P NMR spectrum a triplet of the PTA ligand at –53.8 ppm can be observed

that cannot be conclusively explained by the suspected structure. Preliminary experiments

showed that the reaction of 56 with 9-ethynyl-9-fluorenol does not allow the formation of

allenylidene complexes as the formation of a complicated mixture of compounds can be

observed. The hot reaction mixture shows an intense red color that disappears upon cooling to

room temperature, which is in good agreement with previous reports. According to these,

PTA, if present in solution, can add to Cα of allenylidene ligands hereby forming an α-

phosphonioallenyl species.[352] Hence it was decided to focus on [Ru(bdmpza)Cl(PTA)(PPh3)]

(55) as precursor as the reaction with propargyl alcohols should displace the PPh3 ligand that

has previously not shown any addition reactions to the allenylidene moiety.

Reacting 55 with twofold excess of 9-ethynyl-9-fluorenol in THF at room temperature for two

days did not lead to any formation of an allenylidene complex in contrast to the

[Ru(bdmpza)Cl(PPh3)2] (14) based fluorenyl substituted complex [Ru(bdmpza)Cl-

(═C═C═(FN))(PPh3)] (7A/7B). However, heating to reflux for 16 h allowed the formation of

139


!! !

a deep red allenylidene complex [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B) that upon

heating for further 24 h under nitrogen atmosphere decomposes (Scheme 64). The

implementation of the polar PTA ligand led to a strongly decreased Rf value for the

CH2Cl2/acetone eluent mixture for column chromatography, which is usually employed in the

purification of bdmpza based allenylidene complexes. Therefore, a solvent mixture of

acetone/water (95:5 v/v) was used to separate the allenylidene complexes from the crude

product, yielding two fractions. The first purple complex was assigned to the structure 57A

and the second red complex was assigned to 57B. Due to the extremely low yields, i.e. 11%

for 57A and below 1% for 57B, only complex 57A could be characterized satisfyingly.

Complex 57A shows the typical IR absorption at 1923 cm–1 in CHCl3 indicating the

successful formation of an allenylidene complex. In the 1H NMR spectrum the asymmetric

bdmpza ligand can be observed, as four methyl substituents are present at 2.89, 2.58, 2.51 and

2.24 ppm. The PTA ligand is characterized by one singlet at 4.52 ppm and a doublet at

4.24 ppm (2JH,H = 6.8 Hz). In the 13C NMR spectrum the allenylidene moiety is

unambiguously assigned to the doublet at 294.2 ppm (2JC,P = 26.0 Hz, Cα) and a singlet at

230.3 ppm (Cβ). The remaining aromatic protons can be assigned to the fluorenyl moiety and

the bdmpza ligand confirms the asymmetric pattern with four different chemical shifts of

16.1, 13.0, 11.5 and 11.3 ppm. The PTA ligand shows the expected two doublets at 73.8

(3JC,P = 6.0 Hz, N–CH2–N) and 52.1 ppm (1JC,P = 18.0 Hz, P–CH2–N) confirming free rotation

around the Ru–P bond in the NMR timescale. A strong indication for the assignment of the

obtained complex is the splitting of the signal of the carbon atom in 4 position of the pyrazole

moiety. This behavior leading to a doublet at 108.4 ppm (4JC,P = 2.7 Hz, C4) is commonly

observed for type A isomers of bdmpza based ruthenium cumulenylidene complexes (for

comparison see: 49, 54A). Finally the 31P NMR spectrum shows one singlet at –37.8 ppm,

which provides further proof that the PPh3 ligand has been replaced and only the PTA ligand

is present in complex 57A.

140


!! !

Scheme 64. Synthesis of [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A, 57B).

The comparison of the solubility between [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (7A/7B) and

[Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A) shows that the exchange of the PPh3 ligand with

PTA increases the solubility of allenylidene complex 57A in polar solvents like ethanol and

methanol. However, the exchange does not significantly increase the solubility in water as

only aqueous solutions with approximately 10 vol% DMSO were stable for extended periods

of time without precipitation.

In analogy to the synthesis described above, a reaction of 1-phenyl-1-(pyren-1-yl)prop-2-yn-

1-ol (51) with [Ru(bdmpza)Cl(PTA)(PPh3)] (55) was examined (Scheme 65). In theory the

targeted allenylidene complex could exfoliate carbon allotropes in a wide range of polar

solvents if a similar solubility to 57A could be achieved. The reaction mixture was again

heated for 16 h under reflux and a complicated mixture of complexes was obtained. The

previously described complex [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A/54B) and the

carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] could be easily removed via column

chromatography with CH2Cl2/acetone (1:1 v/v) as eluent. The desired complex [Ru(bdmpza)-

Cl(═C═C═C(PyrPh))(PTA)] (58A/58B) could be eluted with a solvent mixture of

acetone/methanol (9:1 v/v) in poor yields. 58A was obtained as purple compound in 5% yield

allowing the characterization by spectroscopic methods.

NN N

N

Me

Me

Me

MeRu

OO

C ClPTA

NN N

N

Me

Me

Me

MeRu

OO

CClPTAC

CC

C

57A57B

++ THF

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P

NN

N

P

55

OH

H

141


!! !

Scheme 65. Synthesis of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PTA)] (58A, 58B).

The strong purple color of the obtained complex as well as the characteristic absorption at

1919 cm–1 in CHCl3 indicate the successful formation of an allenylidene complex. The NMR

data recorded was assigned to a type A isomer. In the 1H NMR spectrum, the aromatic

protons can be observed between 8.50 and 7.32 ppm similar to the complex [Ru(bdmpza)Cl-

(═C═C═C(PyrPh))(PPh3)] (54A/54B). The PTA ligand shows one doublet at 4.14 ppm

(2JH,H = 13.1 Hz) that consists of three protons and a multiplet around 3.94 ppm consisting of

nine protons. In comparison to complex 57A this indicates a reduced symmetry of the PTA

ligand and possibly a hindered rotation around the Ru–P axis due to the sterically demanding

pyrenyl moiety. Furthermore the methyl substituents of the bdmpza ligand are spread over a

wider range in the 1H NMR spectrum at 2.78, 2.51, 2.29 and 1.97 ppm. In the 13C NMR

spectrum the allenylidene moiety leads to signals in the expected region with a doublet at

300.6 ppm (2JC,P = 26.3 Hz, Cα) and a singlet upfield shifted at 228.0 ppm (Cβ). As described

for complex 57A the splitting of the carbon signal in 4 position of the pyrazole moiety at

108.0 ppm (4JC,P = 3.5 Hz, C4) confirms the assignment to the suggested structure. The PTA

ligand is, in the 13C NMR spectrum, symmetrical with two doublets at 73.3 (3JC,P = 6.1 Hz, N–

CH2–N) and 52.0 ppm (1JC,P = 17.5 Hz, P–CH2–N) indicating that the unexpected results of

the 1H NMR spectrum indicate a dynamic behavior of the PTA ligand. The shorter relaxation

NN N

N

Me

Me

Me

MeRu

OO

C ClPTA

NN N

N

Me

Me

Me

MeRu

OO

CClPTAC

CC

C

58A

58B

+THF

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P

NN

N

P

55

OH

H

+

51

142


!! !

times of the 1H nuclei in comparison to the 13C nuclei might explain the difference in the

observed symmetry in solution. The 31P NMR spectrum shows a series of multiplets

indicating possible protonation equilibria in solution resulting in unsymmetrical PTA ligands.

Furthermore, ESI-MS experiments detected the corresponding molecular ion (m/z 803.17

(100%) [M]+).

As can be seen from the solvents used for column chromatography the larger pyrenyl

substituent decreases the solubility in highly polar solvents like water. Complex 58A shows

high solubility in ethanol and methanol but is completely insoluble in water. Furthermore, the

combination of the smaller PTA ligand in comparison to PPh3 and the large pyrenyl

substituent decreases the stability of complex 58A. The PPh3 based complex

[Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A) is stable in CH2Cl2 solution for several

weeks without any noticeable decomposition. The PTA based complex [Ru(bdmpza)Cl-

(═C═C═(FN))(PTA)] (57A) did not show any signs of decomposition within days in CH2Cl2.

However, complex 58A completely decomposes under aerobic conditions in less than three

days and possibly forms a complex [Ru(bdmpza)Cl(CO)(PTA)] (59) as indicated by the

appearance of an IR absorption band at 1979 cm–1 in CHCl3. This value is in good agreement

with the comparable carbonyl complexes [Ru(Tp)Cl(CO)(PTA)][352] (1963 cm–1 (KBr)) and

[Ru(bdmpza)Cl(CO)(PPh3)][61] (1969 cm–1 (CH2Cl2)).

While the synthesis of PTA substituted bdmpza based ruthenium allenylidene could be

demonstrated the low yields, the reduced stability and the remaining insolubility in water is a

major drawback. Therefore, water-soluble carbon-rich ruthenium allenylidene complexes

bearing the bdmpza ligand seem inconvenient and the use of cationic Cp based allenylidene

complexes might be required. Thus complexes of the general formula

[Ru(Cp)(═C═C═CAr2)(PPh3)(PTA)]X or [Ru(Cp)(═C═C═CAr2)(PTA)2]X (X = PF6–,

CF3SO3–) might be target molecules for future studies.

143


!! !

4.6 Arenium Cation or Radical Cation Pathway: Mechanistic Analysis and

Experimental Proof of the Scholl Reaction of Pyrenophenone

The first report on oxidative coupling was published in 1868 by J. LÖWE,[353] 42 years later

R. SCHOLL reported that anhydrous AlCl3 was a suitable medium for several aromatic

compounds to undergo oxidative coupling.[295] Given the recent interest in polycyclic aromatic

hydrocarbons (PAHs) oxidative aromatic coupling reactions and the classical Scholl Reaction

have been extensively reviewed by H. BUTENSCHÖN and D. GRYKO.[354] The difference

between both reactions has since the earlier review by A. BALABAN and C. NENITZESCU lost a

clear demarcation as the term Scholl reaction is oftentimes used as synonym for oxidative

coupling reactions of electron-rich aromatic compounds.[355]

The versatility of the reaction parameters has allowed the formation of up to 126 bonds in one

step as reported by K. MÜLLEN and co-workers.[356] The broad applications for intramolecular

C–C bond formation has been demonstrated in a series of papers. One of the most prominent

PAHs remains hexa-peri-benzocoronene (HBC), which can be obtained via different

precursors,[357-359] but also the intermediary phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3-

pqrst]pentaphene could be isolated,[360] which indicates a stepwise reaction mechanism in

comparison to a concerted planarization. For the reaction mechanism, two pathways are

discussed in dependence of the substrate and reaction conditions in literature. On the one

hand, the Arenium Cation Pathway, which has been calculated by B. KING as favourable

pathway for the formation of HBC with oxidizing agents like FeCl3,[361-363] and on the other

hand, the Radical Cation Pathway, which is reported by R. RATHORE for DDQ as oxidant.[364-

365] H. BUTENSCHÖN and D. GRYKO concluded their review about the mechanistic debate with

the statement that the Arenium Cation Mechanism might be operating in the presence of

strong Lewis acids like AlCl3 as isolated intermediates are still missing.[354]

As mentioned earlier the Scholl reaction of pyrenophenone (50) is known to literature,

however, the results obtained differ significantly from the literature and will be discussed in

detail in the following section.

The first report on the reaction of pyrenophenone (50, see Scheme 66) in a mixture of

AlCl3/NaCl was in 1937, when H. STREECK and H. VOLLMANN demonstrated that these

conditions were favourable to the previously employed pure AlCl3.[345] After complicated

144


!! !

workup they obtained a yellow ketone that they described as 60. However, S. DICKERMAN and

W. FEIGENBAUM revaluated the obtained compound in 1966 and proposed that the given

structure is not in agreement with the IR spectrum obtained, as the keto moiety shows an

absorption at 1695 cm–1 in CHCl3 representative for a 9-fluorenone, indicating that the

compound 64 was obtained.[347] C. RÜCHARDT and co-worker prepared the same compound

after a “cumbersome workup” in 1999 and assigned it in analogy to the original report to

structure 60.[291]

Scheme 66. Radical Cation and Arenium Cation Pathway for the intramolecular Scholl Reaction of pyrenophenone (50).

Hence, the synthesis was performed according to the original literature procedure starting

from pyrenophenone (50).[345] However, during workup several well-ordered aliphatic protons

O

∗∗ CH2

OO

O

O

O

H H

H HH H

O

O

+HCl-Cl-

-e-

+Cl-

-HCl

5060

61

62

6364

65

66

+Cl-

-HCl, -H

Radical CationPathway

Arenium CationPathway

- H2

145


!! !

were observed in the 1H NMR spectrum of the crude product that could not be explained by

the proposed products. Several steps of column chromatography allowed the isolation of

compound 64 in low yields, which shows identical spectroscopic properties to the data

reported by C. RÜCHARDT, S. DICKERMAN and W. FEIGENBAUM.[291, 347] A single crystal X-ray

structure determination of 64 confirmed the suggested formation of a five-membered ring

(Figure 60), as opposed to the initially reported six-membered ring by H. VOLLMANN et al.[345]

11H-indeno[2,1-a]pyren-11-one (64) crystallizes in space group P212121 as planar compound

with an almost symmetrical cyclopentanone ring.

Figure 60. Molecular structure of 64. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): C(1)–O(1) = 1.213(3), C(1)–C(2) = 1.499(4), C(1)–C(21) = 1.485(4), C(2)–C(3) = 1.399(4), C(3)–C(4) = 1.378(4), C(21)–C(26) = 1.413(4), C(25)–C(26) = 1.379(4); O(1)–C(1)–C(2) = 128.0(3), O(1)–C(1)–C(21) = 126. 5(3), C(2)–C(1)–C(21) = 105.5(2).

A second red slightly fluorescent compound could be isolated that was responsible for the

previously observed aliphatic proton signals. The structure could be unambiguously assigned

to the racemic mixture of compound 63 via 1H and 13C NMR spectroscopy, IR spectroscopy,

mass spectrometry and a single crystal X-ray structure determination. The compound

crystallizes in space group Pna21 as enantiomeric pure form and is depicted as (S)-enantiomer

in Figure 61. Since no heavy atoms but only oxygen, carbon and hydrogen atoms are present,

based on the Flack parameter no reliable decision regarding the stereochemistry can be made.

In comparison to 64 compound 63 shows a reduced pyrenyl moiety leading to a non-planar

geometry with an angle of 108.9° between the methylene carbon atom and its neighbouring

carbon atoms.

C10C9

C11

C8

C12C17

C7

C13

C6

C16

C14

C5

C15

C4

H4

C2C3

O1

C1

C26

C21

C25

C22

C24

C23

146


!! !

Figure 61. Molecular structure of 63 depicted as (S)-enantiomer. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): C(1)–O(1) = 1.222(3), C(1)–C(2) = 1.476(4), C(1)–C(21) = 1.490(4), C(2)–C(3) = 1.525(4), C(3)–C(4) = 1.493(5), C(21)–C(26) = 1.398(4), C(25)–C(26) = 1.380(4); O(1)–C(1)–C(2) = 128.5(3), O(1)–C(1)–C(21) = 126.1 (3), C(2)–C(1)–C(21) = 105.4(2).

As indicated in the introduction, it is commonly accepted as working theory and backed by

computational studies for the Scholl reaction that the Arenium Cation Mechanism is favoured

in the presence of AlCl3. Compound 63 is however, the first isolated intermediate that

unambiguously can be assigned to the Arenium Cation Pathway as no protonation in the

6-postion of the pyrenyl moiety can be explained via the Radical Cation Pathway (Scheme

66). Previous reports have shown that the presence of HCl in AlCl3 leads to the initial

protonation of pyrenophenone (50) forming cation 61.[366] After C–C bond formation cation

62 is deprotonated at the phenyl moiety to regain aromaticity and leads to the partially

reduced pyrenyl moiety in compound 63. This protonation-deprotonation cycle is in good

agreement with an expected catalytic protonation step that has been previously calculated.

Apparently, the oxidation step to obtain compound 64 under dehydrogenation appears only

partially, explaining the low yields that were reported previously. In addition to the described

products, large amounts of black insoluble residue, unsubstituted pyrene and dibenzoylpyrene

can be observed confirming a series of side reactions. Currently calculations are performed by

C. WICK form the group of T. CLARK at the CCC (Computer Chemie Centrum) to gain further

insights into the transition states and possible radical intermediates.

C11

C10

C9

C13

C12

C8

C14

C17

C7

C16

H4A

C15

C6C5

O1

C2

C4

C1

H4B

C3

C21

C26

C22

H3

C25

C23

C24

147

5 SUMMARY AND OUTLOOK

148

!Summary and Outlook

!! !

In previous work of the BURZLAFF group, the design of suitable N,N,O ligands for a wide

variety of applications ranging from catalysis to bioinorganic model compounds has been

extensively investigated. Especially the methyl substituted bis(3,5-dimethylpyrazol-1-yl)

acetate (bdmpza) ligand has shown manifold chemistry, comparable to the anionic

cyclopentadienyl (Cp) and hydridotris(pyrazol-1-yl)borato (Tp) ligand.

In the first part of this thesis the new tricarbonylmanganese(I) complexes bearing the

heteroscorpionate ligand 3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (bpzp) and the tris-

imidazole complex [Mn(CO)3(HIm)3]Br were prepared. These and the literature-known

tricarbonyl complexes based on bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza), bis(pyrazol-

1-yl)acetate (bpza), 3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (bdmpzp) and [MnBr(CO)3-

(Hpz)2] were tested for their potential to act as photoactivable CO-releasing molecules

(PhotoCORMs) by the UV/Vis spectroscopy-based myoglobin assay. The manganese(I)

complexes of the monodentate imidazole and pyrazole ligands lack stability in solution and

show fast CO-release already in the dark. In the four heteroscorpionate complexes, the

substitution pattern and the chain length of the carboxylate moiety have a pronounced

influence on the stability in solution and the CO-release properties.

The second part of this work contains the synthesis and characterization of ruthenium

carbonyl complexes bearing heteroscorpionate ligands and was accomplished in collaboration

with S. TAMPIER and G. TÜRKOGLU. The syntheses of the two dicarbonyl complexes !

[Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl(CO)2] (10), !bearing a bis(3,5-

dimethylpyrazol-1-yl)acetato (bdmpza) or a 2,2- !bis(3,5-dimethylpyrazol-1-yl)propionato

(2,2-bdmpzp) scorpionate! ligand, have been previously described by S. TAMPIER and

G. TÜRKOGLU and following the same procedure the bis(pyrazol-1-yl)acetato (bpza) based

complex has been obtained. All three complexes were synthesized by reacting the! polymer

[RuCl2(CO)2]n with the potassium salt of the corresponding ligand (K[bdmpza], K[bpza] or

K[2,2-bdmpzp]). !Reaction of the acid Hbdmpza with [Ru3(CO)12] resulted in the !formation of

two structural isomers of a hydrido complex, [Ru !(bdmpza)H(CO)2] (11A/11B). Under aerobic

conditions the conversion of ! [Ru(bdmpza)H(CO)2] (11A/11B) to form the Ru(I) dimer

[Ru(bdmpza)(CO)(μ2-CO)]2 (12) seems to be hindered compared to the η5-C5H5 (Cp)

analogues. Dimer 12 was obtained via reaction of ! Hbdmpza with catena-[Ru(OAc)(CO)2]n

instead.

149


!! !

In the third part, a topic with bioinorganic focus was described. The reaction of

[Ru(bdmpza)Cl(PPh3)2] with aminophenol (APH) and 2-amino-4,6-di-tert-butylphenol

(tBuAPH) led to the corresponding complexes [Ru(bdmpza)Cl(ISQ)(PPh3)] or

[Ru(bdmpza)Cl(IBQ)(PPh3)] (16) and [Ru(bdmpza)Cl(tBuISQ)(PPh3)] or [Ru(bdmpza)Cl-

(tBuIBQ)(PPh3)] (15). In both complexes the uncommon κ1 coordination of the imino moiety

was observed and not the expected κ2 N,O coordination. From the single crystal X-ray

structure determination and the diamagnetic NMR spectra it was concluded that the complex

could best be described as [Ru2+–IBQ] or [Ru3+–ISQ] with strong antiferromagnetic coupling.

This gives rise to the question of the occurring redox chemistry as future work will have to

determine the dependence of the reaction on oxidizing agents and in consequence an

optimization of the reaction.

In the main part of this work a series of ruthenium allenylidene complexes bearing

polyaromatic substituents was prepared starting from [Ru(bdmpza)Cl(PPh3)2] (14). Reacting

14 with 1,1-bis-(3,5-di-tert-butylphenyl)-1-methoxy-2-propyne results in the formation of two

structural isomers of an allenylidene complex [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)]

(19A/19B) and the related carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A/18B).

Conversion of 9-ethynyl-9-fluorenol led to the corresponding allenylidene complex

[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) (FN = fluorenyl). Based on anthraquinone a

new synthetic route towards 10-ethynyl-10-hydroxyanthracen-9-one via the TMS protected

propargyl alcohol is described. Starting thereof, the synthesis of the allenylidene complex

([Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B) (AO = anthrone) is reported and showed

interesting π-π stacking interactions in the solid state between two anthrone units. In a next

step the larger acene pentacenequinone was used as starting material in cooperation with A.

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

15 (IBQ); R = tBu16 (IBQ); R = H

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

15 (ISQ); R = tBu16 (ISQ); R = H

or

RR

RR

150


!! !

WATERLOO of the group of R. TYKWINSKI to synthesize [Ru(bdmpza)Cl(═C═C═(PCO))-

(PPh3)] (29A/29B) (PCO = pentacenone). In comparison with other ruthenium allenylidene

complexes, the Ru–C3 chain was extremely bent and these distorted angles, which were

unprecedented for mononuclear ruthenium allenylidene complexes, might have be caused by

crystal packing effects. As again only dimerization in the solid state could be observed, it was

decided to use polyaromatic ketones with extended π systems along the allenylidene

direction. As suitable compound 7H-benzo[no]tetraphen-7-one (34) was used and the route

from 34 towards the propargyl alcohol 7-ethynyl-7H-benzo[no]tetraphen-7-ol (36) and the

transformation into the allenylidene complex [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)]

(37A/37B) (BT = benzotetraphene) was described. Especially complex 37A is a promising

candidate for future studies metal-tuned FET studies, since several short-contact interactions

between the benzotetraphene throughout the entire crystal could be observed possibly

allowing charge transport along this axis. All aforementioned complexes showed weak

absorptions in the NIR region that could be assigned to forbidden MLCT transitions.

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CR2CR2 =

tBu

tBu

tBu

tBu

O O

NC CN

CNCN

19A/19B20A/20B

25A/25B 29A/29B

31 37A/37B

H

151


!! !

TD-DFT calculations that were performed by E. HÜBNER starting from the single crystal X-

ray structure determinations proved this assignment to transitions involving mainly the

HOMO–2, HOMO–1, HOMO and LUMO. In addition cyclic voltammetry has been used to

probe the electrochemistry of each complex. In summary, it was shown that the arrangement

observed for several compounds in the crystalline state renders the presented complexes

promising candidates for metal-tuned FETs or “organic” metal–semiconductor field-effect

transistors (OMESFETs), whereas the electron-accepting ability and low-energy absorption

characteristics might be tuned for an application in solar cells. Both aspects present an

appealing starting point for new kinds of functionalized organic semiconductors. In an

attempt to obtain an allenylidene complex starting from 2-(13-(dicyanomethyl)-13-

ethynylpentacen-6(13H)-ylidene)malononitrile (30), the corresponding vinylidene complex

[Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (PCN = pentacenone based tetracyano derivative)

(31) was isolated. The strong push-pull character of the cyano substituents leads to an

intensive blue color of the vinylidene complex 31. For comparisons and possible catalytic

applications the 16 VE ruthenium allenylidene complexes [RuCl2(═C═C═(FN))(PPh3)2] (45),

[RuCl2(═C═C═(AO))(PPh3)2] (46) and [RuCl2(═C═C═(PCO))(PPh3)2] (47) were prepared.

However, in solution all three showed the tendency to form a mixture of a cationic and a

neutral dimeric 18 VE complex, leading to an unfavorable equilibrium.

The work presented in the next chapter focuses on the preparation of ruthenium

cumulenylidene complexes that might be suitable for exfoliation of carbon nanotubes.

Therefore, the two vinylidene complexes [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))-

(PPh3)] (48) and [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) were prepared. While remarkably

stable for ruthenium vinylidene comlexes, the degradation within days was a major drawback

NN N

N

Me

Me

Me

MeRu

OO

CClPTA CC

57A

NN N

N

Me

Me

Me

MeRu

OO

CClPTA CC

58A

NN N

N

Me

Me

Me

MeRu

OO

CClPPh3 CC

54A

152


!! !

for both complexes. Therefore, the idea was to again focus on allenylidene complexes and in

this case the pyrene substituted propargyl alcohol 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51)

was prepared from pyrenophenone (50). The corresponding ruthenium allenylidene complex

[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B) was isolated and showed absorption

propeties closely related to the complex [Ru(bdmpza)Cl(═C═C═CPh2)-(PPh3)], indicating

that no conjugation between the allenylidene moiety and the pyrene substituent was present.

To enhance the solubility of the allenylidene complexes in polar protic solvents, the exchange

of the PPh3 ligand with the PTA ligand (1,3,5-triaza-7-phosphaadamantane) was investigated.

While the complexes [Ru(bdmpza)Cl(═C═C═(FN))-(PTA)] (57A) and [Ru(bdmpza)Cl-

(═C═C═C(PhPyr))(PTA)] (58A) could be prepared from [Ru(bdmpza)Cl(PTA)(PPh3)] (55),

the stability was strongly decrased, leaving both complexes unsuitable for further

applications. In the future, especially complex 54A/54B should be studied for possible non-

covalent functionalizations of carbon nanotubes in polar solvents.

In the last chapter, the intramolecular Scholl Reaction of pyrenophenone (50) was discussed

in detail. Opposing to the literature the extended polyaromatic compound could be

unambiguously identified as 11H-indeno[2,1-a]pyren-11-one (64). Furthermore, the possible

intermediary reduced compound 6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one (63) could be

isolated. Currently calculations are performed in the CLARK group by C. WICK to understand

the mechanistic pathway from 50 to 64 and to see if the Arenium Cation Pathway is suitable

or radical intermediates are preferred.

O

∗∗ CH2

O O

5063

64

153

6 ZUSAMMENFASSUNG UND AUSBLICK

154

!Zusammenfassung und Ausblick

!! !

In vorhergehenden Arbeiten der Arbeitsgruppe BURZLAFF wurde die Entwicklung von

verschiedenartigen N,N,O-Liganden für Anwendungen in der Katalyse und in bio-

anorganischen Modellkomplexen untersucht. Insbesondere der methylsubstituierte Ligand

Bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) besitzt eine vielfältige Chemie, welche viele

Parallelen zu den anionischen Cyclopentadienyl- (Cp) und Hydridotris(pyrazol-1-

yl)boratoliganden (Tp) aufweist.

Im ersten Teil dieser Arbeit wurde die Darstellung von Tricarbonylmangan(I)komplexen mit

dem Heteroskorpionatliganden 3,3-Bis(3,5-dimethylpyrazol-1-yl)propionato (bpzp) und die

Synthese des Trisimidazolylkomplexes [Mn(CO)3(HIm)3]Br (6) untersucht. Diese beiden

Komplexe, sowie die analogen Tricarbonylmangankomplexe mit den Hetero-

skorpionatliganden Bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza), Bis(pyrazol-1-yl)acetato

(bpza) und 3,3-Bis(3,5-dimethylpyrazol-1-yl)propionato (bdmpzp), und der Komplex

[Mn(CO)3(HIm)3]Br, wurden auf ihre Eigenschaften als photoaktivierbare Kohlenstoff-

monoxid-freisetzende Moleküle hin untersucht. Hierzu wurde das Myoglobin-Assay

verwendet, mit dessen Hilfe gezeigt werden konnte, dass die beiden Komplexe mit den

monodentaten Imidazolyl- und Pyrazolylliganden eine geringe Stabilität in Lösung aufweisen

und bereits im Dunklen Kohlenstoffmonoxid freisetzen. Für die vier Hetero-

skorpionatkomplexe ließ sich eine starke Abhängigkeit der Freisetzungsgeschwindigkeit von

dem Substitutionsmuster der Heterozyklen und der Kettenlänge der Carboxylateinheit

erkennen.

Der zweite Teil dieser Arbeit beinhaltet die Synthese und Charakterisierung von

Rutheniumcarbonylkomplexen und wurde in Zusammenarbeit mit S. TAMPIER und G.

TÜRKOGLU bearbeitet. Die Synthese der beiden Dicarbonylkomplexe [Ru(bdmpza)Cl(CO)2]

(9) und [Ru(2,2-bdmpzp)Cl(CO)2] (10) !mit einem Bis(3,5-dimethylpyrazol-1-yl)acetato-

(bdmpza) oder einem 2,2- !Bis(3,5-dimethylpyrazol-1-yl)propionatoligand (2,2-bdmpzp)

wurden bereits von S. TAMPIER und G. TÜRKOGLU beschrieben. In Analogie wurde der auf

dem Bis(pyrazol-1-yl)acetatoligand (bpza) basierende Komplex [Ru(bpza)Cl(CO)2]

dargestellt. Alle drei Komplexe sind durch die Reaktion des Polymers [RuCl2(CO)2]n mit dem

Kaliumsalz des jeweiligen Heteroskorpionatliganden (K[bdmpza], K[bpza] oder K[2,2-

bdmpzp]) zugänglich. Die Reaktion der freien Säure Hbdmpza mit [Ru3(CO)12] führte zu der

Bildung von zwei Strukturisomeren des Hydridokomplexes [Ru!(bdmpza)H(CO)2] (11A/11B).

Unter aeroben Bedingungen scheint die Umsetzung von ! [Ru(bdmpza)H(CO)2] (11A/11B) zu

dem Ru(I)-Dimer [Ru(bdmpza)!(CO)(μ2-CO)]2 (12) im Vergleich zu dem η5-C5H5-Analogon

155


!! !

(Cp) gehindert zu sein. Dimer 12 konnte hingegen durch die Reaktion von Hbdmpza mit

catena-[Ru(OAc)(CO)2]n erhalten werden.

Der dritte Abschnitt behandelt einen bioanorganischen Themenbereich und beinhaltet zwei

Rutheniumkomplexe mit Aminophenolliganden. Die Reaktion von [Ru(bdmpza)Cl(PPh3)2]

mit Aminophenol (APH) und 2-Amino-4,6-di-tert-butylphenol (tBuAPH) führte zu den

zugehörigen Komplexen [Ru(bdmpza)Cl(ISQ)(PPh3)] bzw. [Ru(bdmpza)Cl(IBQ)(PPh3)] (16)

und [Ru(bdmpza)Cl(tBuISQ)(PPh3)] bzw. [Ru(bdmpza)Cl(tBuIBQ)(PPh3)] (15). In beiden

Komplexen konnte die ungewöhnliche κ1-Koordination durch die Iminofunktion beobachtet

werden und nicht die erwartete κ2-N,O-Koordination. Aus den beobachteten Bindungslängen

in den Röntgenstrukturanalysen und den diamagnetischen NMR-Spektren konnte geschluss-

folgert werden, dass es sich bei den beiden Komplexen um ein [Ru2+–IBQ]-System oder ein

[Ru3+–ISQ]-System mit starker antiferromagnetischer Kopplung handelt. Weitere Arbeiten

müssen in Zukunft zeigen welche Redoxprozesse im Detail während der Bildung der

Komplexe ablaufen und ob infolgedessen eine Optimierung der Reaktion möglich ist.

Der Hauptfokus dieser Arbeit liegt auf einer Serie von kohlenstoffreichen

Rutheniumallenylidenkomplexen, die ausgehend von dem Rutheniumprecursor [Ru(bdmpza)-

Cl(PPh3)2] (14) dargestellt wurden. Die Umsetzung von 14 mit 1,1-Bis-(3,5-di-tert-

butylphenyl)-1-methoxy-2-propin führte zu der Bildung von zwei Strukturisomeren des

Allenylidenkomplexes [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A/19B) und den durch

Zersetzung entstehenden Carbonylkomplex [Ru(bdmpza)Cl(CO)(PPh3)] (18A/18B). Die

analoge Umsetzung von 9-Ethinyl-9-fluorenol mit 14 führte zu dem analogen

fluorensubstituierten Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B)

(FN = Fluorenyl). Ausgehend von Anthrachinon wurde die Synthese von 10-Ethinyl-10-

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

15 (IBQ); R = tBu16 (IBQ); R = H

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

15 (ISQ); R = tBu16 (ISQ); R = H

oder

RR

RR

156


!! !

hydroxyanthracen-9-on über den TMS-geschützten (TMS = Trimethylsilyl) Propargylalkohol

beschrieben. Anschließend erfolgte die Synthese des Allenylidenkomplexes ([Ru(bdmpza)-

Cl(═C═C═(AO))(PPh3)] (25A/25B) (AO = Anthron), der im Falle beider Strukturisomere im

Festkörper starke π-π-Wechselwirkungen zwischen zwei Anthroneinheiten aufweist. Im

nächsten Schritt wurde in Kooperation mit A. WATERLOO aus der Arbeitsgruppe von R.

TYKWINSKI die Synthese eines größeren acenbasierten, in diesem Fall

pentacenchinonbasierten, Allenylidenkomplexes [Ru(bdmpza)Cl-(═C═C═(PCO))(PPh3)]

(29A/29B) (PCO = Pentacenon) erzielt. Im Gegensatz zu anderen

Rutheniumallenylidenkomplexen zeigte 29B eine stark gewinkelte Ru–C3-Kette. Diese

Geometrie konnte auf das Packungsmotiv im Festkörper zurückgeführt werden, da dieses

Verhalten für 29A nicht beobachtet wurde.

Da erneut nur eine Dimerbildung, aber keine Schichtstruktur der aromatischen Einheiten, im

Festkörper vorlag, wurde entschieden, ein weiteres polyaromatisches Keton als

Ausgangsverbindung zu wählen. Hierbei wurde 7H-Benzo[no]tetraphen-7-on (34) als

vielversprechender Kandidat verwendet, da dieser ein erweitertes π-System auf der dem

Keton abgewandten Seite besitzt. Ausgehend von 34 wurde die Synthese des

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CR2CR2 =

tBu

tBu

tBu

tBu

O O

NC CN

CNCN

19A/19B20A/20B

25A/25B 29A/29B

31 37A/37B

H

157


!! !

Propargylalkohols 7-Ethinyl-7H-benzo[no]tetraphen-7-ol (36) und die anschließende

Umsetzung zu dem Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B)

(BT = Benzotetraphen) beschrieben. Hervorzuheben ist Komplex 37A, da eine Reihe an

kurzen π-π-Abständen zwischen den Benzotetrapheneinheiten entlang einer Achse im Kristall

auftritt, die möglicherweise einen Ladungstransport entlang dieser Achse erlauben könnte.

Studien der Absorptionsspektren der bisher erwähnten Komplexe zeigten, dass schwache

Banden im NIR-Bereich zu verbotenen MLCT-Übergängen gehören. TD-DFT Berechnungen

wurden von E. HÜBNER ausgehend von Röntgenstrukturanalysen durchgeführt. Diese

Berechnungen erlauben die Zuordnung dieser NIR-Banden, die durch

Absorptionsspektroskopie beobachtet wurden, zu Übergängen, die vor allem HOMO–2,

HOMO–1, HOMO und LUMO betreffen. Des Weiteren wurden cyclovoltammetrische

Messungen durchgeführt um ein Verständnis für den Einfluss der Substituenten auf den

Allenylidenkomplex zu erhalten. Zusammenfassend lässt sich sagen, dass die räumliche

Anordnung, die für einige Komplexe im Festkörper beobachtet wurde, diese zu

vielversprechenden Kandidaten für Metall-beeinflusste Feldeffekttransistoren macht. Darüber

hinaus könnte das reversible Redoxverhalten und das breite Absorptionsverhalten sie zu guten

Ausgangsverbindungen für Farbstoffsolarzellen machen. Diese beiden möglichen

Anwendungsbeispiele machen diese Komplexe zu interessanten Ausgangsverbindungen für

weitere funktionalisierte organische Halbleiter. Der Versuch, einen Allenylidenkomplex

ausgehend von 2-(13-(Dicyanomethyl)-13-ethinylpentacen-6(13H)-yliden)malononitril (30)

zu erhalten, führte zu dem Rutheniumvinylidenkomplex [Ru(bdmpza)Cl(═C═CH(PCN))-

(PPh3)] (PCN = Pentacenonbasiertes Tetracyanoderivat) (31). Charakteristisch ist die

Farbintensität der Verbindung in Lösung, welche stark an Allenylidenkomplexe erinnert und

sich vermutlich auf den starken Push-Pull-Charakter der Cyanosubstituenten in Verbindung

mit der Vinylideneinheit zurückführen lässt. Für Vergleichszwecke und mögliche katalytische

Anwendungen wurden die 16-VE-Rutheniumallenylidenkomplexe [RuCl2(═C═C═(FN))-

(PPh3)2] (45), [RuCl2(═C═C═(AO))(PPh3)2] (46) und [RuCl2(═C═C═(PCO))(PPh3)2] (47)

dargestellt. Jedoch zeigen diese drei Komplexe in Lösung die Tendenz zu dimerisieren und

eine Mischung aus einem neutralen und kationischen 18-VE-Komplex zu bilden, was diese

für weitere Anwendungen unattraktiv macht.

Die Arbeit befasst sich im anschließenden Kapitel mit Rutheniumkumulenylidenkomplexen,

die eine Exfoliation von beispielsweise Kohlenstoffnanoröhren oder Graphenmonolagen

erlauben soll. Hierzu wurden zunächst die beiden Rutheniumvinylidenkomplexe

158


!! !

[Ru(bdmpza)Cl(═C═CH(6-Methoxynaphthalen))(PPh3)] (48) und [Ru(bdmpza)Cl-

(═C═CH(Pyr))(PPh3)] (49) dargestellt. Obwohl Komplexe 48 und 49 bemerkenswerte

Stabilität für Vinylidenkomplexe zeigen, erfolgt eine Zersetzung durch Sauerstoff in Lösung

innerhalb weniger Tage.

Um diesen Nachteil zu umgehen, sollte im Folgenden die Synthese von pyrenbasierten

Allenylidenkomplexen untersucht werden. Hierzu wurde zunächst, ausgehend von

Pyrenophenon, (50) der Propargylalkohol 1-Phenyl-1-(pyren-1-yl)prop-2-in-1-ol (51)

dargestellt. Der zugehörige Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)]

(54A/54B) wurde isoliert und zeigt Absorptionsspektren ähnlich derer des phenylbasierten

Allenylidenkomplexes [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)]. Dies verdeutlicht, dass keine

Konjugation zwischen dem Pyrensubstituenten und der Allenylideneinheit erfolgt. Um die

Löslichkeit in polaren, protischen Lösungsmitteln zu steigern, wurde der Austausch des PPh3-

Liganden durch den PTA-Liganden untersucht. Zwar waren die Allenylidenkomplexe

[Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A) und [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)]

(58A), ausgehend von [Ru(bdmpza)Cl(PTA)(PPh3)] (55), in sehr schlechter Ausbeute

darstellbar, jedoch zeigten beide Komplexe 57A und 58A eine schnelle Zersetzung in Lösung.

In zukünftigen Arbeiten sollten daher Untersuchungen zu möglichen nicht-kovalenten

Funktionalisierungen von Kohlenstoffallotropen, insbesondere mit dem Komplex 54A/54B,

durchgeführt werden.

Im letzten Kapitel dieser Arbeit wurde die intramolekulare Scholl-Reaktion von

Pyrenophenon (50) detailliert betrachtet. Im Gegensatz zu den bisherigen Veröffentlichungen

konnte das Reaktionsprodukt durch eine Röntgenstrukturanalyse als 11H-indeno[2,1-a]pyren-

NN N

N

Me

Me

Me

MeRu

OO

CClPTA CC

57A

NN N

N

Me

Me

Me

MeRu

OO

CClPTA CC

58A

NN N

N

Me

Me

Me

MeRu

OO

CClPPh3 CC

54A

159


!! !

11-on (64) identifiziert werden. Zusätzlich konnte ein mögliches Intermediat in Form des

reduzierten 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-on (63) isoliert werden. Derzeit werden

Berechnungen von C. WICK aus der Arbeitsgruppe von T. CLARK durchgeführt, die zur

Aufklärung des Mechanismus beitragen sollen, da sowohl der Arenium-Kationen

Mechanismus als auch ein radikalischer Mechanismus denkbar ist.

O

∗∗ CH2

O O

5063

64

161

7 EXPERIMENTAL SECTION

162

!Experimental Section

!! !

7.1 General Remarks

Working Techniques All air sensitive compounds were prepared under dry nitrogen atmosphere using conventional

Schlenk techniques. Purchased solvents (p.a. grade, <50 ppm H2O) were degassed prior to use

and stored under N2 atmosphere.

7.1.1 Chemicals !

The following chemicals were used as purchased without further purification:

" [Mn2(CO)10]

" [Ru3(CO)12]

" 1-ethynylpyrene

" 2-aminophenol

" 2-ethynyl-6-methoxynaphthalene

" 7H-benzo[no]tetraphen-7-one

" 9-ethynyl-9-fluorenol

" anthraquinone

" bianthrone

" ethynylmagnesium bromide

" imidazole

" KOtBu

" n-BuLi

" PTA

" pyrazole

" trimethylsilylacetylene

The group of R. TYKWINSKI provided the following chemicals:

" 1,1-bis-(1,3-di-t-butylphenyl)-1-methoxy-2-propyne

163


!! !

" 13-ethynyl-13-hydroxypentacen-6-one

" 2-(13-(dicyanomethyl)-13-ethynylpentacen-6(13H)-ylidene)malononitrile

" 6,13-diethynyl-6,13-dihydropentacene-6,13-diol

The following chemicals were synthesized by literature methods:

" [Mn(bdmpza)(CO)3][42]

" [Mn(bdmpzp)(CO)3][173]

" [Mn(bpza)(CO)3][42]

" [MnBr(CO)5][367]

" [MnBr(HPz)2(CO)3][193]

" [Ru(bdmpza)Cl(PPh3)2][168]

" [Ru(OAc)(CO)2]n

[368]

" [RuCl2(CO)2]n[369]

" [RuCl2(PPh3)3][370]

" 5-ethynyl-10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-ol[371]

" 5-ethynyl-5H-dibenzo[a,d][7]annulen-5-ol

" Hbdmpza[372]

" Hbpza[42]

" Hbpzp[173]

" Pyrenophenone[346]

7.1.2 Instrumentation

Elemental analyses were determined with a Euro EA 3000 (Euro Vector) and EA 1108 (Carlo

Erba) instrument (σ = ± 1% of the measured content). IR spectra were recorded with an

Excalibur FTS-3500 FTIR in CaF2 cuvettes (0.2 mm) or as KBr pellets. KBr pellets were

prepared using a Perkin-Elmer hydraulic press (10 t cm–2). 1H, 13C, APT 13C and 31P NMR

spectra were measured with a Bruker Avance DRX400 WB and a Bruker Avance DPX300

NB instrument. The δ values are given relative to tetramethylsilane (1H), the deuterated

solvent (13C) or to H3PO4 as internal standard. ESI-MS spectra were recorded with a Bruker

164


!! !

Daltonics maXis ultrahigh resolution ESI-TOF MS. Peaks were identified by using simulated

isotopic patterns created within the Bruker Data Analysis software. X-ray structure

determinations were carried out with a Bruker-Nonius Kappa-CCD diffractometer or an

Agilent Technologies SuperNova dual source diffractometer. UV/Vis and NIR spectroscopy

was performed with a Shimadzu UV-2401PC, a Varian Cary 5000 or a Varian Cary 5G

spectrometer.

7.1.3 CO-Release Studies

In a 1 cm quartz cuvette, horse skeletal muscle myoglobin (Sigma-Aldrich) dissolved in 0.1 M

phosphate buffer (pH 7.4) and phosphate buffer were mixed to a volume of 890 µL and a final

concentration of myoglobin of 50 µM. The mixture was degassed by bubbling N2 through the

solution. While still bubbling with N2, 0.1 M sodium dithionite (100 µL) in the same solvent

and each complex (10 µL of a 1000 µM DMSO stock solution) were added. The solution was

then either kept in the dark for 6 h or irradiated under N2 with a UV hand lamp (Benda 8W) at

365 nm, positioned perpendicular to the cuvette at a distance of 3 cm. Irradiations were

interrupted in regular intervals to take UV/Vis spectra on a Cary 5 spectrophotometer. The

irradiation experiments were carried out in triplicate.[196-197]

7.1.4 Cyclic Voltammetry

Cyclic voltammetry experiments were done using a AUTOLAB PGSTAT 100. A three-

electrode cell was used, using a gold disk working electrode, a platinum wire counter

electrode and a silver wire as a pseudo-reference electrode. Cyclic voltammetry was

performed in MeCN or CH2Cl2 solution (1.00 mM complex) containing 0.1 M n-Bu4NPF6 as

supporting electrolyte. All solutions were deoxygenated with N2 before each experiment and a

blanket of N2 was used to cover the solution during the experiment. The potential values (E)

were calculated using the following equation: E = (Epc + Epa)/2, where Epc and Epa correspond

to the cathodic and anodic peak potentials, respectively. Potentials are referenced to the

ferrocenium/ferrocene (Fc+/Fc) couple used as an internal standard.[373]

165


!! !

7.2 Synthesis of Compounds

7.2.1 Manganese Based Photo-CORMs

7.2.1.1 [Mn(bpzp)(CO)3] (4)

To a solution of Hbpzp (299 mg, 1.45 mmol) in THF (50 mL) KOtBu (163 mg, 1.45 mmol)

was added. The reaction mixture was stirred at room temperature for 1 h. After addition of

[MnBr(CO)5] (400 mg, 1.45 mmol) the suspension was stirred under reflux for 14 h and the

reaction was monitored via IR spectroscopy. The yellow suspension was filtered and the

residue was washed with THF (3 × 30 mL), H2O (3 × 30 mL) and Et2O (3 × 10 mL) and dried

in vacuo. The crude product (4) was recrystallized from CH2Cl2. Yield 251 mg (0.73 mmol,

50%).

1H NMR (300 MHz, DMSO-d6): δ = 8.07 (s, 2H, pz–CH), 7.93 (s, 2H, pz–CH), 7.51 (t, 3JH,H = 7.5 Hz, 1H, CH), 6.51 (vt, 2H, pz–CH), 3.67 (d 3JH,H = 7.7 Hz, 2H, CH2) ppm; IR

(THF): ṽ 2026 (s), 1932 (s), 1915 (s) cm–1; Due to poor solubility no 13C NMR spectrum

could be recorded; IR (KBr): ṽ 2028 (s, CO), 1947 (s, CO), 1929 (w, CO), 1914 (s, CO) cm–1;

Elemental analysis calcd (%) for C12H9MnN4O5: C 41.88, H 2.64, N 16.28; found: C 41.72,

H 2.53, N 15.65.

7.2.1.2 [Mn(HIm)3(CO)3]Br (6)

To a solution of imidazole (89.0 mg, 1.30 mmol) in CH2Cl2 (35 mL) [MnBr(CO)5] (178 mg,

0.65 mmol) was added and stirred at room temperature for 5 h. The solvent was removed in

vacuum, the yellow residue dispersed in THF (20 mL) to remove excess [MnBr(CO)5] and

filtered off yielding the yellow complex (6). Yield 87 mg (0.21 mmol, 32%).

NN N

N

MnOC COCO

OO

166


!! !

1H NMR (300 MHz, DMSO-d6): δ = 12.97 (s, 3H, NH), 7.83 (s, 3H, C2H), 7.37 (s, 3H, CH),

6.68 (s, 3H, CH) ppm; 13C NMR (75 MHz, DMSO-d6): δ = 220.3 (CO), 139.4 (C2H), 129.6

(CH), 118.6 (CH) ppm; IR (KBr): ṽ 2024 (s, CO), 1907 (s, CO) cm–1; MS (ESI-TOF, MeCN)

m/z (%): calcd: 343.0351; found: 343.0455 (100) [M – Br]+; Elemental analysis calcd (%)

for C12H12BrMnN6O3: C 34.06, H 2.86, N 19.86; found: C 33.86, H 2.63, N 20.13.

7.2.2 Ruthenium Carbonyl Complexes Bearing Heteroscorpionate Ligands

7.2.2.1 [Ru(bdmpza)H(CO)2] (11A/B)

To a suspension of [Ru3(CO)12] (522 mg, 0.810 mmol) in toluene (50 mL) was added

Hbdmpza (811 mg, 3.26 mmol). The suspension was stirred under reflux for 24 h until

complete decolorization was achieved. The white residue was filtered off, washed with

toluene (2 × 10 mL), and dried in vacuo to yield a mixture of isomers 11A,B in a 1:0.7 ratio.

Yield: 887 mg (2.19 mmol, 90%).

Data for isomer 11A are as follows. 1H NMR (CDCl3, 300 MHz): δ = 6.48 (s, 1H, CH), 6.02

(s, 2H, pz–H4, pz–H4´), 2.42 (s, 6H, pz–Me5, pz–Me5´), 2.38 (s, 6H, pz–Me3, pz–Me3´), –13.32

(s, 1H, Ru–H) ppm; 1H NMR (CD2Cl2, 300 MHz): δ = 6.42 (s, 1H, CH), 6.04 (s, 2H, pz–H4,

pz–H4´), 2.42 (s, 6H, pz–Me5, pz–Me5´), 2.37 (s, 6H, pz–Me3, pz–Me3´), –13.09 (s, 1H, Ru–

H) ppm.

MnOC

N N

CO

N

CO

HNHN

NH

Br

NN N

N

Me

Me

Me

MeRu

OO

OC COH

NN N

N

Me

Me

Me

MeRu

OO

OC HCOA B

167


!! !

Data for isomer 11B are as follows. 1H NMR (CDCl3, 300 MHz): δ = 6.43 (s, 1H, CH), 6.07

(s, 1H, pz–H4´), 6.05 (s, 1H, pz–H4), 2.45 (s, 3H, pz–Me5´), 2.42 (s, 3H, pz–Me5), 2.41 (s, 3H,

pz–Me3´), 2.38 (s, 3H, pz–Me3), –10.10 (s, 1H, Ru–H) ppm; 1H NMR (CD2Cl2, 300 MHz): δ

6.39 (s, 1H, CH), 6.09 (s, 1H, pz–H4´), 6.07 (s, 1H, pz–H4), 2.44 (s, 3H, pz–Me5´), 2.42 (s, 3H,

pz–Me5), 2.41 (s, 3H, pz–Me3´), 2.40 (s, 3H, pz–Me3), –10.10 (s, 1H, Ru–H) ppm.

Data for both isomers 11A/11B are as follows. IR (KBr): ṽ 3014 (w, CH), 2037 (s, CO), 2002

(w, Ru–H), 1961 (s, CO), 1664 (s, as-CO2–), 1560 (w, C═N) cm–1; MS (ESI-TOF, MeCN)

m/z (%): 407.03 (32) [M + H]+, 812.05 (100) [2 × M + H]+, 835.03 (27) [2 × M + Na]+, 851.01

(13) [2 × M + K]+, 1240.06 (28) [3 × M + Na]+, 1646.08 (22) [4 × M + Na]+, 2050.11 (4)

[4 × M + Na]+; Elemental analysis calcd (%) for C14H16N4O4Ru: C 41.48, H 3.98, N 13.82;

found: C 41.48, H 3.84, N 14.03.

7.2.2.2 [Ru(bdmpza)(CO)(μ2-CO)]2 (12)

To a suspension of [Ru2(O2CCH3)2(CO)2]n (233 mg, 1.07 mmol) in THF (30 mL) was added

Hbdmpza (293 mg, 1.18 mmol). The suspension was heated at reflux for 24 h, forming the

dinuclear product [Ru2(bdmpza)(CO)(μ2-CO)]2. The yellow precipitate (12) was filtered off,

washed with THF (2 × 20 mL), and dried in vacuo. Yield: 132 mg (0.16 mmol, 30%).

1H NMR (CDCl3, 300 MHz): δ = 6.31 (s, 2H, CH), 6.04 (s, 4H, pz–H4, pz–H4´), 2.62 (s, 12H,

pz–Me5, pz–Me5´), 2.35 (s, 12H, pz–Me3, pz–Me3´) ppm; 1H NMR (CD2Cl2, 300 MHz):

δ = 6.35 (s, 2H, CH), 6.15 (s, 4H, pz–H4, pz–H4´), 2.67 (s, 12H, pz–Me5, pz–Me5´), 2.43 (s,

12H, pz–Me3, pz–Me3´) ppm; Due to poor solubility no 13C NMR spectrum could be recorded;

IR (KBr): ṽ 2930 (w, CH), 1982 (s, CO), 1762 (s, μ2-CO), 1675 (s, as-CO2–), 1561 (w, C═N)

cm–1; IR (CHCl3): ṽ 2076 (vw), 2069 (vw), 2010 (vw-sh), 1978 (s, CO), 1950 (w), 1761 (s,

O

NN

NNOO

NN

N

O

Ru

OC

RuCO

CO

OC

Me

Me

Me

Me

Me

Me

Me

Me N

168


!! !

μ2-CO), 1673 (s, as-CO2–), 1602 (vw), 1559 (w, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%):

405.02 (100) [Ru(bdmpza)(CO)2]+, 810.05 (4) [M]+, 828.06 (42) [M + H2O]+, 881.11 (62)

[M + 4 × H2O]+, 899.10 (60) [M + 5 × H2O]+; UV/Vis (CH2Cl2): λmax (log ε) 287.0 (3.88),

342.9 (3.23), 403.0 nm (3.09); Mp.: 282–285 °C dec; Elemental analysis calcd (%) for

C28H30N8O8Ru2: C 41.58, H 3.74, N 13.86; found: C 41.95, H 3.72, N 13.67.

7.2.2.3 [Ru(bpza)Cl(CO)2] (13)

A solution of Hbpza (192 mg, 1.00 mmol) in THF (20 mL) was treated with KOtBu (112 mg,

1.00 mmol) and stirred for 2 h at room temperature. After addition of [RuCl2(CO)2]n (228 mg,

1.00 mmol), the reaction mixture was heated under reflux and controlled by IR spectroscopy

on a regular basis. After completion of the reaction (approx. 24 h), the cream white precipitate

(13) was filtered off, washed with H2O (2 × 10 mL) and Et2O (3 × 10 mL) and dried in vacuo.

Yield 219 mg (0.57 mmol, 57%).

1H NMR (DMSO-d6, 300 MHz): δ = 8.50 (d, 3JH,H = 2.3 Hz, 1H, pz–H3´), 8.46 (d, 3JH,H = 2.6

Hz, 1H, pz–H3), 8.45 (d, 3JH,H = 2.8 Hz, 1H, pz–H5´), 8.24 (d, 3JH,H = 2.3 Hz, 1H, pz–H5), 7.64

(s, 1H, CH), 6.74 (t, 3JH,H = 2.4 Hz, 1H, pz–H4´), 6.69 (t, 3JH,H = 2.6 Hz, 1H, pz–H4) ppm; 13C NMR (DMSO-d6, 75 MHz): δ = 194.8 (CO), 193.9 (CO), 163.6 (CO2

–), 148.1 (pz–C3´),

144.7 (pz–C3), 135.5 (pz–C5´), 134.5 (pz–C5), 109.1 (pz–C4´), 108.7 (pz–C4), 73.2 (CH) ppm;

IR (KBr): ṽ 3121 (w, CH), 2996 (w, CH), 2081 (s, CO), 2014 (s, CO), 1768 (vw), 1760 (vw)

1668 (s, as-CO2–), 1514 (w, C═N) cm–1; MS (ESI-TOF, DMSO) m/z (%): 406.91 (100)

[M + Na]+, 789.83 (60) [2 × M + Na]+, 1172.75 (30) [3 × M + Na]+, 1557.67 (80)

[4 × M + Na]+, 1942.59 (50) [5 × M + Na]+, 2325.52 (50) [6 × M + Na]+; Elemental analysis

calcd (%) for C10H7ClN4O4Ru: C 31.30, H 1.84, N 14.60; found: C 31.21, H 1.81, N 14.51.

NN N

N

Ru

OO

OC ClCO

169


!! !

7.2.3 Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands

7.2.3.1 [Ru(bdmpza)Cl(IBQ)(PPh3)] or [Ru(bdmpza)Cl(ISQ)(PPh3)] (16)

2-Aminophenol (164 mg, 1.50 mmol) was dissolved in THF (50 mL) and deprotonated with

KOtBu (168 mg, 1.50 mmol) for 1h. [Ru(bdmpza)Cl(PPh3)2] (14) (908 mg, 1.00 mmol) was

added to the solution and the mixture was stirred for 24 h at room temperature. The solvent

was removed in vacuo, the solid residue was dissolved in CH2Cl2 (10 mL) and loaded on a

column (silica, length 10 cm, Ø 4 cm) and washed with a mixture of EtOH/n-pentane (1:1

v/v). A dark blue spot could be eluted with CH2Cl2/acetone (1:1 v/v) and a second purple spot

could be isolated by changing the solvent to MeOH. Further chromatography steps of the

purple fraction did not lead to purified samples for analysis. The blue crude product was again

loaded on a column (silica, length 30 cm, Ø 2 cm) and eluted with CH2Cl2/acetone (1:1 v/v).

The solvent was removed in vacuo and the complex was dissolved in CH2Cl2, precipitated by

the addition on n-pentane, filtered off and the complex was obtained as a dark blue powder

(16). Yield 25.0 mg (0.033 mmol, 2%).

1H NMR (CD2Cl2, 300 MHz): δ = 14.77 (s, 1H, NH), 7.36 – 7.14 (m, 19H, PPh3 + Ar–C),

6.63 (s, 1H, CH), 6.07 (s, 1H, pz–H4’), 5.97 (s, 1H, pz–H4), 2.62 (s, 3H, pz–Me5’), 2.54 (s, 3H,

pz–Me5), 2.10 (s, 3H, pz–Me3), 1.91 (s, 3H, pz–Me3´) ppm; 13C NMR (CD2Cl2, 75 MHz):

δ = 171.3 (C═O), 166.3 (CO2–), 158.5 (C═NH), 154.4 (pz–C3`), 151.8 (pz–C3), 142.6 (pz–

C5’), 141.9 (APH–CH), 141.3 (pz–C5), 134.2 (vd, 2JC,P = 9.6, o-PPh3), 132.7 (vd, 1JC,P = 42.9,

i-PPh3), 132.4 (APH–CH), 132.1 (APH–CH), 130.9 (APH–CH), 130.0 (vd, 4JC,P = 2.6, p-

PPh3), 128.1 (vd, 3JC,P = 9.0, m-PPh3), 108.9 (pz–C4´), 109.0 (pz–C4), 69.6 (CH), 15.1 (pz–

Me3´), 13.6 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm; 31P NMR (CD2Cl2, 122 MHz):

δ = 32.7 ppm; MS (ESI-TOF, MeCN) m/z (%):753.12 (5) [M]+, 742.15 (100) [M – Cl + Na]+;

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

O

IBQ

NN N

N

Me

Me

Me

MeRu

OO

ClPh3PNH

Oor

ISQ

170


!! !

Elemental analysis calcd (%) for C36H35ClN5O3PRu: C 57.41, H 4.68, N 9.30; found: C

56.85, H 4.67, N 9.05.

7.2.4 Carbon-Rich Ruthenium Allenylidene Complexes

7.2.4.1 [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A/19B)

To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (205 mg, 0.22 mmol) in THF (50 mL) 1,1-

bis-(1,3-di-t-butylphenyl)-1-methoxy-2-propyne (150 mg, 0.34 mmol) was added. The

suspension was stirred for 72 h at room temperature and consequently heated for 4 h under

reflux. The solvent of the purple solution was removed in vacuo yielding the crude product.

The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length

15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with

CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation of isomers was

achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v)

yielding a purple isomer 19A (allenylidene trans to pyrazole) that could not be completely

separated from the formed carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)2] and a red isomer

19B (allenylidene trans to carboxylate). 19A (data extracted from spectra containing the

carbonyl complex). Yield: 52 mg.

1H NMR (CDCl3, 300 MHz): δ = 7.66 (s, 4H, Ar–H), 7.61 (s, 2H, Ar–H), 7.57 (m, 6H,

m-PPh3), 7.16 (m, 3H, p-PPh3), 7.00 (m, 6H, o-PPh3), 6.69 (s, 1H, CH), 5.81 (s, 1H, pz–H4´),

5.69 (s, 1H, pz–H4), 2.59 (s, 3H, pz–Me5´), 2.46 (s, 3H, pz–Me5), 2.33 (s, 3H, pz–Me3), 1.35

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

CtBu

tBu tBu

tBu

tBu

tBu

tButBu

A B

171


!! !

(s, 3H, pz–Me3´), 1.24 (s, 36H, t-Bu) ppm; 31P NMR (CDCl3, 122 MHz): δ = 37.6 ppm; IR

(KBr): ṽ 1912 (m, C═C═C), 1672 s (s, as-CO2–), 1565 (w, C═N) cm–1; MS (ESI-TOF,

MeCN) m/z (%): 1025.46 (100) [M – Cl]+, 1061.43 (12) [M + H]+.

19B: Yield: 18 mg (0.017 mmol, 5 %).

1H NMR (CDCl3, 300 MHz): δ = 7.68 (s, 4H, Ar–H), 7.61 (s, 2H, Ar–H), 7.57 (m, 6H, m-

PPh3), 7.57 (m, 6H, m-PPh3), 7.16 (m, 3H, p-PPh3), 7.03 (m, 6H, o-PPh3), 6.71 (s, 1H, CH),

5.83 (s, 1H, pz–H4´), 5.70 (s, 1H, pz–H4), 2.52 (s, 3H, pz–Me5´), 2.47 (s, 3H, pz–Me5), 2.25 (s,

3H, pz–Me3), 1.40 (s, 3H, pz–Me3´), 1.24 (s, 36H, t-Bu) ppm; 13C NMR (CDCl3, 75 MHz):

δ = 314.7 (d, 2JCP = 18.3 Hz, Cα), 234.6 (Cβ), 165.9 (CO2–), 155.6 (pz–C3´), 154.8 (pz–C3),

152.4 (Cγ), 151.2 (m-Ph–C), 146.3 (i-Ph–C), 141.3 (pz–C5´), 139.5 (pz–C5), 134.5 (d, 2JCP = 9.2 Hz, o-PPh3), 133.5 (d, 1JCP = 46.8 Hz, i-PPh3), 129.3 (p-PPh3), 127.5 (d, 3JCP = 9.2 Hz, m-PPh3), 123.9 (o-Ph–C), 123.6 (p-Ph–C), 108.4 (pz–C4´), 108.3 (pz–C4), 69.7

(CH), 34.9 (Met-Bu), 14.6 (pz–Me3´), 13.9 (pz–Me3), 11.6 (pz–Me5´), 11.1 (pz–Me5) ppm; 31P NMR (CDCl3, 122 MHz): δ = 34.5 ppm; IR (KBr): ṽ 1907 (m, C═C═C), 1666 (s, as-

CO2–), 1559 (m, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%): 1025.46 (100) [M – Cl]+,

1061.43 (12) [M + H]+.

7.2.4.2 [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B)

To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (1.614 g, 1.78 mmol) in THF (50 mL) 9-

ethynyl-9-fluorenol (550 mg, 2.67 mmol) was added, stirred for 48 h at room temperature and

finally heated to reflux for 6 h. The solvent of the purple solution was removed in vacuo

yielding the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded

on a column (silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1

v/v), eluted with CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation

of isomers was achieved on a second column (silica, length 25 cm, Ø 4 cm) with

CH2Cl2/acetone (1:1 v/v) yielding a purple isomer 20A (allenylidene trans to pyrazole) and a

red isomer 20B (allenylidene trans to carboxylate). (Nomenclature of the fluorenyl moiety is

according to IUPAC nomenclature.)

172


!! !

20A: Yield: 738 mg (0.88 mmol, 49 %).

1H NMR (CDCl3, 300 MHz): δ = 7.56 (m, 6H, m-PPh3), 7.46 (m, 3H, p-PPh3), 7.34 (m, 6H,

o-PPh3), 7.27 (m, 2H, FN–H1 & FN–H8), 7.23 (m, 2H, FN–H4 & FN–H5), 7.00 (m, 2H, FN–

H3 & FN–H6), 6.91 (m, 2H, FN–H2 & FN–H7), 6.69 (s, 1H, CH), 6.04 (s, 1H, pz–H4´), 6.00 (s,

1H, pz–H4), 2.57 (s, 3H, pz–Me5´), 2.50 (s, 3H, pz–Me5), 2.45 (s, 3H, pz–Me3), 1.92 (s, 3H,

pz–Me3´) ppm; 13C NMR (CDCl3, 75 MHz): δ = 300.6 (d, 2JC,P = 27.6 Hz, Cα), 236.4 (d, 3JC,P = 4.6 Hz, Cβ), 166.6 (CO2

–), 156.1 (pz–C3´), 154.6 (pz–C3), 144.1 (FN–C4b), 143.9 (FN–

C4a), 141.0 (FN–C9), 141.0 (pz–C5´), 139.6 (pz–C5), 136.2 (FN–C8a), 136.2 (FN–C9a), 134.3 (d, 2JC,P = 9.6 Hz, o-PPh3), 132.9 (d, 1JC,P = 47.0 Hz, i-PPh3), 129.8 (p-PPh3), 129.3 (FN–C2 &

FN–C7), 129.2 (FN–C3 & FN–C6), 128.0 (d, 3JC,P = 10.3 Hz, m-PPh3), 121.7 (FN–C1 & FN–

C8), 121.2 (FN–C4 & FN–C5), 109.4 (pz–C4´), 108.6 (pz–C4), 69.0 (CH), 14.5 (pz–Me3´), 13.6

(pz–Me3), 11.4 (pz–Me5´), 11.2 (pz–Me5) ppm; 31P NMR (CDCl3, 122 MHz): δ = 34.6 ppm;

Mp.: 230-235 °C (dec.); IR (KBr): ṽ 1910 (m, C═C═C), 1664 (s, as-CO2–), 1560 (w, C═N)

cm–1; MS (ESI-TOF, MeCN) m/z (%): 755.19 (17) [M – Cl – CO2]+, 825.16 (100) [M + H]+;

Elemental analysis calcd. (%) for C45H38ClN4O2PRu: C 64.78, H 4.59, N 6.72; found: C

64.71, H 4.34, N 6.71.

20B: Yield: 228 mg (0.27 mmol, 15 %).

1H NMR (CDCl3, 300 MHz): δ = 7.64 (m, 6H, m-PPh3), 7.50 (m, 3H, p-PPh3), 7.38 (m, 6H,

o-PPh3), 7.24 (m, 2H, FN–H1 & FN–H8), 7.18 (m, 2H, FN–H4 & FN–H5), 7.16 (m, 2H, FN–

H3 & FN–H6), 6.99 (m, 2H, FN–H2 & FN–H7), 6.75 (s, 1H, CH), 5.90 (s, 1H, pz–H4´), 5.71 (s,

1H, pz–H4), 2.55 (s, 3H, pz–Me5´), 2.51 (s, 3H, pz–Me5), 2.19 (s, 3H, pz–Me3), 1.42 (s, 3H,

pz–Me3´) ppm; 13C NMR (CDCl3, 75 MHz): δ = 314.4 (d, 2JC,P = 19.3 Hz, Cα), 256.2 (Cβ),

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

A B

173


!! !

165.8 (CO2–), 155.7 (pz–C3´), 154.9 (pz–C3), 145.1 (FN–C4b), 143.5 (FN–C4a), 141.6 (FN–C9),

140.0 (pz–C5´), 139.9 (pz–C5), 136.5 (FN–C8a), 136.5 (FN–C9a), 134.5 (d, 2JC,P = 9.6 Hz, o-

PPh3), 132.5 (d, 1JC,P = 47.6 Hz, i-PPh3), 129.7 (p-PPh3), 129.7 (FN–C2 & FN–C7), 129.4 (FN–

C3 & FN–C6), 127.8 (d, 3JC,P = 10.2 Hz, m-PPh3), 122.1 (FN–C1 & FN–C8), 121.1 (FN–C4 &

FN–C5), 108.4(pz–C4´), 108.3 (pz–C4), 69.6 (CH), 14.3 (pz–Me3´), 13.9 (pz–Me3), 11.8 (pz–

Me5´), 11.2 (pz–Me5) ppm; 31P NMR (CDCl3, 122 MHz): δ = 30.9 ppm; Mp.: 235-240 °C

(dec.); IR (KBr): ṽ 1903 (m, C═C═C), 1666 (s, as-CO2–), 1564 (w, C═N) cm–1; MS (ESI-

TOF, MeCN) m/z (%): 755.19 (17) [M – Cl – CO2]+, 825.16 (100) [M + H]+; Elemental

analysis calcd. (%) for C45H38ClN4O2PRu: C 64.78, H 4.59, N 6.72; found: C 64.89, H 4.28,

N 6.71.

7.2.4.3 10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23)

To a solution of trimethylsilylacetylene (1.39 mL, 0.980 g, 10.0 mmol) in THF (20 mL)

cooled to –40 °C n-BuLi (1.6 M in hexanes, 4.90 mL, 7.80 mmol) was added dropwise. The

solution was allowed to stir for 30 min before being transferred slowly via cannula into a

suspension of anthraquinone (2.09 g, 10.1 mmol) in THF (40 mL) at room temperature. The

reaction mixture was stirred for 40 h at room temperature, cooled to 0 °C and quenched via

the addition of water (10 mL). The suspension was filtered off, washed with H2O/THF

(2 × 4 mL, H2O:THF = 1:1), pure THF (3 × 10 mL) and saturated aq. NH4Cl (100 mL) was

added to the filtrate. The aqueous phase was extracted with CH2Cl2 (3 × 100 mL), dried over

Na2SO4 and the solvent was removed in vacuo to yield a red powder. The crude product was

separated from unreacted anthraquinone via column chromatography with CH2Cl2 as eluent

(silica, length 15 cm, Ø 4 cm) to obtain 23 as pink solid. Yield 2.74 g (8.95 mmol, 89 %).

O

OH

Si

174


!! !

1H NMR (300 MHz, CDCl3): δ = 8.17 (m, 2H, AO-H), 8.08 (d, 3JH,H = 7.7 Hz, 2H, AO-H),

7.71 (m, 2H, AO-H), 7.51 (m, 2H, AO-H), 3.16 (s, 1H, OH), 0.16 (s, 9H, Si(CH3)3) ppm; 13C NMR (75 MHz, CDCl3): δ = 183.1 (C=O), 143.7, 134.3, 129.4, 129.2, 128.4, 127.3,

106.7 (Calkyne-Si), 91.5 (Calkyne), 66.4 (C-OH), –0.2 (Si(CH3)3) ppm; IR (KBr): ṽ 3072 (w, CH),

2957 (w, CH), 2899 (w, CH), 2172 (w, C≡C), 1649 (vs, CO), 1599 (s), 1582 (s), 1456

(m) cm–1; MS (ESI-TOF, MeCN) m/z (%): 305.10 (100) [M – H]–; Elemental analysis calcd

(%) for C19H18O2Si: C 74.47, H 5.92; found: C 74.64, H 5.91.

7.2.4.4 10-Ethynyl-10-hydroxyanthracen-9-one (24)

To a solution of the TMS protected propargyl alcohol 23 (1.00 g, 3.26 mmol) in MeOH

(20 mL) a solution of KOH (5.00 mL, 4.00 M in H2O) was added. The resulting mixture was

stirred for 2 h under ambient conditions. The solvent was removed in vacuo, the crude

product was extracted with CH2Cl2 (5 × 100 mL), washed with H2O (3 × 100 mL), dried over

Na2SO4 and the solvent was removed in vacuo to obtain a grey powder (24). Yield 649 mg

(2.77 mmol, 85 %).

1H NMR (300 MHz, CDCl3): δ = 8.26 (m, 2H, AO-H), 8.11 (d, 3JH,H = 7.9 Hz, 2H, AO-H),

7.74 (m, 2H, AO-H), 7.55 (m, 2H, AO-H), 2.98 (s, 1H, OH), 2.71 (s, 1H, CH) ppm; 1H NMR

(300 MHz, DMSO-d6): δ = 8.09 (m, 4H, AO-H), 7.83 (m, 2H, AO-H), 7.60 (m, 2H, AO-H),

7.15 (s, 1H, OH), 3.70 (s, 1H, CH) ppm; 13C NMR (75 MHz, DMSO-d6): δ = 182.4 (C=O),

145.1, 134.3 (2 × CH), 128.9 (CH), 128.4, 128.4 (2 × CH), 126.2 (CH), 87.1 (Calkyne), 76.1

(Calkyne-H), 64.2 (C-OH) ppm; IR (KBr): ṽ 3256 (m, OH), 2956 (s, CH), 2918 (vs, CH), 2849

(s, CH), 2112 (w, C≡C), 1772 (m, CO), 1733 (m), 1656 (m) cm–1; MS (ESI-TOF, MeCN) m/z

(%): 233.06 (19) [M – H]–; Elemental analysis calcd (%) for C16H10O2: C 82.04, H 4.30;

found: C 82.36, H 4.30.

O

OH

H

175


!! !

7.2.4.5 [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B)

[Ru(bdmpza)Cl(PPh3)2] (14) (341 mg, 0.400 mmol) and 10-ethynyl-10-hydroxyanthracen-9-

one (24) (300 mg, 1.28 mmol) were suspended in THF (80 mL) and stirred at room

temperature for 48 h. The solvent of the purple solution was removed in vacuo yielding the

crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column

(silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with


achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v)

yielding a purple isomer 25A (allenylidene trans to pyrazole) and a red isomer 25B

(allenylidene trans to carboxylate).

25A: Yield: 185 mg (0.215 mmol, 54 %).

1H NMR (CDCl3, 300 MHz): δ = 8.18 (d, 3JH,H = 7.5 Hz, 2H, AO–H), 7.94 (t, 3JH,H = 7.4 Hz,

2H, AO–H), 7.78 (m, 2H, AO–H), 7.54 (m, 6H, m-PPh3), 7.32 (m, 3H, p-PPh3), 7.25 (m, 6H,

o-PPh3), 7.18 (m, 2H, AO–H), 6.77 (s, 1H, CH), 6.08 (s, 1H, pz–H4'), 5.98 (s, 1H, pz–H4),

2.60 (s, 3H, pz–Me5'), 2.55 (s, 3H, pz–Me5), 2.21 (s, 3H, pz–Me3), 2.00 (s, 3H, pz–Me3') ppm; 13C NMR (CDCl3, 75 MHz): δ = 292.1 (d, 2JC,P = 26.8 Hz, Cα), 251.0 (d, 3JC,P = 5.0 Hz, Cβ),

187.1 (C=O), 166.3 (CO2–), 156.3 (pz–C3'), 154.7 (pz–C3), 141.4 (d, 4JC,P = 3.0 Hz, Cγ), 141.1

(pz–C5'), 139.8 (d, 4JC,P = 2.0 Hz, pz–C5), 134.3 (2 × AO–CH), 134.1 (d, 3JC,P = 6.9 Hz, o-

PPh3), 133.3 (d, 1JC,P = 38.6 Hz, i-PPh3), 132.4 (2 × AO–C), 132.0 (2 × AO–C), 130.0 (d, 4JC,P = 2.0 Hz, p-PPh3), 128.8 (2 × AO–CH), 128.3 (2 × AO–CH), 128.2 (2 × AO–CH), 128.0

(d, 2JC,P = 9.9 Hz, o-PPh3), 109.5 (pz–C4'), 108.2 (pz–C4), 69.1 (CH), 14.5 (pz–Me3'), 13.2 (pz–

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

C

C

A B

O

O

176


!! !

Me3), 11.4 (pz–Me5'), 11.1 (pz–Me5) ppm; 31P NMR (CDCl3, 122 MHz): δ = 30.1 ppm; IR

(CH2Cl2): ṽ 1880 (m, C═C═C), 1666 (s, as-CO2–), 1592 (m, C═N) cm–1; UV/vis (CH2Cl2):

λmax (log(ε)): 363 nm (3.17), 580 nm (3.44); MS (ESI-TOF, MeCN) m/z (%): 783.18 (12)

[M – Cl – CO2]+, 824.21 (13) [M – Cl – CO2 + MeCN]+, 863.14 (100) [M + H]+; Elemental analysis calcd. (%) for C46H38ClN4O3PRu: C 64.07, H 4.44, N 6.50; found: C 63.83, H 4.42,

N 6.51.

25B: Yield: 56.0 mg (0.0650 mmol, 16 %).

1H NMR (CDCl3, 300 MHz): δ = 8.18 (d, 3JH,H = 7.5 Hz, 2H, AO–H), 7.98 (t, 3JH,H = 7.4 Hz,

2H, AO–H), 7.77 (d, 3JH,H = 7.8 Hz, 2H, AO–H), 7.64 (m, 6H, m-PPh3), 7.47 (m, 6H, o-PPh3,

2H, AO–H), 7.13 (m, 3H, p-PPh3), 6.84 (s, 1H, CH), 5.89 (s, 1H, pz–H4'), 5.74 (s, 1H, pz–H4),

2.60 (s, 3H, pz–Me5'), 2.54 (s, 3H, pz–Me5), 2.06 (s, 3H, pz–Me3), 1.39 (s, 3H, pz–Me3') ppm; 13C NMR (CDCl3, 75 MHz): δ = 309.6 (d, 2JC,P = 19.8 Hz, Cα), 277.0 (Cβ), 187.8 (C=O),

165.9 (CO2–), 155.4 (pz–C3'), 154.7 (d, 3JC,P = 2.0 Hz, pz–C3), 141.6 (Cγ), 140.5 (pz–C5'), 140.1

(d, 4JC,P = 2.0 Hz, pz–C5), 134.4 (2 × AO–CH), 134.3 (2 × AO–CH), 133.0 (d, 1JC,P = 35.7 Hz,

i-PPh3), 132.1 (d, 3JC,P = 9.9 Hz, o-PPh3), 132.0 (d, 4JC,P = 3.0 Hz, p-PPh3), 131.9 (2 × AO–C),

129.2 (2 × AO–C), 128.0 (d, 2JC,P = 11.9 Hz, o-PPh3), 127.8 (2 × AO–CH), 127.7 (2 × AO–

CH), 108.3 (pz–C4'), 108.3 (pz–C4), 69.6 (CH), 14.0 (pz–Me3'), 13.5 (pz–Me3), 11.7 (pz–Me5'),

11.2 (pz–Me5) ppm; 31P NMR (CDCl3, 122 MHz): δ = 29.1 ppm; IR (CH2Cl2): ṽ 1896 (m,

C═C═C), 1667 (s, as-CO2–), 1605 (w, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%): 412.11

(62) [M – Cl – CO2 + MeCN]2+, 687.11 (31) [Ru(bdmpza)Cl(PPh3)(MeCN)]+, 783.18 (88)

[M – Cl – CO2]+, 824.21 (100) [M – Cl – CO2 + MeCN]+, 863.14 (4) [M + H]+; Elemental analysis calcd. (%) for C46H38ClN4O3PRu: C 64.07, H 4.44, N 6.50; found: C 63.38, H 4.41,

N 6.40.

7.2.4.6 [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B)

A suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (101 mg, 0.111 mmol) and 13-ethynyl-13-

hydroxypentacen-6-one (28) (60 mg, 0.17 mmol) in THF (25 mL) was stirred at room

temperature for 4 d and the reaction was monitored by IR spectroscopy. The solvent was

removed in vacuo and the residue was loaded with CH2Cl2 on a column (silica, length 10 cm,

Ø 4 cm). The column was washed with n-pentane/Et2O (1:1, v/v) and eluted with

177


!! !

CH2Cl2/acetone/n-hexane (1:1:1, v/v). Separation of the main isomer from a mixture of both

isomers was achieved by an additional column chromatographic step (CH2Cl2/acetone/n-

hexane, 1:1:1, v/v/v) on a longer column (silica, length 35 cm, Ø 6 cm). The fractions were

evaporated, redissolved in CH2Cl2 (2 mL) and precipitated by the addition of n-pentane

(50 mL).

29A: Yield 20 mg (0.021 mmol, 19%).

1H NMR (CD2Cl2, 300 MHz): δ = 8.80 (s, 2H, PCO–H), 8.47 (s, 2H, PCO–H), 8.01 (d, 3JH,H = 8.1 Hz, 1H, PCO–H), 7.80 (app. t, 3JH,H = 7.1 Hz, 2H, PCO–H), 7.73 – 7.70 (m, 5H,

Ar–H), 7.62 (app. t, 3JH,H = 8.7 Hz, 2H, PCO–H), 7.50 – 7.40 (m, 5H, Ar–H), 7.35 – 7.29 (m,

2H, Ar–H), 7.25 – 7.21 (m, 6H, Ar–H), 6.81 (s, 1H, CH), 6.13 (s, 1H, pz–H4´), 6.10 (s, 1H,

pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–Me5), 2.29 (s, 3H, pz–Me3), 2.01 (s, 3H, pz–

Me3´) ppm; 13C NMR (75 MHz, CD2Cl2): δ = 302.0 (d, 2JC,P = 19.3 Hz, Cα), 255.6 (Cβ), 186.0

(C=O), 166.2 (CO2–), 156.2 (pz–C3´), 154.9 (pz–C3), 142.5 (pz–C5´), 140.9 (pz–C5), 139.4

(Cγ), 137.4 (PCO–C), 134.7 (d, 2JC,P = 8.7 Hz, o-PPh3), 133.3 (d, 1JC,P = 41.8 Hz, i-PPh3) 132.9

(PCO–C), 132.2 (p-PPh3), 131.0 (PCO–CH), 131.0 (PCO–CH), 129.8 (PCO–CH), 128.8 (d, 2JC,P = 12.3 Hz, m-PPh3), 128.2 (PCO–CH), 128.1 (PCO–CH), 127.9 (PCO–CH), 108.8 (pz–

C4´), 108.6 (pz–C4), 69.9 (CH), 14.5 (pz–Me3´), 13.7 (pz–Me3), 11.9 (pz–Me5´), 11.3 (pz–Me5)

ppm; 31P NMR (122 MHz, CD2Cl2): δ = 33.1 ppm; IR (CH2Cl2): ṽ 1916 (m, C═C═C), 1663

(s, as-CO2–), 1564 (m, C═N) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 742.12 (100)

[M + H + MeCN – PPh3]+; Elemental analysis calcd (%) for

C54H42ClN4O3PRu × 1.25 CH2Cl2: C 62.10, H 4.20, N 5.24; found C 62.11, H 4.19, N 5.23.

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

C

C

A B

C

O

O

178


!! !

29B: Yield of 29A/29B: 46 mg (0.048 mmol, 43%).

The most prominent signals of compound 29B could be extracted from the combined spectra.

Due to the strong contamination with 29A the signals for Cα and Cβ could not be observed. 1H NMR (300 MHz, CD2Cl2): δ = 8.81 (s, 2H, PCO–H), 8.59 (s, 2H, PCO–H), 6.85 (s, 1H,

CH), 5.95 (s, 1H, pz–H4´), 5.79 (s, 1H, pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–Me5),

2.21 (s, 3H, pz–Me3), 1.52 (s, 3H, pz–Me3´) ppm; 13C NMR (75 MHz, CD2Cl2): δ = 185.6

(C=O), 166.6 (CO2–), 156.4 (pz–C3´), 154.8 (pz–C3), 142.0 (pz–C5´), 140.4 (Cγ), 140.3 (pz–

C5), 137.4 (PCO–C), 134.4 (d, 2JC,P = 9.6 Hz, o-PPh3), 132.9 (PCO–C), 132.6 (d, 1JC,P = 36.6 Hz, i-PPh3), 132.3 (p-PPh3), 131.3 (PCO–CH), 130.3 (PCO–CH), 130.2 (PCO–

CH), 128.3 (d, 2JC,P = 15.7 Hz, m-PPh3), 128.2 (PCO–CH), 128.1 (PCO–CH), 127.8 (PCO–

CH), 108.6 (pz–C4´), 108.5 (pz–C4), 69.5 (CH), 14.8 (pz–Me3´), 13.4 (pz–Me3), 11.6 (pz–

Me5´), 11.4 (pz–Me5) ppm; 31P NMR (122 MHz, CD2Cl2): δ = 27.4 ppm; IR (CH2Cl2): ṽ 1916

(m, C═C═C), 1663 (s, as-CO2–), 1564 (w, C═N) cm–1.

7.2.4.7 [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31)

To a solution of 2-(13-(dicyanomethyl)-13-ethynylpentacen-6(13H)-ylidene)malononitrile

(50 mg, 0.12 mmol) in THF (20 mL) [Ru(bdmpza)Cl(PPh3)2] (14) (91 mg, 0.10 mmol) was

added. The yellow suspension turned immediately dark brown and within 30 min dark blue.

The solution was stirred for 16 h at room temperature and the solvent removed in vacuo. The

isolation of the complex was achieved via column chromatography under N2 atmosphere. The

crude dark blue product was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica,

length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with

CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation from further

residues was achieved on a second column (silica, length 25 cm, Ø 4 cm) with

CH2Cl2/acetone (1:1 v/v) yielding a blue complex 31 (vinylidene trans to pyrazole). Yield:

43.0 mg (0.040 mmol, 30 %).

179


!! !

1H NMR (300 MHz, CDCl3): δ = 8.68 (s, 2H, PCN–H), 8.47 (d, 3JH,H = 8.5 Hz, 2H, PCN–H),

8.02 (m, 4H, PCN–H), 7.65 (m, 13H, o-PPh3, p-PPh3, PCN–H), 7.40 (m, 6H, m-PPh3), 6.48 (s,

1H, CH), 5.93 (s, 1H, pz–H4´), 4.98 (s, 1H, pz–H4), 3.82 (s, 1H, Hß), 3.47 (s, 1H, HC(CN)2),

2.51 (s, 3H, pz–Me5´), 2.15 (s, 3H, pz–Me5), 1.94 (s, 3H, pz–Me3), 1.91 (s, 3H, pz–Me3´) ppm; 13C NMR (75 MHz, CDCl3): δ = 365.1 (d, 2JC,P = 39.1 Hz, Cα), 167.6 (CO2

–), 157.1 (pz–C3´),

156.9 (C═C(CN)2), 155.6 (d, 3JC,P = 2.9 Hz, pz–C3), 140.7 (pz–C5´), 138.5 (pz–C5), 134.6

(PCN–CH), 134.1 (d, 2JC,P = 9.5 Hz, o-PPh3), 133.7 (PCN–C), 133.3 (d, 1JC,P = 42.2 Hz, i-

PPh3), 132.7 (PCN–C), 132.5 (PCN–C), 129.8 (PCN–CH), 129.7 (p-PPh3), 129.6 (PCN–CH),

129.5 (PCN–CH), 129.3 (PCN–CH), 129.1 (PCN–CH), 129.1 (PCN–CH), 128.9 (PCN–CH),

128.7 (PCN–CH), 128.5 (PCN–CH), 128.4 (PCN–CH), 128.1 (d, 3JC,P = 9.6 Hz, m-PPh3),

127.9 (PCN–C), 127.8 (PCN–CH), 127.1 (PCN–C), 126.9 (PCN–C), 119.1 (CN), 113.4 (CN),

110.6 (CN), 110.1 (CN), 113.3 (Cß), 109.3 (pz–C4), 106.6 (d, 4JC,P = 2.9 Hz, pz–C4´), 82.5

(C═C(CN)2), 68.0 (CH), 49.9 (Cγ) 39.5 (CH(CN)2), 14.2 (pz–Me3´), 12.9 (pz–Me3), 10.4 (pz–

Me5´), 10.0 ppm (pz–Me5), 2 tertiary carbon atoms of the pentacenequinone moiety could not

be observed; 31P NMR (122 MHz, CD2Cl2): δ = 44.6 ppm; IR (CHCl3): ṽ 3009 (m), 2198 (m,

C≡N), 2126 (w, C≡N), 1658 (s, as-CO2–) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 1077.21 (15)

[M + H]+, 1099.20 (100) [M + Na]+, 1115.17 (20) [M + K]+, 2176.40 (30) [2 × M + Na]+;

7.2.4.8 7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35)

To a solution of trimethylsilylacetylene (99.0 µL, 68.3 mg, 0.713 mmol) in THF (20 mL)

cooled to –80 °C n-BuLi (1.6 M in hexanes, 401 µL, 0.642 mmol) was added dropwise. The

solution was allowed to stir for 30 min before being transferred slowly via cannula into a

solution of 7H-benzo[no]tetraphen-7-one (34) (50.0 mg, 0.178 mmol) in THF (20 mL) at

room temperature. The reaction mixture was stirred for 16 h at room temperature. The

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

CNNC

CNCN

180


!! !

reaction was cooled to 0 °C and quenched via the addition of water (3 mL). The solvent was

removed in vacuo, the crude product was dissolved in CH2Cl2 and dried over Na2SO4 to yield

35 as yellow powder. Yield 66.0 mg (0.17 mmol, 98%).

1H NMR (300 MHz, CDCl3): δ = 8.70 (m, 1H), 8.38 (d, 3JH,H = 7.4 Hz, 1H), 8.30 (m, 2H),

7.94 (m, 4H), 7.68 (m, 2H), 7.54 (m, 2H), 2.59 (s, 1H, OH), 0.23 (s, 9H, Si(CH3)3) ppm; 13C NMR (75 MHz, CDCl3): δ = 135.6 (C), 135.6 (C), 135.1 (C), 133.4 (C), 130.2 (C), 129.1

(CH), 128.8 (CH), 128.7 (CH), 128.7 (C), 128.3 (CH), 127.8 (C), 127.7 (CH), 127.5 (CH),

126.7 (CH), 126.6 (CH), 126.5 (CH), 126.2 (CH), 126.0 (CH), 125.7 (CH), 107.6 (Calkyne-Si),

93.2 (Calkyne), 69.9 (C–OH), 0.01 (Si(CH3)3) ppm (one tertiary carbon atom not observed); MS

(ESI-TOF, MeCN) m/z (%): 413.11 (18) [M + Cl]–.

7.2.4.9 7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36)

To a solution of 35 (66.0 mg, 0.174 mmol) in MeOH (20 mL) a solution of KOH (0.50 mL,

4.00 M in H2O) was added. The resulting mixture was stirred for 3 h under ambient

conditions. The solvent was removed in vacuo, the crude product was extracted with CH2Cl2

(50 mL), washed with H2O (3 × 25 mL), dried over Na2SO4 and then the solvent was removed

under vacuum to yield 7-ethynyl-7H-benzo[no]tetraphen-7-ol (36) as an orange-brown

powder. Yield 37.3 mg (0.12 mmol, 70%).

OH

Si

181


!! !

1H NMR (300 MHz, CDCl3): δ = 8.67 (m, 1H), 8.29 (m, 3H), 7.91 (m, 4H), 7.67 (m, 2H),

7.52 (m, 2H), 2.92 (s, 1H, OH), 2.91 (s, 1H) ppm; 13C NMR (75.5 MHz, CDCl3): δ = 135.7

(C), 135.3 (C), 135.2 (C), 135.0 (C), 133.3 (C), 130.0 (C), 128.9 (C), 129.0 (CH), 128.9 (CH),

128.6 (CH), 128.3 (CH), 128.3 (CH), 127.5 (CH), 127.4 (CH), 126.6 (CH), 126.5 (CH), 126.2

(CH), 126.2 (C), 125.7 (CH), 125.5 (CH), 86.6 (Calkyne), 76.4 (Calkyne–H), 69.1 (C–OH) ppm;

MS (ESI-TOF, MeCN) m/z (%): 289.10 (48) [M – OH]+.

7.2.4.10 [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B)

[Ru(bdmpza)Cl(PPh3)2] (14) (111 mg, 0.122 mmol) and 7-ethynyl-7H-benzo[no]tetraphen-7-

ol (36) (37.3 mg, 0.122 mmol) were suspended in THF (80 mL) and stirred at room

temperature for 72 h. The solvent of the deep blue solution was removed in vacuo to yield the

crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column

(silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with

CH2Cl2/acetone (1:1 v/v) and then the solvent was removed in vacuo. Separation of isomers

was achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1

v/v) yielding a blue isomer 37A (allenylidene trans to pyrazole) and a blue isomer 37B


OH

H

182


!! !

37A: Yield: 62.6 mg (0.067 mmol, 55%).

1H NMR (300 MHz, CD2Cl2): δ = 9.11 (d, 3JH,H = 7.4 Hz, 1H, BT–H), 8.92 (d, 3JH,H = 8.5 Hz,

1H, BT–H), 8.70 (d, 3JH,H = 7.9 Hz, 1H, BT–H), 8.42 (d, 3JH,H = 7.9 Hz, 1H, BT–H), 8.13 (d, 3JH,H = 7.4 Hz, 1H, BT–H), 7.98 (d, 3JH,H = 8.7 Hz, 1H, BT–H), 7.82 (s, 2H, BT–H), 7.57 (m,

8H, PPh3 + BT–H), 7.33 (m, 10H, PPh3 + BT–H), 7.13 (t, 3JH,H = 7.7 Hz, 1H, BT–H), 6.74 (s,

1H, CH), 6.10 (s, 1H, pz–H4´), 6.09 (s, 1H, pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–

Me5), 2.31 (s, 3H, pz–Me3), 1.93 (s, 3H, pz–Me3´) ppm; 13C NMR (75 MHz, CD2Cl2):

δ = 273.6 (d, 2JC,P = 19.2 Hz, Cα), 221.1 (d, 3JC,P = 3.5 Hz, Cß), 166.4 (CO2–), 156.3 (pz–C3´),

154.8 (pz–C3), 141.6 (pz–C5´), 140.5 (pz–C5), 139.8 (d, 4JC,P = 1.7 Hz, Cγ), 139.1 (BT–C),

136.2 (BT–C), 134.6 (d, 2JC,P = 7.0 Hz, o-PPh3), 134.4 (BT–C), 134.2 (BT–C), 133.8 (BT–C),

132.6 (d, 1JC,P = 48.9 Hz, i-PPh3), 130.5 (BT–CH), 130.0 (d, 4JC,P = 2.6 Hz, p-PPh3), 129.8

(BT–C), 129.7 (BT–CH), 129.7 (BT–CH), 129.1 (BT–C), 129.1 (BT–CH), 128.8 (BT–CH),

128.7 (BT–CH), 128.1 (d, 3JC,P =9.7 Hz, m-PPh3), 127.9 (BT–CH), 127.8 (BT–CH), 127.7

(BT–CH), 127.5 (BT–CH), 126.9 (BT–CH), 126.0 (BT–CH), 109.3 (pz–C4´), 108.4 (pz–C4),

69.4 (CH), 14.4 (pz–Me3´), 13.5 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm (one tertiary

carbon atom not observed); 31P NMR (122 MHz, CD2Cl2): δ = 35.2 ppm; IR (KBr): ṽ 1903

(m, C═C═C), 1661 (s, as-CO2–), 1560 (m, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%):

934.18 (100) [M]+, 855.22(23) [M – Cl – CO2]+; Elemental analysis calcd. (%) for

C53H42ClN4O2PRu: C 68.12, H 4.53, N 6.00; calcd. (%) for C53H42ClN4O2PRu × 0.15 CH2Cl2:

C 67.43, H 4.50, N 5.92; found: C 67.43, H 4.51, N 5.89.

37B: Yield: 17.1 mg (0.018 mmol, 15%).

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

C

C

A B

C

183


!! !

1H NMR (300 MHz, CD2Cl2): δ = 9.12 (d, 3JH,H = 7.5 Hz, 1H, BT–H), 8.93 (d, 3JH,H = 8.6 Hz,

1H, BT–H), 8.71 (d, 3JH,H = 7.9 Hz, 1H, BT–H), 8.44 (d, 3JH,H = 8.1 Hz, 1H, BT–H), 8.24 (d, 3JH,H = 7.5 Hz, 1H, BT–H), 8.03 (d, 3JH,H = 8.8 Hz, 1H, BT–H), 7.80 (d, 3JH,H = 3.9 Hz, 2H,

BT–H), 7.60 (m, 9H, PPh3 + BT–H), 7.38 (d, 3JH,H = 8.8 Hz, 1H, BT–H), 7.19 (m, 9H,

PPh3 + BT–H), 6.76 (s, 1H, CH), 5.91 (s, 1H, pz–H4´), 5.74 (s, 1H, pz–H4), 2.59 (s, 3H, pz–

Me5´), 2.55 (s, 3H, pz–Me5), 2.20 (s, 3H, pz–Me3), 1.40 (s, 3H, pz–Me3´) ppm; 13C NMR

(75 MHz, CD2Cl2): δ = 289.5 (d, 2JC,P = 18.4 Hz, Cα), 237.2 (Cß), 166.4 (CO2–), 156.2 (pz–

C3´), 154.8 (pz–C3), 142.4 (pz–C5´), 140.5 (pz–C5), 138.9 (BT–C), 138.3 (BT–C), 138.0 (Cγ),

135.4 (d, 1JC,P = 46.0 Hz, i-PPh3), 134.7 (d, 2JC,P = 9.2 Hz, o-PPh3), 134.2 (BT–C), 133.6 (BT–

C), 132.4 (BT–C), 132.2 (BT–CH), 132.0 (BT–C), 131.4 (BT–CH), 130.8 (BT–CH), 130.6

(BT–C), 130.2 (BT–CH), 129.8 (d, 4JC,P = 1.8 Hz, p-PPh3), 129.6 (BT–CH), 129.5 (BT–CH),

129.3 (BT–CH), 128.8 (BT–CH), 128.4 (BT–CH), 128.0 (d, 3JC,P = 9.2 Hz, m-PPh3), 127.8

(BT–CH), 127.6 (BT–CH), 126.5 (BT–CH), 125.3 (BT–C), 108.5 (pz–C4´), 108.3 (pz–C4),

70.0 (CH), 14.4 (pz–Me3´), 13.7 (pz–Me3), 11.9 (pz–Me5´), 11.3 (pz–Me5) ppm; 31P NMR

(122 MHz, CD2Cl2): δ = 32.3 ppm; IR (KBr): ṽ 1907 (m, C═C═C), 1662 (s, as-CO2–), 1560

(m, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%): 934.18 (100) [M]+.

7.2.4.11 Bisanthenequinone (39)

Bisanthenequinone was prepared similar to a route described by T. A. PAVICH et al.[306]

A solution of bianthrone (1.00 g, 2.60 mmol) in benzene (200 mL) was irradiated with a

mercury vapor lamp for 8 h under argon without external heating (approx. 40 °C). The

resulting brown precipitate (39) was filtered off, washed with benzene (2 × 20 mL) and

CH2Cl2 (3 × 10 mL) and dried in vacuo. Yield 200 mg (0.53 mmol, 20%).

A second crop of bisanthenequinone (39) could be obtained by irradiating the benzene

solution under aerobic conditions for 8 h. The resulting orange precipitate was filtered off,

washed with benzene (2 × 20 mL) and CH2Cl2 (3 × 10 mL) and dried in vacuo. Yield 360 mg

(0.95 mmol, 37 %). Total yield 560 mg (1.47 mmol, 57 %)

184


!! !

The compound is highly insoluble in any organic solvent and only allows the recording of a 1H NMR spectrum in D2SO4.

1H NMR (300 MHz, D2SO4): δ = 8.63 (d, 3JH,H = 8.3 Hz, 4H), 8.22 (d, 3JH,H = 8.1 Hz, 4H),

7.26 (t, 3JH,H = 7.9 Hz, 4H) ppm; IR (KBr): ṽ 3077 (w, CH), 2920 (w, CH), 2851 (w, CH),

1970 (vw), 1659 (vs), 1582 (vs), 1482 (m), 1450 (m), 1410 (m), 1340 (m), 1299 (m) cm–1;

Elemental analysis calcd. (%) for C28H12O2: C 88.41, H 3.18; found: C 87.47, H 3.28.

7.2.4.12 [RuCl2(═C═C═(FN))(PPh3)2] (45)

[RuCl2(PPh3)3] (839 mg, 0.84 mmol) and 9-ethynylfluoren-9-ol (380 mg, 1.84 mmol) was

dissolved in THF (50 mL) and stirred under reflux for 2 h. The solvent was removed in vacuo,

the crude product was dissolved in CH2Cl2 (5 mL) and n-pentane (100 mL) was added. The

resulting solution was stored overnight at 5 °C, the formed precipitate was filtered off,

washed with n-pentane (3 × 50 mL) and dried in vacuo. Complex 45 was obtained as a red

powder. Yield 650 mg (0.74 mmol, 88 %).

O

O

Ru

Ph3P Cl

PPh3Cl

C C C

185


!! !

1H NMR (CDCl3, 300 MHz): δ = 7.78–6.82 ppm (m, 38H, PPh3, FN); 1H NMR (CD2Cl2,

300 MHz): δ = 7.74–6.87 (m, 38H, PPh3, FN) ppm; 13C NMR (CD2Cl2, 75 MHz): δ = 313.8

(Cα), 239.1 (Cβ), 148.6–126.7 (Cγ, C(PPh3), C(FN)) ppm (The equilibrium between the 16 VE

complex and the two dimeric structures did not allow a definitive assignment of the aromatic

carbon atoms); 31P NMR (CDCl3, 122 MHz): δ = 29.1 ppm; IR (KBr): ṽ 1922 (m, C═C═C),

1599 (m), 1482 (m), 1434 (s) cm–1; MS (ESI-TOF, MeCN) m/z (%): 849.12 (100) [M – Cl]+,

890.15 (28) [M – Cl + MeCN]+; Elemental analysis calcd. (%) for C51H38Cl2P2Ru: C 69.23,

H 4.33; found: C 69.38, H 4.30.

45A, 45B: 31P NMR (CD2Cl2, 122 MHz): δ = 47.8 (d, 2JP,P = 35.6 Hz), 47.1 (d, 2JP,P = 37.3 Hz), 37.3 (d, 2JP,P = 26.7 Hz), 34.8 (d, 2JP,P = 26.7 Hz) ppm.

7.2.4.13 [RuCl2(═C═C═(AO))(PPh3)2] (46)

[RuCl2(PPh3)3] (200 mg, 0.21 mmol) and 10-ethynyl-10-hydroxyanthracen-9-one (46)

(150 mg, 0.64 mmol) were suspended in THF (50 mL) and stirred under reflux for 4 h. The

solvent was removed in vacuo, the crude product was dissolved in CH2Cl2 (3 mL) and

n-pentane (100 mL) was added. The resulting solution was stored overnight at 5 °C, the

Ru C C C

C C C Ru Cl

Cl

Cl

Cl

PPh3

Ph3PPPh3

Ph3P

Ru C C C

C C C Ru Cl

Cl

Cl

PPh3Ph3P

Ph3P PPh3

Cl

A

B

186


!! !

resulting precipitate was filtered off, washed with n-pentane (3 × 50 mL) and dried in vacuo.

Complex 46 was obtained as purple powder. Yield 159 mg (0.17 mmol, 83%).

1H NMR (CDCl3, 300 MHz): δ = 8.26 – 6.75 ppm (m, 38H, PPh3, AO); 13C NMR (CDCl3,

75 MHz): δ = 321.0 (Cα), 271.9 (Cβ), 136.8 – 125.6 (Cγ, C(PPh3), C(AO)) ppm (The

equilibrium between the 16 VE complex and the two dimeric structures did not allow a

definitive assignment of the aromatic carbon atoms); 31P NMR (CDCl3, 122 MHz):

δ = 25.1 ppm; IR (KBr): ṽ 1904 (w, C═C═C), 1677 (s), 1590 (m), 1284 (s) cm–1; MS (ESI-

TOF, MeCN) m/z (%): 661.06 (100) [RuCl(PPh3)2]+; Elemental analysis calcd. (%) for

C58H38Cl2OP2Ru: C 68.42, H 4.20; found: C 69.52, H 4.38.

46A, 46B: 31P NMR (CDCl3, 122 MHz): δ = 48.3 (d, 2JP,P = 35.6 Hz), 46.8 (d, 2JP,P = 37.9 Hz), 36.3 (d, 2JP,P = 26.7 Hz), 33.2 (d, 2JP,P = 26.7 Hz) ppm.

Ru

Ph3P Cl

PPh3Cl

C C C O

Ru C C C

C C C Ru Cl

Cl

Cl

Cl

PPh3

Ph3PPPh3

Ph3P

Ru C C C

C C C Ru Cl

Cl

Cl

PPh3Ph3P

Ph3P PPh3

Cl

A

B

O

O

O

O

187


!! !

7.2.4.14 [RuCl2(═C═C═(PCO))(PPh3)2] (47)

A suspension of [RuCl2(PPh3)3] (287 mg, 0.30 mmol) and 13-ethynyl-13-hydroxypentacen-6-

one (150 mg, 0.45 mmol) in THF (50 mL) was stirred under reflux for 3 h. The deep-blue

solution was filtered and the solvent removed in vacuo. The residue was dissolved in CH2Cl2

(10 mL), precipitated by the addition of n-pentane (100 mL) and removed by filtration. This

cycle was repeated three times and the product 47 was obtained as a dark-blue solid. Yield

235 mg (0.23 mmol, 77%).

Ru

Ph3P Cl

PPh3Cl

C C C O

188


!! !

1H NMR (CDCl3, 300 MHz): δ = 8.87 (s, 1H, PCO–H), 8.54 (s, 1H, PCO–H), 8.01 (d, 3JH,H = 8.3 Hz, 1H, PCO–H), 7.84 – 7.81 (m, 1H, PCO–H), 7.78 – 7.69 (m, 2H, PCO–H),

7.58 – 7.51 (m, 3H, Ar–H), 7.41 (s, 3H, Ar–H), 7.36 – 7.30 (m, 6H, Ar–H), 7.18 – 7.10 (m,

4H, Ar–H), 7.06 – 6.89 (m, 14H, Ar–H), 6.82 – 6.70 (m, 6H, Ar–H) ppm; 13C NMR (CDCl3,

75 MHz): δ = 298.3 (Cα), 238.5 (Cβ), 185.6 (C=O), 138.2 (Cγ), 137.2 – 126.6 (CAr) ppm (The

equilibrium between the 16 VE complex and the two dimeric structures did not allow a

definitive assignment of the aromatic carbon atoms); 31P NMR (CDCl3, 122 MHz): δ = 29.0

ppm; IR (CH2Cl2): ṽ 1918 (m, C=C=C), 1660 (s), 1617 (m), 1434 (s) cm–1; MS (ESI-TOF,

CH2Cl2) m/z (%): 977.15 (100) [M – Cl]+; Elemental analysis calcd (%) for C60H42Cl2OP2Ru:

C 71.15, H 4.18; found C 71.61, H 4.23.

47A, 47B: 31P NMR (122 MHz, CDCl3): δ = 47.8 (d, 2JP,P = 36.7 Hz), 46.1 (d, 2JP,P = 36.7 Hz), 38.7 (d, 2JP,P = 25.6 Hz), 35.4 (d, 2JP,P = 27.8 Hz) ppm.

Ru C C C

C C C Ru Cl

Cl

Cl

Cl

PPh3

Ph3PPPh3

Ph3P

Ru C C C

C C C Ru Cl

Cl

Cl

PPh3Ph3P

Ph3P PPh3

Cl

A

B

O

O

O

O

189


!! !

7.2.5 Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides

7.2.5.1 [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48)

To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (363 mg, 0.40 mmol) in THF (50 mL) 2-

ethynyl-6-methoxynaphthalene (150 mg, 0.82 mmol) was added and the reaction mixture was

stirred at room temperature for 16 h. The solvent was reduced in vacuo to 5 mL until

precipitation occurred. The precipitation was completed by storing in a freezer (–20 °C) for

24 h. The product was filtered off, washed with Et2O (3 × 20 mL) and n-pentane (20 mL) and

dried in vacuo. The complex 48 was obtained as orange crystals. Yield: 287 mg (0.26 mmol,

64%).

1H NMR (300 MHz, CD2Cl2): δ = 7.58 (t, 6H, 3JH,H = 9.1 Hz, o-PPh3), 7.43 (s, 1H, NAPH–

H1), 7.41 (s, 1H, NAPH–H5), 7.34 (t, 3H, 3JH,H = 7.5Hz, p-PPh3), 7.23 (t, 6H, 3JH,H = 7.2 Hz,

m-PPh3), 7.05 (m, 3H, NAPH–H3, NAPH–H4, NAPH–H8), 6.92 (d, 1H, 3JH,H = 8.4 Hz,

NAPH–H7), 6.59 (s, 1H, CH), 5.99 (s, 1H, pz–H4´), 5.96 (s, 1H, pz–H4), 5.11 (d, 4JH,P = 4.7 Hz, Hß), 3.88 (s, 3H, OMe), 2.53 (s, 3H, pz–Me5´), 2.46 (s, 3H, pz–Me5), 2.39 (s,

3H, pz–Me3), 1.87 (s, 3H, pz–Me3´) ppm; 13C NMR (75 MHz, CD2Cl2): δ = 363.2 (d, 2JC,P = 24.8 Hz, Cα), 166.6 (CO2

–), 157.2 (NAPH–C6), 155.4 (pz–C3´), 155.3 (d, 3JC,P = 2.0 Hz,

pz–C3), 141.6 (pz–C5´), 140.9 (d, 4JC,P = 2.0 Hz, pz–C5), 134.6 (d, 2JC,P = 8.9 Hz, o-PPh3),

133.0 (NAPH–C4a), 132.8 (d, 1JC,P = 48.6 Hz, i-PPh3), 130.2 (d, 4JC,P = 2.0 Hz, p-PPh3), 129.5

(NAPH–C8a), 129.1 (NAPH–C1), 128.1 (d, 3JC,P = 8.9 Hz, m-PPh3), 127.9 (NAPH–C3), 126.6

(NAPH–C8), 125.9 (d, J = 3.0 Hz, NAPH–C4a), 122.9 (NAPH–C7), 118.5 (NAPH–C5), 115.8

(d, 4JC,P = 4.0 Hz, NAPH–C2), 109.1 (pz–C4´), 109.0 (d, 3JC,P = 3.0 Hz, Cß), 106.1 (pz–C4), 68.9

(CH), 55.6 (OMe), 14.4 (pz–Me3´), 14.3 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm; 31P NMR (122 MHz, CD2Cl2): δ = 37.3 ppm; IR (KBr): ṽ 3053 (w, CH), 2990 (w, CH), 2957

(w, CH), 2924 (w, CH), 1671 (s, as-CO2–), 1635 (m), 1589 (m), 1562 (w, C═N) cm–1; MS

(ESI-TOF, CH2Cl2) m/z (%): 867.12 (100) [M + K]+, 851.15 (15) [M + Na]+, 829.16 (5)

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

OMe

190


!! !

[M + H]+; Elemental analysis calcd. (%) for C43H40ClN4O3PRu: C 62.35, H 4.87, N 6.76;

found: C 61.75, H 5.00, N 6.34.

7.2.5.2 [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49)

To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (909 mg, 1.00 mmol) in THF (150 mL)

1-ethynylpyrene (500 mg, 2.21 mmol) was added and the reaction mixture was stirred at room

temperature for 16 h. The solvent was reduced in vacuo to 30 mL until precipitation occurred.

The precipitation was completed by storing in a freezer (–20 °C) for 24 h. The product was

filtered off, washed with Et2O (3 × 20 mL) and n-pentane (20 mL) and dried in vacuo. The

complex 49 was obtained as orange crystals. Yield: 544 mg (0.79 mmol, 79%).

1H NMR (400 MHz, CD2Cl2): δ = 8.09 (m, 2H, Pyr–H), 7.96 (m, 4H, Pyr–H), 7.91 (m, 1H,

Pyr–H), 7.85 (d, 3JH,H = 8.1 Hz, 1H, Pyr–H), 7.57 (m, 6H, o-PPh3), 7.51 (d, 3JH,H = 8.1 Hz, 1H,

Pyr–H), 7.30 (m, 3H, p-PPh3), 7.18 (m, 6H, m-PPh3), 6.65 (s, 1H, CH), 6.00 (s, 1H, pz–H4´),

5.93 (s, 1H, pz–H4), 5.78 (d, 4JH,P = 4.7 Hz, 1H, Hß), 2.55 (s, 3H, pz–Me5´), 2.49 (s, 3H, pz–

Me5), 2.39 (s, 3H, pz–Me3), 1.88 (s, 3H, pz–Me3´) ppm; 13C NMR (100 MHz, CD2Cl2):

δ = 359.1 (d, 2JC,P = 23.1 Hz, Cα), 166.7 (CO2–), 155.6 (pz–C3´), 155.6 (pz–C3), 141.7 (pz–C5´),

141.0 (pz–C5), 134.7 (d, 2JC,P = 9.0 Hz, o-PPh3), 131.9 (Pyr–C), 131.5 (Pyr–C), 132.6 (d, 1JC,P = 47.6 Hz, i-PPh3), 129.4 (Pyr–C), 130.3 (d, 4JC,P = 2.6 Hz, p-PPh3), 128.1 (Pyr–CH),

128.1 (d, 3JC,P = 9.0 Hz, m-PPh3), 127.8 (Pyr–CH), 126.7 (Pyr–CH), 126.2 (Pyr–CH), 126.1

(Pyr–CH), 125.8 (Pyr–C), 125.6 (Pyr–C), 125.5 (Pyr–C), 125.4 (Pyr–C), 125.2 (Pyr–CH),

125.0 (Pyr–CH), 124.8 (Pyr–CH), 124.7 (Pyr–CH), 111.8 (d, 3JC,P = 2.6 Hz, Cß), 109.1 (pz–

C4´), 109.1 (d, 4JC,P = 3.9 Hz, pz–C4), 69.0 (CH), 14.4 (pz–Me3´), 14.4 (pz–Me3), 11.5 (pz–

Me5´), 11.4 (pz–Me5) ppm; 31P NMR (122 MHz, CD2Cl2): δ = 37.1 ppm; IR (KBr): ṽ 3048

NN N

N

Me

Me

Me

MeRu

OO

CClPh3P CH

191


!! !

(w, CH), 2955 (w, CH), 2922 (w, CH), 2853 (w, CH), 1672 (s, as-CO2–), 1632 (m), 1621 (m),

1592 (m), 1562 (w, C═N) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 872.16 (100) [M]+, 646.08

(90) [M – C18H10]+; Elemental analysis calcd. (%) for C48H40ClN4O2PRu: C 66.09, H 4.62, N

6.42; found: C 65.93, H 5.18, N 5.88.

7.2.5.3 1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51)

To a solution of pyrenophenone (50) (1.00 g, 3.27 mmol) in THF (60 mL) ethynylmagnesium

bromide (2.09 g, 16.33 mmol, 5.0 eq.) was added. The solution was stirred for 16 h at room

temperature and the reaction was quenched by the addition of water (50 mL). The solution

was extracted with CH2Cl2 (3 × 20 mL), dried (Na2SO4) and the solvent was removed in

vacuo. The product 51 was obtained as brownish tacky solid. Yield: 1.06 g (3.18 mmol, 97%).

1H NMR (300 MHz, CDCl3): δ = 8.68 (d, 3JH,H = 8.1 Hz, 1H, Pyr–H), 8.36 (d, 3JH,H = 9.4 Hz,

1H, Pyr–H), 8.17 (d, 3JH,H = 8.1 Hz, 1H, Pyr–H), 8.10 (d, 3JH,H = 7.7 Hz, 1H, Pyr–H), 8.02 (m,

4H, Pyr–H), 7.92 (d, 3JH,H = 7.7 Hz, 1H, p-Ph), 7.86 (m, 1H, Pyr–H), 7.58 (m, 2H, m-Ph), 7.28

(m, 2H, o-Ph), 3.86 (s, 1H, OH), 2.98 (s, 1H, CH) ppm; 13C NMR (75 MHz, CDCl3):

δ = 145.0 (Pyr–C1), 136.3 (i-Ph), 131.7 (Pyr–C), 131.2 (Pyr–C), 130.4 (Pyr–C), 128.6 (m-Ph),

128.1 (Pyr–CH), 128.0 (Pyr–C), 127.8 (Pyr–CH), 127.4 (Pyr–CH), 126.9 (p-Ph), 126.6 (o-

Ph), 126.1 (Pyr–CH), 125.8 (Pyr–CH), 125.4 (Pyr–CH), 125.4 (Pyr–CH), 124.7 (Pyr–C),

124.6 (Pyr–CH), 124.3 (Pyr–CH), 86.7 (Calkyne), 76.8 (Calkyne–H), 74.7 (C–OH) ppm; IR

(CH2Cl2): ṽ 3299 (s, OH), 2114 (w, C≡C) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 355.11 (30)

[M + Na]+, 687.23 (100) [2 × M + Na]+, 1019.35 (5) [3 × M + Na]+; Elemental analysis

calcd. (%) for C25H16O: C 90.33, H 4.85; found: C 89.43, H 4.54.

OH

H

192


!! !

7.2.5.4 [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B)

[Ru(bdmpza)Cl(PPh3)2] (14) (1.82 g, 2.00 mmol) and 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol

(51) (500 mg, 1.55 mmol) were suspended in THF (50 mL) and stirred at room temperature

for 4 d. The solvent of the red solution was removed in vacuo to yield the crude product. The

isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length

15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with


achieved by a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v)

yielding a purple isomer 54A (allenylidene trans to pyrazole) and a red isomer 54B


54A: Yield: 591 mg (0.62 mmol, 40%).

1H NMR (400 MHz, CD2Cl2): δ = 8.28 (d, 3JH,H = 7.4 Hz, 1H, Ar–H), 8.22 (m, 3H, Ar–H),

8.11 (d, 3JH,H = 8.8 Hz, 1H, Ar–H), 8.04 (m, 2H, Ar–H), 7.98 (d, 3JH,H = 7.9 Hz, 1H, Ar–H),

7.87 (d, 3JH,H = 9.3 Hz, 1H, Ar–H), 7.74 (d, 3JH,H = 7.5 Hz, 2H, Ar–H), 7.69 (t, 3JH,H = 7.4 Hz,

1H, Ar–H), 7.45 (t, 3JH,H = 7.5 Hz, 6H, PPh3), 7.34 (m, 3H, PPh3), 7.22 – 7.08 (m, 6H, PPh3,

2H, Ar–H), 6.60 (s, 1H, CH), 6.05 (s, 1H, pz–H4´), 5.13 (s, 1H, pz–H4), 2.56 (s, 3H, pz–Me5´),

2.25 (s, 3H, pz–Me5), 1.89 (s, 3H, pz–Me3), 1.81 (s, 3H, pz–Me3´) ppm; 13C NMR (101 MHz,

CD2Cl2): δ = 304.6 (d, 2JC,P = 26.3 Hz, Cα), 231.2 (Cβ), 166.8 (CO2–), 155.8 (pz–C3´), 154.5 (d,

3JC,P = 2.6 Hz, pz–C3), 147.2 (pz–C5´), 143.1 (d, 4JC,P = 2.6 Hz, pz–C5), 141.7 (Cγ), 139.9 (Ar–

C), 133.7 (d, 1JC,P = 47.3 Hz, i-PPh3), 134.3 (d, 3JC,P = 9.2 Hz, m-PPh3), 134.1 (Ar–C), 133.9

NN N

N

Me

Me

Me

MeRu

OO

C ClPh3P

NN N

N

Me

Me

Me

MeRu

OO

CClPh3PC

CC

C

A B

193


!! !

(Ar–C), 133.9 (Ar–CH), 133.4 (Ar–C), 132.2 (Ar–CH), 131.8 (Ar–C), 131.5 (Ar–C), 131.3

(Ar–C), 129.8 (d, 4JC,P = 6.6 Hz, p-PPh3), 129.3 (Ar–CH), 128.9 (m, Ar–CH), 128.6 (Ar–C),

128.1 (Ar–CH), 127.9 (Ar–CH), 127.7 (m, o-PPh3), 127.6 (Ar–CH), 126.6 (Ar–CH), 126.3

(Ar–CH), 125.4 (Ar–CH), 125.5 (Ar–CH), 125.4 (Ar–CH), 124.5 (Ar–C), 109.2 (pz–C4´),

108.0 (d, 4JC,P = 2.6 Hz, pz–C4), 69.1 (CH), 14.5 (pz–Me3´), 12.9 (pz–Me3), 11.5 (pz–Me5´),

11.0 (pz–Me5) ppm; 31P NMR (162 MHz, CD2Cl2): δ = 32.2 ppm; IR (CH2Cl2): ṽ 1918 (w,

C═C═C), 1663 (s, as-CO2–), 1559 (m, C═N) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 721.15

(100) [M –PPh3 + Na]+, 908.17 (0.3) [Ru(bdmpza)Cl(PPh3)2]+, 960.19 (0.2) [M]+; Elemental

analysis calcd. (%) for C55H44ClN4O2PRu: C 68.78, H 4.62, N 5.83; found: C 67.76, H 4.71,

N 5.94.

54B: Yield: 327 mg (0.34 mmol, 22%).

1H NMR (400 MHz, CD2Cl2): δ = 8.27 (m, 3H, Ar–H), 8.05 (m, 6H, Ar–H), 7.90 (d, 3JH,H = 7.2 Hz, 2H, Pyr–H), 7.69 – 7.48 (m, 10H, Ar–H/PPh3), 7.48 (s, 2H, Ar–H), 7.17 – 7.07

(m, 6H, PPh3), 6.65 (s, 1H, CH), 5.69 (s, 1H, pz–H4´), 5.32 (s, 1H, pz–H4), 2.56 (s, 3H, pz–

Me5´), 2.29 (s, 3H, pz–Me5), 1.97 (s, 3H, pz–Me3), 1.39 (s, 3H, pz–Me3´) ppm; 13C NMR

(75 MHz, CD2Cl2): δ = 315.6 (d, 2JC,P = 19.8 Hz, Cα), 241.9 (Cβ), 165.7 (CO2–), 155.4 (pz–

C3´), 154.2 (d, 3JC,P = 2.0 Hz, pz–C3), 147.4 (pz–C5´), 146.4 (d, 4JC,P = 3.0 Hz, pz–C5), 143.1

(Cγ), 142.3 (Ar–C), 139.8 (Ar–C), 134.1 (d, 2JC,P = 8.9 Hz, o-PPh3), 133.4 (d, 1JC,P = 46.6 Hz,

i-PPh3), 132.0 (Ar–CH), 131.9 (Ar–CH), 131.5 (Ar–C), 131.1 (Ar–C), 130.9 (Ar–C), 129.5

(d, 4JC,P = 8.9 Hz, p-PPh3), 129.0 (Ar–CH), 128.6 (Ar–CH), 128.5 (Ar–CH), 128.2 (Ar–C),

128.0 (Ar–CH), 127.6 (Ar–CH), 127.5 (d, 3JC,P = 9.9 Hz, m-PPh3), 126.9 (Ar–CH), 126.4 (Ar–

CH), 125.5 (Ar–CH), 125.1 (Ar–C), 125.0 (d, J = 9.9 Hz, Ar–CH), 124.3 (Ar–CH), 124.2

(Ar–C), 108.3 (pz–C4´), 107.6 (d, J = 3.0 Hz, pz–C4), 69.2 (CH), 14.4 (pz–Me3´), 13.1 (pz–

Me3), 11.6 (pz–Me5´), 10.8 (pz–Me5) ppm; 31P NMR (122 MHz, CD2Cl2): δ = 32.2 ppm; IR

(CH2Cl2): ṽ 1916 (m, C═C═C), 1670 (s, as-CO2–), 1565 (m, C═N) cm–1; MS (ESI-TOF,

MeCN) m/z (%): 646.08 (100) [Ru(bdmpza)Cl(PPh3)]+, 662.08 (52)

[Ru(bdmpza)Cl(PPh3) + O]+, 908.17 (37) [Ru(bdmpza)Cl(PPh3)2]+, 917.21 (8) [M –

CO2 + H]+, 960.19 (14) [M]+.

7.2.5.5 [Ru(bdmpza)Cl(PTA)(PPh3)] (55)

[Ru(bdmpza)Cl(PPh3)2] (14) (908 mg, 1.00 mmol) and PTA (157 mg, 1.00 mmol, 1.0 eq.)

were suspended in THF (50 mL) and heated under reflux for 1 h. The solvent was reduced in

194


!! !

vacuo (5 mL) and the product was precipitated with n-pentane (3 × 50 mL). The residue was

filtered off and dried in vacuo. The crude product was dissolved in CH2Cl2 and layered with

n-pentane leading to a yellow crystalline solid (55) that can be filtered off. Yield: 720 mg

(0.90 mmol, 90%).

1H NMR (400 MHz, CDCl3): δ = 7.66 (m, 6H, PPh3), 7.26 (m, 9H, PPh3), 6.40 (s, 1H, CH),

5.96 (s, 1H, pz–H4´), 5.64 (s, 1H, pz–H4), 4.37 (d, 3JH,H = 13.1 Hz, 3H, PTA–H), 4.23 (d, 3JH,H = 12.8 Hz, 3H, PTA–H), 3.89 (d, 3J = 15.2 Hz, 3H, PTA–H), 3.78 (s, 3H, PTA–H), 2.81

(s, 3H, pz–Me5´), 2.41 (br-s, 6H, pz–Me5, pz–Me3´), 1.59 (s, 3H, pz–Me3) ppm; 13C NMR (75 MHz, CDCl3): δ = 168.4 (CO2

–), 158.3 (d, 3JC,P = 1.9 Hz, pz–C3´), 155.7 (d, 3JC,P = 1.9 Hz,

pz–C3), 141.8 (pz–C5´), 141.2 (pz–C5), 137.1 (d, 1JC,P = 40.5 Hz, i-PPh3), 134.7 (d, 3JC,P = 9.7 Hz, o-PPh3), 129.3 (d, 4JC,P = 1.9 Hz, p-PPh3), 127.6 (d, 3JC,P = 9.0 Hz, m-PPh3),

109.5 (d, 4JC,P = 9.0 Hz, pz–C4), 109.5 (pz–C4´), 73.1 (d, 3JC,P = 5.8 Hz, N–CH2–N), 69.1 (CH),

52.4 (d, 1JC,P = 14.8 Hz, P–CH2–N), 16.7 (pz–Me3´), 14.0 (pz–Me3), 11.5 (pz–Me5´), 11.5 (pz–

Me5) ppm; 31P NMR (162 MHz, CDCl3): δ = 41.2 (d, 2JP,P = 43.5 Hz, PPh3), –27.5 (d, 2JP,P = 43.5 Hz, PTA) ppm; IR (CH2Cl2): ṽ 1661 (s, as-CO2

–), 1569 (m, C═N) cm–1; MS (ESI-

TOF, CH2Cl2) m/z (%): 803.17 (100) [M]+; Elemental analysis calcd. (%) for

C36H42ClN7O2P2Ru × CH2Cl2: C 50.04, H 4.99, N 11.04; found: C 49.97, H 4.85, N 11.06.

7.2.5.6 [Ru(bdmpza)Cl(PTA)2] (56)

[Ru(bdmpza)Cl(PPh3)2] (14) (200 mg, 0.25 mmol) and PTA (86.0 mg, 0.55 mmol, 2.2 eq.)

were suspended in THF (50 mL) and heated under reflux for 20 h. The solvent was reduced in

vacuo (5 mL) and precipitated with Et2O (25 mL). The residue was filtered off and dried in

vacuo yielding a pale yellow powder (56). Yield: 75 mg (0.11 mmol, 43%). The product

shows contamination with unreacted PTA.

NN N

N

Me

Me

Me

MeRu

OO

ClPh3P

NN

N

P

195


!! !

1H NMR (400 MHz, CD2Cl2): δ = 6.63 (s, 1H, CH), 5.79 (s, 2H, pz–H4, pz–H4´), 4.50 (m,

12H, N–CH2–N), 4.17 (t, 3JH,H = 14.6 Hz, 6H, P–CH2–N), 4.01 (m, 6H, P–CH2–N), 2.21 (s,

3H, pz–Me5´), 2.12 (s, 3H, pz–Me5), 1.80 (br s, 6H, pz–Me3´, pz–Me3) ppm; 13C NMR (75 MHz, CDCl3): δ = 170.3 (CO2

–), 147.3 (pz–C3, pz–C3´), 141.5 (pz–C5, pz–C5´), 106.8 (pz–

C4, pz–C4´), 74.7 (CH), 73.2 (m, N–CH2–N), 58.9 (d, 1JC,P = 13.9 Hz, P–CH2–N), 58.0 (d, 1JC,P = 16.1 Hz, P–CH2–N), 13.6 (pz–Me3, pz–Me3´), 11.6 (pz–Me5, pz–Me5´) ppm; 31P NMR

(162 MHz, CDCl3): The 31P NMR revealed several multiplets that might be attributed to a

possible equilibrium of protonated PTA ligands; IR (CH2Cl2): ṽ 1662 (s, as-CO2–), 1569 (m,

C═N) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%):977.33 (30) [Ru + (bdmpza) + 4 × PTA]+;

Elemental analysis calcd. (%) for C24H39ClN10O2P2Ru: C 41.29, H 5.63, N 20.06; found: C

39.83, H 5.89, N 19.17.

7.2.5.7 [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B)

[Ru(bdmpza)Cl(PTA)(PPh3)] (55) (150 mg, 0.19 mmol) and 9-ethynyl-9-fluorenol (77.0 mg,

0.37 mmol) were suspended in THF (50 mL) and stirred at room temperature for 2 d. At room

temperature no reaction occurs and the suspension was heated under reflux for 16 h leading to

a dark red solution. The solvent was removed in vacuo to yield the crude product. The

isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length

15 cm, Ø 4 cm), washed with a mixture of CH2Cl2/acetone (1:1 v/v) and the two structural

isomers were separated with acetone/H2O (95:5 v/v) yielding a purple isomer 57A

(allenylidene trans to pyrazole) Yield: 12.0 mg (0.02 mmol, 11%). The second isomer

appears as a red spot 57B (allenylidene trans to carboxylate) but the amount of isolated

complex did not allow further characterizations. The data reported in the following section

belong to the structural isomer with the allenylidene unit positioned trans to the pyrazole

moiety.

NN N

N

Me

Me

Me

MeRu

OO

Cl

NN

N

P

NN

N

P

196


!! !

1H NMR (300 MHz, CD2Cl2): δ = 7.76 (m, 4H, FN–H1, FN–H8, FN–H4, FN–H5), 7.57 (d,

3J = 7.4 Hz, 2H, FN–H3, FN–H6), 7.17 (m, 2H, FN–H2, FN–H7), 6.60 (s, 1H, CH), 6.31 (s, 1H,

pz–H4´), 6.04 (s, 1H, pz–H4), 4.52 (s, 6H, N–CH2–N), 4.24 (d, 2JH,H = 6.8 Hz, 6H, P–CH2–N),

2.89 (s, 3H, pz–Me5´), 2.58 (s, 3H, pz–Me5), 2.51 (s, 3H, pz–Me3´), 2.24 (s, 3H, pz–Me3) ppm; 13C NMR (75 MHz, CD2Cl2): δ = 294.2 (d, 2JC,P = 26.0 Hz, Cα), 230.3 (Cβ), 166.5 (CO2

–),

155.0 (pz–C3’), 154.0 (d, 3JC,P = 2.7 Hz, pz–C3), 144.8 (FN–C4b), 144.8 (FN–C4a), 144.3 (FN–

C9), 142.3 (Cpz-5’), 140.6 (d, 3J = 1.8 Hz, Cpz-5), 130.1 (FN–C2, FN–C7, FN–C3, FN–C6), 122.1

(FN–C1, FN–C8), 121.2 (FN–C4, FN–C5), 109.5 (pz–C4´), 108.4 (d, 4JC,P = 2.7 Hz, pz–C4), 73.8

(d, 3JC,P = 6.0 Hz, 3 × N–CH2–N), 69.3 (CH), 52.1 (d, 1JC,P = 18.0 Hz, 3 × P–CH2–N), 16.1

(pz–Me3´), 13.0 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm; 31P NMR (162 MHz, CD2Cl2):

δ = – 37.8 ppm; IR (CHCl3): ṽ 1923 (m, C═C═C), 1654 (s, as-CO2–), 1560 (w, C═N) cm–1;

MS (ESI-TOF, MeCN) m/z (%): 796.19 (33) [M + 2 × MeCN]+.

7.2.5.8 [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B)

[Ru(bdmpza)Cl(PTA)(PPh3)] (55) (300 mg, 0.37 mmol) and 1-phenyl-1-(pyren-1-yl)prop-2-

yn-1-ol (250 mg, 0.75 mmol) were suspended in THF (50 mL) and stirred under reflux for

16 h. The solvent was removed in vacuo to yield the crude product. The isomeric mixture was

dissolved in CH2Cl2 (3 mL) and loaded on a column (silica, length 25 cm, Ø 4 cm), washed

with a mixture of CH2Cl2/acetone (1:1 v/v) and the two structural isomers were separated with

acetone/MeOH (9:1 v/v) yielding a purple isomer 58A (allenylidene trans to pyrazole) Yield:

14.0 mg (0.02 mmol, 5%). The second isomer appears as a red spot 58B (allenylidene trans to

carboxylate) but the amount of isolated complex did not allow further characterizations. The

data reported in the following section belong to the structural isomer with the allenylidene

unit positioned trans to the pyrazole moiety.

NN N

N

Me

Me

Me

MeRu

OO

C ClPTA

NN N

N

Me

Me

Me

MeRu

OO

CClPTAC

CC

C

A B

197


!! !

1H NMR (400 MHz, CD2Cl2): δ = 8.50 (d, 3JH,H = 9.3 Hz, 1H, Pyr–H), 8.25 (m, 4H, Pyr–H),

8.14 (m, 2H, Pyr–H), 8.07 (m, 2H, o-Ph–H), 8.03 (d, 3JH,H = 7.6 Hz, 1H, Pyr–H), 7.97 (d, 3JH,H = 9.3 Hz, 1H, Pyr–H), 7.81 (t, 3JH,H = 7.5 Hz, 1H, p-Ph–H), 7.32 (t, 3JH,H = 7.6 Hz, 2H,

m-Ph–H), 6.48 (s, 1H, CH), 6.23 (s, 1H, pz–H4´), 5.36 (s, 1H, pz–H4), 4.14 (d, 2JH,H = 13.1 Hz,

3H, N–CH2–N), 3.94 (m, 9H, N–CH2–N, P–CH2–N), 2.78 (s, 3H, pz–Me5´), 2.51 (s, 3H, pz–

Me5), 2.29 (s, 3H, pz–Me3´), 1.97 (s, pz–3H, Me3) ppm; 13C NMR (75 MHz, CD2Cl2):

δ = 300.6 (d, 2JC,P = 26.3 Hz, Cα), 228.0 (Cβ), 166.9 (CO2–), 154.5 (pz–C3´), 154.2 (d,

3JC,P = 1.8 Hz, pz–C3), 147.9 (d, J = 1.8 Hz, i-Ph–C), 143.5 (d, J = 2.6 Hz, Pyr–C1), 142.1 (pz–

C5´), 140.0 (d, 4JC,P = 1.8 Hz, pz–C5), 139.6 (d, J = 2.6 Hz, Pyr–C), 132.0 (Pyr–C), 131.6 (d,

J = 1.8 Hz, 2 × Pyr–C), 130.2 (m-Ph–C), 129.7 (Pyr–CH), 128.9 (o-Ph–C), 128.7 (Pyr–C),

128.5 (Pyr–CH), 128.4 (Pyr–CH), 128.1 (p-Ph–C), 126.9 (Pyr–CH), 126.4 (Pyr–CH), 125.9

(Pyr–CH), 125.7 (Pyr–CH), 125.5 (Pyr–CH), 124.8 (Pyr–CH), 124.6 (Pyr–C), 109.3 (pz–C4´),

108.0 (d, 4JC,P = 3.5 Hz, pz–C4), 73.3 (d, 3JC,P = 6.1 Hz, 3 × N–CH2–N), 69.1 (CH), 52.0 (d, 1JC,P = 17.5 Hz, 3 × P–CH2–N), 15.9 (pz–Me3´), 12.8 (pz–Me3), 11.4 (pz–Me5´), 11.1 (pz–

Me5) ppm; 31P NMR (162 MHz, CD2Cl2): δ = –34.5 ppm; IR (CHCl3): ṽ 1919 (m, C═C═C),

1658 (s, as-CO2–), 1565 (w, C═N) cm–1; MS (ESI-TOF, CH2Cl2) m/z (%): 856.20 (9) [M]+,

1012.27 (100) [M + PTA]+.

NN N

N

Me

Me

Me

MeRu

OO

C ClPTA

NN N

N

Me

Me

Me

MeRu

OO

CClPTAC

CC

C

A B

198


!! !

7.2.6 Intramolecular Scholl Reaction of Pyrenophenone

7.2.6.1 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63); 11H-Indeno[2,1-a]pyren-11-one (64)

This procedure was adapted from literature.[291, 345]

AlCl3 (8.20 g, 61.5 mmol) and NaCl (1.80 g, 30.8 mmol) were melted at 130°C under aerobic

conditions. Pyrenophenone (50) (1.00 g, 3.26 mmol) was added under stirring in one portion

and the mixture was heated to 170°C and stirred for further 20 min. The yellow substance

turned to black and finally changed its colour to dark-red. After cooling to room temperature,

water (100 mL) was carefully added to the mixture. The crude product was extracted with

CH2Cl2 (3 × 100 mL) and after removal of the solvent a brown powder was obtained.

Purification was achieved via column chromatography with CH2Cl2:n-pentane = 3:1 as eluent

(silica, Ø = 6 cm, L = 30 cm) allowing the isolation of 64 (Rf = 0.70) and almost pure 63

(Rf = 0.35). Purification of 5 was achieved via a second column chromatography step with

pure CH2Cl2 as eluent (silica, Ø = 2 cm, L = 30 cm, Rf = 0.50).

6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one (63); yield: 148 mg (0.483 mmo, 15%); red

solid.

1H NMR (CD2Cl2, 300 MHz): δ = 8.39 (d, 3JH,H = 9.6 Hz, 1H), 7.86 (dd, 3JH,H = 8.3 Hz, 3JH,H = 2.8 Hz, 2H), 7.78 (dd, 3JH,H = 6.8 Hz, 3JH,H = 2.5 Hz, 1H), 7.65 (d, 3JH,H = 3.8 Hz, 2H),

7.55 (d, 3JH,H = 8.3 Hz, 1H), 7.47 (m, 3H), 7.23 (d, 3JH,H = 9.6 Hz, 1H), 4.31 (dd, 3JX,A = 18.1 Hz, 3JX,M = 6.4 Hz, 1H, C*H), 3.58 (dd, 3JM,A = 15.5 Hz, 3JM,X = 6.4 Hz, 1H, syn-

H), 2.99 (dd, 3JA,X = 17.9 Hz, 3JA,M = 15.8 Hz, 1H, anti-H) ppm; APT 13C NMR (CD2Cl2,

75.5 MHz): δ = 207.6 (CO), 150.8 (C), 142.6 (C), 139.7 (C), 138.3 (C), 134.0 (CH), 133.3

(CH), 132.5 (C), 131.3 (C), 130.6 (CH), 129.8 (CH), 129.7 (C), 128.6 (C), 128.3 (CH), 128. 2

(CH), 128.0 (CH), 127.6 (C), 127.0 (CH), 125.0 (CH), 124.9 (CH), 123.9 (CH), 38.9 (CH),

∗∗ CH2

O O

199


!! !

33.2 (CH2) ppm; IR (CHCl3): ṽ 1662 (m, C═O), 1620 (w, C═C), 1605 (m, C═C), 1597 (s,

C=C) cm–1; HRMS (ESI-TOF, MeOH/CH2Cl2) m/z (%): 307.1116 (100) [M + H]+; Mp.: 205–208°C; Elemental analysis calcd (%) for C23H14O: C 90.17, H 4.61; found: C 90.21, H

4.57.

11H-indeno[2,1-a]pyren-11-one (64); yield: 247 mg (0.812 mmol, 25%); yellow solid.

1H NMR (CD2Cl2, 300 MHz): δ = 9.17 (d, 3JH,H = 9.2 Hz, 1H), 8.19 (m, 5H), 8.07 (d, 3JH,H = 8.9 Hz, 1H), 7.99 (t, 3JH,H = 7.5 Hz, 1H), 7.73 (d, 3JH,H = 7.5 Hz, 1H), 7.66 (d, 3JH,H = 7.1 Hz, 1H), 7.53 (dt, 3JH,H = 7.4 Hz, 3JH,H = 1.1 Hz, 1H), 7.33 (dt, 3JH,H = 7.3 Hz,

3JH,H = 0.7 Hz, 1H) ppm; APT 13C NMR (CD2Cl2, 75.5 MHz): δ = 180.2 (CO), 144.8 (C),

144.5 (C), 142.9 (C), 140.9 (C), 136.7 (C), 134.9 (CH), 131.8 (CH), 131.4 (C), 130.9 (C),

130.8 (CH), 130.4 (C), 129.8 (CH), 128. 1 (CH), 127.9 (CH), 127.6 (CH), 126.9 (CH), 125.7

(C), 125.0 (C), 124.1 (CH), 123.3 (CH), 121.0 (CH), 116.8 (CH) ppm; IR (KBr): ṽ 1698 (s,

CO), 1625 (m), 1611 (s), 1590 (s, C═C) cm–1; HRMS (ESI-TOF, MeOH/CH2Cl2) m/z (%):

304.2624 (100) [M]+, 631.1679 (20) [2 × M + Na]+; Mp.: 245–248°C; Elemental analysis

calcd (%) for C23H12O: C 90.77, H 3.97; found: C 90.23, H 3.90.

201

8 APPENDIX

202

!Appendix

!! !

8.1 Details of the Structure Determinations

A Bruker-Nonius Kappa CCD, an Agilent SuperNova (Dual Source) or a Bruker Smart

APEXII diffractometer was used for data collection. Single crystals were coated with

perfluoropolyether, picked with a glass fiber, and immediately mounted in the nitrogen cold

gas stream of the diffractometer. The structures were solved by using direct methods and

refined with full-matrix least squares against F2(Siemens SHELX-97).[374] A weighting

scheme was applied in the last steps of the refinement with w = 1/[σ2(F02) + (aP)2 + bP] and

P = [2Fc2 + max(F0

2,0)]/3. Hydrogen atoms were included in their calculated positions and

refined in a riding model. All further details and parameters of the measurements are

summarized in Table 13 to Table 20. The structure pictures were prepared with the program

Diamond 2.1e.[375-377] The unit cell of 25B contains one n-hexane molecule which has been

treated as a diffuse contribution to the overall scattering without specific atom positions by

SQUEEZE/PLATON.[378-379]

Compound Dissolved in Layered with

[Ru(bdmpza)Cl(tBuISQ/IBQ)(PPh3)] (15) CH2Cl2/n-hexane n-hexane [Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16) CH2Cl2 n-hexane [Ru(bdmpza)Cl(CO)(PPh3)] (18B) CH2Cl2 n-hexane [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A) CH2Cl2 n-hexane

[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20B) CH2Cl2 n-hexane

[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A) CH2Cl2 n-hexane [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B) CH2Cl2 n-hexane

[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A) CH2Cl2 n-hexane

[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B) CH2Cl2 n-hexane

[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A) CH2Cl2 n-hexane [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) CH2Cl2 n-pentane Pyrenophenone (50) CH2Cl2/n-hexane slow evaporation

[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)]

(54B)

CH2Cl2 n-hexane [Ru(bdmpza)Cl(PTA)(PPh3)] (55) CH2Cl2 n-hexane 6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one

(63)

CH2Cl2 Et2O 11H-indeno[2,1-a]pyren-11-one (64) CH2Cl2/n-pentane slow evaporation

Table 12. Solvents used for crystallization.

203

!Appendix

!! !

[Ru(bdmpza)Cl(tBuISQ/IBQ)-(PPh3)] (15)

[Ru(bdmpza)Cl(ISQ/IBQ)-(PPh3)] (16)

empirical formula C44H51ClN5O3PRu C36H35ClN5O3PRu × 0.25 CH2Cl2 formula weight [g mol–1] 865.39 774.41 crystal color / habit green block blue block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 10.9262(8) 9.777(3) b [Å] 12.5322(12) 12.733(3) c [Å] 17.0543(16) 14.860(4) α [°] 107.131(7) 91.91(2) β [°] 93.042(8) 102.05(3) γ [°] 111.744(7) 108.86(2) V [Å3] 2037.9(3) 1701.8(8) θ [°] 6.2-26.5 6.25-26.5 h min, max – 13 to 13 – 12 to 12 k min, max – 15 to 15 – 15 to 15 l min, max – 21 to 21 – 18 to 17 F(000) 900 793 μ(Mo-Kα) [mm–1] 0.536 0.67 crystal size [mm] 0.254 × 0.225 × 0.169 0.165 × 0.099 × 0.079 Dcalcd [g cm–3] 1.41 1.511 T [K] 150(2) 150(2) reflections collected 17293 15195 indep. reflections 8277 6951 obs. reflections (>2σI) 6961 4138 parameter 504 450 wt. Parameter a 0.0206 0.0681 wt. Parameter b 1.2936 0.0000 R1, wR2 (obsd.) 0.0316, 0.0661 0.0738, 0.1428 R1, wR2 (overall) 0.0435, 0.071 0.1389, 0.1703 Diff. Peak / hole [e/Å3] 0.358 / –0.502 1.29 / –0.748 Goodness-of-fit on F2 1.041 1.014

Table 13. Structure determination details of complexes 15 and 16.

204

!Appendix

!! !

[Ru(bdmpza)Cl(═C═C═(FN))-(PPh3)] (20A)

[Ru(bdmpza)Cl(═C═C═(FN))-(PPh3)] (20B)

empirical formula C45H38ClN4O2PRu × H2O C45H38ClN4O2PRu × 2 CH2Cl2 formula weight [g mol–1] 852.30 1004.14 crystal color / habit brown block red block crystal system orthorombic triclinic space group, Z Pbca (No. 61), 8 P–1 (No. 2), 2 a [Å] 15.534(3) 12.0270(10) b [Å] 19.993(4) 12.4223(6) c [Å] 24.814(5) 14.9179(13) α [°] 90 98.766(5) β [°] 90 95.117(8) γ [°] 90 97.919(6) V [Å3] 7707(3) 2167.9(3) θ [°] 6.21-26.5 6.21-26.5 h min, max – 19 to 19 – 13 to 15 k min, max – 24 to 24 – 15 to 15 l min, max – 30 to 31 – 18 to 18 F(000) 3504.0 1024.0 μ(Mo-Kα) [mm–1] 0.565 0.752 crystal size [mm] 0.320 × 0.141 × 0.094 0.250 × 0.170 × 0.102 Dcalcd [g cm–3] 1.469 1.538 T [K] 150(2) 150(2) reflections collected 62130 25952 indep. reflections 7851 8825 obs. reflections (>2σI) 6066 7812 parameter 506 554 wt. Parameter a 0.0116 0.0901 wt. Parameter b 17.0595 10.8236 R1, wR2 (obsd.) 0.0389, 0.0762 0.0654, 0.1739 R1, wR2 (overall) 0.0622, 0.0855 0.0737, 0.181 Diff. Peak / hole [e/Å3] 0.819 / –0.523 1.513 / –1.81 Goodness-of-fit on F2 1.172 1.061

Table 14. Structure determination details of complexes 20A and 20B.

205

!Appendix

!! !

[Ru(bdmpza)Cl(═C═C═(AO))-(PPh3)] (25A)

[Ru(bdmpza)Cl(═C═C═(AO))-(PPh3)] (25B)

empirical formula C46H38ClN4O3PRu × CH2Cl2 C46H38ClN4O3PRu formula weight [g mol–1] 947.22 862.29 crystal color / habit brown block red block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 12.7183(13) 12.1411(7) b [Å] 12.9619(4) 12.4107(11) c [Å] 14.5615(11) 14.8427(12) α [°] 86.985(5) 93.010(8) β [°] 69.949(6) 98.019(5) γ [°] 77.142(6) 98.291(5) V [Å3] 2197.7(3) 2185.4(3) θ [°] 6.22-26.5 6.2-26.5 h min, max – 15 to 15 – 15 to 15 k min, max – 16 to 16 – 15 to 15 l min, max – 18 to 18 – 18 to 18 F(000) 968 884 μ(Mo-Kα) [mm–1] 0.621 0.499 crystal size [mm] 0.307 × 0.168 × 0.112 0.305 × 0.282 × 0.254 Dcalcd [g cm–3] 1.431 1.310 T [K] 153(2) 150(2) reflections collected 54811 31254 indep. reflections 8972 8938 obs. reflections (>2σI) 8522 8005 parameter 585 509 wt. Parameter a 0.0188 0.0510 wt. Parameter b 6.5351 1.7391 R1, wR2 (obsd.) 0.0450, 0.1097 0.0315, 0.0932 R1, wR2 (overall) 0.0475, 0.1111 0.0362, 0.096 Diff. Peak / hole [e/Å3] 1.378 / –0.753 0.612 / –0.557 Goodness-of-fit on F2 1.233 1.089


206

!Appendix

!! !

[Ru(bdmpza)Cl(═C═C═(PCO))-(PPh3)] (29A)

[Ru(bdmpza)Cl(═C═C═(PCO))-(PPh3)] (29B)

empirical formula C54H42ClN4O3PRu × 2 CH2Cl2 C54H42ClN4O3PRu × 2 CH2Cl2 formula weight [g mol–1] 1132.26 1132.26 crystal color / habit violet plate yellow block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 12.4473(11) 12.3917(5) b [Å] 13.2515(10) 13.4181(7) c [Å] 15.4170(9) 15.9204(3) α [°] 82.283(6) 90.222(3) β [°] 83.333(6) 93.896(4) γ [°] 85.279(6) 109.245(17) V [Å3] 2497.1(3) 2492.46(17) θ [°] 6.2-26.5 6.2-26.5 h min, max – 15 to 15 – 14 to 15 k min, max – 16 to 16 – 16 to 16 l min, max – 19 to 18 – 19 to 16 F(000) 1156.0 1156 μ(Mo-Kα) [mm–1] 0.664 0.665 crystal size [mm] 0.272 × 0.154 × 0.113 0.223 × 0.226 × 0.389 Dcalcd [g cm–3] 1.506 1.509 T [K] 150(2) 153(2) reflections collected 46376 24746 indep. reflections 10207 10166 obs. reflections (>2σI) 7515 9079 parameter 662 662 wt. Parameter a 0.0243 0.0859 wt. Parameter b 3.7984 0.5338 R1, wR2 (obsd.) 0.0506, 0.091 0.029, 0.0742 R1, wR2 (overall) 0.0829, 0.1015 0.0351, 0.078 Diff. Peak / hole [e/Å3] 0.749 / –0.677 1.735 / –0.789 Goodness-of-fit on F2 1.037 1.054


207

!Appendix

!! !

[Ru(bdmpza)Cl(CO)(PPh3)] (18B)

[Ru(bdmpza)Cl(═C═C═(BT))-(PPh3)] (37A)

empirical formula C31H30ClN4O3PRu C53H42ClN4O2PRu × 2 CH2Cl2 formula weight [g mol–1] 674.08 1104.25 crystal color / habit red block blue plate crystal system monoclinic triclinic space group, Z P 21/n (No. 14), 4 P–1 (No. 2), 2 a [Å] 16.4731(10) 11.095(2) b [Å] 10.7331(8) 11.579(2) c [Å] 18.2521(13) 20.263(4) α [°] 90 103.341(18) β [°] 113.487(4) 92.260(13) γ [°] 90 94.627(16) V [Å3] 2959.7(4) 2520.1(8)

θ [°] 6.2-26.5 6.21-26.5 h min, max – 12 to 20 – 13 to 13 k min, max – 9 to 13 – 14 to 14 l min, max – 22 to 20 – 25 to 25 F(000) 1376.0 1128.0 μ(Mo-Kα) [mm–1] 0.713 0.654 crystal size [mm] 0.165 × 0.135 × 0.120 0.216 × 0.143 × 0.139 Dcalcd [g cm–3] 1.513 1.455 T [K] 150(2) 150(2) reflections collected 19549 27332 indep. reflections 6050 10282 obs. reflections (>2σI) 4479 6684 parameter 374 644 wt. Parameter a 0.0368 0.0663 wt. Parameter b 3.7134 7.1940 R1, wR2 (obsd.) 0.0443, 0.0909 0.0792, 0.1699 R1, wR2 (overall) 0.073, 0.1019 0.1302, 0.1928 Diff. Peak / hole [e/Å3] 0.76 / –0.521 1.942 / –1.012 Goodness-of-fit on F2 1.021 1.047

Table 17. Structure determination details of complexes 18B and 37A.

208

!Appendix

!! !

[Ru(bdmpza)Cl(═C═CH(Pyr))-(PPh3)] (49)

[Ru(bdmpza)Cl-(═C═C═C(PhPyr))(PPh3)] (54B)

empirical formula C48H40ClN4O2PRu × C5H12 C55H44ClN4O2PRu formula weight [g mol–1] 1029.4 960.43 crystal color / habit red prism black block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 11.995(6) 11.8575(4) b [Å] 15.01(3) 12.6866(5) c [Å] 15.12(6) 14.7270(4) α [°] 108.26(16) 89.741(3) β [°] 103.18(11) 84.460(2) γ [°] 94.47(7) 81.454(3) V [Å3] 2484(11) 2180.46(13) θ [°] 6.21-26.5 2.82-26.73 h min, max – 15 to 15 – 14 to 14 k min, max – 18 to 18 – 15 to 16 l min, max – 18 to 18 – 18 to 18 F(000) 1064 988 μ(Mo-Kα) [mm–1] 0.554 0.507 crystal size [mm] 0.249 × 0.211 × 0.202 0.2259 × 0.1757 × 0.1611 Dcalcd [g cm–3] 1.376 1.463 T [K] 150(2) 180(2) reflections collected 28077 19715 indep. reflections 10098 9197 obs. reflections (>2σI) 6629 8051 parameter 608 581 wt. Parameter a 0.0961 0.0169 wt. Parameter b 3.2770 2.4714 R1, wR2 (obsd.) 0.0746, 0.1735 0.0349, 0.0759 R1, wR2 (overall) 0.1257, 0.2024 0.0428, 0.0796 Diff. Peak / hole [e/Å3] 1.363 / –1.283 0.402 / –0.344 Goodness-of-fit on F2 1.027 1.102

Table 18. Structure determination details of complexes 49 and 54B.

209

!Appendix

!! !

[Ru(bdmpza)Cl(PTA)(PPh3)] (55) Pyrenophenone (50)

empirical formula C36H42ClN7O2P2Ru × CH2Cl2 C23H14O formula weight [g mol–1] 888.15 306.34 crystal color / habit yellow block yellow block crystal system orthorombic triclinic space group, Z Pbca (No. 61), 8 P–1 (No. 2), 2 a [Å] 20.263(3) 8.6960(5) b [Å] 9.0183(6) 8.9100(3) c [Å] 41.404(5) 11.1780(4) α [°] 90 69.723(3) β [°] 90 80.622(4) γ [°] 90 69.626(4) V [Å3] 7566.0(14) 760.71(6) θ [°] 6.21-27.5 2.97-27.49 h min, max – 26 to 25 – 11 to 11 k min, max – 11 to 11 – 11 to 11 l min, max – 53 to 53 – 14 to 14 F(000) 3648 320 μ(Mo-Kα) [mm–1] 0.756 0.08 crystal size [mm] 0.25 × 0.13 × 0.08 0.26 × 0.20 × 0.11 Dcalcd [g cm–3] 1.559 1.337 T [K] 150(2) 150(2) reflections collected 90917 21718 indep. reflections 8575 3482 obs. reflections (>2σI) 6344 2743 parameter 473 217 wt. Parameter a 0.0400 0.0836 wt. Parameter b 20.5593 0.1325 R1, wR2 (obsd.) 0.0504, 0.1036 0.0454, 0.1301 R1, wR2 (overall) 0.0797, 0.1146 0.061, 0.1434 Diff. Peak / hole [e/Å3] 1.007 / –1.318 0.358 / –0.293 Goodness-of-fit on F2 1.061 1.099

Table 19. Structure determination details of compounds 55 and 50.

210

!Appendix

!! !

6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one (63)

11H-indeno[2,1-a]pyren-11-one (64)

empirical formula C23H14O C23H12O formula weight [g mol–1] 306.34 304.33 crystal color / habit red block yellow block crystal system orthorombic orthorombic space group, Z Pna21 (No. 33), 4 P212121 (No. 19), 4 a [Å] 14.4440(18) 4.5831(8) b [Å] 7.484(4) 15.039(3) c [Å] 13.509(3) 20.610(4) α [°] 90 90 β [°] 90 90 γ [°] 90 90 V [Å3] 1460.3(9) 1420.6(4) θ [°] 3.2-27.52 1.98-27.19 h min, max – 18 to 18 – 5 to 2 k min, max – 9 to 9 – 19 to 19 l min, max – 17 to 13 – 26 to 26 F(000) 640 632 μ(Mo-Kα) [mm–1] 0.084 0.086 crystal size [mm] 0.22 × 0.16 × 0.12 0.24 × 0.18 × 0.14 Dcalcd [g cm–3] 1.393 1.423 T [K] 150(2) 150(2) reflections collected 16840 11834 indep. reflections 3115 3150 obs. reflections (>2σI) 2450 2385 parameter 217 217 wt. Parameter a 0.0636 0.074 wt. Parameter b 0.6588 0.0000 R1, wR2 (obsd.) 0.00546, 0.1231 0.0498, 0.1224 R1, wR2 (overall) 0.00774, 0.1362 0.0787, 0.1446 Diff. Peak / hole [e/Å3] 0.519 / –0.303 1.513 / –1.81 Goodness-of-fit on F2 1.069 1.106

Table 20. Structure determination details of compounds 63 and 64.

211

!Appendix

!! !

8.2 Cyclic Voltammetry

Figure 62. Cyclic voltammogram for complexes 14, 19B, 20A, 20B, 25A, 25B, 37A, 37B, 54A and 54B in CH2Cl2 with nBu4NPF6 (0.1 M) as supporting electrolyte at a scan rate of 100 mV/s (vs. Fc/Fc+) (* indicates signal corresponding to Fc/Fc+).

212

!Appendix

!! !

Figure 63. Cyclic voltammogram for complex 29B in MeCN with nBu4NPF6 (0.1 M) as supporting electrolyte at a scan rate of 200 mV/s (vs. Fc/Fc+).

213

!Appendix

!! !

Table 21. Cyclic voltammograms were recorded at 20 °C in dichloromethane, with nBu4NPF6 (0.1 M) as electrolyte, potentials are given relatively to ferrocenium/ferrocene as internal standard, at a scan rate of 100 mV/s.

Compound

E1/2 (m

V)

ΔEp a (m

V)

ipa /ipc

E1/2 (m

V)

ΔEp a (m

V)

ipa /ipc

E1/2 (m

V)

ΔEp a (m

V)

ipa /ipc

reduction processes

Ru(II)/ Ru(III)

14 - - - - - -

394

73

0.80

19B

–1631

92

0.67

- - -

265

82

0.71

20A

–1932

85

0.45

–1273

64

0.76

389

73

0.94

20B

–1937

74

0.96

–1273

64

0.64

371

73

0.91

25A

–1479

74

0.99

–1013

73

0.94

466

64

0.98

25B

–1315

91

0.88

–870

82

0.94

641

83

0.95

37A

–1914

82

0.83

–1228

83

0.71

87

73

0.86

37B

–1859

64

0.97

–1168

73

0.61

188

72

0.97

54A

–2178

105

0.23

–1548

64

0.17

252

73

0.85

54B

- - -

–1182

64

0.07

320

64

0.55

214

!Appendix

!! !

8.3 Myoglobin Assay of CORMs

Figure 64. CO release of [Mn(bpzp)(CO)3] 4 in the dark measured via myoglobin assay.

Figure 65. CO release of [MnBr(HPz)2(CO)3] 5 in the dark measured via myoglobin assay.

0 200 400 600 8000.0

0.2

0.4

0.6

0.8

1.0

eq. (

CO

)

t [min]

0 50 100 150 200 250 300 350 400 4500.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

eq. (

CO

)

t [min]

215

!Appendix

!! !

Figure 66. CO release of [Mn(HIm)3(CO)3]Br 6 in the dark measured via myoglobin assay.

0 50 100 150 200 250 300 3500.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

eq. (

CO

)

t [min]

216

!Appendix

!! !

8.4 List of Abbreviations and Symbols

!HOMO highest occupied molecular orbital

!MeCN acetonitrile!

!OAc acetate!

AO anthrone

APH aminophenol

APT attached proton test

Ar aryl

bpy 2,2´-bipyridine

br broad

BT benzotetraphene

calcd. calculated

Cp cyclopentadienyl

d doublet (NMR spectroscopy)!

dd double doublet (NMR spectroscopy)!

dec. decomposition!

DFT density functional theory !

DMSO dimethyl sulfoxide

dppe 1.2-bis(diphenylphosphino)ethane

dppm 1.1-bis(diphenylphosphino)methane

EA elemental analysis !

ESI electrospray ionization

FN fluorene

h hour

Hbdmpza 2,2-bis(3,5-dimethylpyrazol-1-yl)acetic acid

2,2-Hbdmpzp 2,2-bis(3,5-dimethylpyrazol-1-yl)-propionic acid

3,3-Hbdmpzp 3,3-bis(3,5-dimethylpyrazol-1-yl)propionic acid

Hbpza 2,2-bis(pyrazol-1-yl)acetic acid

3,3-Hbpzp 3,3-bis(pyrazol-1-yl)propionic acid

Hz Hertz

i ipso

IBQ iminobenzoquinonate

217

!Appendix

!! !

IR infrared!

ISQ iminobenzosemiquinonate

J coupling constant!

LUMO lowest unoccupied molecular orbital!

m medium (IR spectroscopy)!

m meta

m multiplet (NMR spectroscopy)!

M.p. melting point

MLCT metal-to-ligand charge-transfer

MS mass spectrometry

n-BuLi n-butyllithium!

NMR nuclear magnetic resonance

o ortho

OTF Trifluoromethanesulfonate

p para

PC pentacene

PCO pentacenone

Ph phenyl

ppm parts per million!

PTA 1,3,5-triaza-7-phosphaadamantane

Pyr pyrene

RCM ring closing metathesis

s singlet (NMR spectroscopy)!

s strong (IR spectroscopy) !

t triplet (NMR spectroscopy)! tBu tert-butyl tBuAPH 2-amino-4,6-di-tert-butylphenol

TD-DFT time-dependent density functional theory

THF tetrahydrofuran

Tol tolyl

TON turnover number

Tp hydridotris(pyrazol-1-yl)borato

Tpm trispyrazolylmethane

triphos 1,1,1-tris(diphenylphosphinomethyl)ethane

218

!Appendix

!! !

UV/Vis ultraviolet/visible

ṽ wavenumber

VE valence electron

w weak

δ chemical shift

ε molar extinction coefficient

219

!Appendix

!! !

8.5 List of Compounds [Mn(bpzp)(CO)3] (4)

[Mn(HIm)3(CO)3]Br (6)

[Ru(bdmpza)H(CO)2] (11A/11B)

[Ru(bdmpza)(CO)(μ2-CO)]2 (12)

[Ru(bpza)Cl(CO)2] (13)

[Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16)

[Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (19A/19B)

[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B)

10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23)

10-Ethynyl-10-hydroxyanthracen-9-one (24)

[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B)

[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B)

[Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31)

7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35)

7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36)

[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B)

Bisanthenequinone (39)

[RuCl2(═C═C═(FN))(PPh3)2] (45)

[RuCl2(═C═C═(AO))(PPh3)2] (46)

[RuCl2(═C═C═(PCO))(PPh3)2] (47)

[Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48)

[Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49)

1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51)

[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B)

[Ru(bdmpza)Cl(PTA)(PPh3)] (55)

[Ru(bdmpza)Cl(PTA)2] (56)

[Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B)

[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B)

6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63)

11H-Indeno[2,1-a]pyren-11-one (64)

221

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10 DANKSAGUNG

242

!Danksagung

!! !

Mein besonderer Dank gilt meinem Doktorvater Prof. Dr. Nicolai Burzlaff für die Aufnahme in

seine Arbeitsgruppe, das interessante Thema, die Freiräume, Themenbereiche neu zu erschließen

und die Unterstützung durch zahlreiche Diskussionen diese Promotion zielführend zu bearbeiten.

Ganz herzlich möchte ich mich auch bei Prof. Dr. Sjoerd Harder und insbesondere dessen

Vorgänger Prof. Dr. Dr. h.c. mult. Rudi van Eldik für die unkomplizierte Aufnahme in den

Lehrstuhl und das positive Arbeitsklima bedanken.

Weiterhin gebührt mein Dank allen Kooperationspartnern, mit denen ich während meiner

Promotionsarbeit zusammenarbeiten durfte. Vielen Dank an Prof. Dr. Rik R. Tykwinski, Andreas

Waterloo und Johanna Januszewski für die Bereitstellung einer Vielzahl an Propargylalkoholen

und die Zusammenarbeit im Rahmen der resultierten Veröffentlichungen. Prof. Dr. Tim Clark und

Christian Wick danke ich für die theoretischen Berechnungen im Rahmen des Projekts über die

Scholl-Reaktion. Prof. Dr. Ulrich Schatzschneider und Dr. Hendrik Pfeiffer danke ich für die

freundlichen Gespräche und die Messungen in Würzburg im Rahmen des CORM-Projekts. Ganz

herzlich danke ich Jun.-Prof. Dr. Eike Hübner für die DFT-Berechnungen zu den

Allenylidenkomplexen.

Des Weiteren gebührt mein Dank allen Mitarbeitern des Departments für Chemie und Pharmazie,

die maßgeblich zum Gelingen dieser Arbeit beigetragen haben. Ich danke Dr. Achim Zahl und

Jochen Schmidt, Dr. Frank Heinemann, Christina Wronna, Ursula Niegratschka, Dr. Carlos

Dücker-Benfer, Dr. Jörg Sutter und Dr. Christian Färber, sowie allen Mitarbeitern der Werkstatt,

der Glasbläserei und der Chemikalienausgabe. Nochmals bedanken möchte ich mich bei Olli und

Max für das Messen der unzähligen Massenspektren und bei Johannes sowie Philipp für das

Vermessen der Kristallstrukturen nach vorhergehenden Suchaktionen.

Ein Dank gilt meinen Laborpartnern, egal ob im 3. Stock oder Keller, Steffi, Andy, Viola, Susy

und Fabi, die mich stets unterstützt haben und für eine angenehme Stimmung sowie interessante

Diskussionen gesorgt haben. Danken möchte ich auch den Ehemaligen (Gazi, Stefan, Fatima,

Tom, Sascha, Nico), den Aktuellen (Eva, Thomas, Tobi, Susy, Philipp) und den Neuen des AKs

(Lisa, Marleen, Fabi, Stephan) für die kollegiale Zusammenarbeit und das positive Arbeitsklima.

Bei Nico möchte ich mich noch einmal Bedanken für die Unterstützung während der gesamten

Promotion, das Aufbauen wenn´s nicht nach Plan läuft und die lustige Zeit in unserem Bunker

ohne Fenster „besonders gegen Ende“.

Der größte Dank gebührt jedoch meiner Freundin Lisa und meiner Familie, ohne deren

Unterstützung und Hilfe in den letzten Jahren diese Dissertation nie gelungen wäre.

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