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Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part I Etherate, Pyridine and Aniline Compounds of Zn(II)

A . G . G a l i n o s * , J . K . K o u i n i s , P . V . I o a n n o u , T h . F . Z a f i r o p o u l o s , a n d S. P . P e r l e p e s

Department of Inorganic Chemistry, University o f Patras, Patras, Greece

Z. Naturforsch. 34b , 1101-1106 (1979); received M a y 11, 1979

Ether, Pyridine, Aniline, Thiocyanate , Zinc

The preparation o f sixteen new etherate, pyridine and aniline c o m p o u n d s of complex halo and pseudohalo acids o f Z n ( I I ) is reported.

The study of some physical and chemical properties as well as the U V and I R spectra o f these compounds are discussed. Tetrahedral structures are proposed for all c ompounds in the solid state.

Introduct ion

A l t h o u g h a l a r g e n u m b e r o f s a l t s o f t h e c o m p l e x

a n i o n s [ M n X 3 ] - a n d [ M n X 4 ] 2 ~ is k n o w n , t h e s i t u a -

t i o n w i t h r e g a r d t o t h e c o r r e s p o n d i n g a c i d s is n o t

v e r y c l e a r . T h e s t u d y o f t h e s e a c i d s is o f s p e c i a l

i n t e r e s t , s ince a g r e a t n u m b e r o f t h e m is u s e d i n

c e r t a i n F r i e d e l - C r a f t s r e a c t i o n s . T h e c a t a l y t i c a c t i o n

o f t h e e t h e r a t e HAICI4 • 2 E t 2 0 h a s b e e n s t u d i e d [1] .

T h e p r e p a r a t i o n o f e t h e r a t e a n d p y r i d i n e c o m p o u n d s

o f t h e a c i d s H Z n C l 2 B r , H Z n B r 3 a n d H Z n I 2 B r h a s

b e e n r e p o r t e d [2-4] . R e c e n t l y , w e p r e p a r e d a n d

s t u d i e d t h e c o m p l e x c o m p o u n d s H Z n C l 3 • 3 A n ,

H Z n B r 2 C l • 3 A n a n d H Z n I 2 C l • 3 A n , w h e r e A n =

a n i l i n e [5].

T h e s t u d y o f c o m p o u n d s o f m i x e d c o m p l e x

m e t a l l o h a l o a c i d s w i t h p s e u d o h a l o g e n s is o f s o m e

t h e o r e t i c a l i n t e r e s t . T h e i s o l a t i o n o f t h e c o m p o u n d s

H Z n C l 2 ( C S N ) • 2 E t 2 0 a n d H Z n B r 2 ( C S N ) • 2 E t 2 0

h a s b e e n a c h i e v e d i n t h e p a s t [6]** . T h e e t h e r a t e ,

p y r i d i n e a n d a n i l i n e c o m p o u n d s o f t h e a c i d s

H I 1 1 X 3 S C N ( X = Cl , B r , I ) h a v e a l s o b e e n p r e p a r e d

a n d s t u d i e d [7, 8].

A s a c o n t i n u a t i o n o f t h e i n t e r e s t o f o u r l a b o r a t o r y

i n t h e c o m p l e x h a l o a c i d s a n d t h e i r c o m p o u n d s i n

t h i s p a p e r w e r e p o r t t h e p r e p a r a t i o n , f o r t h e f i rs t

t i m e , o f t h r e e e t h e r a t e , f i v e p y r i d i n e a n d e i g h t

a n i l i n e c o m p o u n d s o f c o m p l e x h a l o a n d p s e u d o h a l o

a c i d s o f Z n ( I I ) . T h i o c y a n a t e w a s u s e d a s a p s e u d o -

h a l o g e n .

Exper imenta l

Reagents H i g h p u r i t y r e a g e n t s w e r e u s e d f o r t h e p r e p a r a -

t i o n o f t h e c o m p l e x c o m p o u n d s . D i e t h y l e t h e r w a s t r e a t e d as u s u a l f o r t h e r e m o v a l o f p e r o x i d e s a n d m o i s t u r e [9]. T h e o r g a n i c b a s e s , p y r i d i n e a n d a n i l i n e , w e r e d o u b l y d i s t i l l e d u n d e r a t m o s p h e r i c p r e s s u r e .

Preparation of the complexes T h e p r e p a r a t i o n o f t h e e t h e r a t e c o m p l e x e s

H Z n C l 2 I • 3 E t 2 0 (1) a n d H Z n B r 2 I • 3 E t 2 0 (2) w a s c a r r i e d o u t b y t h e " e t h e r o h a l o g e n o s i s " m e t h o d [3]. A s s t a r t i n g m a t e r i a l s a n h y d r o u s Z n C l 2 a n d Z n B r 2

a n d a n e t h e r s o l u t i o n o f H I , 0.3 N w e r e u s e d ; t h e l a s t r e a g e n t w a s i n 2 0 % e x c e s s . T h e e x p e r i m e n t a l t e m p e r a t u r e w a s k e p t a t — 5 0 °C ( m i x t u r e o f d r y i ce a n d a c e t o n e ) . T h e p r e p a r a t i o n o f H Z n I 2 ( C S N ) • 3 E t 2 0 (3) w a s a c h i e v e d b y a m e t h o d p r e v i o u s l y d e s c r i b e d [7]. T h e e t h e r s o l u t i o n o f H S C N , 0.05 N , w a s a d d e d i n 8 0 % e x c e s s . T h e r e a c t i o n p r o d u c t s 1 , 2 a n d 3, t h i c k o i l y l i q u i d s , w e r e p u r i f i e d b y w a s h i n g w i t h s m a l l p o r t i o n s o f a b s o l u t e e t h e r .

F o r t h e p r e p a r a t i o n o f t h e p y r i d i n e a n d a n i l i n e c o m p o u n d s t h e f o l l o w i n g p r o c e d u r e w a s u s e d : T o s m a l l a m o u n t s o f f r e s h l y p r e p a r e d e t h e r a t e c o m p l e x h a l o a c i d s a s l i g h t e x c e s s o f p y r i d i n e or a n i l i n e w a s a d d e d d r o p w i s e . T h e r e a c t i o n w a s v i g o r o u s a n d e x o t h e r m i c a n d w a s a c c o m p a n i e d b y t h e e v o l u t i o n o f v a p o u r s . I m m e d i a t e l y a f t e r t h e a d d i t i o n o f t h e b a s e , t h e w h o l e r e a c t i o n m i x t u r e so l id i f ied . T h e a d d i t i o n o f m o r e b a s e c a u s e d d i s s o l u t i o n o f t h e s o l i d p r o d u c t a n d t h e a p p e a r a n c e o f a c l e a r s o l u t i o n . S u b s e q u e n t l y , t h e r e a c t i o n v e s s e l w a s p l a c e d i n a v a c u u m d e s i c c a t o r o v e r c o n c e n t r a t e d s u l f u r i c a c i d . T h e f i n a l c r y s t a l l i n e p r o d u c t w a s o b t a i n e d b y r e p e a t e d p u m p i n g . T h e p r o d u c t w a s w a s h e d w i t h s m a l l p o r t i o n s o f a b s o l u t e e t h e r a n d h e a t e d t o 3 5 °C f o r 1 5 m i n .

Analyses a) I n s t r u m e n t s a n d a p p a r a t u s

F o r t h e P o t e n t i o m e t r i e d e t e r m i n a t i o n s o f t h e a c i d i c h y d r o g e n a n d t h e o r g a n i c b a s e s a p H m e t e r R a d i o m e t e r C o p e n h a g e n N V . - T y p e P H M 26 c a n d

* Reprint requests to Prof . A . G. Galinos. ** Thiocyanate will be indicated as CNS whenever

the actual m o d e of bonding is undetermined. 0340-5087/79/0800-1101/5 01.00/0

1102 A. G. Galinos et al. • Etherate, Pyridine and Aniline Compounds of Zn(II)

g l a s s a n d c a l o m e l e l e c t r o d e s w e r e e m p l o y e d . I n t h e d e t e r m i n a t i o n s o f t h e a c i d i c h y d r o g e n in t h e p y r i d i n e a n d a n i l i n e c o m p o u n d s t h e s a t u r a t e d a q u e o u s solu-t i o n K C l o f t h e c a l o m e l e l e c t r o d e w a s r e p l a c e d b y a m e t h a n o l i c o n e [10]. F o r t h e P o t e n t i o m e t r i e d e t e r -m i n a t i o n s o f t h e h a l o g e n s a n d t h e t h i o c y a n a t e a p o t e n t i o m e t e r C o r n i n g - E e l , m o d e l 12 w a s u s e d w i t h c a l o m e l a n d su l f ide e l e c t r o d e s , b) A n a l y t i c a l p r o c e d u r e s

F o r t h e q u a n t i t a t i v e d e t e r m i n a t i o n o f t h e e t h e r a t e c o m p o u n d s a s o l u t i o n w a s p r e p a r e d b y d e c o m p o s i n g a d e f i n i t e a m o u n t o f e a c h c o m p o u n d w i t h w a t e r . T h e a c i d i c h y d r o g e n w a s d e t e r m i n e d p o t e n t i o m e t r i -c a l l y w i t h a s t a n d a r d 0.1 N K O H s o l u t i o n [ 1 1 a ] . T h e h y d r o l y s i s o f Z n ( I I ) w a s t a k e n i n t o a c c o u n t . Z i n c w a s d e t e r m i n e d v o l u m e t r i c a l l y w i t h a 0.05 M E D T A s o l u t i o n [ l i b ] . T h e t o t a l h a l o g e n w a s d e t e r m i n e d v o l u m e t r i c a l l y b y t h e V o l h a r d m e t h o d [ 1 1 c ] a n d p o t e n t i o m e t r i c a l l y w i t h a 0.1 N A g N 0 3 s o l u t i o n [12] . T h e i o d i d e i o n i n t h e p r e s e n c e o f c h l o r i d e o r b r o m i d e w a s d e t e r m i n e d b y t h e P d C l 2 m e t h o d [ l i d ] . T h e s u m o f i o d i d e a n d t h i o c y a n a t e i o n s a s w e l l a s e a c h o f t h e m i n t h e p r e s e n c e o f t h e o t h e r w e r e d e t e r m i n e d p o t e n t i o m e t r i c a l l y w i t h a 0.1 N A g N 0 3 s o l u t i o n [12]. E t h e r w a s d e t e r m i n e d b y w e i g h t d i f f e r e n c e .

T h e a c i d i c h y d r o g e n o f t h e p y r i d i n e a n d a n i l i n e c o m p o u n d s w a s d e t e r m i n e d p o t e n t i o m e t r i c a l l y w i t h a 0.1 N K O H s o l u t i o n , a f t e r d i s s o l v i n g t h e m i n a b s o l u t e D M S O [10]. T h e c o n t e n t o f t h e o r g a n i c b a s e w a s d e t e r m i n e d b y d i s s o l v i n g t h e c o m p o u n d i n g l a c i a l C H 3 C O O H a n d P o t e n t i o m e t r i e t i t r a t i o n w i t h a 0.1 M H C I O 4 s o l u t i o n i n C H 3 C O O H o r s i m p l e t i t r a t i o n w i t h 0.1 M H C I O 4 a n d C r y s t a l v i o l e t a s t h e i n d i c a t o r [ 1 3 ] ; t o t h e s a m p l e b e i n g a n a l y z e d w e r e a d d e d 5 - 8 m l o f 6 % H g ( C H 3 C O O ) 2 s o l u t i o n i n C H 3 C O O H . Z i n c w a s d e t e r m i n e d as d e s c r i b e d a b o v e ; a 1 5 % a q u e o u s s o l u t i o n o f C 2 H 5 O H w a s e m p l o y e d a s a s o l v e n t . T h e h a l o g e n s a n d t h i o c y a n a t e w e r e d e t e r m i n e d a s d e s c r i b e d a b o v e , t h e s a m p l e s b e i n g d i s s o l v e d i n 2 N H N 0 3 . T h e c h l o r i d e a n d b r o m i d e ions , t h e c h l o r i d e a n d t h i o c y a n a t e ions , a n d t h e b r o m i d e a n d t h i o c y a n a t e i o n s w e r e d e t e r m i n e d p o t e n t i o m e t r i c a l l y [12],

Stability test for the pyridine and aniline compounds [4]

A s m a l l a m o u n t o f t h e c o m p o u n d w a s d i s s o l v e d i n a b s o l u t e e t h a n o l . N o p r e c i p i t a t e a p p e a r e d b y t h e a d d i t i o n o f a 0 . 5 % e t h a n o l i c s o l u t i o n o f A g C 1 0 4 . A s l i g h t c l o u d i n e s s a p p e a r e d a f t e r a f e w m i n u t e s . D i l u t i o n w i t h w a t e r c a u s e d t h e A g ( I ) h a l i d e s a n d A g S C N t o p r e c i p i t a t e .

Physicochemical measurements T h e m . p . o f t h e p y r i d i n e a n d a n i l i n e c o m p o u n d s

w e r e o b t a i n e d i n a B ü c h i 5 1 0 a p p a r a t u s . F o r t h e c o n d u c t i v i t y m e a s u r e m e n t s 10~3 M s o l u t i o n s w e r e p r e p a r e d i n C H 3 N O 2 , w h i c h w a s p r o p e r l y p r e t r e a t e d [14]. A c o n d u c t i v i t y a p p a r a t u s , E h r h a r d t - M e t z g e r

N a c h f . t y p e L 2 1 , w a s e m p l o y e d . T h e ce l l c o n s t a n t w a s C = 1 c m - 1 a n d t h e m e a s u r e m e n t s w e r e c a r r i e d o u t a t 2 5 ± 0.1 °C. T h e U V s p e c t r a o f t h e p y r i d i n e a n d a n i l i n e c o m p o u n d s w e r e t a k e n i n a B a u s c h L o m b - S h i m a d z u S p e c t r o n i c 2 1 0 U V d o u b l e b e a m s p e c t r o p h o t o m e t e r w i t h a d e u t e r i u m l a m p . T h e s o l v e n t w a s s p e c t r o s c o p i c q u a l i t y C 2 H 5 O H , t h e con-c e n t r a t i o n s 1 0 - 5 - 1 0 - 4 M a n d t h e r e g i o n s c a n n e d 2 1 0 - 3 2 0 n m . T h e I R s p e c t r a o f t h e s e c o m p o u n d s w e r e r e c o r d e d i n P e r k i n - E l m e r s p e c t r o p h o t o m e t e r s 4 5 7 a n d 5 7 7 . T h e s a m p l e s w e r e u s e d i n t h e f o r m o f K B r p e l l e t s . T h e s p e c t r a c o v e r e d t h e r e g i o n 4 0 0 0 - 2 5 0 c m - 1 .

Results and Discussion F o r t h e p r e p a r a t i o n o f c o m p o u n d s 1 a n d 2 a l o w

t e m p e r a t u r e is r e q u i r e d , s i n c e a t h i g h t e m p e r a t u r e s

e t h e r is c l e a v e d b y H I [15] . T h e e t h e r a t e s f u m e i n

a i r a n d a r e i n s o l u b l e i n n o n p o l a r s o l v e n t s . T h e

p y r i d i n e a n d a n i l i n e c o m p o u n d s a r e f o r m e d b y t h e

c o m p l e t e r e p l a c e m e n t o f t h e e t h e r b y p y r i d i n e or

a n i l i n e :

P y

H Z n I 2 ( C S N ) • 3 E t 2 0 + 3 P y >

e x c e s s

H Z n l a S C N • 3 P y + 3 E t 2 0

w h e r e P y = p y r i d i n e . T h e p y r i d i n e a n d a n i l i n e

c o m p o u n d s a r e c r y s t a l l i n e so l ids a n d s t a b l e i n t h e

a i r . T h e y a r e i n s o l u b l e i n n o n p o l a r s o l v e n t s , s o m e -

w h a t s o l u b l e i n w a t e r a n d a l c o h o l s a n d s o l u b l e i n

o t h e r p o l a r s o l v e n t s . T h e y d i s s o l v e r e a d i l y i n d i l u t e

m i n e r a l a c i d s .

T h e a n a l y t i c a l r e s u l t s , c o l o r s , m e l t i n g p o i n t s

( u n c o r r e c t e d ) a n d A m v a l u e s a r e g i v e n i n T a b l e I .

T h e s t a b i l i t y t e s t f o r t h e p y r i d i n e a n d a n i l i n e

c o m p o u n d s l e n d s a s t r o n g s u p p o r t t o t h e a s s u m p t i o n

t h a t a l l h a l i d e i o n s a n d t h e t h i o c y a n a t e a r e co-

o r d i n a t e d t o Z n ( I I ) ; t h e n e w c o m p o u n d s , t h e r e f o r e ,

a r e c o m p l e x c o m p o u n d s a n d n o t d o u b l e sa l ts [4].

T h e s l i g h t c l o u d i n e s s , a p p e a r i n g a f t e r a s h o r t t i m e ,

is a t t r i b u t e d t o t h e s l i g h t d i s s o c i a t i o n o f t h e c o m p l e x

i o n s i n e t h a n o l .

F r o m t h e A m v a l u e s o b t a i n e d , i t is c o n c l u d e d t h a t

a l l p y r i d i n e a n d a n i l i n e c o m p l e x e s in n i t r o m e t h a n e

b e h a v e a s 1 : 1 e l e c t r o l y t e s [16].

T h e U V s p e c t r a o f t h e p y r i d i n e c o m p o u n d s s h o w

a b s o r p t i o n m a x i m a a t 233, 240, 245, 250, 257 a n d

2 6 3 n m . T h e s e m a x i m a a r e a t t r i b u t e d t o n -> n * a n d

n - + 7 i * e l e c t r o n i c t r a n s i t i o n s [ 1 7 , 18]. T h e m a x i m u m

a t 290 n m i n t h e s p e c t r a o f c o m p o u n d s 4, 5 a n d 8

is v e r y p e c u l i a r ; i t c a n n o t b e d u e t o a n n -> 71*

t r a n s i t i o n [ 1 7 , 18]. T h e U V s p e c t r u m o f p u r e a n i l i n e

1103 A. G. Galinos et al. • Etherate, Pyridine and Aniline Compounds of Zn(II)

Table I. Analytical results, colors, m.p. and /IM values of the new etherate, pyridine and aniline compounds of the complex halo and pseudohalo acids of Zn(II).

No. Compound [%] Acidic hydro-gen

Zn Cl Br I SCN B Color m.p. [°C] [S cm2 mol -1]

1 HZnCl2I • 3 Et20 Calcd 0.20 13.44 14.57 26.08 45.70 crimson Found 0.18 13.70 14.33 25.60 46.19

2 HZnBr2I • 3 Et20 Calcd 0.17 11.36 27.77 22.05 38.64 crimson Found 0.16 10.99 27.02 21.96 39.87

8 HZnI2(CSN) • 3 Et20 Calcd 0.17 10.88 42.31 9.66 36.98 orange-Found 0.17 10.53 43.18 9.86 36.29 red

4 HZnCl2I • 3 Py Calcd 0.20 13.04 14.14 25.30 47.32 yellow 110 72 Found 0.17 13.93 14.28 23.15 48.23

yellow

5 HZnBr2I • 3 Py Calcd 0.17 11.07 27.07 21.49 40.19 straw 117 86 HZnBr2I • 3 Py Found 0.17 11.28 27.72 20.45 41.22

6 HZnCl2SCN • 3 Py Calcd 0.23 15.12 16.42 13.41 54.81 flesh 191 84 HZnCl2SCN • 3 Py Found 0.23 16.02 16.79 13.69 53.33

7 HZnBr2SCN • 3 Py Calcd 0.19 12.54 30.69 11.12 45.45 straw 210 79 HZnBr2SCN • 3 Py Found 0.18 13.01 31.18 11.31 43.06

8 HZnI2SCN • 3 Py Calcd 0.16 10.63 41.27 9.42 38.51 grey 182 76 HZnI2SCN • 3 Py Found 0.16 11.03 42.96 10.21 38.24

grey

9 HZnCl2Br • 3 An Calcd 0.20 13.17 14.28 16.09 56.26 white 185d 69 Found 0.18 13.38 13.74 17.28 54.15

10 HZnBr3 • 3 An Calcd 0.17 11.17 40.94 47.72 pale 162d 87 Found 0.17 10.99 40.46 47.97 pink

11 HZnI2Br • 3 An Calcd 0.15 9.62 11.76 37.35 41.12 light beige

168- 73 Found 0.15 9.88 12.34 35.11 42.52

light beige 170

12 HZnCl2I • 3 An Calcd 0.18 12.03 13.04 23.34 51.40 whitish- 150d 81 Found 0.16 12.80 13.12 23.02 51.05 yellow

13 HZnBr2I • 3 An Calcd 0.16 10.34 25.27 20.06 44.17 yellowish 162- 68 Found 0.15 10.43 26.13 19.25 43.79

yellowish 165d

14 HZnCl2NCS • 3 An Calcd 0.21 13.78 14.97 12.23 58.81 flesh 238d 77 Found 0.21 14.03 15.06 12.18 58.59

15 HZnBr2NCS • 3 An Calcd 0.18 11.61 28.40 10.29 49.52 pale 245 74 Found 0.17 12.10 29.04 10.21 50.52 pink

16 HZnlaNCS • 3 An Calcd 0.15 9.95 38.64 8.82 42.44 yellow 217 81 Found 0.16 10.17 39.04 9.04 43.58

yellow

B = Et20, Py, An. a Values of molar conductance for 10~3 M solutions in CH3N02 at 25 °C. d = decomposes.

Table II. IR spectral assignments of some absorption bands of diagnostic value for the pyridine complexes.

Complex v(C-N) f(C-S) <5(NCS) Vibrations of the pyridine ring

i»(Zn-Cl)t »(Zn-Br)t

4 632 s 420 s 413 sh 323 s 290 s 5 631s 421s 411 sh 251 s 6 2078 s overlapped by absorption 638 vs 422 s 325 s 295 s 7 2078 s bands of the coordinated 638 vs 422 s 418 s 255 s 8 2078 m pyridine 640 s 425 s 418 m s = strong, sh = shoulder, m = medium, vs = very strong.

Table III. IR spectral assignments of some absorption bands of diagnostic value for the aniline complexes.

Complex v(C-N) v(C-S) <5(NCS) J'asym(N-H) f s y m (N-H) v(Zn-An) i>(Zn-Cl)t v(Zn-Br)t

9 3270 m 3225 m 400 sh 357 s 290 s 274 sh <250 10 3263 m 3220 m 399 sh 355 s 250 s 11 3262 m 3219 m 400 sh 341 s 253 m 12 3265 m 3220 m 400 w 358 s 290 s 275 sh 13 3270 m 3224 m 400 sh 347 m 252 m 14 2090 s overlapped 477 m 3260 vs 3220 vs 405 m 365 s 296 s 15 2090 s by bands of the 475 m 3260 vs 3220 vs 400 s 357 s <250

coordinated 16 2080 s aniline 471 m 3265 s 3215 s 395 m 343 s

1104 A. G. Galinos et al. • Etherate, Pyridine and Aniline Compounds of Zn(II)

i n e t h a n o l s h o w s a b s o r p t i o n m a x i m a a t 2 3 5 a n d

285 n m . T h e s p e c t r a o f t h e s a l t s A n H X ( X = C l ,

B r , I , S C N ) i n e t h a n o l a l s o s h o w r e g u l a r m a x i m a a t

2 3 5 a n d 2 8 5 n m a s w e l l a s s u c c e e d i n g a b s o r p t i o n s i n

t h e f o r m o f s h o u l d e r s a t 2 5 5 , 260 a n d 2 6 5 n m . T h e s e

s h o u l d e r s a r e d u e t o t h e A n H + i o n [19] . T h e m a x i m a

a t 230 a n d 285 n m i n t h e s p e c t r a o f a l l a n i l i n e

c o m p l e x e s o b t a i n e d a r e d u e t o e l e c t r o n i c t r a n s i t i o n s

o f a n i l i n e , s i n c e t h e y a p p e a r i n t h e s p e c t r a o f a n i l i n e ,

A n H X a n d c o o r d i n a t i o n c o m p o u n d s o f a n i l i n e [20].

T h e s h o u l d e r a t 260 n m i n t h e s p e c t r a o f m o s t ani -

l i n e c o m p l e x e s is a t t r i b u t e d t o t h e A n H + i o n [19] .

S o m e c h a r a c t e r i s t i c a n d o f d i a g n o s t i c v a l u e I R

f r e q u e n c i e s ( c m - 1 ) o f t h e p y r i d i n e a n d a n i l i n e

c o m p l e x e s a r e g i v e n i n T a b l e s I I a n d I I I , r e s p e c -

t i v e l y .

Study of IR spectra of the pyridine complexes T h e t w o o r t h r e e w e a k a b s o r p t i o n b a n d s i n t h e

r e g i o n 3 2 2 0 - 3 1 0 0 c m - 1 i n t h e s p e c t r a o f t h e p y r i d i n e

c o m p l e x e s a r e d u e t o t h e P y H + i o n ; t h e i r l o w

i n t e n s i t y i n d i c a t e s t h a t t h e P y H + i o n is i n v o l v e d i n

h y d r o g e n b r i d g i n g [ 2 1 ] . T h e a b s e n c e , a l so , o f a

s t r o n g b r o a d b a n d j u s t b e l o w 3000 c m - 1 e x c l u d e s

t h e p r e s e n c e o f h y d r o g e n b o n d i n g o f t h e c a t i o n -

a n i o n t y p e , N + - H - - - X - [ 2 1 ] ; t h i s is , o f c o u r s e ,

e x p e c t e d s i n c e , a l l h a l i d e i o n s a n d t h e t h i o c y a n a t e

a r e c o o r d i n a t e d t o Z n ( I I ) . T h e p r e s e n c e o f P y H + i o n

i n t h e m o l e c u l e s o f t h e p r e p a r e d c o m p l e x e s is

c l e a r l y i n d i c a t e d b y t h e a b s o r p t i o n b a n d s a t 1630,

1600, 1 5 2 5 , 1480, 1 3 2 5 , 1 2 4 0 a n d 1 1 8 5 c m - 1 [22, 23],

T h e t w o a b s o r p t i o n b a n d s a t 1 5 7 0 a n d 1 4 4 5 c m - 1

a s w e l l a s t h e s t r o n g o n e s a t 1 2 1 5 , 1 1 5 0 , 1065, 1040,

1 0 1 0 , 7 5 0 a n d 6 9 5 c m - 1 a r e d u e t o c o o r d i n a t e d

p y r i d i n e [23]. T h e s t r o n g b a n d s a t 6 3 5 a n d 420 c m - 1

a r e t h o u g h t o f b e i n g s h i f t s o f t h e b a n d s a t 604 ( a n

i n - p l a n e r i n g d e f o r m a t i o n ) a n d 4 0 5 ( a n o u t - o f - p l a n e

r i n g d e f o r m a t i o n ) c m - 1 o f f r e e p y r i d i n e . T h e s h i f t i n g

o f t h e s e b a n d s t o h i g h e r f r e q u e n c i e s i n d i c a t e s co-

o r d i n a t e d p y r i d i n e [22, 2 4 ] ; c o n s i s t e n t w i t h t h i s is

t h e s p l i t t i n g o f t h e b a n d a t 420 c m - 1 i n t h e s p e c t r a

o f t h e c o m p l e x e s 4, 5 , 7 , a n d 8 [22, 24], T h e b a n d a t

635 c m - 1 i n d i c a t e s a t e t r a h e d r a l e n v i r o n m e n t a r o u n d

Z n ( I I ) [24, 25] . A b s o r p t i o n b a n d s d u e t o Z n - N ( P y )

s t r e t c h i n g v i b r a t i o n s a p p e a r b e l o w 2 5 0 c m - 1 [ 2 4 - 2 6 ] .

T h e s t r o n g b a n d s i n t h e r e g i o n 3 2 5 - 2 9 0 c m - 1 i n

t h e s p e c t r a o f c o m p o u n d s 4 a n d 6 a r e a t t r i b u t e d t o

Z n - C l t e r m i n a l s t r e t c h i n g v i b r a t i o n s , r ( Z n - C l ) t ,

s ince t h e y a r e a b s e n t i n t h e s p e c t r a o f c h l o r i n e - f r e e

c o m p l e x e s ; t h e f r e q u e n c i e s o f t h e s e b a n d s c l e a r l y

s h o w t h a t t h e s t r u c t u r e o f c o m p o u n d s 4 a n d 6 is

t e t r a h e d r a l [24, 26], L i k e w i s e , t h e s t r o n g b a n d s a t

2 5 1 a n d 2 5 5 c m - 1 i n t h e s p e c t r a o f 5 a n d 7 , r e s p e c -

t i v e l y a r e a t t r i b u t e d t o v ( Z n - B r ) t a n d t h e i r f re-

q u e n c i e s i n d i c a t e a t e t r a h e d r a l l i g a n d a r r a n g e m e n t

a r o u n d Z n ( I I ) [24]. T h e Z n - I s t r e t c h i n g v i b r a t i o n s

o c c u r b e l o w 250 c m - 1 [24].

T h e t h i o c y a n a t e g r o u p h a s t h r e e d i a g n o s t i c I R

r e g i o n s ; C - N s t r e t c h i n g v ( C - N ) , C - S s t r e t c h i n g

v ( C - S ) a n d N C S b e n d i n g <5(NCS). T h e a b s o r p t i o n

b a n d s i n t h e s e r e g i o n s a r e a f f e c t e d b y d i f f e r e n t

t y p e s o f c o o r d i n a t i o n . T h e a b s o r p t i o n b a n d s i n t h e

C N r e g i o n a p p e a r a t 2078 c m - 1 i n o u r s p e c t r a , a f a c t

i n d i c a t i n g t h e a b s e n c e o f b r i d g e d - S C N - g r o u p s [27]

or f r e e t h i o c y a n a t e i o n s [28]. T h e C - S s t r e t c h i n g

r e g i o n h a s b e e n w e l l d e a l t w i t h i n t h e c h e m i c a l

l i t e r a t u r e a n d h a s b e e n u s e d as a d i a g n o s t i c r e g i o n

f o r t h e t y p e o f b o n d i n g o f t h e t h i o c y a n a t e g r o u p i n

t h e c o m p l e x e s . T u r c o a n d P e c i l e [29], s t u d y i n g I R

s p e c t r a o f c o m p l e x e s o f k n o w n s t r u c t u r e s h o w e d

t h a t t h e r ( C - S ) f o r t h e S - b o n d e d c o m p l e x e s o c c u r s

i n t h e r e g i o n 6 9 0 - 7 2 0 c m - 1 a n d i n t h e r e g i o n 7 8 0 -

860 c m - 1 f o r t h e N - b o n d e d o n e s . S i n c e o u r s p e c t r a

d o n o t s h o w a b s o r p t i o n b a n d s i n t h e r e g i o n 7 8 0 -

860 c m - 1 , t h e p r e s e n c e o f Z n - N C S b o n d is e x c l u d e d .

T h e a s s i g n m e n t o f r ( C - S ) i n t h e r e g i o n 6 9 0 - 7 2 0 c m - 1

is i m p o s s i b l e d u e t o t h e s i m u l t a n e o u s a p p e a r a n c e o f

a b s o r p t i o n b a n d s o f c o o r d i n a t e d p y r i d i n e . T h e

t h i o c y a n a t e c o m p l e x e s s h o w a b s o r p t i o n b a n d s i n

t h e r e g i o n 4 4 0 - 4 0 0 c m - 1 a n d t h e i s o t h i o c y a n a t e

o n e s i n t h e r e g i o n 4 9 0 - 4 5 0 c m - 1 [30, 3 1 ] . I n o u r

case , t h e a b s e n c e o f a b a n d i n t h e r e g i o n 4 9 0 -

450 c m - 1 e x c l u d e s or r u l e s o u t t h e p r e s e n c e o f

Z n - N C S b o n d ; i n t h e r e g i o n 4 4 0 - 4 0 0 c m - 1 co-

o r d i n a t e d p y r i d i n e a b s o r b s t o o .

C a r e f u l e x a m i n a t i o n o f t h e s p e c t r a o f a l l p r e p a r e d

p y r i d i n e c o m p o u n d s c l e a r l y s h o w s t h e a b s e n c e o f

c h a r a c t e r i s t i c b a n d s o f f r e e p y r i d i n e ; h e n c e t h e s e

c o m p o u n d s c o n t a i n n o l a t t i c e p y r i d i n e [32].

Study of IR spectra of the aniline complexes T h e s p e c t r a o f a l l a n i l i n e c o m p l e x e s s h o w t w o

s t r o n g a n d b r o a d b a n d s a t 2850 a n d 2580 c m - 1 ,

w h i c h a r e i n d i c a t i v e o f t h e A n H + i o n i n v o l v e d i n

h y d r o g e n b r i d g i n g [33, 34]. T h e n u m e r o u s w e a k

b a n d s i n t h e r e g i o n 2 5 5 0 - 1 6 5 0 c m - 1 a r e m a i n l y

c o m b i n a t i o n b a n d s a n d o v e r t o n e s , s o m e o f w h i c h

a r e d u e t o t h e a b s o r p t i o n o f t h e - N H 3 + g r o u p

[33, 35]. T h e a s s i g n m e n t s i n t h e r e g i o n 1620 t o

1500 c m - 1 a r e d i f f i c u l t , s i n c e b a n d s i n t h i s r e g i o n

1105 A . G. Galinos et al. • Etherate, Pyridine and Aniline Compounds o f Z n ( I I )

a r e d u e t o s t r e t c h i n g v i b r a t i o n s o f t h e b e n z e n e r i n g

a n d b e n d i n g v i b r a t i o n s o f t h e - N H 3 + g r o u p [33].

T h e b a n d s a t 1600, 1 5 6 0 , 1 5 1 5 , 1490, 1 4 6 5 , 1 3 2 5 ,

1290, 1 1 9 0 , 1 1 7 5 , 1 1 5 0 , 1 1 1 0 , 1080, 1025, 1000, 960,

900, 840, 800, 740, 680, 6 1 5 , 5 2 5 a n d 380 c m - 1 a r e

d u e t o A n H + i o n s i n c e t h e s e a p p e a r a l s o i n t h e

s p e c t r a o f A n H X .

T h e s p e c t r u m a l s o s h o w s t h a t a n i l i n e is co-

o r d i n a t e d t o Z n ( I I ) . A l l s p e c t r a s h o w t w o a b s o r p t i o n

b a n d s i n t h e r e g i o n 3 3 0 0 - 3 2 0 0 c m - 1 . T h e b a n d a t

t h e h i g h e r f r e q u e n c y is a t t r i b u t e d t o - N H 2 a n t i -

s y m m e t r i c s t r e t c h i n g v i b r a t i o n w h i l e t h e o n e a t t h e

l o w e r f r e q u e n c y t o - N H 2 s y m m e t r i c s t r e t c h i n g

v i b r a t i o n . T h e f r e q u e n c i e s o f t h e s e b a n d s (signifi-

c a n t l y l o w e r t h a n t h e c o r r e s p o n d i n g i n f r e e a n i l i n e )

i n d i c a t e c o o r d i n a t e d a n i l i n e [20, 36]. T h e s h i f t i n g

a n d s p l i t t i n g o f t h e b a n d s a t 740, 680, 6 1 5 a n d

5 2 5 c m - 1 s h o w a l s o c o o r d i n a t e d a n i l i n e [37]. T h e

t w o b a n d s i n t h e r e g i o n 4 0 5 - 3 4 1 c m - 1 o f e v e r y

s p e c t r u m a r e a t t r i b u t e d t o Z n - N ( A n ) s t r e t c h i n g

v i b r a t i o n o r t o v i b r a t i o n m o d e s o f a n i l i n e ; t h e l a t t e r

h a v e , p o s s i b l y , s h i f t e d o r b e c o m e i n f r a r e d a c t i v e

u p o n t h e c o o r d i n a t i o n o f a n i l i n e [36, 38].

F r o m t h e j>(Zn-Cl)t a n d v ( Z n - B r ) t v a l u e s (see

T a b l e I I I ) i t is c o n c l u d e d t h a t t h e c o m p l e x e s 9, 10,

1 1 , 1 2 , 1 3 a n d 1 4 h a v e t e t r a h e d r a l s t r u c t u r e [24, 26,

36, 38]. T h e a b s e n c e o f a b a n d , d u e t o Z n - B r

s t r e t c h i n g v i b r a t i o n , a b o v e 2 5 0 c m - 1 i n t h e spec-

t r u m o f c o m p o u n d 1 5 , is r e a s o n a b l e , s i n c e t h i s b a n d

o f t e n o c c u r s s l i g h t l y b e l o w 2 5 0 c m - 1 f o r t e t r a h e d r a l

c o m p l e x e s o f Z n ( I I ) [26, 38],

T h e p r e s e n c e o f t h e S C N g r o u p i n t h e i n n e r s p h e r e

o f t h e a n i l i n e c o m p l e x e s is s h o w n b y t h e a p p e a r a n c e

o f b a n d s a t 2090 a n d 4 7 5 c m - 1 .

T h e p o s i t i o n o f t h e C - N s t r e t c h i n g r u l e s o u t t h e

p r e s e n c e o f t h e t h i o c y a n a t e g r o u p i n t h e i o n i c o r

b r i d g e d f o r m . T h e p o s i t i o n a l s o o f t h e N C S b e n d i n g

s h o w s t h a t t h e b o n d i n g o f t h e t h i o c y a n a t e g r o u p t o

Z n ( I I ) is v i a t h e n i t r o g e n a t o m .

F i n a l l y , t h e a b s e n c e o f l a t t i c e a n i l i n e is c e r t a i n .

Correlation of the data regarding the stereochemistry of the pyridine and aniline complexes in the solid state

F r o m t h e s t a b i l i t y t e s t i t is c o n c l u d e d t h a t t h e

n e w c o m p o u n d s a r e c o m p l e x c o m p o u n d s ; t h e U V

s p e c t r a a l s o s h o w t h a t t h e a n i l i n e c o m p o u n d s

c o n t a i n t h e A n H + i o n .

F r o m t h e I R s p e c t r a l a n a l y s i s i t is c o n c l u d e d

t h a t :

a) A l l c o m p o u n d s c o n t a i n c o o r d i n a t e d o r g a n i c b a s e .

b) I n a l l c o m p l e x e s t h e P y H + a n d A n H + i o n s a r e

i n v o l v e d i n h y d r o g e n b o n d i n g .

c) A l l c o m p l e x a n i o n s a r e t e t r a h e d r a l m o n o m e r s .

d) N o n e o f the.se c o m p o u n d s c o n t a i n s l a t t i c e p y r i -

d i n e o r a n i l i n e .

e) N o n e o f t h e s e c o m p o u n d s c o n t a i n s i o n i c o r

b r i d g e d t h i o c y a n a t e . T h e p y r i d i n e c o m p l e x e s ,

c o n t a i n i n g t h e t h i o c y a n a t e , a r e S - b o n d e d , w h i l e

t h e c o r r e s p o n d i n g a n i l i n e c o m p l e x e s a r e N -

b o n d e d .

O n t h e b a s i s o f a l l t h e s e f i n d i n g s t h e f o l l o w i n g

g e n e r a l s t r u c t u r a l f o r m u l a is p r o p o s e d f o r t h e n e w

p y r i d i n e a n d a n i l i n e c o m p o u n d s :

[ Z n X 2 Y B ] - [ B - - - H - - - B ] + ,

w h e r e X = C1, B r , I ; Y = B r , I , S C N ; B = P y , A n .

T h e s y m b o l - - - r e p r e s e n t s a h y d r o g e n b r i d g e be-

t w e e n t h e p r o t o n i c h y d r o g e n a n d t w o n i t r o g e n

a t o m s o f t w o m o l e c u l e s o f t h e o r g a n i c b a s e i n t h e

o u t e r s p h e r e o f t h e c o m p l e x ; s u c h a h y d r o g e n b o n d

h a s b e e n o b s e r v e d i n n u m e r o u s c o m p o u n d s o f

c o m p l e x h a l o a c i d s [4, 5 , 7 , 8, 37] .

T h e a u t h o r s w i s h t o t h a n k t h e N a t i o n a l H e l l e n i c R e s e a r c h F o u n d a t i o n f o r t h e financial s u p p o r t o f p a r t o f t h i s w o r k . O n e o f u s ( S . P . P . ) is e s p e c i a l l y g r a t e f u l t o t h e s a i d F o u n d a t i o n f o r t h e financial s u p p o r t h e r e c e i v e d f o r t h e d u r a t i o n o f t h i s r e s e a r c h .

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[10] K . K . Barnes and C. K . Mann, Anal . Chem. 36, 2502 (1964).

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1106 A. G. Galinos et al. • Etherate, Pyridine and Aniline Compounds of Zn(II)

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