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Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part H [1] Etherate and Aniline Compounds of Cd(H)

S. P. Perlepes, Th. F. Zafiropoulos, J. K. Kouinis, and A. G. Galinos* Department of Inorganic Chemistry, University of Patras, Patras, Greece

Z. Naturforsch. 35 b, 1241-1243 (1980); received April 24, 1980 Ether, Aniline, Cadmium, Mixed Haloacids

The preparation of new etherate and aniline compounds of the mixed complex halo-acids HCdCl2l and H2CdI2Cl2 is reported.

Analytical, conductometric, spectral (UV and IR) and data from X-ray powder spectra were used for the characterization of the complexes. The structure of the aniline com-plexes, in the solid state, cannot be deduced with certainty.

The literature contains reports of a large number of salts of the complex anions [CdXs] - and [CdX^ 2 - , where X = Cl, Br, I. The situation, however, with regard to the corresponding free acids is not very clear. The study of these acids is of special interest, because they have been proposed as intermediates in some Friedel-Crafts reactions and in chain poly-merizations.

Several years ago, one of us prepared and studied the properties of the etherate compounds of the mixed complex haloacids HCdCLBr, HCdBr2Cl, HCdI2Cl and HCdI2Br [2]. Salts of the general type (acrH)CdX2Y and (acrH)2CdX2Y2 (X, Y different halogens and acr = acridine) have, also, been re-ported [3]. Very recently, we have established the preparative conditions and conducted a detailed

study of the compounds of the acids HCdl3 and H2Cdl4 with various Lewis organic bases [4].

The analytical results and some physicochemical data of the complexes prepared are given in the Table.

Etherate Complexes The etherates are viscous, oily liquids, fume in

the air and are insoluble in nonpolar solvents. The Am values for completely dissociated 1 : 1 and 1 : 2 electrolytes in CH3NO21, are larger than those found for the ether complexes HCdCLI • 3 Et 2 0 and H2CdI2Cl2 • 4 Et 2 0, respectively [5]. This suggests that either the ionic migration velocity of the ether complexes is low or that some ion-pair formation has taken place [6].

Table. Analytical results, yields, colors, melting points and Am values of the new etherate and aniline compounds of the mixed complex haloacids of Cd(II).

Complex [%] Acidic hydro-gen

Cd Cl I B Yield» [%] Color m.p.b

[°C] Am'

[S cm2 mol-1]

HCdCl2I • 3 Et20 Calcd Found

0.19 0.18

21.06 20.87

13.29 12.11

23.78 24.62

41.67 42.19

83 pale orange

44 e

H2CdI2Cl2 • 4 Et20 Calcd Found

0.27 0.27

15.28 15.01

9.64 9.07

34.50 33.68

40.30 41.97

71 crimson 112 e

HCdCl2I • 3 An Calcd Found

0.17 0.17

19.03 19.19

12.00 11.10

21.49 21.84

47.31 46.63

79 white 160d 63 99

H2CdI2Cl2 • 4 An Calcd Found

0.25 0.26

13.85 14.86

8.73 8.50

31.27 31.83

45.90 46.42

59 yellow 111 139 189

Et20 = diethyl ether; An = aniline; B = Et20, An. a Based on the metal. b Uncorrected. 0 Values of molar conductance for ca. 10~3 M solutions in CH3NO2 (left column) and in CH3COCH3 at 25 °C; the compounds were assumed monomeric in solution, d = decomposition, e No data.

* Reprint requests to Prof. A. G. Galinos. 0340-5087/80/1000-1241/$ 01.00/0

1242 S. P. Perlepes et al. • Compounds of Complex Halo and Pseudohalo Acids

The IR spectra of the complexes are similar. The only absorption bands that do not correspond to bands of the spectrum of diethyl ether, are a broad band of medium intensity at 3350 cm - 1 and two others at 2900 and 1095 cm-i. The first of these bands shows, probably, that the Et2OH+ ion is involved in hydrogen bonding [7]. In addition, in the spectrum of H2CdI2Cl2 • 4 Et20 a medium band appeared at 260 cm-1, a frequency which is closely similar to that found for the asymmetric stretching vibration (v3) of the tetrahedral [CdCl4]2- ion [8]. We assign this band to a stretching mode Cd-Cl of the anion [CdI2Cl2]2~ (C2>, symmetry). The existence of Cd<- 0 bonds cannot be established from the spectra.

It is, therefore, concluded, that the two proton acids exist as their complexes, and that their properties are consistent with the formulations [CdCl2I]-[(Et20)2H]+ and [CdI2Cl2]2- • 2 [(Et20)2H]+. Such formulations have been established [2, 6].

Aniline Complexes The aniline complexes are formed by the complete

replacement of the ether by aniline molecules. They are crystalline solids and stable in the normal laboratory atmosphere over a long period of time. The complexes are insoluble in nonpolar solvents, somewhat soluble in H 2 0 and alcohols and soluble in CH3N02, C6H5N02, DMF and DMSO. They are readily decomposed by dilute mineral acids.

From the /IM values obtained, it is concluded that HCdCloI • 3 An behaves in CH3N02 and CH3C0CH3 as 1 : 1 electrolyte, while H2CdI2Cl2 • 4An as 2 : 1 electrolyte in both solvents [5].

The UV spectra of the aniline complexes in C2HsOH, show the presence of the AnH+ ion in solution [1, 4, 9].

The X-ray powder patterns of the two complexes are different; both patterns suggest, by the multi-tude of the reflections, that the crystals formed are of low symmetry.

The complexes have IR spectra, in the solid state, indicative of the presence of coordinated aniline and of the existence of a Cd-N bond [10]. The anti-symmetric and symmetric -NH 2 stretching vibra-tions of the coordinated aniline occur at 3295 and 3235 cm - 1 respectively for both complexes. The band near 340 cm -1, present in the spectra of both complexes, is associated with a v(Cd-N) vibration or with an aniline deformation vibration that be-

comes strongly IR active on coordination [10]. Both spectra exhibit additional absorption bands, characteristic of the AnH+ ion [1, 4, 9]. The only marked difference between the two spectra is the region at ca. 3000 cm -1. The appearance, in the IR spectrum of HCdCl2I • 3An, of two strong and broad bands at ca. 2900 and 2600 cm - 1 is attributed to the AnH+ ion, involved in hydrogen bridging [1, 4, 9], while the appearance of well separated bands between 3040 and 2920 cm -1, in the spectrum of H2CdI2Cl2 • 4 An, is a good evidence of the presence of the -NH3+ group, not involved in strong hydrogen bond [9]. No strong band, which would be assigned to a Cd-Cl stretching mode, is observed above 250 cm - 1 (the low frequency limit of the instrument used); thus, the IR evidence is strongly in favour of an octahedral environment about cadmium [11].

Since terminal Cd-Cl stretching vibrations i>(Cd-Cl)t in monomeric and polymeric complexes of cadmium occur, usually, near or below 250 cm-1

[12-14], there is no positive evidence for the coordi-nation arrangement in the aniline complexes.

For the compound H2CdI2Cl2 • 4An the most probable spatial arrangement is [CdI2Cl2(An)2]2- • 2[AnH]+. For the compound HCdCl2I • 3An there is a possible monomeric pseudotetrahedral struc-ture of the type [CdCl2IAn]-[An H An]+, even though a polymeric octahedral one cannot be ruled out; this is in accord with the fact that cad-mium complexes, having, in addition to others, halogens as ligands, show a notable and much varied structural behaviour [12-17].

Experimental The preparation of the etherate complexes was

carried out by the "etherohalogenosis" method [2], The compound HCdCl2I • 3 Et20 was prepared by a method similar to that for HZnCl2I • 3 Et 20 [1]. For the preparation of H2CdI2Cl2 • 4 Et20, anhy-drous Cdl2 (5.49 mmol) and an ether solution of HCl (14.50 mmol) were used as starting materials. The reaction time was ca. 12 h. The preparation of H2CdI2Cl2 • 4An has been achieved by a method previously described [1, 4, 9]. For the preparation of HCdCl2I • 3 An, aniline Avas added in an ether suspension of HCdCl2I • 3 Et20 Avith the immediate precipitation of the Avhite aniline complex.

The instruments, apparatus and procedures for the quantitative analysis and for the physico-chemical measurements of the complexes have been previously described in detail [1,4].

One of us (S. P. P.) is grateful to the National Hellenic Research Foundation for financial support.

1243 S. P. Perlepes et al. • Compounds of Complex Halo and Pseudohalo Acids

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