coordination chemistr of y transition metals with ... · measurements i dmsn shoo thw non-ionie...

COORDINATION CHEMISTRY OF TRANSITION METALS WITH HETEROCYCLIC

LIGANDS CONTAINING OXYGEN, NITROGEN AND SULPHUR

ABSTRACT

^ u b m i t t e ^ J f o r t h t B e g r e c of

ISottor of ^hiloj5opl|p IN

CHEMISTRY

BY

Under the Supcrvislo* of

Prof. Saiyid Aftab Ahmad Zaidi

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALiGARH (INDIA)

1 9 9 3

ABSTRACT

T h e n u m b e r of N , N ' , N , S and N , 0 c h e l a t i n g b i h e t e r o -

a r o m a t i c l i g a n d s used by c o o r d i n a t i o n c h e m i s t s is v e r y s m a l l

and t h u s t h e area has v a s t p o t e n t i a l i t i e s o f f e r i n y the

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

T h e m a j o r o b j e c t i v e of t h i s w o r k w a s t o i n v e s t i g a t e

some c h e m i c a l r e a c t i o n s l e a d i n g to t h e f o r m a t i o n of nev/

m o l e c u l e s w i t h m u l t i d e n t a t e d o n o r s i t e s and to study t h e i r

l i g a n d p r o p e r t i e s . C o m p o u n d s l i k e i n d a z o l o c o n t a i n i n g N-H

g r o u p r e a c t v;ith h a l o d e r i v a t i v e s of s o m e h e t e r o c y c l i c

c o m p o u n d s like 2 - b r o m o p y r i m i d i n e to f o r m 2 - ( 1 - i n d a z o l y l )

p y r i m i d i n e w h i c h is a m u l t i d e n t a t e h e t e r o c y c l i c c o m p o u n d .

T h i s r e a c t i o n is c a r r i e d o u t in t w o s t e p s v/hen a t f i r s t t h e

h y d r o g e n a t t a c h e d to the h e t e r o c y c l e is r e p l a c e d by s o d i u m

v/hen it r e a c t s w i t h s o d i u m h y d r i d e and then t h i s s o d i u m

d e r i v a t i v e of t h e h e t e r o c y c l i c c o m p o u n d is a l l o w e d to r e a c t

w i t h the h a l o g e n d e r i v a t i v e , of the o t h e r h e t e r o c y c l i c

r e s u l t i n g in the f o r m a t i o n of a new c o m p o u n d . T h e f i n a l

p r o d u c t in t h i s case as w e l l as v/ith s e v e r a l o t h e r v a r i a n t s

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

from the p o i n t of v i e w of its m a n y p o s s i b i l i t i e s of t h e

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

t r a n s i t i o n m e t a l s . T h e s y n t h e s e s of s e v e r a l s u c h l i g a n d s and

t h e i r c o m p l e x e s and the study of t h e i r p h y s i c o - c h e m i c a l

p r o p e r t i e s h a v e been u n d e r t a k e n in this p r o j e c t .

T h e n u c l e o p h i l i c d i s p l a c e m e n t of h a l i d e from v a r i o u s

h a l o g e n a t e d h e t e r o c y c l e s by s o d i u m i n d a z o l i d e , s o d i u m s a l t

of p y r i d i n e - 2 - t h i o n e , s o d i u m s a l t of s u c c i n i m i d e or s o d i u m

s a l t of 2 , 4 , 6 - p y r i m i d i n e t r i o n e in dry t e t r a h y d r o f u r a n or

e t h a n o l or a n h y d r o u s x y l e n e has been e f f e c t e d . T h e

c o m p l e t i o n of f o r m a t i o n of the s o d i u m s a l t of a b o v e l i g a n d s

has been a s c e r t a i n e d by the e v o l u t i o n of t h e c o r r e s p o n d i n g

m o l e s of h y d r o g e n g a s .

• ^ P r e p a r a t i o n of 13 nevi; l i g a n d s v/hich c o n s i s t of

i n d a z o l e , p y r i d i n e - 2 - t h i o n e , s u c c i n i m i d e , 2 - m e r c a p t o b e n z o -

t h i a z o l e or 2,4,6 p y r i m i d i n e t r i o n e ring d i r e c t l y l i n k e d

t h r o u g h n i t r o g e n to a n o t h e r h e t e r o c y c l e such as p y r i d i n e ,

p y r i m i d i n e b e n z o x a z o l e and b e n z o t h i a z o l e is r e p o r t e d f o r

t h e f i r s t t i m e .

In t h e s e c o n d c h a p t e r ''the s y n t h e s i s of a s e r i e s of

i n d a z o l e d e r i v e d l i g a n d s n a m e l y 2 - ( 1 - i n d a z o l y l ) p y r i m i d i n e ,

2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e and t h e i r c o m p l e x e s w i t h s o m e

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

p r e p a r e d have been c h a r a c t e r i z e d by i . r . , ^H N M R u v - v i s i b l e

and m a g n e t i c m o m e n t m e a s u r e m e n t s . A l l c o m p l e x e s are s o l u b l e

in u s u a l o r g a n i c s o l v e n t s such as D M S O , n i t r o b e n z e n e and

t e t r a h y d r o f u r a n . The low m o l a r c o n d u c t a n c e v a l u e s of the

c o m p l e x e s in D M S O s h o w s t h e i r n o n - i o n i c n a t u r e . T h e

m a g n i t u d e of the n e p h e l a u x e t i c p a r a m e t e r B i n d i c a t e s a lov/

d e g r e e of c o v a l e n c y in t h e s e c o m p l e x e s . T h e r e p l a c e m e n t of

c h l o r i d e ions in M L ^ C l ^ t y p e c o m p l e x e s has been follov/ed

c o n d u c t o m e t r i c a l l y . A d d i t i o n of p y r i d i n e in D M S O s o l u t i o n of

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

to the r e l e a s e of c o o r d i n a t e d c h l o r i d e ions w h i c h a r e

r e p l a c e d by p y r i d i n e . F u r t h e r a d d i t i o n of p y r i d i n e i n c r e a s e s

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

s e c o n d c h l o r i d e i o n . A f t e r t h e r e p l a c e m e n t of b o t h t h e

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

c h a n g e the c o n d u c t a n c e . T h e ^H NMR s p e c t r a of the l i g a n d s

2 - ( 1 - i n d a z o l y 1 ) b e n z o x a z o l e and 2 - { 1 - i n d a z o l y l ) b e n z o t h i a z o l e

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

been r e c o r d e d and it can be seen t h a t as e x p e c t e d m o s t of

the p e a k s are s h i f t e d dov/nfield a f t e r c o m p l e x a t i o n . A l l

c o m p l e x e s of t h e f o u r l i g a n d s a p p e a r to h a v e an o c t a h e d r a l

s t r u c t u r e e x c e p t t h e P d ( I I ) c o m p l e x e s w h i c h a r e s q u a r e

p l a n a r .

In the t h i r d c h a p t e r t h e s y n t h e s i s of t h r e e new l i g a n d s

d e r i v e d from p y r i d i n e 2 - t h i o n e ; 2 - ( p y r i d i n e - 2 - t h i o n a t o )

p y r i m i d i n e , 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o x a z o l e and 2 - ( p y r i -

d i n e - 2 - t h i o n a t o ) b e n z o t h i a z o l e and t h e i r c o m p l e x e s w i t h C r d l l )

rin(II), F e ( I I I ) , C o ( I I ) , N i ( l l ) , C u ( I I ) , Z n ( I I ) , Ilg(II),

P d ( I I ) , Ru( II I)., Rh( III) and A u ( I I I ) h a s been d e s c r i b e d . T h e

c o m p l e x e s of d i v a l e n t and t r i v a l e n t m e t a l ions v;ere p r e p a r e d

in 1:2 and 1:3 (M:L) r a t i o r e s p e c t i v e l y . T h e y w e r e c h a r a c -

t e r i z e d by e l e m e n t a l a n a l y s i s , i . r . m a g n e t i c m o m e n t and

e l e c t r o n i c s p e c t r a . On the b a s i s of t h e s e s t u d i e s M n ( I I ) a n d

N i d i ) c o m p l e x e s of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) p y r i m i d i n e a p p e a r

to be o c t a h e d r a l . Hov/ever Z n ( I I ) , C o ( I I ) and C u ( I I )

c o m p l e x e s a r e s u p p o s e d to h a v e a t e t r a h e d r a l g e o m e t r y a r o u n d

the m e t a l i o n s . T h e l i 9 a n d 2 ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o x a -

zole y i e l d e d o c t a h e d r a l c o m p l e x e s v/ith t h e m e t a l s d e s c r i b e d

a b o v e e x c e p t for the P d ( I I ) and A u ( I I ) . S i m i l a r r e s u l t s v/ere

o b t a i n e d in the c a s e of 2 ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o t h i a z o l e

c o m p l e x e s . T h e c o m p l e x e s of a l l l i g a n d s a r e i n s o l u b l e in

u s u a l o r g a n i c s o l v e n t s . O n l y P d ( I I ) , R u ( I I I ) , R h ( I I I ) a n d

A u ( I I I ) c o m p l e x e s a r e s o l u b l e in D M S O . T h e y are s t a b l e

t o w a r d s l i g h t and a i r . T h e m o l a r c o n d u c t a n c e v a l u e s of

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

in n a t u r e .

In the f o u r t h c h a p t e r the s y n t h e s i s and c h a r a c t e r i z a -

tion of C r ( I I I ) , M n ( I I ) , F e ( I I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) ,

Z n ( I I ) , H g ( I I ) , P d ( l l ) , R u ( I I I ) , R h ( I I I ) , A u ( I I I ) and P t ( I V )

c o m p l e x e s of 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) p y r i d i n e 2 , 6 b i s

( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) p y r i m i d i n e and 2 - { 2 ' - m e r c a p t o -

b e n z o t h i a z o l y l ) b e n 2 o x a 2 o l e a r e r e p o r t e d . E l e m e n t a l

a n a l y s i s , m o l a r c o n d u c t a n c e s , m a g n e t i c and s p e c t r a l ( i . r . ,

^H NMR and u v - v i s i b l e ) m e a s u r e m e n t s h a v e been u s e d to

c h a r a c t e r i z e the c o m p l e x e s . T h e i . r . s p e c t r a l d a t a s h o w t h a t

the l i g a n d s b e h a v e as a b i d e n t a t e o n e s . C o n d u c t i v i t y

m e a s u r e m e n t s in D M S O s h o w the n o n - i o n i c n a t u r e of the

c o m p l e x e s . On the b a s i s of t h e s e s t u d i e s an o c t a h e d r a l

g e o m e t r y has been p r o p o s e d for all t h e c o m p l e x e s e x c e p t f o r

the P d ( I I ) and A u ( I I I ) c o m p l e x e s . T h e l i y a n d f i e l d

p a r a m e t e r s l O D q , B and p v a l u e s h a v e b e e n c a l c u l a t e d

w h e r e v e r p o s s i b l e w i t h t h e h e l p of T a n a b e - S u g a n o d i a g r a m s .

T h e f i f t h c h a p t e r of the t h e s i s d e a l s w i t h t h e

s y n t h e s i s and c h a r a c t e r i z a t i o n of C r ( I I I ) , M n ( I l ) ,

F e ( I I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) , Z n ( I I ) , H g ( I I ) , R u ( I I I ) ,

R h ( I I I ) and P d ( I I ) c o m p l e x e s of tv/o nev/ l i g a n d s 2 - ( N -

s u c c i n i m i d y l ) p y r i d i n e and 2 - ( N - s u c c i n i m i d y l ) p y r i m i d i n e . T h e y

h a v e b e e n c h a r a c t e r i z e d by e l e m e n t a l a n a l y s i s , i . r . ^H N M R ,

m o l a r c o n d u c t a n c e / m a g n e t i c m o m e n t s and e l e c t r o n i c s p e c t r a .

2 - ( N - s u c c i n i m i d y l ) p y r i m i d i n e c o m p l e x e s shov/ high m e l t i n g

p o i n t s and i n s o l u b l i t y in c o m m o n o r g a n i c s o l v e n t s

i n d i c a t i n g t h e i r p o l y m e r i c n a t u r e . R u ( I I I ) , P d ( I I ) and

C u ( I I ) c o m p l e x e s a r e s o l u b l e in D M S O . T h e o b s e r v e d m a g n e t i c

m o m e n t v a l u e s of the c o m p l e x e s of b o t h t h e l i g a n d s a r e v e r y

c l o s e to t h o s e c a l c u l a t e d for t h e m e t a l in an o c t a h e d r a l

e n v i r o n m e n t of l i g a n d s . T h e v a l u e of l O D q , B and jP h a v e a l s o

been d e t e r m n i n e d in c a s e w h e r e p o s s i b l e .

T h e sixth c h a p t e r d e a l s w i t h t h e s y n t h e s i s of 1,3

b e n z o x a z o l y l ( 2 , 4 , 6 p y r i m i d i n e t r i o n e ) and e l e v e n new

c o m p l e x e s from i t . T h e s e h a v e b e e n c h a r a c t e r i z e d by

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

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

a r e f o r m u l a t e d as M X ^ L ^ and M 2 X g L 2 a r e p r e s u m a b l y o c t a h e d r a l

v^ith t h e m e t a l b e i n g b o u n d to t h e n e u t r a l l i g a n d and t w o

h a l i d e i o n s . T h e c o m p l e x e s w e r e n o t s o l u b l e in c o m m o n

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

of t h e c o m p l e x e s in u s u a l o r g a n i c s o l v e n t s s h o w s t h a t t h e y

a r e p o l y m e r i c in n a t u r e .

COORDINATION CHEMrSTRY OF TRANSITION METALS WrTH HETEROCYqLIC

LIGANDS CONTAINING OXYGEN^ NITROGEN AND SULPHUR

^ t t b m i t t e ^ ^ o r i ^ t M t q x t t of

Bottor of ^hilojjopjip IN

CHEMISTRY

BY

Un<l«r tiM Supervi«ion of

Prof. Saiyid Aftab Ahmad Zaidi

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1 9 9 3

M.Sc (Alig), M.A., Ph.D. (ToronW) A.R.I.C. (London), F.N.A.Sc.

Phnn.c fOffico : 25615 : 27324

Telex; 564-230 AMU IN AUGARH MUSLIM UNIVERSITY

ALIGARH—202002 ( INDIA)

Date: 13th May, 1993

Certified that the work embodied in this thesis

entitled "Coordination Chemistry of Transition Metals

with Heterocyclic Llgands Containing Oxygen, Nitrogen and

Sulphur" is the result of the original research work of

Miss Shahjahan carried out under my supervision. This

work has not been submitted for any other degree and is

suitable for submission for the award of Ph.D. degree in

Chemistry of Aligarh Muslim University.

(SAIYID AFTAB AHMAD ZAIDI)

CONTENTS

Page No.

A c k n o w l e d g e m e n t s

L i s t of P u b l i c a t i o n s

CHAPTER - I 1-13

I n t r o d u c t i o n

CHAPTER - II

S y n t h e s i s and C h a r a c t e r i z a t i o n of C o m p l e x e s of I n d a z o l e D e r i v e d L i g a n d s ;

(i) 2 - ( 1 - i n d a z o l y l ) p y r i m i d i n e 14-25

(ii) 2 - ( l - i n d a z o l y l ) p y r i d i n e 26-36

( i i i ) 2 - ( l - i n d a z o l y l ) b e n z o x a z o l e 37-48

(iv) 2 - ( l - i n d a z o l y l ) b e n z o t h i a z o l e 49-59

CHAPTER - III

S y n t h e s i s and C h a r a c t e r i z a t i o n of C o m p l e x e s of S o m e N e w P y r i d i n e 2 - t h i o n e D e r i v e d L i g a n d s ;

(i) 2 - ( P y r i d i n e - 2 - t h i o n a t o ) p y r i m i d i n e 16-69

(ii) 2 - ( P y r i d i n e - 2 - t h i o n a t o ) b e n z o x a z o l e .... 70-78

( i i i ) 2 - ( P y r i d i n e - 2 - t h i o n a t o ) b e n z o t h i a z o l e . . . 79-89

CHAPTER - IV

S y n t h e s i s and C h a r a c t e r i z a t i o n of S o m e N e w B i h o t e r o a r o m a t i c C h e l a t i n g L i g a n d s ;

(i) 2 - ( N - S u c c i n i m i d y l ) p y r i d i n e 92-104

(ii) 2 - ( N - S u c c i n i m i d y l ) P y r i m i d i n e 1 0 5 - 1 1 6

CHAPTER - V

S y n t h e s i s and C h a r a c t e r i z a t i o n of C o m p l e x e s O b t a i n e d f r o m P y r i d i n e , B e n z o x a z o l e and P y r i m i d i n e S u b s t i t u t e d 2 - m o r c a p t o b c n z o t h i a z o l c L i g a n d s ;

(i) 2 - ( 2 ' - m e r c a p t o b e n z a t h i a z o l y l ) p y r i d i n e 1 1 7 - 1 3 1

(ii) 2 , 6 - b i s ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) 1 3 2 - 1 4 4 P y r i m i d i n e

( i i i ) 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) 1 4 5 - 1 5 8 b e n z o x a z o l e

CHAPTER - VI

S y n t h e s i s and C h a r a c t e r i z a t i o n of 1 5 9 - 1 7 2 C o m p l e x e s O b t a i n e d fom 2 , 4 , 6 - P y r i m i d i n o t r i o n e D e r i v e d L i g a n d ; 1 , 3 - b e n z o x a z o l y l ( 2 , 4 , 6 - P y r i m i d i n c t r i o n e )

P h y s i c a l M e a s u r e m e n t s 173

R e f e r e n c e s 1 7 4 - 1 8 2

ACKNOWLEDGEMENTS

It Is my privilege to acknowledge with deep sense of gratitude the enthusiastic support and never failing encouragement extended by my supervisor Prof. Saiyid Aftab Ahmad Zaidi. M.Sc. (Aligarh), M.A., Ph.D. (Toronto) A.R.I.C. (London), F.N.A.Sc., who made it possible for me to carry to out the work to completion. Without his valuable suggestions and stimulating discussion this thesis would not have seen the light of the day.

I wish to express my sincere thanks to Dr.Khwaja Salauddin Siddiqi, M.Sc,, Ph.D. (Aligarh) for sparing his time in much helpful discussions.

I am also beholden to my laboratory colleagues and friends Kauser Jahan, Ghazia, Soofia, Namita, Afshan, Naheed and Farah for their friendly attitude and immense help.

My special thanks to Mrs. R.Rizvi (U.S.A.) and Mrs. R. Kureshy for facilitating me with the provision of IR and 'HNMR spectra.

I shall be ever indebted to my brothers and sisters for their moral support. I shall not forget my Wasi mamu for his continuous consolations and encouragement through out the course of this work.

Financial support from the University in the form of a University fellowship is gratefully acknowledged. I thank Prof. Saiyid Aftab Ahmad Zaidi and Prof. M.A.Beg, Chairmen, Department of Chemistry for providing necessary research facilities.

Last but not the least J must record my gratefu Iness to my dear parents whose loving encouragement, moral and material support and inexhaustible store of affection has sustained me throughout the duration of this work.

( S H A H J A H A N )

L i s t of p u b l i c a t i o n s

1. C o o r d i n a t i o n p r o p e r t i e s of new i n d a z o l e d e r i v a t i v e s .

T r a n s i t i o n M e t . C h e m . , 1 8 , 51 ( 1 9 9 3 ) .

2. S y n t h e s i s of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) p y r i m i d i n e and a

study of its l i g a n d p r o p e r t i e s . S y n t h . R e a c t . I n o r g .

O r g . m e t . C h e m . , (In p r e s s )

3. T r a n s i t i o n m e t a l c o m p l e x e s of 2 - ( N - s u c c i n o n r a i d y l ) p y r i -

m i d i n e . S y n t h . R e a c t . I n o r g . M e t . O r g . C h e m . , (In

p r e s s ) .

4. S y n t h e s i s and l i g a n d p r o p e r t i e s of 2 - ( 1 - i n d a z o l y l )

b e n s o x a z o l e and 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e . S y n t h .

R e a c t . I n o r g . M e t . - O r g . C h e m . , (Comrainicated).

5. S y n t h e s i s and c h a r a c t e r i z a t i o n of c o m p l e x e s o b t a i n e d

from b e n z o x a z o l e and b e n z o t h i a z o l e s u b s t i t u t e d p y r i d i n e

- 2 - t h i o n e l i g a n d s . T r a n s i t i o n M e t . C h e m . , ( C o m m u n i c a t e d )

CHAPTER - I

Introduction

INTRODUCTION

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

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

r i n g . T h e m o s t c o m m o n t y p e of h e t e r o c y c l i c c o m p o u n d s

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

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

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

even b r o m i n e are a l s o k n o w n to be p a r t of t h e r i n g . T h e

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

a r e e s s e n t i a l to life in v a r i o u s w a y s . P y r i d i n e , p y r o l e ,

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

e x t r a c t e d f r o m c o a l t a r . S e v e r a l of the o t h e r n a t u r a l l y

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

h e t e r o c y c l i c r i n g s e g . t h e m e m b e r s of v i t a m i n B c o m p l e x

g r o u p , the a l k a l o i d s , some a n t i b i o t i c s , h a e m i n , c h l o r o p h y l l ,

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

g e n e t i c m a t e r i a l s like D N A e t c .

P y r o l e is s p e c i a l l y i m p o r t a n t a m o n g a l l the f i v e

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

in s e v e r a l i m p o r t n a t n a t u r a l p r o d u c t s .

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

to its p r e s e n c e in p l a n t g r o w t h h o r m o n e h e t e r o a u x i n e , in t h e

C < a m i n o a c i d s ( T r y p t o p h a n ) and in some a l k a l o i d s (viz e r g o t

(1-2) a l k a l o i d s , s t r y c h n i n e and r e s e r p i n e ) found in p l a n t s .

P y r i d i n e and p i p e r i d i n e h e t e r o c y c l e s a r e f o u n d to be

p r e s e n t in n u m e r o u s i m p o r t a n t n a t u r a l p r o d u c t s N i c o t i n a m i d e

and N i c o t i n i c acid a r e a m o n g the i m p o r t a n t c o n s t i t u e n t s of

V i t a m i n B c o m p l e x . N i c o t i n a m i d e a d e n i n e d i n u c l e o t i d e (NAD)

and its p h o s p h a t e (NADP) f o r m t h e p r o s t h e t i c p a r t ( c o e n z y m e s )

of m a n y e n z y m e s w h i c h are i n v o l v e d in o x i d a t i o n - r e d u c t i o n

p r o c e s s e s in l i v i n g o r g a n i s m s . S u l p h a p y r i d i n e was t h e m o s t

f a m o u s d r u g of t h e l a s t q u a r t e r c e n t u r y . It is p a r t i c u l a r l y

e f f e c t i v e a g a i n s t p n e u m o c o c c i b u t has a d v e r s e side e f f e c t s .

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

f a i l u r e d r u g and is a l s o u s e d in c a r b o n - m o n o x i d e p o i s o n i n g .

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

I s o n i a z i d has been used in t h e t r e a t m e n t of t u b e r c l o s i s .

V a r i o u s a l k a l o i d s a l s o p o s s e s s t h e p y r i d i n e n u c l e u s e g .

c o n i i n e , r i c i n i n e and n i c o t i n e . ^ ^ ^^ R e c e n t l y it has b e e n

s h o w n t h a t p r e s e n c e of p l a n a r l i g a n d s l i k e p y r i d i n e in t r a n s

[ P t C l 2 ( p y ) 2 ] g r e a t l y e n h a n c e s the c y t o t o x i c i t y of t h i s

c o m p o u n d and it is at l e a s t e q u i v a l e n t if not s u p e r i o r to

c i s p l a t i n in t r e a t m e n t of c e r t a i n k i n d s of t u m o u r e g . m u r i n e

t u m o u r . ^ ^

Q u i n o l i n e m o l e c u l e is o b t a i n e d by t h e f u s i o n of b e n z e n e

and a p y r i d i n e r i n g and t h u s it b e a r s t h e same r e l a t i o n s h i p

to p y r i d i n e as n a p t h a l e n e d o e s to b e n z e n e . Q u i n o l i n e n u c l e u s

is f o u n d in v a r i o u s t y p e s of o r g a n i c c o m p o u n d s viz c i n c h o n a

a l k a l o i d s , c h e m o t h e r a p e u t i c a g e n t s and a n a l y t i c a l r e a g e n t s .

C i n c h o n a a l k a l o i d s are q u i n o l i n e d e r i v a t i v e s w h i c h o c c u r in

c i n c h o n a b a r k . T w o i m p o r t a n t c i n c h o n a a l k a l o i d s a r e q u i n i n e

and c i n c h o n i n e . 8 - h y d r o x y - q u i n o l i n e is a l s o a good

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

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

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

than as dyes for f a b r i c s . Q u i n o l i n e y e l l o w is used as d y e

for t e x t i l e s . Q u i n o l i n e b l u e e t h y l red d y e , p s e u d o c y a n i n o

d y e s and s e n s i t o l red d y e a r e s o m e o t h e r m o r e i m p o r t a n t o n e s

w h i c h are w i d e l y u s e d . I s o q u i n o l i n e is i s o m e r i c w i t h

q u i n o l i n e and is a l w a y s p r e s e n t w i t h q u i n o l i n e in c o a l tar

and b o n e o i l . T h e i s o q u i n o l i n e n u c l e u s is f o u n d in a l a r g e

n u m b e r of a l k a l o i d s e g . p a p a v e r i n e , l a n d a n o s i n e , n a r c o t i n e ,

b a r b i t u r i c a c i d and e m e t i n e , b e n z o q u i n o l i n e or d i b e n z o p y r i -

d i n e k n o w n as a c r i d i n e s . A c r i d i n e is f o u n d to be the p a r e n t

s u b s t a n c e of a n u m b e r of d y e s and a n t i s e p t i c s .

I m i d a z o l e , p y r a z o l e , b e n z i m i d a z o l e and b e n z o p y r a z o l e

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

t i o n s . ^^ I m i d a z o l e n u c l e u s is f o u n d in a v a r i e t y of n a t u r a l

p r o d u c t s viz a m i n o a c i d s and p e p t i d e s in p u r i n e s and

a l k a l o i d s . H i s t i d i n e ( c<.-amino-;S-imidazyl p r o p i n o n i c a c i d ) ,

h i s t a m i n e ( ^ - i m i d a z y l e t h y l a m i n c ) and d i p e p t i d e s c a r n o s i n e

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

( 8)

p o s s e s s i n g i m i d a z o l e r i n g .

H i s t a m i n e is found in the f r e s h n u c l e u s m e m b r a n e of the

s m a l l i n t e s t i n e . It is f o r m e d from h i s t i d i n e by b a c t e r i a l

p u t r e f a c t i o n and is b e l i e v e d t o be r e s p o n s i b l e for c e r t a i n

a l l e r g i c r e a c t i o n s such as A s t h m a . H i s t a m i n e is a l s o f o u n d

to be p r e s e n t in e r g o l p r e p a r a t i o n , w h e r e it is b e l i e v e d to

be c o n c e r n e d w i t h the a c t i v i t y of the d r u g . T h e a l k l o i d

p i l o c a r p i n e p r e s e n t in J a b o r a n d i l e a v e s is a d e r i v a t i v e of

N - m e t h y l - i m i d a z o l e .

T h i o - h e t e r o c y c l i c c o m p o u n d s h a v e t h e ring c o m p o s e d of

c a r b o n o x y g e n and s u l p h u r l i k e t h i a z o l e . T h i a z o l e and t h e i r

d e r i v a t i v e s a r e f o u n d in c e r t a i n n a t u r a l p r o d u c t s viz

V i t a m i n B ^ ( t h i a m i n e ) and t h e p e n i c i l l i n s . S u l p h a t h i a z o l e is

a l s o a d e r i v a t i v e of t h i a z o l e w h i c h is u s e d as a d r u g .

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

0 - d i a z i n e ( p y r i d a z i n e ) , p y r i m i d i n e and p y r a z i n e . P y r i d a z i n e

c o m p o u n d s a r e of some i m p o r t a n c e as t h e s e are u s e d as a

s e l e c t i v e p l a n t g r o w t h i n h i b i t o r . A few p y r a z i n e s are

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

e g . s u l p h a p y r a z i n e and c h l o r o c y c l i z i n e ( A n t i h i s t a m i n e

d r u g ) .

R e c e n t l y a l a r g e n u m b e r of b i o l o g i c a l l y a c t i v e p y r i m i -

d i n e d e r i v a t i v e s h a v e b e e n s y n t h e s i z e d in w h i c h p y r a z o l o

(9)

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

used as a n t i m i c r o b i a l , a n t i b a c t e r i a l and a n t i m a l a r i a l

d r u g s . ^ ^ ^ ^ S o m e p y r i m i d i n y l u r e a s and t h i o u r e a s h a v e b e e n

shown to a c t as e f f e c t i v e h e r b i c i d e s . ^ ^ ^ ^^^ F l o u r i n a t e d

p y r i m i d i n e s a r e u s e f u l in c a n c e r c h e m o t h e r a p y . ^ ^ ^ ^ S e v e r a l

p y r i m i d i n e s e g . c y s t o s i n e , u r a c i l and t h i a m i n e h a v e b e e n

i s o l a t e d from the n u c l e i c acid h y d r o l y s a t e s . N u c l e i c a c i d s

are e s s e n t i a l c o n s t i t u e n t s of a l l c e l l s a n d l i v i n g m a t t e r .

C y s t o s i n e is found to be p r e s e n t in b o t h t y p e s of

n u c l e i c acid e g . r i b o n u c l e i c a c i d (RNA) and d e o x y r i b o n u c l i c

a c i d (DNA) w h i l e u r a c i l is p r e s e n t only in R N A and t h i a m i n e

o n l y in D N A . P y r i m i d i n e r i n g is a l s o f o u n d in v i t a m i n e B^^,

b a r b i t u r i c acid and its s e v e r a l d e r i v a t i v e s e g . v e r o n a l

w h i c h a r e u s e d as h y p n o t i c s . P l a t i n u m c o m p l e x of b a r b i t u r i c

(14)

acid is used as a n t i t u m o u r a g e n t . T h e 5,5 s u b s t i t u t e d

d e r i v a t i v e s of b a r b i t u r i c a c i d are a l s o w e l l k n o w n c h e m o t h e -

r a p t e n t i c a g e n t s .

Fused d i a z i n e h e t e r o c y c l e s are a l s o very i m p o r t a n t e g .

p u r i n e s and p t e r i d i n e s . T h e p t e r i d i n e n u c l e u s o c c u r s in the

p i g m e n t s of b u t t e r f l y w i n g s such as x a n t h o p t e r i n f o l i c acid

(growth f a c t o r ) , v i t a m i n B^ and c o e n z y m e f l a v i n - a d e n i n e - d i -

n u c l e o t i d e .

P y r i d i n e - 2 - t h i o l a l s o k n o w n as 2 - m e r c a p t o p y r i d i n e

c o n t a i n i n g the - N ( H ) - C ( C = S ) - c h r o m o p h o r e b e l o n g s to the

c a t e g o r y of some i m p o r t a n t b i o l o g i c a l c o m p o u n d s . ^ ^ ^ ^

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

p u r i n e and p y r i m i d i n e b a s e . S i n c e t h e k e t o form of p y r i d i n e -

2 - t h i o l is c o n s i d e r e d as a m o d e l c o m p o u n d for 6 - t h i o g u a n o s i n

( 2 - a m i n o - 1 , 2 - d i h y d r o - 9 ^ - D - r i b o f u r a n o s y l - 6 H - p u r i n e - 6 - t h i o n e ) ,

it f i n d s use in p r e p a r i n g and t e s t i n g c l i n i c a l l y u s e f u l

d r u g s .

M a n y t r a n s i t i o n m e t a l c o m p l e x e s of p y r i d i n e - 2 - t h i o l

h a v e b e e n r e p o r t e d . I m p o r t a n t a m o n g them b e i n g t h e [RuCl

( P y S ) ( P y S H ) ( P P h ^ ) ^ ] [ P y S H = P y r i d i n e - 2 - t h i o l and P y S = d e p r o t o -

nated p y r i d i n e - 2 - t h i o l ] w h i c h was r e p o r t e d by G i l b e r t and

W i l k i n s o n ^ ^ ^ ^ and f o r m u l a t e d as a d i m e r . some o t h e r

ruthenium d e r i v a t i v e s e g . [ Ru ( PyS) 2 (CgHj^2 ^ (

o c t a - 1 5 d i e n e ) R u ( P y S ) ( P P h ^ ) 2 have a l s o been p r e p a r e d

r e c e n t l y . M e t a l c o m p l e x e s of

c a d m i u m ^ ^ ^ ^ m e r c u r y ^ ^ t i t a n i u m ^ ^ ^ ^ m o l y b d e n u m ^ ^

t u n g s t e n ^ 2 6 ) ^ iron^^S)^ c o b a l t ^ 2 9 - 3 0 ) ^ n i c k e l ( 3 1 ^ s i l v e r ^ ^ ^ )

(23) (22) (32-33) lead , t i n , b i s m i t h and p l a t i n u m and for at

(34 )

least one f b l o c k m e t a l m a i n l y u r a n i u m have been

r e p o r t e d with PySH or P y S .

S t u d i e s of the c o o r d i n a t i o n of C u ( l ) to n e u t r a l t h i o n e

and d e p r o t o n a t e d t h i o l a t e give i n s o l u b l e c o m p l e x e s of the

g e n e r a l formula [ C u X ( C ^ H ^ N S ) ^ ] (X=C1, Br or I, n=2 or 3) and

C U ( C 5 H ^ N S ) and [ Cu (C^H^NS ) (f Ph^ ) ] . The c o m p l e x [ Cu (C^H^NS ) 3 ]

has been shown by X - r a y c r y s t a l l o g r a p h i c s t u d i e s to have a

d i s t o r t e d t r i g o n a l c o n f i g u r a t i o n a b o u t the c o p p e r c e n t r e

d e f i n e d by three S - d o n o r a t o m s . T h e c o m p l e x c a t i o n [ Cu (C^H^NS) ]

has the c o p p e r atom t e t r a g o n a l l y c o o r d i n a t e d by four S - d o n o r

atom^^^^ and the c o m p l e x [ C U 2 ( C ^ H ^ N S ) g ] C I 2 e x i s t s as a d i m e r

as a r e s u l t of two b r i d g i n g C ^ H ^ N S l i g a n d . The c r y s t a l

s t r u c t u r e of m i x e d ligand c o m p l e x ( C u C l ( C ^ H ^ N S ) ( P P h ^ ) 2 ] has

a l s o been reported.^ ^ T h e F e ( I I ) c o m p l e x e s are h o w e v e r

r e p o r t e d to be the t e t r a h e d r a l Fe X 2 ( L H ) 2 t y p e (X=C1, Br)

w h e r e PySH is c o o r d i n a t e d to iron t h r o u g h the t h i o n e S a t o m .

S i n c e c o o r d i n a t i o n by the t h i o l a t o f u n c t i o n a l g r o u p is w e l l

d o c u m e n t e d in F e ( I I ) c h e m i s t r y , it is r a t h e r s u r p r i s i n g

F i g u r e I

(B)

t h a t n o F e d l ) c o m p l e x of P y 2 S H is r e p o r t e d w h e r e the l i g a n d

is b o u n d to t h e m e t a l c e n t r e t h r o u g h t h e p y r i d i n e N and

t h i o l a t o S a t o m s . T e t r a e t h y l a m m o n i u m t r i e ( p y r i d i n e - 2 -

t h i o l a t o ) f e r r a t e (II) , vi/hich is t h e f i r s t o c t a h e d r a l c o m p l e x

of F e ( I I ) w i t h all t h r e e P y 2 S H l i g a n d s in the b i d e n t a t e

' t h i o l a t e ' form has a l s o been p r e p a r e d . ^

D u r i n g the l a s t few y e a r s w e h a v e b e e n i n t e r e s t e d in

t h e study of i n t e r a c t i o n of o r g a n i c c o r r o s i o n i n h i b i t o r s

such as 2 - m e r c a p t o b e n z o t h i a z o l e and i n d a z o l e w i t h m e t a l l i c

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

s h o w n a v a s t p o t e n t i a l in t h e f i e l d of b i o i n o r g a n i c s . R e c e n t

d e v e l o p m e n t s in c o p p e r t h i o l and c o p p e r i n d a z o l e c l u s t e r

c h e m i s t r y p r o v i d e s e v e r a l new c o m p o u n d s w h i c h seem q u i t e

( 3 8 - 4 0 ) i n t e r e s t i n g T h e u s e of 2 - m e r c a p t o b e n z o t h i a z o l e as a

a n a l y t i c a l r e a g e n t a n d of its c o m p l e x e s in i n d u s t r y and

( 4 1 - 4 4 ) m e d i c i n e has b e e n k n o w n for a long t i m e . T h e

o . / / - S H

N

F i g u r e II

O •N'

I H

o / /

H

H

.N <:Io F i g u r e III

s t r u c t u r e of its c o m p l e x e s w i t h m e t a l ion has b e e n i n v e s t i -

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

A s e a r c h of t h e l i t e r a t u r e s h o w s t h a t the c h e m i s t r y of

t h e i n t e r a c t i o n of 2 - m e r c a p t o b e n z o t h i a z o l e w i t h t r a n s i t i o n

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

s e p a r a t i o n of t h e p l a t i n u m g r o u p e l e m e n t s h a s a l s o b e e n

(45)

r e p o r t e d . T h i s c o m p o u n d m a y e x i s t e i t h e r in t h i o n e or in

t h i o l f o r m ( F i g u r e I I ) . H o w e v e r , it is a s s u m e d h e r e t h a t in

s o l u t i o n it is b e h a v i n g as a t a u t o m e r r a t h e r than in any o n e ( 4 6 - 4 7 )

p a r t i c u l a r f o r m ( F i g u r e I I I ) . It is e v i d e n t t h a t in

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

t h i o c a r b o n y l s u l p h u r a t o m and the n i t r o g e n a t o m . S i n c e t h e

l o n e p a i r s on t h e s u l p h u r a t o m p r e s e n t in t h e s k e l e t o n of

the ring a r e i n v o l v e d in the r e s o n a t i n g s t r u c t u r e s of t h e

m o l e c u l e , it is e x p e c t e d t h a t it s h o u l d h a v e v e r y w e a k c o -

o r d i n a t i n g a b i l i t y . ^ It is t h e r e f o r e r e a s o n a b l e to

a s s u m e t h a t it w i l l n o t c o o r d i n a t e v/ith t h e m e t a l i o n s . O u t

of t h e r e m a i n i n g two b o n d i n g s i t e s on t h e l i g a n d m o l e c u l e

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

b u t in some c o m p l e x e s it a c t s as a b i d e n t a t e o n e i n v o l v i n g

b o t h s i t e s .

T h e c h e m i s t r y of I n d a z o l e is of g r e a t r e l e v a n c e in the

f i e l d of b i o i n o r g a n i c s . ^ ^ ^ ^^^ I n d a z o l e (Figure - I V A ) is an i s o m e r of the b i o l o g i c a l l y a c t i v e m o l e c u l e b e n z i m i d a z o l e

( 54)

( F i g u r e - I V B ) . I n d a z o l e and its d e r i v a t i v e s h a v e b e e n

f o u n d to be u s e f u l in the s y n t h e s i s of d y e s . T h e c o o r d i n a -

10

tion b e h a v i o u r of i n d a z o l e and its d e r i v a t i v e s w i t h t r a n s i -

tion m e t a l s has been e x t e n s i v e l y s t u d i e d in t h e s e l a b o r a t o -

(55-58) r i e s .

F i g u r e IV

B a r b i t u r i c acid and s u c c i n i m i d e are o x y g e n and n i t r o g e n

c o n t a i n i n g ligands r e s p e c t i v e l y . B a r b i t u r i c acid is an

a n a l o g u e of p y r i m i d i n e , w h i c h is h a v i n g d i f f e r e n t c o o r d i n a -

tion s i t e s . It exists in two t a u t o m e r i c forms C and D as

given b e l o w .

(C)

HO OH

N. N

DM (D)

F i g u r e XIII

11

H o w e v e r on the b a s i s of h a l o g e n a t i o n r e a c t i o n s it has

been s h o w n to e x i s t p r e d o m i n a n t l y in the f o r m C .

F a i r l y g o o d d e a l of w o r k on i n d a z o l e , i m i d a z o l e , p y r a -

z o l e , i n d o l , 2 - m e r c a p t o b e n z o t h i a 2 o l e and t h e i r d e r i v a t i v e s

h a s been r e p o r t e d f r o m this l a b o r a t o r y in t h e l a s t t w o

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

been s t u d i e d w i t h a v i e w to l o c a t i n g the m o d e of c o o r d i n a -

tion in the c o m p l e x e s f o r m e d and i n v e s t i g a t i n g t h e i r p h y s i c o

u • 1 (59-65) c h e m i c a l p r o p e r t i e s .

In t h e p a s t ten y e a r s a n u m b e r of c o m p o u n d s of t h e s e

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

c h e l a t e c o m p o u n d s from t h e s e l i g a n d h a v e b e e n r e p o r t e d . ^ ^ ^ ^^^

T h e r e h a v e b e e n m a n y a r t i c l e s d e t a i l i n g the s y n t h e s i s and

c h a r a c t e r i z a t i o n of m e t a l c o m p l e x e s b o u n d t h r o u g h n o v e l

n i t r o g e n a r o m a t i c h e t e r o c y c l i c l i g a n d s . ^ ^ ^ ^^^ L i g a n d s w i t h

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

in t h e f o r m a t i o n of b i a n d p o l y m e t a l l i c m e t a l - l i g a n d

(74) c o m p l e x e s w i t h a p p l i c a t i o n s as o l i g o m e r m e t a l c o m p l e x e s ,

rgy tr;

( 7 8 - 8 0 )

as i n t r a m o l e c u l a r e n e r g y t r a n s f e r c e n t e r s ^ ^ ^ 77)^ ^ ^ ^^^

s o l v a t o c h r o m i c s t u d i e s .

R e c e n t l y m a n y p a p e r s d e t a i l i n g the s y n t h e s i s and c h a -

r a c t e r i z a t i o n of m e t a l c o m p l e x e s f r o m n o v e l a r o m a t i c n i t r o -

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

of Ru(bpy;P^ ( b p y = b i p y r i d i n e ) as e l e c t r o n t r a n s f e r c a t a l y s t

in p h o t o i n d u c e d r e a c t i o n has a r o u s e d m u c h i n t e r e s t in t h e

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

12

(81-83) with v a r i o u s m o d i f i c a t i o n .

M a n y p y r a z o l e d e r i v e d l i y a n d s are of i n t e r e s t . M o r e

i m p o r t a n t a m o n g them are N , N ' - c h e l a t i n y b i h e t e r o a r o m a t i c

l i g a n d s such as 3,5 d i m e t h y l - 1 - ( 2 - p y r i d y l ) p y r a 2 o l e (DMPP),

3 , 5 - d i m e t h y l - l - ( 2 - 2 - p y r i m i d y l ) p y r a z o l e ( D M P ' P ' ) , 3,5-

d i m e t h y l - 1 ( 2 - p y r a z i n e ) p y r a z o l e and ( 2 - p y r i d y l ) t r i o z o l e

(84—86) (Figure V I ) have been r e c e n t l y s t u d i e d . C o m p l e x e s of

a n u m b e r of r e l a t e d h e t e r o a r o m a t i c l i g a n d s such as 2-

( 2 - p y r i d y l ) t h i a z o l e (Pyth)^'^^^ 2 - 2 ' b i t h i a z o l e (bth)^®^"®®^

2-( 2 ' - p y r a z i n e ) t h i a z o l e (Pzth) , 2-(2-pyridyl )oxo2ole(Pyox)

( D M P P ) (DMP"P'5

( D M P Z P )

F i g u r e V I

13

2 , 2 ' - b i p y r a z i n e ( b p z ) ("78,7 9 , 9 1 ) ^ d i p y r ido ( 2 , 3-a , 2 ' , 3 ' - h ) p h e n a

z i n e ( d p o p ) , 4 ' , 7 ' - p h e n a n t h r o l i n o - 5 ' , 6': 5 , 6 - p y r a z i n e ( p p z ) ,

6,7 d i m e t h y l 2 , 3 - b i s ( 2 - p y r i d y 1 ) q u i n o x a l i n e ( d d p q ) and 2 , 3 - b i s

(9 2-9 4)

( 2 - p y r i d y l ) p y r a z i n e ( b p p z ) ' ( F i g u r e - V I I ) w i t h t r a n s i -

tion m e t a l h a v e a l s o been s t u d i e d .

(pyth) (Pzth)

I / H \

(bth)

r ^ N N

( p y o x )

n'/ V N

.N- T Z I N

\\ // (ddpq)

F i g u r e

V I I

/ / •N

(bpz)

.N N.

(PPZ)

(bppz)

CHAPTER - II

Synthesis and characterization of complexes of

IndazGle derived ligands;

(I) 2-(l-indazolyl)pyrlmldlne

(II) 2-l(-lndazolyl)pyrldlne

(III) 2-(l-lndazolyl)benzoxazole

(Iv) 2-(l-lndazolyl)benzothlazole

Complexes of 2-(l-lnclazolyl)pyrimlcline

14

Experimental

M a t e r i a l a n d m e t h o d s

I n d a z o l e ( F l u k a ) , s o d i u m h y d r i d e ( 8 0 % s u s p e n s i o n in o i l )

2 - b r o m o p Y r i d i n e , 2 - b r o m o p y r i m i d i n e , 2 - b r o m o b e n z o x a z o l e and

2 - b r o m o b e n z o t h i a z o l e ( A l d r i c h ) w e r e u s e d as s u c h . M e t a l

c h l o r i d e (BDH and J o h n s o n M a t h e y ) w e r e'Used as r e c e i v e d .

P r e p a r a t i o n of s o d i u m i n d a z o l i d e

I n d a z o l e (4.0 g ) w a s a d d e d to a s u s p e n s i o n of s o d i u m

h y d r i d e (1.66 g of 80% s u s p e n s i o n in o i l ) in dry t e t r a -

h y d r o f u r a n (100 m L ) and t h e r e s u l t i n g m i x t u r e w a s s t i r r e d

u n d e r r e f l u x for 24 h o u r s and t h e n p o u r e d i n t o 200 m L w a t e r .

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

p u r i f i e d by c o l u m n c h r o m a t o g r a p h y on s i l i c a gel u s i n g C H C l ^

and h e x a n e , to g i v e c o l o u r l e s s c r y s t a l s . Y i e l d 30% M . P .

1 4 0° C .

P r e p a r a t i o n of 2 - ( l - i n d a z o l y l ) p y r i m i d i n e

2 - b r o m o p y r i m i d i n e (1.96 g) and s o d i u m i n d a z o l i d e

(2.42 g ) in 1 : 1 m o l a r r a t i o w e r e t a k e n t o g e t h e r a n d r e f l u x e d

w i t h s t i r r i n g in d r y t e t r a h y d r o f u r a n (150 m L ) f o r 24 h o u r s .

T h e s o l u t i o n w a s t h e n p o u r e d i n t o 50 m L w a t e r . A c r u d e

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

c o l u m n c h r o m a t o g r a p h y on s i l i c a gel u s i n g c h l o r o f o r m and

h e x a n e ( 1 : C H C l ^ : h e x a n e ) . Y i e l d 6 0 % , M . P . 170°C.

15

P r e p a r a t i o n of t h e c o m p l e x e s

A m i x t u r e of e t h a n o l i c s o l u t i o n of 2 - ( 1 - i n d a z o l y l )

p y r i m i d i n e and m e t a l c h l o r i d e in 1:2 or 1:3 (MtL)) r a t i o w a s

s t i r r e d u n d e r r e f l u x for 12 h o u r s on a w a t e r b a t h . It w a s

k e p t o v e r n i g h t at r o o m t e m p e r a t u r e w h e n it y i e l d e d a

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

u n d e r v a c u o . T h e r e a c t i o n m a y be r e p r e s e n t e d as b e l o w :

(where M = M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( l l ) Z n ( l l ) and P d ( I I )

(where M = R u ( I I I ) and R h ( I I I )

16

Results and discussion

2 - ( l - i n d a z o l y l ) p y r i m i d i n e m a y a c t as m o n o b i d e n t a t e or

b i s b i d e n t a t e ( b r i d g i n g ) l i g a n d . It is v e r y s i m i l a r t o b i p y -

r i d i n e ( F i g u r e - i x )•

In a d d i t i o n the l i g a n d 2 - ( l - i n d a z o l y l ) p y r i m i d i n e

o f f e r e d the p o s s i b i l i t y of f o r m i n g a six m e m b e r e d ring by

c h e l a t i n g t h r o u g h n i t r o g e n a t o m of p y r i m i d i n e a t p o s i t i o n - 1

and c a r b o n a t o m of i n d a z o l e at p o s i t i o n - 7 .

T h e c o m p l e x e s a r e s t a b l e to h e a t and m o i s t u r e . T h e y d o

n o t u n d e r g o o x i d a t i o n or r e d u c t i o n , t h e y a r e s o l u b l e in D M S O ,

THF and n i t r o g e n z e n e . T h e low m o l a r c o n d u c t a n c e of t h e

c o m p l e x e s in D M S O and n i t r o b e n z e n e i n d i c a t e s t h e i r n o n -

(85)

e l e c t r o l y t e n a t u r e . T h e s u b s t i t u t i o n of t h e c h l o r i d e

ions in t h e c o m p l e x e s M L 2 C I 2 (where L = 2 - ( l - i n d a z o l y l ) p y r i m i -

d i n e , M = M n C l 2 / C0CI2/ NiCl2/ C U C I 2 and Z n C l 2 ) by p y r i d i n e in

D M S O s o l u t i o n w a s s t u d i e d and it was f o u n d t h a t b o t h t h e

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

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

c a l l y . T h e r e is a s h a r p i n c r e a s e in c o n d u c t a n c e by t h e

a d d i t i o n of p y r i d i n e and c o n s e q u e n t r e l e a s e of c h l o r i d e ion

f r o m the c o m p l e x e s .

M L 2 C I 2 + py f [ML2Clpy]"^ + Cl~

[ML2Clpy]"^ + py ^ [ M L 2 P y 2 + C l "

17

T h e r e is a n o t h e r i n c r e a s e w h e n the second c h l o r i d e ion

is s u b s t i t u t e d by p y r i d i n e and t h e r e a f t e r f u r t h e r a d d i t i o n

of p y r i d i n e does not m a k e any c h a n g e in c o n d u c t a n c e .

T h e infrared s p e c t r u m of s o d i u m i n d a z o l i d e d o e s not

show any ^^N-H a b s o r p t i o n in the 3 3 0 0 - 3 5 0 0 cm ^ region

c o n f i r m i n g t h a t the a n i o n i c h y d r o g e n atom of the i n d a z o l e

has been r e p l a c e d by sodium a t o m .

In 2 - ( 1 - i n d a z o l y l ) p y r i m i d i n e the C=N a b s o r p t i o n bands

are s h i f t e d to lower f r e q u e n c i e s as c o m p a r e d to those sodium

i n d a z o l i d e (Table I I ) . In the i . r . spectra of the c o m p l e x e s ,

the 2yC=N and iJC=C are shifted to l o w e r v a l u e by a p p r o x i -

n-

(95)

m a t e l y 10 cm ^ and 20 cm ^ r e s p e c t i v e l y , i n d i c a t i n g s u b s t a n -

tial c o v a l e n t b o n d i n g b e t w e e n the n i t r o g e n and m e t a l i o n s .

Some very w e a k new b a n d s in the 4 0 0 - 3 8 0 cm ^ r e g i o n , in the

spectra of the c o m p l e x e s may be a s s i g n e d to the m e t a l

n i t r o g e n s t r e t c h i n g f r e q u e n c i e s . ^ ^ ^ ^

F i g u r e V I I I

tN e o

o N

ro

c •H

(N

M 0 (H

rO

fl 13

(0 U •rl +J >1 H (0 C (0

-a c ro o u c fO •p o 3

c 0 u

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c •H 0 cx

CP c •H 4J H OJ S

13 H (U •H >1

U 3 0

H

(U rH ja to E-"

to Q) X (U tH 04

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w

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0) c •H V •H e •H M

0 >1 U &

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c D o fe w •H U) > rH (T3 C vo V£> VO

O CM vo vo CM o ro 00 00 <Ti in O LD 00 o

• • • • • • • • •

1 J r- 00 00 • 00 cr> CT> <Ti

rH rH <H iH 00 rH iH tH rH H ~ — rH

—^ ^ ^

o rr O o o o O O 00 lO o^ m m CM CM O cri rH o CO

• • t • • f 00 • • * • •

00 00 VD • m in m in CN (N rH rH iH iH m iH rH rH rH rH

rH

o o O CM o o cn CTl O o n o o CO 00 OO o

• ( • • • • • • • • 9 • • m ro ro ro ro 00 ro OO

—

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19

in

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cn

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CTl rH 00 CO

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O iH 00 • •

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o rH CN

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u I s

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2 II U

20

o O o o in o o o o o o iH O n rH r-H iH m cTi m cn rH

ro fO ro n OO 00 (N ro (N ro

1 1 00 O o in o o o o o O o o cn rH o o <Ti

ro ro << ro

o o o in o o 0 in 0 m in in in in in <0 VO vo ro ro ro ro ro m ro ro ro ro rH iH rH rH H rH rH rH iH iH rH

0 CM 0 0 m 0 V£> 0 0 m 0 >H <H CTl 00 O^ CO CO cn 00 a

in m in in in in in m in rH rH rH rH rH iH rH rH rH rH

VD VD CM rM rsi rM r\i rH rH « rH t-i rH rH rH iH U u rH

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f—N ^ s -—» ,—V -—^

H rvi •a" z Z H (0 IS s Z z Z 2 Z CO CO 2

in CO CO 00 CO CO CO K X CO 1 c K E 3: X K X tH rH X

3 r- 2 rH rH rH rH rH rH rH rH rH (1) 0 u 00 U u rH r-i —' rc u U u U U u ^ •— u jQ a + rH —- w fNJ (M 5 0 (0 rH c 0 •H c tJl x: -a u s u s u 2 u N X « Pi Oi

21

Electronic spectra

U V - v i s s p e c t r u m of M n ( I I ) c o m p l e x of 2 - ( 1 - i n d a z o l y l ) -

p y r i m i d i n e shov/s t h r e e m a i n b a n d s in a d d i t i o n t o a c h a r g e

t r a n s f e r o n e . T h e b a n d s o b s e r v e d at 1 7 , 4 8 0 c m ~ ^ , 2 3 , 3 3 0 c m ^

and 2 5 , 2 0 2 c m ~ ^ m a y be a s s i g n e d to '^T^g(G) *

(G) Â, (S) and < (S) t r a n s i t i o n s 2g Ig Ig ig

r e s p e c t i v e l y . T h e m a g n e t i c m o m e n t v a l u e of 5.80 BM of t h i s

c o m p l e x e is c o n s i s t e n t v/ith an o c t a h e d r a l g e o m e t r y of t h e

c o m p l e x .

T h e m a g n e t i c m o m e n t v a l u e of 4.72 BM in C o ( I I ) c o m p l e x

i n d i c a t e s an o c t a h e d r a l g e o m e t r y . T h e C o ( I I ) c o m p l e x

e x h i b i t e d t w o m a i n b a n d s a t 1 1 , 3 2 0 cm ^ and 1 9 , 3 0 0 cm ^

4 4 r e s p e c t i v e l y a t t r i b u t e d t o T 2 g ( F ) < "Îg^^^

4 4

T ^ g ( P ) -t T (F) t r a n s i t i o n s . In a d d i t i o n t h e r e is

o b s e r v e d a c h a r g e t r a n s f e r b a n d at 3 4 , 4 5 0 c m ~ ^ . T h e N i ( I I )

c o m p l e x s h o w s a m a g n e t i c m o m e n t v a l u e of 3.11 BM c h a r a c t e r -

i s t i c of an o c t a h e d r a l g e o m e t r y . T h e e l e c t r o n i c s p e c t r u m

s h o w s an i n t e n s e c h a r g e t r a n s f e r b a n d at 3 3 , 3 4 0 cm ^ in

a d d i t i o n to t h r e e b a n d s o b s e r v e d a t 9,400 c m ~ ^ , 1 5 , 0 0 0 c m " ^ _ 1 3 3

and 2 4 , 500 c m " r e s p e c t i v e l y a s s i g n a b l e to

^ T ^ ^ ( F ) < ^"Îg^^^ ^^ t r a n s i t i o n s .

T h e s e d a t a i n d i c a t e an o c t a h e d r a l e n v i r o n m e n t a r o u n d t h e

n i c k e l i o n .

T h e m a g n e t i c m o m e n t v a l u e of 1.80 BM for C u ( I I ) c o m p l e x

c l e a r l y i n d i c a t e s an o c t a h e d r a l g e o m e t r y a b o u t this m e t a l

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

22

at 35,000 H o w e v e r , t h e w e a k b a n d o b s e r v e d at 1 4 , 5 0 0 cm ^

2 2 a s s i g n e d to T „ E t r a n s i t i o n is c h a r a c t e r i s t i c of an 2g y

o c t a h e d r a l g e o m e t r y

T h e e l e c t r o n i c s p e c t r u m of R u ( I I I ) c o m p l e x shov/s o n e

s t r o n g b a n d at 1 8 , 3 0 0 c m ~ ^ w h i c h can b e a s s i g n e d to

2 2

t r a n s i t i o n . T h e m a g n e t i c m o m e n t v a l u e ( 2 . 2 0 B M )

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

a r o u n d R u ( I I I ) i o n . T h e D i m a g n e t i c P d ( I I ) c o m p l e x of 2-

( l - i n d a z o l y l ) p y r i m i d i n e s h o w s t h r e e m a i n b a n d s at 1 7 , 5 0 0 c m " ^ ,

1 9 , 300 cm ^ and 2 1 , 5 5 0 cm ^ a s s i g n a b l e to ^ ^ I g ' ^Bj^^ < '^^Ig ^ ^ g * ^^Ig ^ s q u a r e p l a n a r

g e o m e t r y .

R h ( I I I ) c o m p l e x of 2 - ( 1 - i n d a z o l y l ) p y r i m i d i n e s h o w s f o u r

c h a r a c t e r i s t i c m a i n b a n d s at 1 1 , 3 4 0 c m ~ ^ , 1 5 , 6 6 0 c m ~ ^ ,

1 9 , 3 3 0 cm ^ and 2 1 , 4 4 0 c m ~ ^ w i t h an i n t e n s e c h a r g e t r a n s f e r

at 34 , 301) cm ^ s u p p o r t i n g an o c t a h e d r a l g e o m e t r y a r o u n d t h e

R h ( I I I ) i o n .

M 0 IM

(0 M dJ •P (U 1 fO M (0 04

ts H 1-0 4J 'H •H S H 'H •H H J3 >1 •H Oi +J ^ 04f-l n O rH 3 0 W N

m U 'O •H C +J -H (U I C (H

H H H

o; H

m

cr Q H

I S I

c CJ

OI •H w w (0

a> H A •H » W 0

o •H H C I o

o . CQ

10 '0 c

0 a i u

23

(N Ol 00

r--00 00

fN

CTi

O CTi VO

O 00 vo o <N

00 m <Ti

o o m <N fM

cn tn w

{71 tj) CJi rH f-H r-l < <

r

u o o tji Cn"^ rH CM r H El <

^ rr rr

cn E-<

U

Cm PM

itT" CD iH tH EH EH

Cm C —- •— CTI Cn • CM rHEH

EH EH .

CM CM CM

Cji (N CM fN < '

I

CM CM D4 01 •

(N rH rH EH EH EH EH •

n n ro CJ

O CJ-

(N

O 00

in

fN rH u CM

z 00

-H rH

U c S

CM

<N rH u <N

2 00

K

U "o u

rri

<N1 rH u <N •a-

2 00

X

u •H 2

o 00

CN rH u <N

2 00

K

U D U

cn (N

Eh CM

CP' f tH

CM U

Cn . (N Eh

<c • CM U

M 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 +J 00 CO rH CN 0 m 0 0 0 0 0 0 n 0 • 'O ro 0 ro m 0 in CO m 0 n ro (U c ^ « ^ •• •• ^ * * *

H (0 fO m LD rH 01 cri m ro in 00 Ci5 XI rH <N CM m r-t r-i m rH fN oo rH ro rH n

o CN <N

rH U CM

2 00

U CM D

24

Cri tT> tj> tJi iH H tH M < < < <

H H rH rH

CP t7> C71 fH rH fH < < <

Cn tJt CT> tJ> • iH CM rH CM E-t

Eh EH E-< E-i CO n M rH u

tj> CP • CN C^ CP EH

i< m w rH rH rH U

0 0 0 0 0 0 0 0 0 <~o CO 0 0 0 m 0

CO CO ro in ro in 0 •k ••

rH 10 rH r-- CP iH rH tH iH CM ro iH iH <NJ ro

'O +J c 0 u

rH u

CM

2 00 tc

u

CM s:

u CM

2 00

ffi

U

25

M

' b

N . M

o I

F i g u r e - IX

CI

M

CI

M = M n ( l l ) , C o ( I I ) , N i ( I I ) , C u ( I I ) and Z n ( I I )

F i g u r e X

Complexes of 2-(l-lnclazolyl)pyridlne

26

Experimental

M a t e r i a l and m e t h o d s

I n d a z o l e ( F l u k a ) , s o d i u m h y d r i d e (80% s u s p e n s i o n in o i l )

2 - b r o m o p y r i d i n e , 2 - b r o m o p y r i m i d i n e , 2 - b r o m o b e n z o x a z o l e and

2 - b r o m o b e n z o t h i a z o l e ( A l d r i c h ) w e r e u s e d as s u c h . M e t a l

c h l o r i d e (BDH and J o h n s o n M a t h e y ) w e r e u s e d as r e c e i v e d .

P r e p a r a t i o n of s o d i u m i n d a z o l i d e

I n d a z o l e (4.0 g) v/as a d d e d to a s u s p e n s i o n of s o d i u m

h y d r i d e (1.66 g of 80% s u s p e n s i o n in o i l ) in d r y t e t r a h y d r o -

f u r a n (100 m L ) and t h e r e s u l t i n g m i x t u r e w a s s t i r r e d u n d e r

r e f l u x for 24 h o u r s and t h e n p o u r e d i n t o 200 m L w a t e r . T h e

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

p u r i f i e d by c o l u m n c h r o m a t o g r a p h y on s i l i c a g e l using C H C l ^

and h e x a n e , to g i v e c o l o u r l e s s c r y s t a l s . Y i e l d 3 0 % , M.P.

140°C.

P r e p a r a t i o n of 2 - ( l - i n d a z o l y l ) p y r i d i n e

A m i x t u r e of 2 - b r o m o p y r i d i n e (1.37 m L ) , s o d i u m i n d a z o -

lide (2.42 g) w a s r e f l u x e d in d r y t e t r a h y d r o f u r a n (30 m L )

for a b o u t 30 h o u r s and then p o u r e d i n t o 80 m L w a t e r . T h i s

r e a c t i o n m i x t u r e on c o o l i n g in i c e - b a t h y i e l d e d a c r y s t a l l i n e

s o l i d v/hich v/as p u r i f i e d by c o l u m n c h r o m a t o g r a p h y on s i l i c a

o

gel u s i n g c h l o r o f o r m and h e x a n e . Y i e l d 3 0 % , M . P . 130 C .

P r e p a r a t i o n of t h e c o m p l e x e s

T h e c o m p l e x e s of 2 - ( 1 - i n d a z o l y l ) p y r i d i n e w e r e p r e p a r e d

27

by m i x i n g t h e m e t a l c h l o r i d e s o l u t i o n (MnCl2* C0CI2/ N i C l 2 /

C U C I 2 ' ZnCl2/ PdCl2/ R u C l ^ and R h C l ^ ) and t h e l i y a n d

s o l u t i o n in 1:1 and 1:3 m o l a r r a t i o in d r y e t h a n o l . T h e

s o l u t i o n w a s h e a t e d on a w a t e r b a t h for 14 h o u r s and t h e n

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

v/hen a sol id a p p e a r e d . T h e p r e c i p i t a t e s o o b t a i n e d w a s

w a s h e d w i t h a l c o h o l and d r i e d in v a c u o . T h e c o m p l e x a t i o n

r e a c t i o n m a y be r e p r e s e n t e d as b e l o w :

C 1 2 H 9 N 3 + M C I 2 >

(where M = M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) Z n ( I I ) and H g ( I I )

(where = R u ( I I I ) and R h ( I I I )

28

Results and discussions

T h e c o m p l e x e s are s t a b l e to h e a t and m o i s t u r e . T h e y do

not u n d e r g o o x i d a t i o n o r r e d u c t i o n . They a r e s o l u b l e in

c o m m o n o r g a n i c s o l v e n t s such as D M S O , D M F , T H F and n i t r o b e n -

z e n e . E l e m e n t a l a n a l y s i s , c o l o u r , m e l t i n g p o i n t s , m o l a r

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

in t a b l e - i V . T h e p r o b a b l e s t r u c t u r e of t h e s e l i g a n d c o m p l e x e s

is s h o w n in f i g u r e X I I .

T h a t the s o d i u m i n d a z o l i d e is f o r m e d by t h e r e m o v a l of

h y d r o g e n f r o m NH g r o u p of i n d a z o l e is i n d i c a t e d by the

a b s e n c e of any a b s o r p t i o n b a n d in the r e g i o n 3 5 0 0 - 3 1 0 0 cm ^

c h a r a c t e r i s t i c of the N-H g r o u p .

T h e i . r . s p e c t u r m of t h e l i g a n d is s i g n i f i c a n t in the

'1600-700 cm ^ r a n g e b e c a u s e a l l the c h a r a c t e r i s t i c f r e q u e n -

c i e s lie in t h i s r e g i o n . T h e s h a r p b a n d s a t 1 6 0 0 - 1 5 5 0 c m ~ ^

a r e a s s i g n e d to C = C and C = N f r e q u e n c i e s , they a r e n o t e a s i l y

d i s t i n g u i s h a b l e as they f a l l in the s a m e r e g i o n and are

q u i e t o f t e n c o u p l e d w i t h e a c h o t h e r . T h e C = C & C = N f r e q u e n c i e s

of t h e c o m p l e x e s a r e s h i f t e d to l o w e r v a l u e s by a b o u t 2 0 - 1 0

cm ^ r e s p e c t i v e l y . It is t h e r e f o r e e x p e c t e d t h a t the m e t a l

m a y be b o n d e d to the n i t r o g e n a t o m of t h e p y r i d i n e as w e l l

(97)

as i n d a z o l e m o l e c u l e .

S o m e new b a n d s o b s e r v e d in all c o m p l e x e s in far i-r

s p e c t r a in the r e g i o n 4 0 0 - 3 0 0 cm ^ a r e t e n t a t i v e l y a s s i g n e d

t o M - N s t r e t c h i n g f r e q u e n c y .

o N (0 TS C •H

I r>4

M 0 m

d) 4J (0

<a u •H •P >1 iH (0 C (0

T3 C (0

0) o c «3 +J o 3 T3 C 0 u

M QJ H 0 6

4J C •H a c •rl •P H 0) £

Ui d) X (U H

I O

M +J •H

'0 fo c

o

>H gj C •H

•H M

5 ^

M §

I

0) iH X) (tJ Eh

H U

<if>

m u

t; c p o IM

•H W >1 rH (0 C •H

29

<N

O (N

(N CTi <y\

o 9 ^ m • • m CO

o o o o o o vo

o

O n

o (N fNj o iH CO o • • • fl •

O ro in

o LD

o u-i

o

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o cn

o 00

o f^ 00

CTl 00

o o ro 00

^ s 00 00 CO 00

° s tn

s s ccJS

° s CM r-H

VD <X>

cn ro ^ 2 ro

o in ro r^ Ln Ln m LD

O CN 00 ro -a- un uo m

O OM O T un in tn tn

o tn

tn <«D

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g s CTi CO

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O "H cn "a"

roô ro*^ roô roô

O O tn 00

in tn

o r^ CM

CN r--

a g -H rH iH M u u u u

1 OJ <N fSJ - — . -—V

CM ro ro CO ro w 2 Z Z '0 tn CTl CTi CTl c X ro K ac a: a: p r^ 2: (N CM rsi CM 0 u cri «H tH rH rH

K U u u U e + CM ' — •—- —-0 fO iH c 0 •H u u u U

30

CM cr> n

LD

m

o <y\

en

o n

o cn m (

o o

O^ CO

"—I .—I

O CM • • -H P

§5

o Co O CTi . — .

cri CN o "a* o cn O LO

• • • • • • ix> cn tN

CN fN CN (N rH rH —'

o o^ 1 1 1 1 9 • 1 1

00 00 rH rH

o o UD

cn ro •

O 00 00 •

00 00 • ro • •

00 00 • •

m CN rH

(N o rH

o rH CN

rH rH o rH rH

Ln cn o

o

o

CTl r-S cn CO

CN m O CM o O r^ cn 'J' CO CN CN CN CN (N rS

• • • • • • • • • •

00 00 CM ^ OJ (N OJ CN fO 00 t-'

o r- r-- r- r- o 00 o o^ o -sr un o

• • • • • • • • • * in oo 00 tn Ln in m o o IT) un 00 PO 00 00 in m

— •

o 00

o CM

O CT) <N

O 00 CM

O 00

CN CN r-

o r-.

o m VD

(U •P •H x:

5 o

01 >H

u ro

iH m

c

o M PQ

<U

CN rH U CN

cn S 01

K CN rH u c IS3

(N iH U CN n S

cri W

CM iH u

E

iH U CN

cn 2 ffi CN rH

U

CN P Pi

VO rH u CN CO S CTl rc CN rH

U

CN x: K

u CN

cn S o

E CN rH u

CM

31

u I s

I s

(U c c 0 (0 •H +J D^T! to c M C (0 XI •H ja •H > 01 -a c c •H m M XI H

E 0 (1) 1 B U M (0

3 H O a.

U II u

II u

w TD C P 0 a E 0 u

O o o o o o o o o o o r-| CN iH (H CN o ro rH m rH iH n rn n n n m n n n ro ro

O o o LD in o O O o o cx) 00 CTl <T> CTl o (Ti

ro 00 m m ro m

1 1 m o o CO ID O o U-) o n ro

vo vo kO

CO o in LD o (N in o in o o 00 on cn on on on CM on on

r- r--

o O in O o O in o tn O m in in m in in m in VD VD m on on on on m m on on on m rH iH iH rH rH iH rH rH rH rH rH

o O o o in m CO o o m o <N rH CTl CTl CX) CO r- <Ti o^

in in in m m m in vn in rH rH rH rH rH rH rH rH r-t rH rH

VD CN Ovj CN og CN CN rH rH CN

rH rH rH rH rH rH u u rH U u u u U U CN 04 U

1 CN CN CN CM CN OM CN ^—^ ,—, ,— ,— s on on ^ ^

(N on on on on on on z Z on z Z Z Z 2 Z Z cn a\ Z tn CTi CTl CTi CTi <T< CTi E E CTi

K on EC K E E E E rvj fSI E z CN CN CN CN CN CM rH rH CN

U <r> rH rH rH rH rH rH U U rH K u U u u U u —' ' U (N (N CN

(0 rH c 0 •H s c Cn D u s u u N E 02 Oh

32

T h e lov^ m o l a r c o n d u c t a n c e s of the coraplexes in n i t r e

b e n z e n e and DMSO i n d i c a t e s their non e l e c t r o l y t i c n a t u r e . ^ ^ ^ ^

The r e p l a c e m e n t of c h l o r i d e ions in the c o m p l e x e s M L 2 C I 2 by

p y r i d i n e in DMSO and n i t r o b e n z e n e w a s s t u d i e d c o n d u c t o -

m e t r i c a l l y . It was observecj that the a d d i t i o n of p y r i d i n e

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

c o o r d i n a t e d c h l o r i d e ion by p y r i d i n e (figure X I I ) . F u r t h e r

a d d i t i o n of p y r i d i n e i n c r e a s e s the c o n d u c t a n c e once again

r e p l a c i n g the second c h l o r i d e ion of the c o m p l e x e s , as shown

b e l o w :

M L 2 C I 2 + py [Ml2PyCl] + Cl"

[ M L 2 P y C l ] " p y [ M L 2 P y 2 ] ^ ^

A d d i t i o n of any excess of p y r i d i n e a f t e r this does n o t

r e s u l t in any c h a n g e in the c o n d u c t a n c e i n d i c a t i n g t h a t

there are no m o r e c h l o r i d e ions a v a i l a b l e for r e p l a c e m e n t .

2 ~ ( l - i n d a z o l y I ) p y r i d i n e

F i g u r e XIII

33

M = M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) a n d Z n ( I I )

M = R u ( l I I ) a n d R h ( I I I )

F i g u r e X I I

34

E l e c t r o n i c s p e c t r a of 2-(1 - i n d a z o l y l ) p y r i d i n e c o m p l e x e s

T h e u v - v i s i b l e s p e c t r u m of M n ( I I ) c o m p l e x of 2 - ( l -

i n d a z o l y l ) p y r i d i n e s h o w s t w o b a n d s in a d d i t i o n to a c h a r g e

t r a n s f e r b a n d at 34, 590 c m ~ ^ (Table - iv) . T h e e x p e r i m e n t a l

m a g n e t i c m o m e n t of 5.98 BM for M n ( I I ) c o m p l e x is w i t h i n t h e

c a l c u l a t e d r a n g e for an o c t a h e d r a l g e o m e t r y a r o u n d the m e t a l

i o n .

T h e m a g n e t i c m o m e n t v a l u e of C o ( I I ) c o m p l e x of 2 - ( l -

i n d a z o l y l ) p y r i d i n e (4.59 B M ) i n d i c a t e s an o c t a h e d r a l

g e o m e t r y a r o u n d t h e m e t a l i o n . C o ( I I ) c o m p l e x s h o w s t w o m a i n

b a n d s at 1 4 , 7 0 5 cm ^ and 2 5 , 7 0 0 cm ^ a s s i g n a b l e to

' ^ T - ^ ( F ) ' ^ T , ( F ) a n d ' ^ T , ( P ) < ' ^ T , ( F ) t r a n s i t i o n s 2g Ig Ig Ig

r e s p e c t i v e l y ( T a b l e - I V ) . In the c a s e of 2 - ( 1 - i n d a z o l y l )

p y r i d i n e c o m p l e x of N i ( I I ) t h e o b s e r v e d m a g n e t i c m o m e n t

v a l u e of 3.12 BM is very c l o s e to c a l c u l a t e d v a l u e for an

o c t a h e d r a l g e o m e t r y a r o u n d the m e t a l i o n . T h e e l e c t r o n i c

s p e c t r u m e x h i b i t s t w o b a n d s at 1 1 , 8 0 0 cm ^ and 1 8 , 7 7 0 cm ^

c o r r e s p o n d i n g to ^ T 2 g ( F ) ^ A 2 g ( F ) and — ? A 2 g ( F )

t r a n s i t i o n s r e s p e c t i v e l y .

T h e m a g n e t i c m o m e n t v a l u e of 1.77 BM for C u ( I I ) c o m p l e x

of 2 - ( l - i n d a z o l y D p y r i d i n e is i n d i c a t i v e of an o c t a h e d r a l

g e o m e t r y a b o u t the m e t a l ion w h i c h is a l s o s u p p o r t e d by t h e

n a t u r e of the l i g a n d field b a n d s o b s e r v e d in this c a s e

(Table- J V ) .

35

T h e m a g n e t i c m o m e n t of R u ( I I ) c o m p l e x of 2 - ( 1 - i n d a z o l y l

p y r i d i n e (2.32 B M ) i n d i c a t e s an o c t a h e d r a l g e o m e t r y . T h e

e l e c t r o n i c s p e c t r u m of R u ( I I ) c o m p l e x d i s p l a y s o n l y o n e b a n d

a t 1 8 , 3 2 0 c m - 1 a s s i g n e d to t r a n s i t i o n a l s o

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

T h e m a g n e t i c m o m e n t v a l u e s of P d ( I I ) and R h ( I I I )

i n d i c a t e t h e m to be d i a m a g n e t i c . T h e e l e c t r o n i c s p e c t r u m of

P d ( I I ) d i s p l a y s t w o m a i n b a n d s a t 1 8 , 9 0 0 c m ~ ^ and 2 3 , 5 5 0

cm ^ a s s i g n e d to t r a n i s i t i o n s f r o m g r o u n d s t a t e to

and e x c i t e d s t a t e s r e s p e c t i v e l y , c h a r a c t e r i s t i c s of a

s q u a r e p l a n a r c o n f i g u r a t i o n . T h e R h ( I I I ) c o m p l e x s h o w s t h r e e

m a i n b a n d s ( T a b l e - v i ) c h a r a c t e r i s t i c s of an o c t a h e d r a l

g e o m e t r y a r o u n d the m e t a l i o n .

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Complexes of 2-(l-lnclazolyl)benzoxazole

37

Experimental

P r e p a r a t i o n of 2 - ( 1 - i n d a z o l y l ) b e n z o x a z o l e

S o d i u m i n d a z o l i d e (2.42 g ) was c a u t i o u s l y a d d e d to a

s o l u t i o n of 2 - b r o m o b e n z o x a z o l e (2.04 m L ) in d r y t e t r a h y d r o -

f u r a n (130 m L ) w h i c h \ms r e f l u x e d for 1 6 - 1 8 h o u r s and then

p o u r e d i n t o 140 m L d i s t i l l e d v/ater. A c r u d e w h i t e p r o d u c t

v;as o b t a i n e d a f t e r a few d a y s v\?hich w a s f i l t e r e d and

p u r i f i e d on s i l i c a g e l u s i n g 1:1 c h l o r o f o r m and h e x a n e

e l u e n t . Y i e l d 3 7 % , M . P . 190°C.

P r e p a r a t i o n of c o m p l e x e s

T h e c o m p l e x e s w e r e p e p a r e d by m i x i n g t h e l i g a n d

s o l u t i o n in e t h a n o l to the m e t a l h a l i d e (CUCI2/ Z n C l 2 ,

M n C l 2 C0CI2/ NiCl2/ P d C l 2 ^ R h C l ^ and R u C l ^ ) s o l u t i o n in t h e

same s o l v e n t in 1:2 and 1:3 (M:L) r a t i o . In e a c h c a s e it w a s

r e f l u x e d w i t h s t i r r i n g . A c o l o u r e d solid p r o d u c t a p p e a r e d

a f t e r k e e p i n g the r e a c t i o n m i x t u r e for a fev/ d a y s w h i c h w a s

t h r o u g h l y w a s h e d v/ith the s a m e s o l v e n t and d r i e d in v a c u o .

38

Results and Discussions

R e a c t i o n of sodium h y d r i d e and i n d a z o l e y i e l d e d s o d i u m

i n d a z o l i d e

rpup ^

F u r t h e r r e a c t i o n of s o d i u m i n d a z o l i d e w i t h 2 - b r o m o b e n -

z o x a z o l e y i e l d e d 2 - ( 1 - i n d a z o l y l ) b e n z o x a z o l e (figure X I I I ) in

y i e l d after p u r i f i c a t i o n .

T h e c o m p l e x e s are stable to h e a t and m o i s t u r e . They are

s o l u b l e in c o m m o n organic s o l v e n t s . T h e low m o l a r c o n d u c -

tance of the c o m p l e x e s in DMSO shov/s t h e i r n o n - i o n i c n a t u r e .

A d d i t i o n of p y r i d i n e in the DMSO s o l u t i o n of the

c o m p l e x e s i n c r e a s e s the c o n d u c t a n c e v/hich is a t t r i b u t e d to

the r e l e a s e of c o o r d i n a t e d c h l o r i d e ions w h i c h are r e p l a c e d

by p y r i d i n e after the f o l l o w i n g e q u a t i o n ;

ML2X2 + py ». [ML2XPy]'^ + X~

(where L = 2 - ( 1 - i n d a z o l y l ) b e n z o x a z o l e , X = c h l o r i d e ion

p y = p y r i d i n e )

F u r t h e r a d d i t i o n of p y r i d i n e i n c r e a s e s the c o n d u c t a n c e

once again i n d i c a t i n g the r e p l a c e m e n t of the second c h l o r i d e

ion (figure X I V ) as follows-

[ML2Xpy]"^ + py • [ M L 2 P y 2 ] + X~

A f t e r the r e p l a c e m e n t of both the CI ions any f u r t h e r

a d d i t i o n of p y r i d i n e d o e s not c h a n g e the c o n d u c t a n c e .

S o d i u m i n d a z o l i d e does n o t show any a b s o r p t i o n b a n d

around 3300-3100 c m ~ ^ due to d e p r o t o n a t i o n of i n d a z o l e

39

6' 5 '

2 - ( 1 - i n d a z o l y l ) b e n z o x a z o l c

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43

c a u s i n g d i s a p p e a r a n c e of t h e N-H g r o u p . T h e l i g a n d 2 - ( l -

i n d a z o l y l ) b e n z o x a z o l e s h o w s a new b a n d in t h e r e g i o n

- 1 (99) 650 cm a s s i g n e d t o V C - 0 . T h e l i g a n d s h o w s a s m a l l s h i f t

in C = N f r e q u e n c y a f t e r c o m p l e x a t i o n , s u g g e s t i n g c o o r d i n a t i o n

via t h e n i t r o g e n a t o m of i n d a z o l e as w e l l as b e n z o x a z o l e

. ^ (100) m o i e t y .

T h e far i . r . s p e c t r a of the c o m p l e x e s s h o w some n e w

b a n d s at 2 8 0 - 4 5 0 c m ~ ^ a t t r i b u t e d to m e t a l n i t r o g e n and m e t a l

c h l o r i n e s t r e t c h i n g f r e q u e n c i e s (Table V I I I ) .

T h e ^H N M R s p e c t r a of t h e l i g a n d 2 - ( 1 - i n d a z o l y l ) -

b e n z o x a z o l e is t a b u l a t e d T a b l e IX i n d i c a t i n g t h e c h e m i c a l

s h i f t of the v a r i o u s p r o t o n s , l a b e l l e d in f i g u r e X I I I . T h e

a s s i g n m e n t of c h e m i c a l s h i f t s to t h e v a r i o u s p r o t o n s in t h e

l i g a n d has been m a d e on t h e p a t t e r n of the p e a k a s s i g n m e n t

g i v e n for 2 - ( 1 - p y r a z o l y l ) b e n z o x a z o l e by S t e e l and

C o n s t a b l e . ^ It can be seen t h a t as e x p e c t e d the p e a k s

are s h i f t e d d o w n f i e l d a f t e r c o o r d i n a t i o n (Table I X ) .

T h e M n ( I I ) c o m p l e x s h o w s t h r e e b a n d s at 1 7 , 5 0 0

21 , 240 c m ~ ^ and 2 5 , 300 c m ~ ^ a s s i g n a b l e to '^Tj^^j(G) -s ^^Îg'

^ E g ( G ) ^Îg '^Îg^'^^ ^Â^^^transitions r e s p e c t i v e l y .

T h e r o o m t e m p e r a t u r e m a g n e t i c m o m e n t v a l u e (5.90 B M ) and its

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

M n ( I I ) ion in this c o m p l e x .

T h e e l e c t r o n i c s p e c t r u m of C o ( I I ) c o m p l e x of 2 - ( l -

i n d a z o l y l ) b e n z o x a z o l e e x h i b i t s a b s o r p t i o n b a n d s at 1 5 , 3 9 0

cm 2 1 , 4 5 0 c m ~ ^ and 2 7 , 3 4 0 cm ^ a s s i g n e d to

t r a n s i t i o n s , r e s p e c t i v e l y . T h e m a g n e t i c m o m e n t v a l u e of 4.82

BM for C o ( I I ) ion in t h i s c o m p l e x is c l o s e to an o c t a h e d r a l

C o { I I ) c o m p l e x in high spin s t a t e . B e s i d e s an i n t e n s e c h a r g e

t r a n s f e r band at 35,000 cm ^ the N i ( I I ) c o m p l e x s h o w s t h r e e

b a n d s at 1 0 , 9 9 0 c m ~ ^ , 1 5 , 5 0 0 c m ~ ^ and 2 1 , 3 2 0 c m ~ ^ a s s i g n e d

to

t r a n s i t i o n s r e s p e c t i v e l y for an o c t a h e d r a l N i ( I I ) i o n . T h e

room t e m p e r a t u r e m a g n e t i c m o m e n t v a l u e 3.09 BM is a l s o in

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

T h e e l e c t r o n i c s p e c t r u m of C u ( I I ) c o m p l e x of 2 - ( l -

i n d a z o l y l ) b e n z o x a s o l e s h o w s o n e b a n d at 1 4 , 5 0 0 cm ^ w i t h

i n t e n s e c h a r g e t r a n s f e r at 33,000 cm T h e m a g n e t i c m o m e n t

v a l u e of 1.92 BM for t h i s c o m p l e x is w e l l w i t h i n the r a n g e

n o r m a l l y e x p e c t e d for an o c t a h e d r a l g e o m e t r y a r o u n d C u ( I I ) .

T h e m a g n e t i c m o m e n t v a l u e of 3.16 BM for t h e R h ( I I I )

c o m p l e x and its l i g a n d f i e l d s p e t r u m s u g g e s t an o c t a h e d r a l

g e o m e t r y a r o u n d the m e t a l ion (Table X ) . T h e R u t h e n i u m

c o m p l e x of 2 - ( l - u n d a z o l y l ) b e n z a x a s o l e s h o w s t h r e e b a n d s at

1 5 , 3 5 0 c m ~ ^ , 1 8 , 3 9 0 c m " ^ and 1 9 , 5 0 0 c m ~ ^ r e s p e c t i v e l y

a s s i g n e d t o ^ ^ ^ g ' S g ^ S g ^ ^ g ^ S g

t r a n s i t i o n s . An i n t e n s e c h a r g e t r a n s f e r b a n d is a l s o

o b s e r v e d a t 33,300 cm T h e s p e c t r a l b a n d s and the m a g n e t i c

m o m e n t v a l u e of 3.29 B M . s u g g e s t an o c t a h e d r a l g e o m e t r y for

this c o m p l e x .

M = M n ( I l ) ' C o ( I I ) , N i ( I I ) , C u ( I I ) , Z n ( I I ) a n d Hcj(II)

//

CI Cl CL 1 N v

M . M

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VD IX)

Pi-i h b

Cn Cji tji

|j-i [i t-i

CTl cn cn

o o a

cn ~cn iH CritH

Eh W <C

EH EH EH < < < n 00 00

M (D 0) H cn cn cn )H fC CM CNJ rH ITS CN rH rH (T3 s: EH < EH x: EH EH EH x: u u 00 00 u

M o O O o o O o o o o o O 4-> w o o o UO 00 CTl o CN O U -a m CN 00 oo •cr 00 00 CTl UO 00 O (U c •• ^ ^ * ^ ^

H 10 rH in 00 LD rH OM o in rH m W XI rH (N OM 00 rH rsi OJ 00 rH rH (N oo

o o-l

(N 00

O-I o

<N t—I u rM

O m

Z o^

K tH

O

C s

(N rH u CM

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K T iH u ^ u

CN i-H u (N

o n

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X

rH U

•H z

48,

CP w

CN

tji tj> Cn rH rH iH rt: < <

Zn Cn

(N fsj

cn CP iH rH

C <



C P C P (-1 rH <N fO

EH EH x : rH rH u

o o o o o o o o O O o o o o CN o o in m ro m m in in O tn n m m ro ro rH CN o

^ * ^

m r- <T\ m m 00 ro ro in m rH m rH rH CM m rH rH ro rH CM ro

(N CTl

cn CN

n

rH

ro

X

(U rH ^ (0

+J c o u

CN rH u

CM

o ro

z CTl

ii:

rH U

P u

u CN

0 ro

2

ffi rH

U ^

01

rH U

CM

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2 <ri

rH u

CN «

rH U (N

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CN x:

Complexes of 2-(l-lndazolyl)ben2othlazole

49,

Experimental

p r e p a r a t i o n of 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e

A solution of sodium i n d a z o l i d e (2.42 g) in 140 m L of

dry t e t r a h y d r o f u r a n was slowly a d d e d w i t h c o n s t a n t s t i r r i n g

to a THF solution of 2 - b r o m o b e n z o t h i a z o l e (1.89 m L ) . It was

then r e f l u x e d for about 36 h o u r s . A f t e r c o o l i n g the s o l u t i o n

150 m L of w a t e r was added to it w h e r e u p o n c o l o u r l e s s

c r y s t a l s w e r e o b t a i n e d a f t e r a few d a y s . This w a s f i l t e r e d

and p u r i f i e d by column c h r o m a t o g r a p h y in the m a n n e r

o d e s c r i b e d in e a r l i e r p a r a g r a p h s . Y i e l d 4 4 % , MP. 140 C .


A s o l u t i o n of 2 - ( l - i n d a z o l y l ) b e n z o t h i a z o l e in e t h a n o l

w a s slowly added w i t h c o n s t a n t s t i r r i n g to a e t h a n o l i c solu-

tion of m e t a l c h l o r i d e in a p p r o p r i a t e r a t i o (1:2 for P d ( I I ) ,

M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) , Zn(II) and H g ( I I ) and 1:3

for R u ( I I I ) and R h ( I I I ) . The c o l o u r l e s s s o l u t i o n i m m e d i a t e -

ly b e c a m e c o l o u r e d . A f t e r r e f l u x i n g this s o l u t i o n a c o l o u r e d

p r o d u c t w a s o b t a i n e d v/hich was f i l t e r e d and d r i e d in v a c u o .

The r e a c t i o n may be r e p r e s e n t e d as b e l o w :

C i 4 H g N 3 S + M C I 2 — ^

+ MCI3 ^M2(C28Hi8N6S2)Clg

50,

Reajlts and discussion

T h e l i g a n d 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e has b e e n

p r e p a r e d by n u c l e o p h i l i c d i s p l a c e m e n t of b r o m i n e in 2-

b r o m o b e n z o t h i a z o l e by s o d i u m i n d a z o l i d e .

Na'^(C^H5N2)~ + B r C ^ H ^ N S ^(C^^HgN^S)

T h e c o m p l e x e s a r e s t a b l e t o w a r d s h e a t and m o i s t u r e .

T h e y a r e s o l u b l e in c o m m o n o r g a n i c s o l v e n t s such as D M S O ,

n i t r o b e n z e n e , v/ater, c h l o r o f o r m , h e x a n e e t c . T h e low m o l a r

c o n d u c t a n c e of t h e c o m p l e x e s in D M S O and n i t r o b e n z e n e s h o w s

(98)

t h e i r n o n - i o n i c n a t u r e . T h e s t r u c t u r e of the c o m p l e x e s

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

m e a s u r e m e n t s , ir and u v - v i s i b l e s p e c t r a l d a t a . T h e l i g a n d

b e h a v e s as a b i d e n t a t e o n e . T h e r e p l a c e m e n t of c h l o r i d e i o n s

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

A d d i t i o n of p y r i d i n e to a D M S O s o l u t i o n of the c o m p l e x e s

i n c r e a s e s t h e c o n d u c t a n c e d u e to t h e r e l e a s e of c h l o r i d e ion

f r o m t h e c o m p l e x . F u r t h e r a d d i t i o n of p y r i d i n e i n c r e a s e s the

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

c o o r d i n a t e d c h l o r i d e i o n . A n y f u r t h e r a d d i t i o n of p y r i d i n e

d o e s not l e a d to c o n d u c t a n c e c h a n g e i n d i c a t i n g t h a t both t h e

c h l o r i d e i o n s h a v e b e e n r e p l a c e d by p y r i d i n e .

T h e ir s p e c t r u m of s o d i u m i n d a z o l i d e d o e s not s h o w any

a b s o r p t i o n b a n d in t h e r e g i o n of 3 3 0 0 - 3 1 0 0 cm ^ as o b s e r v e d

i n d a z o l e . C o m p a r i s o n of t h e s p e c t r u m of 2 - ( 1 - i n d a z o l y l ) -

b e n z o t h i a z o l e ligand w i t h t h a t of its c o m p l e x e s r e v e a l s t h a t

the l i g a n d a b s o r p t i o n s u n d e r g o s i g n i f i c a n t c h a n g e s on

51,

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

1510 cm 1630 cm ^ and 730 cm ^ o b s e r v e d in t h e s p e c t r u m

of the u n c o o r d i n a t e d l i g a n d a r e a t t r i b u t e d t o v C = C , V'C=N and

t h e r i n g s t r e t c h i n g m o d e s . T h e s e b a n d s a r e s h i f t e d to t h e

l o w e r f r e q u e n c y side d u e to the c o o r d i n a t i o n v i a n i t r o g e n

a t o m s of t h e i n d a z o l e as w e l l as b e n z o t h i a z o l e m o i e t y .

S o m e new b a n d s o b s e r v e d in t h e c o m p l e x e s in the r a n g e

4 5 0 - 3 0 0 c m ~ ^ and 3 0 0 - 2 0 0 c m ~ ^ h a v e b e e n a t t r i b u t e d to i;M-N

and M - C l m o d e s . T h i s M - C l a b s o r p t i o n b a n d s a r e

s t r o n g e r and a p p e a r at l o w e r w a v e n u m b e r s as c o m p a r e d to M - N

a b s o r p t i o n b a n d s . It is t h u s c o n c l u d e d t h a t n i t r o g e n a t o m of

i n d a z o l e as v^ell as the n i t r o g e n in b e n z o t h i a z o l e a r e

s i m u l t a n e o u s l y c o o r d i n a t e d to the m e t a l w h i c h a c q u i r e s an

o c t a h e d r a l s t r u c t u r e .

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

s u p p o r t f r o m ^H N M R s p e c t r a d a t a of the l i g a n d and t h e i r

c o m p l e x e s . T h e ^H NMR s p e c t r a of 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a -

zole show a dov/nfield s h i f t in all t h e a r o m a t i c p e a k s

i n d i c a t i n g the c o o r d i n a t i o n of n i t r o g e n a t o m of b e n z o t h i a -

zole as w e l l as n i t r o g e n a t o m of i n d a z o l e m o i e t y to m e t a l

i o n s . In t h e s p e c t r a of c o m p l e x e s t h e l a r g e d o w n f i e l d s h i f t

of the h y d r o g e n a t o m in p o s i t i o n 3 ' & 4 ( n e a r to n i t r o g e n a t o m

of i n d a z o l e ) i n d i c a t e s t h e c o o r d i n a t i o n of n i t r o g e n a t o m of

i n d a z o l e m o i e t y (Table X I I I ) .

0 N (T!

c •H 1

H

fNJ

M O tH

0) •P to

•O

H

u •H 4J >1

H (0 c to

c (0

(U u c (13 +J 0 !3

- o c o u

M (U fH o s

+J c

•H o & C71 C

•H •M

(U •H

M O 0 H O u

H X

ja ITJ tH

in 0)

(U H

I U

CO •p •H

(U t) 6 C

(0

'O 0) o N (a

•H s: 4J 0 N C (1) £t

rtJ U

c

o 4-1

tn •rH w >1 r-t (0 c ri:

H u

u

S 0 u

na H (U tfp

•H fH

M a 0

H

5

m T ) C P O

0 u

52,

(N tM ro CM CTi 1 1 cn CM CO « • • • • o O rH rH rH

V£><N rv (N ro ro rv in O (N CM cn ro rH <Tl rH CD o o CM O » • • • • • • • • • • • 1 rHrH o o O O o o o o o o rHrH rH rH rH rH rH rH rH rH rH rH —^

CM n CT» ro (T> m CM og ro ro <7i <N CM rH C7i CO ID rvj • • • • • • • • • • 1 1 rH rH rH rH rH rH O o rH rH rH rH rH rH rH rH rH rH rH rH

OJ 00 ID CO o r- ro (N O in CM in <n <J\ ro CO <D CM CO rH o rH rH • • • • • « • • • • • • • • CD <T> KD ro ro ro ro ro ro ro ro ro ro rH iH ci rH rH rH rH rH rH rH rH •H rH ^

^

_ in <T> 00 00 O 'S' CM CM o rH in H fN ro <ji in CO CO CO CO <7. CO CO CO <T> CO • • • • • • • • • • • • • • m oi CO ro CM CN (N CM CM CM CM CM CM CM

-—^ •s—» '—^ —

.—. o o o CO o o cn D <J0 O ro o ro <7l O Cri ID in in CM rH CTi r- <o ID • f 1 * * • • • • • • • • • • o o lO CM n ro ro CM CM CM CM CM CM VD m in in in in m in m in in

o O o o o o o ^ cn 00 o a CO rH rH <N CM ro <N CM

O o CM m o O n in m m yD r-

(U 01 C C C C (V 4J -p > (U 0) •P •H •H 0 0 (U 0) •H JZ x: u u VH U s s . CQ CQ 15 CJ) s

<N S tn

K

U

(0 2

in fO

2 CTi EC iH

U

(N rH u

CM

CO fO

z <71

ft U

c s

(N f rH t u •

<N —

W 00 Z <71

K t r-l

u

0 • u

OJ rH u <NI

W ro

Z

K rr rH

u

•H Z

(N rH u CM

W m

z

X

rH

U

u

(N rH U

(N

CO ro Z

CT. E

rH

u

c Cs]

H X

I

0) rH XI fO EH

-a +j c 0 u

o 00 CM <Ti

• (Tv 00 o • •

o o

cn CN a^ CO CO o o CT^ CTl

• • • • • • crt IX) kD

CN <<D (N o O ro CTl CN o H

( • • • « •

O o ro ro ro ro rH rH Cvl Cvl r-1

" •

<N 00 CO f J O ro rH rH H rH

• • • • • • 00 CTl (J\ CTl

-H rH

o in CTl 00 in CN o o 00 CTl

• • • • • • m (M rH rH rH rH

ro oo <y\ CTl CM o (N cn t • • • • • o o in uo in in ro ro ro ro

o o o o o o ro ro ro

o in uo r- VD in

S 0 c

iH u s rH to 0 0) rH )H >H m CQ

u (N

U) n

tc

rH

U

Xi cu

rH U fN

w m

2

a: rH

u

fN P a

iH U rsi

W ro

(Ti rc

rH u

CM XI K

53,

OJ rH 0 N

•H £ •P 0 N > c X a ^

CJ H M >1 3 H CJi 0 •H N n '0 c •H 1 1 H

1 fN

u I s

2 I s

C 0 •H +J (0 M

•H >

D-C

•H M

03 I

U

I U

u II u

c m

nj M X!

O, c

-a c fO

4-1 X)

° c

+J tti

O D.

U

w 'O c 3 0 cu e o u

54,

in o o o o o o o o o rH (N (N o rH rH iH (Ti 00 (N

oo 00 00 00 OO on CM OO oo

o o

o <N

O o

o o

o

ro

O in n

o

o o o in o O O m m C-J ro CN ro vn

<x> <X> kD

o o o o o o m o o 00 (N CM CM rH CM CM o o

r- r- r- r-

o in in o o m o m m 00 00 00 00 00 00 OM CM

r - r-

o o in O O o o o O tH o o rH O o rH o rH in in m m m in m in in rH rH rH rH rH rH rH rH rH

o o o in o in o o in 00 o cn CTl cyi a\ (N CM CM

m m m in rH rH rH rH rH rH rH rH rH

rsj vo rH CM Osl CM CM rH rH U rH rH rH rH rH u U

CM U u u U u <N rsj CM (M CM CM CM ' — . -—^

w ,—, S CO CO 00 W CO CO CO CO 00 00

00 00 00 00 oo 2 2 CTl 2 2 2 2 (Ti en

10 CTl <yi CTi CTi a: K 00 ^ rc cc E X X

z rH ^ •rr rH rH (Ti rH rH rH rH rH u U

U U U u u U —• —-CM (N

rH C 0 •H 3 c •0 3 s: u s u 2 U N K K

m di X 1 H 0 N fl -a c •H 1

I (S

iw 0 (0 +J

(0

z 33

H H H X

Q; r-l XI (0 H

o n (N CO rH rH « in m un m in m m m in 1 • t • • • • • • •

r- r- r- r- r-

(N IT) CN o rH in CM CN 53 n rH r-l CM <N rH CM 1 • rH • • • • • • •

vo r- r- r-- r- r- r-

o in 00 (N tN rH rH oo K CM m in m m in 1 • • * • • • • » •

in r-- r- r-- r- r-

o o in <N o m rsi vo 03 in in vo r-- in 1 • • • • • • t • t

^ r - r -

K (N (N o IX) <X) CTi vo 1 00 00 00 r- 00 r- 00

» • • • • • • • k r r- r- r- r

a 1

o o rH CM (H in in CM a 1 CM n m rn ro (N1 CM m

« • • « • • * • 1 r - r- r- r-

a I

m

n I

03 I

n

w -a c a 0 Oj e 0 u

55,

CO o CM m o o o m CT) CTl cn cn CM 00

• • • • • * t * •

r - r - r - r--

m o

00

00

ro

K

iH U

vo o 00 o CM 00 CO in in vo vo VO in vo m • • • • • t • •

00 00 00 00 00 00 CO 00

ro o o o o vo vo O rH fO CO CM o o 00 • • • • • • • •

00 00 00 00 oo 00 00 00

VD vo CM CM CM CM CM rH rH

rH rH rH rH rH rH U u u U u U U u CM CM

CM (N CM CM CM CM ^—, ^—^ ^ V ^—> w

W to W W cn CO ro CO m ro CO m n 2

Z Z 2 z z CTl CTi Ch <Ti E

a : K •-r X •X. ^ ^ •T rH rH

rH rH rH rH rH rH U U U U u u u U ^

•w — •w ' CM CM c 0 •H P ID 3 x : s u u CSl CL, « Pi

56,

E l e c t r o n i c s p e c t r a

T h e e l e c t r o n i c s p e c t r u m of r'jndl) c o m p l e x of 2 - ( l -

i n d a z o l y l ) b e n z o t h i a z o l e s h o w s a b s o r p t i o n b a n d s at 1 5 , 5 0 0

1 8 , 9 0 0 c m ~ ^ and 2 4 , 660 c m ~ ^ a s s i g n e d to ^^^^.(G)

' E (G) < Â, and 'Â, (G)-< -Â, t r a n s i t i o n s , r e s p o c -g ig ig ig

t i v o l y . Its n a y n e t i c m o n o n t v a l u e (5.82 B H ) an o c t a h e d r a l

y e o n e t r y for the M n ( I I ) i o n s .

T h e C o ( I I ) c o m p l e x of 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e

sho\;s a n a y n c t i c m o m e n t v a l u e of 4.75 BM w h i c h a y r o e s \;ith

the e x p e c t e d v a l u e for a high spin C o ( l l ) ion in an

o c t a h e d r a l e n v i r o n m e n t . T h e ^H NMR of the c o m p l e x s h o w s a

broad p e a k c o n s i s t e n t w i t h t h e p a r a m a g n e t i c n a t u r e of t h e

c o m p l e x . T h e l i y a n d fiel d s p e c t r u m of t h i s c o m p l e x b e s i d e s

s h o w i n g a c h a n g e t r a n s f e r b a n d s at 3 4 , 4 0 0 cm ^ s h o w s t w o

m a i n b a n d s at 1 8 , 3 4 0 c m ~ ^ and 2 1 , 2 9 0 c m ~ ^ . T h e s e b a n d s a r e

a s s i g n e d to < "'^'Îg^^^ t r a n s i -

t i o n s , r e s p e c t i v e l y w h i c h is a g a i n c o n s i s t e n t w i t h an

o c t a h e d r a l g e o m e t r y .

T h e m a g n e t i c m o m e n t v a l u e for t h e N i ( I I ) c o m p l e x of

2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e as w e l l as its e l e c t r o n i c

s p e c t r u m a r e c o n s i s t e n t w i t h an o c t a h e d r a l g e o m e t r y of the

N i ( I I ) c o m p l e x . T h e b a n d s o b s e r v e d at 1 2 , 3 2 0 1 4 , 6 7 0

c m ~ ^ and 2 2 , 3 3 0 c m ~ ^ are as e x p e c t e d for t h e (F)

^T (F)y (F) and ^T^ ( P ) < (F) t r a n s i t i o n s in the Ig 2y Ig 2y

c a s e of N i ( I I ) ion having an o c t a h e d r a l g e o m e t r y .

57

T h e m a g n e t i c m o m e n t v a l u e for t h e N i ( I I ) c o m p l e x of

2 - ( 1 - i n d a z o l y l ) b o n z o t h i a z o l e as w e l l as its e l e c t r o n i c

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

N i ( I I ) c o m p l e x , t h e b a n d s o b s e r v e d at 1 2 , 3 2 0 cm 1 4 , 6 7 0

1 —1 3 3 c m " and 2 2 , 330 cm are as e x p e c t e d for the T 2 g ( F ) )

and ? A 2 g ( F ) t r a n s i t i o n s in t h e

c a s e of N i ( I I ) ion h a v i n g an o c t a h e d r a l g e o m e t r y .

T h e o b s e r v e d m a g n e t i c m o m e n t and e l e c t r o n i c s p e c t r u m of

the C u ( I I ) c o m p l e x of 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e s u g g e s t

an o c t a h e d r a l g e o m e t r y of the m o l e c u l e (Table - X I V ) .

T h e o b s e r v e d m a g n e t i c m o m e n t for R u ( I I I ) and R h ( I I I )

c o m p l e x e s of 2 - ( 1 - i n d a z o l y l ) b e n z o t h i a z o l e (3.35 BM and 3.28

B M ) a r e v e r y c l o s e to the v a l u e c a l c u l a t e d for t h e m e t a l ion

in an o c t a h e d r a l e n v i r o n m e n t . R u ( I I I ) c o m p l e x s h o w s t h r e e

m a i n b a n d s a t 1 5 , 3 5 0 c m " ^ , 1 8 , 3 9 0 c m ~ ^ and 19,500 c m ~ ^

a s s i g n e d to ^^g"^ t r a n s i -

t i o n s r e s p e c t i v e l y . R h ( I I I ) c o m p l e x a l s o e x h i b i t s two m a i n

b a n d s at 2 2 , 3 5 0 cm ^ and 2 4 , 3 3 0 w i t h an i n t e n s e c h a r g e

t r a n s f e r at 3 3 , 3 0 0 c m ~ ^ (Table - X I V ) s u p p o r t i n g an


T h e d i a m a g n e t i c P d ( I I ) c o m p l e x d i s p l a y s t h r e e m a i n

a b s o r p t i o n b a n d s at 1 9 , 5 0 0 2 1 , 6 6 0 c m ~ ^ and 2 5 , 7 0 0

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F i g u r e - X V I

CHAPTER - 111

Synthesis and characterization of complexes of some new

Pyridine-2-thione derived llgands;

(i) 2-(pyridine-2-thionato)pyrimidine

(ii) 2-(pyridine-2-thionato)benzoxazole

(ill) 2-(pyrldine-2-thlonato)benzothlazole

Complexes of 2-(pyridlne-2-thionato)pyrimidine

60,

Experimental

M a t e r i a l s a n d m e t h o d s

P y r i d i n e - 2 - t h i o l , 2 - b r o m o p y r i m i d i n e , 2 - b r o m o b e n z o x a z o l e

and 2-bromolDenzothiazole w e r e u s e d as r e c e i v e d . A l l m e t a l

c h l o r i d e s C r ( I I I ) , M n ( I I ) , F e ( I I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) ,

Z n ( I I ) and H g ( I I ) , (BDH) and R u ( I I I ) , R h d I I ) , P d ( I I )

(Johnson M a t h e y ) w e r e used as s u c h .

P r e p a r a t i o n of s o d i u m p y r i d i n e - 2 - t h i o n a t e

P y r i d i n e - 2 - t h i o l ( 5 . 5 g ) and a s u s p e n s i o n of s o d i u m

h y d r i d e ( 2 . 4 g , 80% s u s p e n s i o n in o i l ) w e r e milled t o g e t h e r in

dry t e t r a h y d r o f u r a n (100 m L ) . T h e r e s u l t i n g m i x t u r e w a s

r e f l u x e d v/ith s t i r r i n g for a b o u t 16 h . A v/hite c r u d e p r o d u c t

w a s o b t a i n e d on c o o l i n g v/hich w a s f i l t e r e d and r e c r y s t a l l i -

o zed f r o m w a t e r . Y i e l d 50% M . P . 292 C .

P r e p a r a t i o n of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) p y r i m i d i n e

S o d i u m p y r i d i n e - 2 - t h i o n a t o (0.27 g^ w a s c a u t i o u s l y

a d d e d to 2 - b r o m o p y r i m i d i n e (0.23 g) in d r y e t h a n o l (100 m L )

and the r e s u l t i n g m i x t u r e r e f l u x e d for 20 h w i t h c o n t i n u o u s

s t i r r i n g . T h e l i g h t yellov/ s o l u t i o n t u r n e d d a r k o r a n g e in

c o l o u r . T h i s s o l u t i o n v/as t h e n p o u r e d into 40 m L of v;ater

\/hen a f t e r a fev/ d a y s , a v/hite c r u d e p r o d u c t w a s o b t a i n e d

v;hich v/as f i l t e r e d and d r i e d in v a c u o . It w a s r e c t y s t a l l i z e d

from w a t e r . Y i e l d 3 0 % , M . P . 270°C.

61,

p r e p a r a t i o n of c o m p l e x e s

E t h a n o l i c s o l u t i o n of the l i g a n d and m e t a l c h l o r i d e

[ M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) and Z n ( I I ) ] in a p p r o p r i a t e

1:1 m o l a r r a t i o w e r e m i x e d t o g e t h e r . T h e r e s u l t i n g m i x t u r e

w a s r e f l u x e d for a b o u t 16 h o u r s . A c o l o u r e d p r e c i p i t a t e v^as

o b t a i n e d v/hich w a s f i l t e r e d off and f i n a l l y v a c u u m d r i e d .

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

g i v e n in T a b l e X V .

62


P y r i d i n e - 2 - t h i o l in t h e solid f o r m e x i s t s p r e d o m i n a n t l y

as the t h i o l s t r u c t u r e ^ ^ ^ ^ ^ ( F i g u r e - lA) w h e r e a s in s o l u t i o n

it c o n s i s t s m a i n l y of t h e t h i o n e form^^^"^^ ( F i g u r e - IB) as

e v i d e n c e d by the S - H b a n d at 2800 cm ^ in the s o l i d and its

d i s a p p e a r a n c e in s o l u t i o n . T h e s o d i u m d e r i v a t i v e (Figure -

X V I I ) c h a r a c t e r i s e d by the a b s e n c e of V S - H and p r e s e n c e in

it of a s t r o n g p e a k at 1050 cm ^ a s s i g n e d to C = S s t r e t c h i n g

f r e q u e n c y ^ ^ ' 1 0 6 ) ^ ^ r e f l u x i n g w i t h 2 - b r o m o p y r i m i d i n e in

e t h a n o l y i e l d e d the m u l t i d e n t a t e l i g a n d ( F i g u r e - XVII')

a f t e r the follov/ing r e a c t i o n :

E t h a n o l Na ( C ^ H ^ N S ) - f C , H 3 N 2 B r [ C g H ^ N 3 S ]

T h e c o m p l e x e s M [ C ^ H ^ N ^ S ) 2 C I 2 ] w h e r e M = M n ( l l ) , C o ( I l ) ,

N i ( I I ) , C u ( I I ) and Z n ( I I ) ( F i g u r e - X V I I I ) h a v e b e e n

p r e p a r e d and c h a r a c t e r i s e d by e l e m e n t a l a n a l y s i s , i r , uv-

v i s i b l o and m a g n e t i c m o m e n t m e a s u r e m e n t s .

Na

F i g u r e X X I I I

63,

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

in the 1600 c m " ^ - 6 0 0 cm ^ r a n g e b e c a u s e all the c h a r a c t e r i s -

t i c f r e q u e n c i e s lie in t h i s r a n g e . T h e ))C=C and V C = N m a y

n o t be d i s t i n g u i s h e d as they f a l l in the s a m e r e g i o n and a r e

q u i t e o f t e n c o u p l e d w i t h each o t h e r . H o w e v e r , the m i x e d

b a n d s a p p e a r in 1 5 9 0 - 1 4 2 0 c m ~ ^ . T h e s h a r p b a n d s at 780 c m ~ ^ ,

980 c m ~ ^ and 1050 c m ~ ^ a p p e a r in b o t h t h e f r e e and c h e l a t e d

l i g a n d . T h e C=N b a n d is s h i f t e d t o w a r d s h i g h e r f r e q u e n c y

r e g i o n on c o m p l e x a t i o n . ^ ^ ^ ' ^ T h e C = S f r e q u e n c y at 1050

cm ^ w i t h a s h o u l d e r a t 1030 c m ^ in t h e l i g a n d d o e s n o t

u n d e r g o any s i g n i f i c a n t c h a n g e a f t e r c o m p l e x a t i o n . ^

B a n d s a p p e a r i n g a t 4 5 0 - 4 0 0 cm ^ in all t h e c o m p l e x e s

a r e a s s i g n e d to M - N s t r e t c h i n g f r e q u e n c i e s . T h e b a n d at

350 c m ~ ^ is o b s e r v e d in C o ( I I ) and 370 c m ~ ^ in N i ( I l )

(95 1 0 9 )

c o m p l e x is a s s i g n e d to i^M-S. ' F r e q u e n c i e s o b s e r v e d a t

430 cm ^ and 330 cm ^ in C o ( I I ) c o m p l e x is a s s i g n e d to V M - N

and jy M - C l w h e r e a s in N i ( I I ) c o m p l e x t h e s e f r e q u e n c i e s a r e

r e s p e c t i v e l y o b s e r v e d a t 425 c m ~ ^ and at 330 c m ~ ^ . T h e

a b s e n c e of any b a n d b e t w e e n 3 5 0 - 4 0 0 c m ~ ^ in t h e M n ( I l ) ,

C u ( I I ) and Z n ( I I ) c o m p l e x e s r u l e s o u t t h e p o s s i b i l i t y of

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

o n l y y M - N and y M - C l h a v e been o b s e r v e d . T h e n i t r o g e n b o n d e d

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

m o e i t y (Figure - X V I I I ) .

T h e c o m p l e x e s a r e not s o l u b l e in u s u a l o r g a n i c s o l v e n t s

but a r e only p a r t i a l l y s o l u b l e in n i t r o b e n z e n e . T h e m o l a r

1 CNes

U

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o fN CN o 00 1 1 CTl O CTl CN CTl

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in o m CO in 00 CT\ CO o cn CTl CN o r- rr (Ti

• • • • • • • t « • 1 1 CM ro m m 00 n n m

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o n in o CN CTl CN o 00 in CTi o CTl CN VO fN ID o m in rr • • • • • • • • • • • • • •

CO -a- tn VD rn CN CN CN CN ro CN CN CN CN CM rH rH rH H rH rH rH rH rH rH rH rH

' — ' '

^ ^

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• • • • • • • • • • • « 4 • o o CN CN VO VD in iO VD iH rH CN CN rH rH rH rH rH rH rH rH rH rH

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04 CM CN r\i CM rH rH rH rH rH u u u u U

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c o n d u c t a n c e (10~^M s o l u t i o n ) in n i t r o b e n z e n e s h o w s the

n o n e l e c t r o l y t i c n a t u r e of the c o m p l e x e s . ^ H o w e v e r ,

a d d i t i o n of a 1 - m o l a r e q u i v a l e n t of p y r i d i n e i n c r e a s e s the

c o n d u c t a n c e i n d i c a t i n g r e p l a c e m e n t of the c h l o r i d e by

p y r i d i n e . F u r t h e r a d d i t i o n of p y r i d i n e i n c r e a s e s the c o n d u c -

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

A d d i t i o n of any e x c e s s of p y r i d i n e a f t e r t h i s s t a g e d o e s

n o t m a k e f u r t h e r c h a n g e i n d i c a t i n g t h a t b o t h t h e c h l o r i d e

ions h a v e been r e p l a c e d by p y r i d i n e .


T h e d i f f u s e r e f l e c t a n c e e l e c t r o n i c s p e c t r u m of M n ( I I )

c o m p l e x s h o w s t h r e e m a i n b a n d s a t 1 5 , 3 8 4 cm 2 3 , 2 5 5 cm ^

and 2 6 , 3 1 5 c m " ^ a s s i g n e d to — ^ A ^ ^

4 6

and Eg(G).* A ^ ^ t r a n s i t i o n s r e s p e c t i v e l y . T h e s e t r a n s i -

t i o n s a r e i n d i c a t i v e of an o c t a h e d r a l g e o m e t r y . T h e m a g n e t i c

v a l u e of 5.83 BM is very c l o s e to the e x p e c t e d v a l u e for an

o c t a h e d r a l g e o m e t r y of the c o m p l e x h a v i n g spin f r e e c o n f i g u -

r a t i o n .

T h e m a g n e t i c m o m e n t of t h e C o ( I I ) c o m p l e x is 4.24 B M .

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

v a l u e is v e r y c l o s e to t h a t in t e t r a h e d r a l C o ( I I ) c o m p l e x .

The electronic spectrum of Co(II) complex shows bands at

1 3 , 800 c m ~ ^ and at 2 1 , 276 c m ~ ^ a s s i g n e d to 4 4

and T2(F)-< t r a n s i t i o n s r e s p e c t i v e l y .

67

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O / C u ( I I ) c o m p l e x

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68

T h e o b s e r v e d m a g n e t i c m o m e n t v a l u e of 3.53 BM f o r t h e

N i ( I I ) c o m p l e x is s l i g h t l y h i g h e r than t h e e x p e c t e d v a l u e

for an o c t a h e d r a l g e o m e t r y . T h e l i g a n d f i e l d s p e c t r u m of t h e

c o m p l e x s h o w s two b a n d s at 14 , 490 cm ^ a n d 1 7 , 5 4 0 cm

T h o s e are a s s i g n e d to ^ T 2 g ( F ) ^"^Ig^^^

t r a n s i t i o n s r e s p e c t i v e l y . T h e m a g n e t i c m o m e n t of C u ( I I )

c o m p l e x is 1.48 BM the l o w e r i n g in ^ e f f of t h i s c o m p l e x m a y

be a t t r i b u t e d to c o p p e r - c o p p e r i n t e r a c t i o n s in t h e p o l y m e r i c

s t r u c t u r e in the c o m p l e x . T h e e l e c t r o n i c s p e c t r u m of t h i s

c o m p l e x e x h i b i t s o n e b a n d at 1 3 , 3 3 0 cm ^ a s s i g n e d to the

2 2

Aj^g Eg t r a n s i t i o n . T h e b a n d p o s i t i o n is in a g r e e m e n t

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

C u ( I I ) .

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^ LD ID o o O O O O ro o 00 m rH ro 00 r - O^ O ro o ro (N ro o OD CN ro un un ro

^ H ^ iri ro <x> ro rH ro rj- r - LT) ro rH CN rM ro rH CN ro rH rH ro rH ro

00

CN .-H U

CO M

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u

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CM -—.

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a: CT

U

C esj

Complexes of 2-(pyridlne-2-thlonato)benzoxazole

20,

Experimental

Preparation of 2-(pyridine-2-thionato)benzoxazole

2 - b r o m o b e n z o x a z o l e (6.8 m L ) was c a u t i o u s l y a d d e d to a

s o l u t i o n of s o d i u m p y r i d i n e 2 - t h i o n a t o (4.0 g) in dry t o t r a -

h y d r o f u r a n (150 m L ) and t h e r e s u l t i n g m i x t u r e w a s r e f l u x e d

for 36 h o u r s . It v\?as t h e i r p o u r e d i n t o 250 m L of w a t e r .

A f t e r 15 d a y s a m i c r o c r y s t a l l i n e p r o d u c t was o b t a i n e d w h i c h

w a s f i l t e r e d , w a s h e d w i t h t e t r a h y d r o f u r a n and r e c r y s t a l l i z e d

f r o m w a t e r . Y i e l d 7 0 % , M . P . 200°C.


D i v a l e n t and t r i v a l e n t m e t a l c h l o r i d e and t h e l i g a n d

2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o x a z o l e w e r e t a k e n in each c a s e

in 1:2 in c a s e of M C I 2 and 1:3 in c a s e of M C l ^ (M:L) r a t i o s ,

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

to the h o t m e t a l c h l o r i d e in the same s o l v e n t (50 m L ) w i t h

c o n t i n u o u s s t i r r i n g w i t h r e f l u x for a b o u t 7 h o u r s . T h e s o l i d

thus o b t a i n e d w a s f i l t e r e d o f f , w a s h e d v/ith e t h a n o l and

d r i e d in v a c u o .

71,


T h e r e a c t i o n of s o d i u m p y r i d i n e - 2 - t h i o n a t o v^ith 2 - b r o m o

b e n z o x a z o l e in t e t r a h y d r o f u r a n r e s u l t e d in t h e s y n t h e s i s of

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

t h e follov/ing e q u a t i o n : -

Na'^CC^H^NS)" + B r C ^ H ^ N O ^ [ Cj_2HgN2SO ] + N a B r

T h e c o m p l e x e s of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o x a z o l e a r e

n o t s o l u b l e in u s u a l o r g a n i c s o l v e n t s . O n l y P d ( I I ) , R u ( I I I ) ,

R h ( I I I ) a n d A u ( I I I ) c o m p l e x e s a r e s o l u b l e in D M S O . T h e y a r e

s t a b l e to\;ards l i g h t a n d a i r . T h e i r e l e m e n t a l a n a l y s i s d a t a

c o r r e s p o n d \^ith M[ ^ ^^2 1 2 ^ 8 ^ 2 ®°

m o l e c u l a r f o r m u l a . T h e m o l a r c o n d u c t a n c e v a l u e of s o l u b l e

- 1 2 - 1

c o m p l e x e s a r e 3 . 9 - 6 . 3 o h m cm m o l , w h i c h i n d i c a t e d t h a t

t h e c o m p l e x e s a r e n o n e l e c t r o l y t e s .

In t h e ir s p e c t r u m of t h e s o d i u m p y r i d i n e 2 - t h i o n a t o

t h e t h r e e m e d i u m i n t e n s i t y b a n d s o b s e r v e d a t 1 4 5 0 c m ~ ^ , 1 5 8 0

c m ~ ^ a n d 1 0 5 0 c m ~ ^ a s s i g n e d t o y c = C ^ y c = N a n d y c = S a n d a r e

c l o s e to t h e v a l u e s f o r t h e p a r e n t p y r i d i n e - 2 - t h i o n e . ^ ^

F r e e c h e l a t i n g l i g a n d 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o x a z o l e

e x h i b i t f o u r d i s t i n c t a b s o r p t i o n s c o r r e s p o n d i n g t o iJC=C,

y c = N , V ' C = S a n d i)C-0 v/hich u n d e r g o e s a s u b s t a n t i a l n e g a t i v e

s h i f t u p o n c h e l a t i o n . ^ ^^^^ T h e U C=S in c a s e of M n ( I I ) ,

Z n ( I l ) , H g ( I I ) , R u ( i n ) is s h i f t e d t o a h i g h e r f r e q u e n c y

r e g i o n by a b o u t 2 0 - 8 0 cm ^ a f t e r c o m p l e x a t i o n .

72,

T h e F e ( I I I ) , C r ( I I I ) , R h ( I I I ) and R u ( I I I ) c o m p l e x e s

s h o w two b a n d s at 3 1 0 - 2 8 0 a s s i g n e d to t e r m i n a l a n d

b r i d g i n g y M - C l r e s p e c t i v e l y . ^^^^^ H o w e v e r , all d i v a l e n t

complexes e x h i b i t o n l y the M - C l s t r e t c h i n g f r e q u e n c y a t

3 1 0 - 2 6 0 c m " ^ . ^ ^ ^ ^ ^ O t h e r d i s t i n c t b a n d s a p p e a r i n g in t h e

r a n g e 4 4 0 - 4 0 0 c m ~ ^ and 3 8 0 - 3 1 0 h a v e b e e n a s s i g n e d to M - N and

M - S s t r e t c h i n g f r e q u e n c i e s .


T h e m a g n e t i c m o m e n t of C r ( I I I ) c o m p l e x (3.80 B M ) is

v e r y c l o s e to t h a t e x p e c t e d for an o c t a h e d r a l g e o m e t r y . T h e

e l e c t r o n i c s p e c t r u m of this c o m p l e x (Table X X ) is a l s o

c o n s i s t e n t w i t h an o c t a h e d r a l g e o m e t r y a r o u n d the C r ( I I I )

i o n . In t h e c a s e of M n ( I I ) c o m p l e x , t h e o b s e r v e d m a g n e t i c

m o m e n t v a l u e (5.92 B M ) is i n d i c a t i v e of an o c t a h e d r a l

g e o m e t r y . T h e e l e c t r o n i c s p e c t r u m of t h i s c o m p l e x s h o w s

t h r e e m a i n b a n d s at 1 7 , 330 c m " ^ , 20,220 c m ~ ^ and 2 5 , 3 4 0 c m ~ ^ .

An i n t e n s e c h a r g e t r a n s f e r at 3 5 , 4 4 0 c m ~ ^ is a l s o o b s e r v e d

in M n d l ) c o m p l e x . B e s i d e a c h a r g e t r a n s f e r b a n d at 3 5 , 0 0 0

cm ^ the e l e c t r o n i c s p e c t r u m of F e ( I I I ) c o m p l e x s h o w s t w o

bands (Table-XX) assigned to Â^^ and F UÂ^^^

t r a n s i t i o n s . T h e m a g n e t i c m o m e n t v a l u e (5.86 B M ) c o r r e s p o n d s

to t h e p r e s e n c e of five, u n p a i r e d e l e c t r o n s and t h e e l e c t r o -

n i c s p e c t r u m s u g g e s t s an o c t a h e d r a l g e o m e t r y for F e ( I I I )

c o m p l e x e s . For C o ( I I ) ion t w o spin allov/ed t r a n s i t i o n s h a v e

been o b s e r v e d at 1 5 , 5 3 0 c m ~ ^ and 2 1 , 3 9 0 c m ~ ^ and a r e

a s s i g n e d to ^ T ^ ^ ( F ) < '^'îg^^^ ^"Îg^^^ ^"îg^^^

73

r e s p e c t i v e l y . T h e o b s e r v e d m a g n e t i c m o m e n t (4.82 B M ) is v e r y

c l o s e to t h a t c a l c u l a t e d for t h r e e u n p a i r e d e l e c t r o n s .

H o w e v e r , t h o s e s t u d i e s a r e i n d i c a t i v e of an o c t a h e d r a l

g e o m e t r y for C o ( I I ) i o n . T h e m a g n e t i c m o m e n t ( 3 . 1 2 BM a n d

1.80 Bfl) and e l e c t r o n i c s p e c t r a of N i ( I I ) and C u ( I I )

c o m p l e x e s r e s p e c t i v e l y s u p p o r t s an o c t a h e d r a l g e o m e t r y

a r o u n d t h e s e i o n s .

T h e R u ( I I I ) and R h ( I I l ) c o m p l e x e s of 2 - ( p y r i d i n o - 2 -

t h i o n a t o ) b e n z o x a z o l e the o b s e r v e d m a g n e t i c m o m e n t 3.93 BM

and 3.62 BM r e s p e c t i v e l y and the e l e c t r o n i c s p e c t r a (Table

XX)of t h e s e c o m p l e x e s s u g g e s t an o c t a h e d r a l g e o m e t r y .

2 - ( p y r i d i n o — 2 — t h i o n a t o ) b e n z o x a z o l e

F i g u r e XXIII

0 •p s (T3 C 0 •H o\o x: •p t hi 1 rH u (N (0 1 u 0 W c -a •H c

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74 1 1 1 1 1

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CM CM r - r - (N CM CM CM 1 1 CM CM rH rH (N CM rH rH rH rH

* '

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o o CTl CTl O^ CTt rH rH —'

cTi 00 00 ^ rH rH O O in • • • • • • • • • • • • • •

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—^ ^ ^ r-l cri 'S' lO CM in CM 30 cr> OO <Tl

• • • • • • • • • • • • • • m cn O rH CTl CTl CO CTl 00 ^ KO ^ 00 00 00 00 00 CO 00 00 00 00

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CM rH rH rH CM (N U U u rH M

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o o o ^

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in ^ rH rH rH CM OSl U 00 U iH U rH rH

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75, Cl ro (Ti

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cr> Ch r-v r- m in IX) CO CO VD 1 ^ —

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rH iH rH rH rH rH rH rH rH H (H

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o o O O O O O O O O O m m 00 in ro rr ro in rH ro rvj rr ro m in VD VD UD UD IX) rH rH rH H rH iH rH H rH H rH rH rH

u II u

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77,

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to 0 (U •H X +J (U 0) H c a, cn B rtJ 0 S u

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CN 00

CN rH u

CM

o cn

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o u

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-a +J c o u

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<H to m C c (B (0

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ti CM <D CD cn cn

tji iri iji M CP u <N rH rH fO <N fO

EH EH EH x; EH x; ro ro ro u U

Cn CM CN

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^ ^ ^ •• ^ ^

rH in in ro in m rH ro o in ro rH rH' CM ro rH ro rH CM ro CM CM ro

CM rH • m

rsi rH u <N

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ro

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77,

A C C No.

-^'•I'Tr, r' • . . \-rs' ^

78

N - ^ S

CI

•M

c

/

M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and H ^ d l )

N-^S CI

M

CI

.CI CI

M

CI

\\ // \\ //

n = C r ( I I I ) , F G ( I I I ) , R U ( I I I ) and R h ( I I I )

0 ' ^ N

'CI

'M CI

\ n M= Au(III)

Fitjuro XX

Complexes of 2-(pyridine-2-thionato)benzothiazGle

79,

Experimental

Prepara±ion of 2-(pyridine-2-thionatt:o)benzothiazole

A m i x t u r e of 2 - b r o m o b e n z o t h i a z o l e (8.80 m L ) and s o d i u m

p y r i d i n e - 2 - t h i o n a t o (4.0 y ) \/as r e f l u x e d in dry t e t r a h y d r o -

f u r a n (150 mL)- for a b o u t 15 h o u r s and t h e r e s u l t i n g m i x t u r e

w a s s t i r r e d for 10 h o u r s . T h e r e a c t i o n m i x t u r e v/as then

p o u r e d into 100 m L v/ater. A c r u d e p r o d u c t w a s p r e c i p i t a t e d

from this s o l u t i o n a f t e r a few d a y s , v;hich v;as then f i l t e r e d

and p u r i f i e d by r e c r y s t a l l i z a t i o n f r o m w a t e r . Y i e l d 30% M . P .

210°C.


An e t h a n o l i c s o l u t i o n of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o -

t h i a z o l e and the m e t a l c h l o r i d e in 1:2 (for M C I 2 ) and 1:3

(for M C l ^ ) (M:L) r a t i o w e r e taken t o g e t h e r . T h e m i x t u r e w a s

r e f l u x e d w i t h s t i r r i n g for a b o u t 12 h o u r s . A c o l o u r e d m i c r o -

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 w h i c h was f i l t e r e d w a s h e d

w i t h e t h a n o l and d r i e d in v a c u o .

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

w h e r e M = M n ( I I ) , C o ( I I ) , N i ( I I ) , C u ( I I ) , Z n ( I I ) and H g ( I I )

M ' = C r ( I I I ) , F e ( I I I ) , R u ( I I I ) and R h ( I I I )

80,


T h e c o m p l e x e s of 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o t h i a z o l e

were characterized by elemejital analysis,i.r. spectra u v - v i s i b l e a n d

m a g n e t i c m o m e n t m e a s u r e m e n t s . In s o d i u m p y r i d i n e - 2 - t h i o n a t o

t h e a b s e n c e of a n y b a n d in t h e 3 5 0 0 - 3 1 0 0 cm ^ r e g i o n s h o w s

t h e r e m o v a l of t h e p r o t o n f r o m N - H g r o u p . In t h e f r e e

c h e l a t i n g l i g a n d 2 - ( p y r i d i n e - 2 - t h i o n a t o ) b e n z o t h i a z o l e t h e

2;C=N, )JC=C a n d C = S s t r e t c h i n g f r e q u e n c i e s a p p e a r at 1 6 4 0

cm""^, 1 5 8 0 cm ^ a n d 1 0 5 5 c m ^ r e s p e c t i v e l y . A b a n d a p p e a r i n g

- 1 (99) at 8 0 0 - 6 0 0 cm is a s s i g n e d to C - S s t r e t c h i n g f r e q u e n c y .

A f t e r c o m p l e x a t i o n a s m a l l s h i f t in C = N b a n d is o b s e r v e d in

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

a t o m of t h e b e n z o t h i a z o l e m o i e t y . T h e IJ C=S a n d o t h e r c h a -

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

r e g i o n by a b o u t 1 0 - 4 5 cm ^ a f t e r c o m p l e x a t i o n . T h e b a n d

a t t r i b u t a b l e t o r i n g b r e a t h i n g v i b r a t i o n a t a b o u t 1000 cm ^

a n d 600 c m ^ a n d t h e b a n d d u e to C - H b e n d i n g a t 650 cm ^ a n d

750 cm ^ a r e s h i f t e d to h i g h e r f r e q u e n c i e s w i t h r e s p e c t t o

(83)

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

N e w b a n d s a p p e a r a r o u n d 5 0 0 - 3 0 0 cm ^ r e g i o n in t h e

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

v i b r a t i o n s , h a v i n g c o n t r i b u t i o n f r o m M - N a n d M - S s t r e t c h i n g

f r e q u e n c y . It is c l e a r t h a t t h e l i g a n d s h o u l d b e b i d e n t a t e .

T r i v a l e n t c o m p l e x e s s h o w t w o b a n d s in t h e r a n g e of 3 0 0 - 2 0 0

cm ^ t e n t a t i v e l y a s s i g n e d to yM-Cl. H o w e v e r in t h e d i v a l e n t

N S

Na

81,

2 - ( p y r i d i n G - 2 - t h i o n a t o ) b o n z o t h i a z o l e

F i g u r e X X I

2 - ( p y r i d i n o - 2 - t h i o n a t o ) b c n z o t h i a z o l c

82,

\ //

.CI

•CI

"CI

n = Mn(II), Co(ll), Ni(II),

Cu(II), Zn(II) and Hg(II).

M = Cr(III)/ Fe(III), Ru(III) and Rh(III)

Figure XXII

83,

0 4J ro c 0

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w tn W CO CM CO fN CM CM CM z z CM

z 2 2 CO 00 s 00 CO CO CO E X 00

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85,

1 o o o o o O O O O O o O iH o n 00 rH IH CO rH rH fSI iH CO on n n 00 fN 00 OO 00 00 <N

I S O o o o o o o o o o o o

00 rr r- 00 00 00 IX) CO in 00 og o 00 00 00 00 00 00 OO 00 00 00 00 00

a I E o o o o o o o o o o o o

CO rH o r- in 00 o o rsi rsi CO rr "cr

w I u o o o o o o o o o o o o o

m 00 <X) r-- in in in CO r- r-

w II u

o o O o o o o O O o O O o m rH 00 00 Ovj 00 in Ovl CM (N 00 o O O o o o o O o rH O O o rH rH rH rH rH rH rH rH rH rH rH rH rH

u o o O O in O o o o o O O O

rH rH rH o CTl OS] o o LO (N in 0 0

>x> VO in VD VO ^ rH rH rH iH rH rH rH rH rH rH rH rH rH

u II u

o o O o O o O o O O O o o rH 'a' m r-- CTi r- CTl 00

in in in in in m m in in m r-H rH rH rH rH rH rH rH rH rH rH rH rH

w -o C

E cu

e u

to 04 rH OvJ (N <N Cvl CM rH rH rH rH U rH rH rH rH rH U U rH 00 U U CM u U u U U eg (N U rH

fN (N OM CN CM Osl CN —^ CM U ^ ^ rvj ^—. ^—N '—^ (N CM in OvJ cn CNJ (N Cvj CM CM cn W CM CM

OvJ m OJ tn 10 Ui 10 m CM CM to tn S rg Z <N <N OJ CvJ CSl 2 2 CM CM

CM 00 00 2 z Z Z 00 00 2 2 C/) K CO X CO 00 00 00 CO a: a: CO 00

CM EC (N a: K cc o: a: CM CM a: a: rH rvj rH CM CM CvJ CvJ og rH rH CM CM

CO u rH U rH rH rH rH rH o CJ iH rH a: u u U u U u ^ ^ u U CN CM CN • — ' -—- —- eg CM - —

rH M c 0) 0 •H D c CT" P x: -v 3 u U s CM u 2 U ISI X PS « OH <

86,

c o m p l e x e s only o n e b a n d at 3 0 0 - 2 0 0 cm ^ is o b s e r v e d . In

t r i v a l e n t c o m p l e x e s t h e s e two b a n d s a r e a t r i b u t e d to the

t e r m i n a l and b r i d y i n y c h l o r i n e f r e q u e n c i e s . ^ ^ ^ ^ ^

T h e d i m e r i c n a t u r e of the c o m p l e x e s is c o n s i s t e n t v/ith

t h e i r h i y h d e c o m p o s i t i o n p o i n t s and i n s o l u b i l i t y . O n l y

P d ( I I ) , R h ( I I I ) , R u ( I I I ) and A u ( I I I ) c o m p l e x e s a r e s o l u b l e

in D M S O and w a t e r . T h e low m o l a r c o n d u c t a n c e (10~^M m o l a r

r a t i o ) v a l u e s of the s o l u b l e c o m p l e x e s in D M S O s h o w s t h e i r

n o n - e l e c t r o l y t i c n a t u r e .

E l e c t r a s p e c t r a

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

of t h e c o m p l e x e s a r e l i s t e d in t a b l e X X I I I . T h e e l e c t r o n i c

s p e c t r u m of C r ( I I I ) c o m p l e x shov-/ t w o b a n d s in the 1 5 , 3 0 0

- 1 - 1 4 4 cm and 2 0 , 000 cm r e y i o n a s s i y n e d to A 2 y ( F )

4 4

and T 2 g ( F ) < A ^ ^ ( F ) t r a n s i t i o n s . T h e v a l u e of m a y n e t i c

m o m e n t 3 . 8 1 BM is shown an o c t a h e d r a l s t r u c t u r e a r o u n d

C r ( I I I ) i o n . Th e r e f l e c t a n c e s p e c t r u m of Ni (II) c o m p l e x Ni ( ^ 2

s h o w t h r o e b a n d s at 1 0 , 3 0 0 c m " ^ , 1 4 , 3 0 0 c m ~ ^ and 2 4 , 6 0 0 c m ~ ^

a s s i y n a b l o t o ^ T 2 y ( F ) < ^ A 2 g { F ) , ^ A 2 g ( F ) , and

3 3

T ^ g ( P ) < A 2 y ( F ) t r a n s i t i o n s r e s p e c t i v e l y . T h e c a l c u l a t e d

v a l u e of 10 D q , B and lie in same r a n y o as e x p e c t e d for an

o c t a h e d r a l c o o r d i n a t e d N i ( I I ) i o n . T h e v a l u e of m a y n e t i c

m o m e n t 3.09 BM a l s o p r o v i d e s an a d d i t i o n a l e v i d e n c e for the

o c t a h e d r a l s t r u c t u r e of the c o m p l e x .

87

T h e m a g n e t i c m o m e n t 4-78 Bfl for C o ( I I ) c o m p l e x f a l l s in

the r a n g e r e p o r t e d for an o c t a h e r a l g e o m e t r y . T h e p r e s e n c e

of a c h a r a c t e r i s t i c s b a n d s at 1 5 , 440 cm 2 0 , 6 0 0 cm ^ and

2 3 , 3 0 0 cm ^ f u r t h e r s u p p o r t an o c t a h e d r a l c o n f i g u r a t i o n .

T h e e l e c t r o n i c s p e c t r u m of C u ( I I ) c o m p l e x shov\?s a b r o a d

- 2 " 2 2 band at 1 3 , 3 3 0 cm a s c r i b e d to ^g t r a n s i t i o n . A

band a t 3 3 , 300 c m ~ ^ r e g i o n m a y be d u e to c h a r g e t r a n s f e r .

T h e m a g n e t i c m o m e n t v a l u e of 1.78 BM a l s o s u p p o r t s an


T h e m a g n e t i c m o m e n t s (Table X X I I I ) of M n ( I I ) , F e ( I I I ) ,

R u ( I I I ) and R h ( I I I ) c o m p l e x e s of 2 - ( p y r i d i n e - 2 - t h i o n a t o )

b e n z o t h i a z o l e lie in 5.90 B M . , 5.79 BM,3.90 and 3.70 BM r a n g e at

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

a r o u n d the m e t a l i o n s . T h e s p e c t r u m of F e ( I I I ) c o m p l e x

e x h i b i t b a n d s at 18,940 c m ~ ^ and 2 1 , 6 6 0 c m ~ ^ a s s i g n e d to

(F) ^ V and ^ T , (F) ^ Â t r a n s i t i o n s . T h e Ig Ig 2g Ig

R u ( I I I ) c o m p l e x s h o w s two b a n d s a t 1 5 , 5 0 0 c m ~ ^ and 2 0 , 6 4 0

cm ^ s u p p o r t i n g an o c t a h e d r a l g e o m e t r y . T h e r e f l e c t a n c e

s p e c t r u m of R h ( I I I ) c o m p l e x s h o w b a n d s at 1 8 , 6 9 0 cm and

23,700 c h a r a c t e r i s t i c an o c t a h e d r a l g e o m e t r y .

T h e r e f l e c t a n c e s p e c t r u m of M n ( I I ) e x h i b i t s t h r e e m a i n

b a n d s at 1 5 , 930 c m ~ ^ , 1 9 , 5 3 0 c m ~ ^ and 2 6 , 6 6 0 c m ~ ^ w h i c h is

4 6 4 6 a s s i g n e d to t r a n s i t i o n s T ^ g ( F ) < : — ^ I g ^ ^ ^ ' — " Ig^^^

and ^"îg^P^ ^Îg^^^ c h a r a c t e r i s t i c of an o c t a h e d r a l

e n v i r o n m e n t a r o u n d the M n ( I I ) i o n .

88,

(U H 0 N ro •H x: 0 N c tu XI

0 +J c 0

•H x: 4J <N 1 0 C •H X} •H M >1 a, 1 CM M 0 m to u

•p (U B <tJ M (U •

04 -O H dJ •H IH

C 05 CP •H H 'O c nj •P n CJ B 0 B •

to 0 QJ •H X

QJ QJ rH C Ck

B (tJ 0 X 0

H n H

1

H ^ (0 EH

« E o

E' o H

•P C 0)

CD •H tt (0

(U H XJ •H to CO 0 Oh

6 u

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4-1 4-1 Q) S

fl^ ffl

to (U X 0) r-t a

e u

a (N in

CO

o

o

o

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m 00 00

o IX)

o in rn

h Ix,

tT> tT> <N CM ^ (U

IH CO C (0 M -P 

DIM iH (N m

EH EH X:

CO CO to

tJi CP CT> iH rH r-H < < <

VO U3 VO

U

M QJ m to c (0

Cn fci fa QJ ^ ^ ^ cr, cr cji CTi >H rH CM rH (D

Eh EH EH X: ^ U

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Cn CP CTi Vh CM rH CN ro

EH EH €H X: ^ CJ

e o O O o o o O o o O o O O o to o O o ro n vo o VD O o o o 'O ro o ••a" CTi m kO oo m o c K *

fO m o in <T, vo rn 00 rH in m o m •n XI rH CM m rH rH CM rt rH (N ro rH CN CM cn

CO

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CD cr> u as j=: u

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^ ^ ^

o 'J' cn CO CO m o OO 00 CO 00 H iH CM CO iH 00 (H CM CO iH CM OO

a^ o

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CN

CM W

CN s

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00 X Cvj (H

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CM x: K

CHAPTER - IV

Synthesis and characterization of complexes of

some new blheteroaromatic chelating llgands;

(I) 2(N-succlnlmldyl)pyridlne

(II) 2(N-succlnlmldyl)pyrlmldlne

Complexes of 2(N-5uccinimiclyl)pyridlne

90,

Experimental

Materials and methods

S u c c i n i m i d e ( S i s c o ) , 2 - b r o m o p Y r i d i n e and 2 - b r o m o p y r i -

m i d i n e ( A l d r i c h ) and s o d i u m h y d r i d e (80% s u s p e n s i o n in o i l )

w e r e used as r e c e i v e d . C r ( l I I ) , M n ( I I ) , F e ( I I I ) , C o ( I I ) ,

N i ( I I ) , C u ( I I ) , Z n ( I I ) , H g ( I I ) (BDH) and R u ( I I I ) , R h ( I I I )

and P d ( l l ) c h l o r i d e (Johnson M a t h e y ) w e r e used as r e c e i v e d .

P r e p a r a t i o n of s o d i u m s u c c i n i m i d e

T o a s o l u t i o n of 9.90 g s u c c i n i m i d e in 150 m L of

e t h a n o l , 4.80 g of s o d i u m h y d r i d e w a s a d d e d s l o w l y w i t h

c o n s t a n t s t i r r i n g . T h e r e a c t i o n m i x t u r e w a s l e f t o v e r n i g h t

at room t e m p e r a t u r e . A f t e r h e a t i n g u n d e r r e f l u x for 6 h o u r s

a vvrhite s olid w a s p r e c i p i t a t e d . It w a s f i l t e r e d and p u r i f i e d

by c o l u m n c h r o m a t o g r a p h y on s i l i c a g e l u s i n g CHCl^J H e x a n e .

Y i e l d 42% M P . 250°C.

Prepara±ion of 2 - ( N - s u c c i n i m i d y l ) p y r i d i n e

S o d i u m s u c c i n i m i d e 6.05 g was c a u t i o u s l y a d d e d to 2-

b r o m o p y r i d i n e 4.90 m L in dry e t h a n o l (100 mL) and the

r e s u l t i n g m i x t u r e r e f l u x e d for 20 h o u r s w i t h c o n t i n u o u s

s t i r r i n g . T h e d a r k o r a n g e m i x t u r e w a s then p o u r e d i n t o 50 m L

of w a t e r . A f t e r a few d a y s a v/hite s o l i d w a s o b t a i n e d w h i c h

w a s f i l t e r e d , d r i e d in v a c u o and r e c r y s t a l l i z e d f r o m

e t h a n o l . Y i e l d 35% M . P . 190°C.

91,

P r e p a r a±io n o f C o m p l e x e s

T o an e t h a n o l i c (25 m L ) s o l u t i o n of t h e l i g a n d and

m e t a l (II) or m e t a l (III) h a l i d e (1:2 for M C I 2 and 1:3 for

M C l n ) s o l u t i o n in the same s o l v e n t w a s a d d e d . T h e r e s u l t i n g

m i x t u r e w a s h e a t e d o v e r a w a t e r bath for 5 h o u r s and then

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

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

in v a c u o . C o l o u r , y i e l d , m e l t i n g p o i n t s and a n a l y t i c a l d a t a

of the c o m p l e x e s a r e l i s t e d in (Table - X X I V ) .

92,


2 - ( N - s u c c i n i m i d y l ) p y r i d i n o has been s y n t h e s i z e d in two

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

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

t h e 2 - b r o m o p y r i d i n e as g i v e n b e l o w :

+ NaH > ( ) "Na"*"

( C ^ H ^ N 0 2 ) " N a ^ + B r C ^ H ^ N y C g H g N 2 0 2

2 ( N - s u c c i n i m i d y l ) p y r i d i n e

C o m p l e x e s w e r e p r e p a r e d by the i n t e r a c t i o n of the 2 - ( N -

s u c c i n i m i d y l ) p y r i d i n e w i t h an e q u i v a l e n t a m o u n t of m e t a l ( I I )

and m e t a l ( I I I ) c h l o r i d e s . A c o l o u r e d p r e c i p i t a t e w a s

o b t a i n e d in h i g h y i e l d (Table - X X I V ) in all c a s e s . T h e s e

c o m p l e x e s a r e s t a b l e t o w a r d s h e a t and m o i s t u r e . They h a v e

been c h a r a c t e r i z e d by i . r . and ^H NMR s p e c t r a .

A l l the c o m p l e x e s are i n s o l u b l e in u s u a l s o l v e n t s

e x c e p t i n g t h o s e of P d ( I I ) , H g ( I I ) , Ru(III) and R h ( I I I ) w h i c h

a r e s o l u b l e in D M S O and w a t e r . T h e s e c o m p l e x e s w e r e found to

be n o n - e l e c t r o l y t e s in D M S O .

T h e i . r . s p e c t r u m of s o d i u m s u c c i n i m i d e d i d not s h o w

any a b s o r p t i o n band in 3 3 0 0 - 3 0 0 0 cm ^ r e g i o n d u e to t h e

a b s e n c e of N-H g r o u p . It s h o w s two b a n d s at 1750 and 1730

cm ^ r e g i o n i n d i c a t i n g p r e s e n c e of y C = 0 g r o u p . T h e

s h i f t in i;c=0 to lower f r e q u e n c y by a b o u t 1 0 0 - 7 0 c m ~ ^ a f t e r

c o m p l e x a t i o n s u g g e s t s the s u g g e s t s the f o r m a t i o n of a m e t a l

( 99) o x y g e n b o n d . L i k e w i s e C=N f r e q u e n c y is a l s o n e g a t i v e l y

\ \ / / - N

O

93

O

+ Na

N

Br

2 - ( N - s u c c i n i m i d y l ) p y r i d i n e


94,

s h i f t e d d u e to c o o r d i n a t i o n of m e t a l via nitrogen a t o m of

(95 97)

p y r i d i n e . ' E v i d e n c e for n i t r o g e n c o o r d i n a t i o n in a l l

c o m p l e x e s is p r o v i d e d by t h e a p p o a r e n c e of a new band in

4 0 0 - 4 5 0 c m ~ ^ r e g i o n a s s i g n a b l e to ^ M - N a b s e n t in the f r e e

l i g a n d s p e c t r u m . In the c o m p l e x e s o x y g e n c o o r d i n a t i o n is

a l s o s u p p o r t e d by the s t r o n g b r o a d M - 0 s t r e t c h i n g f r e q u e n c y

in 4 5 0 - 5 0 0 cm ^ r e g i o n . B a n d s in t h e far i . r . s p e c t r a of

t r i v a l e n t c o m p l e x e s s h o w two b a n d s at 2 8 0 - 3 3 0 cm ^ r e g i o n

a s s i g n e d to b r i d g i n g and t e r m i n a l M - C l f r e q u e n c y (Table -

X X V ) 1 ' ^ ^ H o w e v e r a l l d i v a l e n t m e t a l c o m p l e x e s e x h i b i t

only o n e M - C l s t r e t c h i n g f r e q u e n c y w h i c h s a t i s f i e s t h e

c o m p o s i t i o n ( M 2 ( L ) 2 C l g ) and ( M ( L ) 2 C l 2 ) and is c o n s i s t e n t

w i t h the p r o p e r g e o m e t r y of t h e c o m p l e x e s .

A l l r e l a v e n t ^H N M R d a t a for the l i g a n d and its c o m p l e x e s

a r e s u m m a r i z e d in (Table - X X V I ) . T h e ^H NMR p e a k s d u e to

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

d e r i v e d l i g a n d s . ^

T h e ^H N M R s p e c t r u m of l i g a n d ( F i g u r e - X X I I I ) d i s p l a y s

f o u r p e a k s in the a r o m a t i c r e g i o n . A l l p e a k s a r e s h i f t e d

d o w n f i e l d upon m e t a l c o o r d i n a t i o n by 1 . 2 4 - 0 . 0 3 p p m . T h e

l a r g e s t d i f f e r e n c e in t h e c h e m i c a l s h i f t of t h e p r o t o n a t

p o s i t i o n 6 in the l i g a n d and t h e c o m p l e x e s (Table - X X V I ) is

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

a t o m a d j a c e n t to the c a r b o n a t o m 6 .

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<Ti Cn -o D x: U 04 « a


T h e o b s e r v e d m a g n e t i c m o m e n t (3.82 BM and 5.84 B M ) for

t h e C r ( I I I ) and F e ( I I I ) c o m p l e x e s a r e w i t h i n the r a n g e for

an o c t a h e d r a l g e o m e t r y . T h e e l e c t r o n i c s p e c t r u m of t h e

C r ( I I I ) c o m p l e x e x h i b i t s b a n d s at 1 5 , 3 3 0 c m ~ ^ and 2 0 , 0 8 0

c m ~ ^ w h i c h m a y be a s s i g n e d to the

4 4 T 2 g ( F ) -t A 2 g ( F ) t r a n s i t i o n s , r e s p e c t i v e l y . F e ( I I I )

c o m p l e x shows t w o b a n d at 1 7 , 8 6 0 cm ^ and 21,000 cm ^

4 6 4 6 a s s i g n e d to ^ I g "Îg t r a n s i t i o n s

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

p o s i t i o n s of t h e s e c o m p l e x e s i n d i c a t e t h a t they are h i g h

spin c o m p l e x and h a v e an o c t a h e d r a l g e o m e t r y .

T h e room t e m p e r a t u r e m a g n e t i c m o m e n t of t h e M n ( I I )

c o m p l e x (5.81 BM) is w i t h i n t h e r a n g e for an o c t a h e d r a l

g e o m e t r y . T h e r e a r e t h r e e m a i n b a n d s (17,500 c m ~ ^ , 1 9 , 5 3 0

c m ~ ^ and 22,350 c m ~ ^ ) a s s i g n e d to ^'îg(G) ^ ^ I g '

^ T 2 g ( G ) Â^g and '^îg^*^) ^Îg t r a n s i t i o n s

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

a p p e a r i n g at 33,330 cm

T h e e l e c t r o n i c s p e c t r u m of N i ( I I ) c o m p l e x s h o w s t w o

b a n d s at 15,550 cm ^ and 2 0 , 3 0 0 cm ^ r e g i o n w i t h a c h a r g e

t r a n s f e r b a n d at 3 3 , 4 0 0 cm T h e m a g n e t i c m o m e n t v a l u e of

3.09 BM a l s o i n d i c a t e s an o c t a h e d r a l s t r u c t u r e . (Table -

X X V I I ) .

101

T h e e l e c t r o n i c s p e c t r u m for t h e C u ( I I ) c o m p l e x s h o w s

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

s u p p o r t e d by the o b s e r v e d m a g n e t i c m o m e n t v a l u e (Table -

X X V I I ) .

P d ( I I ) c o m p l e x as e x p e c t e d is d i a m a g n e t i c . It d i s p l a y

b a n d s in its d i f f u s e r e f l e c t a n c e s p e c t r u m at 1 7 , 5 5 0 c m ~ ^ ,

2 3 , 2 2 0 c m ~ ^ and 2 6 , 3 0 0 c m ~ ^ (Table - X X V I I ) s u g g e s t i n g a

s q u a r e p l a n a r g e o m e t r y a r o u n d the m e t a l i o n . ^ ^ ^ ^ ^

T h e C o ( I I ) c o m p l e x s h o w s a m a g n e t i c m o m e n t v a l u e of

4.65 BM w h i c h a g r e e s w i t h t h e e x p e c t e d v a l u e for h i g h spin

C o ( I I ) ion in an o c t a h e d r a l g e o m e t r y . It s h o w s t w o b a n d s at

1 4 , 1 5 0 cm ^ and 2 2 , 3 5 0 cm ^ w i t h a c h a r g e t r a n s f e r b a n d a t

3 4 , 0 0 0 c m ~ ^ . T h e s e b a n d s a r e a s s i g n e d to ^ T 2 g ( F ) <

4 4 and t r a n s i t i o n s r e s p e c t i v e l y .

R u ( I I I ) c o m p l e x s h o w s t w o b a n d s at 1 5 , 5 0 0 cm ^ and

-1 4 2 2 0 , 1 3 0 cm r e s p e c t i v e l y a s s i g n e d to "^Ig* '^2g

4' 2

T 2 y t r a n s i t i o n s . A m a g n e t i c m o m e n t v a l u e of 3.64

BM s u g g e s t an o c t a h e d r a l g e o m e t r y a r o u n d t h e R u ( I I I ) i o n .

T h e m a g n e t i c m o m e n t of R h ( I I I ) c o m p l e x is 3.58 B M . T h e

l i g a n d fie ld s p e c t r u m of t h i s c o m p l e x an o c t a h e d r a l

g e o m e t r y . It shov/s t w o b a n d s a t 2 1 , 530 cm 2 5 , 6 7 0 cm ^

w i t h an i n t e n s e c h a r g e t r a n s f e r at 33,330 cm T h e s e b a n d s

a r e a s s i g n e d to ^T, < ^ A , and ^A t r a n s i t i o n s ^ lg"= Ig 2g g r e s p e c t i v e l y .

0) J3 +J

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O - ^ N

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N - C r ( i r i ) » F c ( I I R ) , K U ( I I I ) and K H ( L I I )

Figure XXIV

Complexes of 2-(N-succinin[iidyl)pyrlmidine

105

Experimental

P r e p a r a t i o n of 2 - ( N - s u c c i n i m i d y l )pyriinidine

An e t h a n o l i c s o l u t i o n of (100 m L ) s o d i u m s u c c i n i m i d e

(1.21 g ) w a s s l o w l y added w i t h s t i r r i n g to a s o l u t i o n of 1.59

g of 2 - b r o m o p y r i m i d i n e in 50 mL e t h a n o l . As t h e a d d i t i o n

p r o g r e s s e d , the l i g h t y e l l o w m i x t u r e t u r n e d d e e p o r a n g e . T h e

r e s u l t i n g s o l u t i o n w a s r e f l u x e d w i t h s t i r r i n g for a b o u t 24

h o u r s and then p o u r e d i n t o 50 m L H 2 O . T h e r e s u l t i n g p r o d u c t

o w a s f i l t e r e d and d r i e d u n d e r v a c u o . Y i e l d 5 2 % , M . P . 206 C .


T h e c o m p l e x e s w e r e p r e p a r e d by m i x i n g an E t O H s o l u t i o n

of 2 - ( N - s u c c i n i m i d y l ) p y r i m i d i n e w i t h t h e all m e t a l c h l o r i d e

in 1:2 and 1:3 m o l a r r a t i o . A c o l o u r e d p r e c i p i t a t e a p p e a r e d

in each c a s e a f t e r r e f l u x i n g the s o l u t i o n for a b o u t 8 h o u r s .

T h i s r e a c t i o n m i x t u r e w a s f i l t e r e d and d r i e d u n d e r v a c u o .

106


T h e l i g a n d w a s p r e a r e d a c c o r d i n g to the f o l l o w i n g

r e a c t i o n s : -

T H P 4. r e f l u x ^ ( C ^ H ^ O ^ ) Na + H^

T h e i.r s p e c t r u m of s o d i u m s u c c i n i m i d e d o e s not s h o w

a n y a b s o r p t i o n band in t h e 3 3 0 0 - 3 1 0 0 cm ^ r e g i o n i n d i c a t i n g

a b s e n c e of the i J N - H , T h e h y d r o g e n a t o m of s u c c i n i m i d e is

r e p l a c e d by s o d i u m a t o m . 2 - ( N - s u c c i n i m i d y l ) p y r i m i d i n e s h o w s

a n e g a t i v e s h i f t in the c a s e of y c = N and \/C=0 a f t e r

c o m p l e x a t i o n , p r o b a b l y d u e to c o o r d i n a t i o n via t h e n i t r o g e n

• ( 1 1 7 - 1 1 8 ) . ^ . a t o m of p y r i m i d i n e and o x y g e n a t o m of

s u c c i n i m i d e . ^ ^ ^ ^ ^ T h e y C = 0 f r u q u e n c y is s h i f t e d to a l o w e r

v a l u e by a b o u t 100 cm ^ as c o m p a r e d to it p o s i t i o n in s u c c i -

n i m i d e and is a l s o n e g a t i v e l y s h i f t e d by a b o u t 15 cm

S o m e new b a n d s of w e a k e r i n t e n s i t y h a v e b e e n o b s e r v e d in

l o w e r w a v e n u m b e r r e g i o n . A band a p p e a r i n g in 4 5 0 - 5 5 0 cm ^

r e g i o n is a s c r i b e d to m e t a l o x y g e n b o n d i n g . A n o t h e r b a n d

b e t w e e n 4 5 0 - 4 0 0 c m ~ ^ is i n d i c a t i v e of t h e c o o r d i n a t i o n of

the n i t r o g e n of the p y r i m i d i n e m o i e t y to the m e t a l a t o m

( F i g u r e - X X V I I ) . ^ ^ ^ ^ ^

T h e c o m p l e x e s a r e s t a b l e to h e a t and m o i s t u r e , they a r e

not s o l u b l e in c o m m o n o r g a n i c s o l v e n t b u t C u ( I I ) , P d ( I I ) and

I z

T CN

u 0 m

fO

(0 xs

H (0 o •H V >1 H (0 C (0

'O C n

o o c (0 ^ 0 3 -O c 0 o

M rtJ H 0 s

+J c •H 0 01

(T« c

•H •P rH flJ s

n3 iH (U •H !H

M 3 0 H 0 u

H

X

(U iH x> to tH

W (U X (1) H 04 e o u

1 cu

>1 V •H s •H C

•H O u 3 W

rH I I H E 0 g ^ W CN e B

0\0

u ^

c 3 0 iw

CO •H 03 >1 M (0 c <

rH u

EC

u

S 0 U

H 0) Ofi •H >H

M 3 O rH 0 u

w -d 3 3 0 Dj E O U

107

o o CN O • •

o o • •

VD O • f

00 oo

o (N CM

O r--

0) +J •H x: S:

(0

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rsi O 'a'

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vo o O <N • •

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00 cri

m in

IX) o r-CN) r-H n ro

O r-H m m CM CM

o CO UD o CM CN

O o cTi 00 (N CM

o iH rO

(N

>1 OJ M

iH u CM

CM z CM

o r-a: 00 U

M u

m VD CN O rH

(N CTi IX) r-m

CO o CTl U-)

VO o CO (N CM

CM O n o o o

o CM ro

O U3

C 0) (i; (-1 o

CM rH U CM

CM

CM O

K o o

U

c

CO

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ro m

r m n CN CN

CN isO m o CN CM

O <Ti O CM CTi 00 CM CM

O (N ro

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c

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rH U CM '—s CM

z CM

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CN <D Ui

cTi cri Cn rH CM CM

CN IX) VD m rH rH

CO in ro

00 CO CM CM

IX) IX) CTi CO O CO n

o o ro

m IX)

c •H

CM

u CN

CN

CM o

00 U

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108

O m

n <N

00

,—, . "s. o ro ro CTl 00 CM 0 1 O o iH (N CT CTi ro (N O t • • • • • • • n CM ro CM 00 CO rH O 1 1 -H iH rH iH rH rH ro ro — —^

^ ^

o O ro o 00 O Og 14D CM rsl in in o 'a' O ro 00 rH CTi ID

* • • • • • • • • • • • "vT CM iH

iH rH rH r-i iH rH rH og CM • —

^ ^

CJ\ ro ro rsl •<:}< in CO CO (Ti CO CO m rH iH O CM 00

• • • • • • • • • • • • r - r-- r - ro CO o o r-i iH rH rH iH rH rH iH rH rH rH rH

^—'

^

Ch CTi VD rM U-) O CM CM O 00 CO CO 00 ro rM o 00 CTl 00

• « • • • • • • • • • • CM CM (N CM OJ <N CM CN CM CM rH fH

-—^ o CTl 143 O ro tn CM in rH O o o Ch ro rsi fH o r- cj^ 00 cr.

• • • • • • * • • * • • o 00 o cr» »H O 00 CO in m

ro ro ro ro ro ro ro ro CM (N "W

o o o o o O iH o CM rH o rH ro ro ro ro ro ro

CM m o in in o vo

c dJ QJ u o

c CD (U 1-1 a

<u 4-1 •w x; s

<u 4-)

iH x: o s

o

0)

u TJ I—I CQ

(N rM U

CM

(N

CM o r-

K 00 u •H z

tN iH U (N

<N 23 fN

O

X 00 U

a u

(N rH u

CM ^ ^

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o r-K 00 U

C to

CM iH U (N

(N o CM

2 h-

K 00 u

Cn K

U CN

(N z CN

o X

00 U

On

iH u rs

CM 2 (N

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X 00 U

CM D K

tn (1) X (U (H Qj

I U

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(1)

•H A

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•H O U 3

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0 w

m 0 (0 u •p 0 (D CX tn «

X H

I

OJ iH

fO EH

C •H Xi O 4-1 QJ M 4-1 W

H I

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01 c

•H x: o +J Q; H

0 M I 1 4-1 e

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•H -a x: c u (0 4J

Q) iH S M I II 4-1 S u w o

cn a

•H JC U 4-1

(U H

4-1 B u w u ?

c •H X! U 4-1 (I) H

FC M I I 4-1 6 CJ W U

W 'O C 13 0 Ck E 0 U

109

in CN

o in in

o N

M

m

QJ

M o

o o

M o

E <N rH M

O 00 •rr

M (N M

M o

o o

e & S e

o o CN o (N1 (N rH 00

m in

in tn CM in (N <M r—1 --H

iH iH i-H 1—1 » »

o m O m ro CM m r--m m in m

w U) in U3 V) in U) in tn o O o O o m o m in m ro in r^ oo r--r- r- vo ^ IXI rH iH iH r-H r-l iH iH rH rH

tn in in in o o o o o (N O o o rH CO o O CO CTl <Ti 00 <Ti O-I CO <N (N OJ (N fN (N rsi

Ti VO •H rH (N rH CM CM e u rH CJ rH rH •H (N u CM U U C (N (M CM •H fN ^—^ <N —. ^—.

O CM 2 CM (N o CM CN 2 2 D O CM o CM CM tn rsi r O O O

S X X r^ E CM 00 a: 00 a: E

O U 00 U 00 00 •H r — u ^ — U U

X CM ^ rsi 0 00 (H c 0 0 •H W U u t, u 2

e e e E e

o o in m o o iH o o r-(

e s e e 6

o o o o o o o 00 in m m

in <N o o o rH M o o CvJ

T ^ rH tH rH tH rH

»

in in o o o CN m ro in m in m in rH tH rH rH

W w 6 e w (N in o o o tH VD r- o 1X> <x> VT) ID rH iH rH

in m (/) cn (/I o o O o O o o o o m cn CTl CTi 00 CN CM (N1 (N <N

X H

(U H JH

5

'O •p

§ u

<N oj CN fH rH rH rH U u u U rH fM CVJ CN CN u

-—^ f—s ^—, CN (N tN CN (N ••

2 z 2 (N cr> E CN CN <N CN 2 c D

O O o o 0 •H r-- E S-i (D

a: E E E 00 4-> (L 0 CO 00 00 00 O tn E U U U u —•

II OW' CN II II II D c Cn X! D U Cs] K O, Pi cn IS s

110

Ill

R u ( I I I ) c o m p l e x e s a r e s o l u b l e in D M S O . T h e low m o l a r c o n d a c -

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

n a t u r e . T h e s u b s t i t u t i o n of c h l o r i d e ions in the c o m p l e x e s

M L 2 C I 2 (where M = P d ( I I ) and C u ( I I ) and L = 2 - ( N - s u c c i n i m i d y l )

p y r i m i d i n e ) by p y r i d i n e in D M S O s o l u t i o n w a s a l s o s t u d i e d .

T h i s r e p l a c e m e n t has been f o l l o w e d c o n d u c t o r a e t r i c a l l y . A d d i -

tion of p y r i d i n e i n c r e a s e s t h e c o n d u c t a n c e i n d i c a t i n g

r e p l a c e m e n t of t h e c h l o r i d e i o n . F u r t h e r a d d i t i o n of

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

s e c o n d c h l o r i d e i o n .

M L 2 C I 2 + py (ML2Clpy)"^ + c l "

(ML Clpy)"^ + py • (ML2Py2)"^'^ + C l ~

A d d i t i o n of any e x c e s s of p y r i d i n e a f t e r t h i s p o i n t

d o e s n o t m a k e f u r t h e r c h a n g e i n d i c a t i n g t h a t b o t h the

c h l o r i d e i o n s h a v e b e e n r e p l a c e d by p y r i d i n e (Figure

X X V I I ) .

In v i e w of the r e s u l t s of e l e m e n t a l a n a l y s i s m a g n e t i c

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

have been t e n t a t i v e l y a s s i g n e d an o c t a h e d r a l s t r u c t u r e .

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

F e ( I I I ) c o m p l e x e s a r e w i t h i n the e x p e c t e d r a n g e for an o c t a -

h e d r a l g e o m e t r y . C r ( I I I ) c o m p l e x s h o w s t w o m a i n b a n d s w h i c h

is c h a r a c t e r i s t i c of an o c t a h e d r a l g e o m e t r y a r o u n d t h e m e t a l

i o n . T h e e x p e r i m e n t a l m a g n e t i c m o m e n t v a l u e of 6.63 BM at

112

2 - ( N - s u c c i n i m i d y l ) p y r i m i d i n e

F i g u r e X X V

r o o m t e m p e r a t u r e in F e ( I I I ) is w i t h i n t h e e x p e c t e d r a n g e and

i n d i c a t e s t h a t it is a high spin c o m p l e x w i t h an o c t a h e d r a l

g e o m e t r y .

In t h e c a s e of M n ( I I ) c o m p l e x t h e m a g n e t i c m o m e n t v a l u e

of 5.87 BM is very c l o s e to t h a t c a l c u l a t e d for f i v e

u n p a i r e d e l e c t r o n s . T h e e l e c t r o n i c s p e c t r u m of M n ( I I )

c o m p l e x e x h i b i t s four w e a k b a n d s at 1 3 , 8 8 0 c m ~ ^ , 1 7 , 8 6 0

cm 20,000 cm ^ and 2 5 , 0 0 0 c m ~ ^ w h i c h a l s o s u p p o r t s in

o c t a h e d r a l g e o m e t r y a r o u n d the M n ( I I ) a t o m .

T h e m a g n e t i c m o m e n t v a l u e s o b s e r v e d f o r C o ( I I ) and

N i ( I I ) (4.23 BM and 3.45 B M ) c o m p l e x e s i n d i c a t e an

o c t a h e d r a l g e o m e t r y a r o u n d the m e t a l i o n . T h e e l e c t r o n i c

s p e c t r u m of C o ( I I ) c o m p l e x e x h i b i t s w e a k b a n d s at 1 6 , 1 3 0

cm 19,600 cm ^ and 2 2 , 7 3 0 c m ~ ^ w h i c h m a y r e a s o n a b l y be

a s s i g n e d to T 2 g ( F ) -t- 'T^g(F) and

- Tj^g(F) t r a n s i t i o n s r e s p e c t i v e l y . T h e N i ( I I )

c o m p l e x e x h i b i t s t h r e e b a n d s at 1 3 , 7 0 0 c m ~ ^ , 1 8 , 1 8 0 c m ~ ^ and

23,260 cm ^ c h a r a c t e r i s t i c of an o c t a h e d r a l g e o m e t r y a r o u n d

113

2 3 , 2 6 0 c h a r a c t e r i s t i c of an o c t a h e d r a l g e o m e t r y a r o u n d

the m e t a l i o n . ^ ^ ^ J )

H i g h m e l t i n g p o i n t and i n s o l u b i l i t y of t h e c o m p l e x e s

i n d i c a t e s t h e p o l y m e r i c n a t u r e of t h e compld^ces. T h e l i g a n d

field p a r a m e t e r s , l O D q , B and h a v e a l s o b e e n c a l c u l a t e d

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

for some of t h e s e c o m p l e x e s s u g g e s t s a low d e g r e e of

c o v a l e n c y .

F i g u r e X X V I

114

'N

CI

CI

N N

M = M n ( l l ) , C o ( l l ) , N i ( I I ) , C u ( l l ) , Z n ( l l ) & Hcj(ll)

V

/ CI CI

CI

X •N

M.

CI

•CI

M

CI

O ^ N ^ O

M ^ C r ( l I I ) , F o ( I I I ) , R h ( I I I ) and R u ( l l l )

Figure XXVII

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CHAPTER - V

Synthesis and characterization of complexes obtained

from pyridine,benzoxazole and pyrlmldlne

sybstituted 2-mercaptobenzothlazole ligands;

(I) 2 - ( 2 ' - m e r c a p t o b e n z o t h l a z o l y l ) p y r l d i n e

(II) 2 , 6 - b l s ( 2 ' - m e r c a p t o b e n z o t h l a z o l y l ) p y r l m l d l n e

(ill) 2 - ( 2 ' - m e r c a p t o b e n z Q t h l a z o l y l ) b e n z o x a z o l e

Complexes 2-(2'-mercaptobenzothlazolyl)pyridine

117

Experimental

M a t e r i a l s a n d m e t h o d s

2-fIercaptobenzothiazole (Koch L i g h t ) , 2 - b r o m o p y r i d i n e ,

2 , 6 - d i c h l o r o p y r i m i d i n e and 2 - b r o m o b e n z o x a z o l e ( A l d r i c h ) a n d

s o d i u m b y d r i d e (80% s u s p e n s i o n in o i l ) w e r e u s e d as s u p p l i e d .

A l l m e t a l c h l o r i d e s [ C r ( I I I ) , M n ( I I ) , F e ( I I I ) , C o ( I I ) ,

N i ( I I ) , C u ( I I ) , Z n ( I I ) , H g ( I I ) (BDH A n a l a r ) and R u ( I I I ) ,

R h ( I I I ) , P d ( I I ) , A u ( I I I ) and P t ( I V ) (Jhonson M a t h e y ) ] w e r e

u s e d as r e c e i v e d .

P r e p a r a t i o n of s o d i u m s a l t of 2 - m e r c a p t o b e n z o t h i a z o l e

T h e l i g a n d s o d i u m 2 - m e r c a p t o b e n z o t h i a z o l i d e w a s f o r m e d

by 2 - m e r c a p t o b e n z o t h i a z o l e (6.65 g ) w i t h s o d i u m h y d r i d e

(2.95 g ) , in dry e t h a n o l (150 m L ) . A f t e r t h e t h e o r e t i c a l

v o l u m e of h y d r o g e n gas w a s e v o l v e d t h e r e a c t i o n w a s s t o p p e d .

o On c o o l i n g to -5 C a l i g h t y e l l o w p r o d u c t w a s o b t a i n e d by a t

o 25 C it t u r n e d i n t o a l i q u i d .

P r e p a r a t i o n of 2 - { 2 - m e r c a p t o b e n z o t h i o z o l y l ) p y r i d i n e

S o d i u m - 2 - m e r c a p t o b e n z o t h i o z o l i d e (2.0 g) and 2 - b r o m o -

p y r i d i n e (1.20 m L ) w e r e m i x e d t o g e t h e r in d r y e t h a n o l (150

m L ) and r e f l u x e d for a b o u t 14 h o u r s . A w h i t e p r o d u c t w a s

o b t a i n e d on h e a t i n g on the w a t e r b a t h , b u t a f t e r 4 h o u r s it

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

r e a c t i o n m i x t u r e , w a s h e d w i t h e t h a n o l and r e c r y s t a l l i z e d

118

f r o m w a t e r . Y i e l d 3 2 % , M . P . 180°C.

P r e p a r a t i o n o f c o m p l e x e s

E t h a n o l i c s o l u t i o n of the l i g a n d and m e t a l c h l o r i d e

( M n C l 2 , F e C l ^ , , N i C l 2 , C U C I 2 , ZnCl2 H g C l 2 , R U C I 3 , R h C l ^ ,

P d C l 2 . H A u C l ^ and H 2 P t C l g ) in 1:2 (in c a s e of M C I 2 ) and 1:3

(in c a s e of M C l ^ ) (M:L) m o l a r r a t i o s w e r e m i x e d t o g e t h e r and

r e f l u x e d for a b o u t 6 h o u r s . A c o l o u r e d p r e c i p i t a t e w a s

o b t a i n e d which", w a s f i l t e r e d off w a s h e d w i t h e t h a n o l and

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

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

T a b l e - X X X I .


2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) p y r i d i n e is p r e p a r e d in

two s t e p s . In the f i r s t step by the a c t i o n of s o d i u m h y d r i d e

on 2 - m e r c a p t o - b c n z o t h i a z o l e r e s u l t s in t h e f o r m a t i o n of t h e

s o d i u m s a l t of 2 - m e r c a p t o b e n z o t h i o z o l e w h i c h in the s e c o n d

step r e a c t s w i t h 2 - b r o m o p y r i d i n e . E l e m e n t a l a n a l y s i s , c o l o u r ,

m e l t i n g p o i n t and p e r c e n t y i e l d of t h e l i g a n d and its

c o m p l e x e s are g i v e n in T a b l e - X X X I . T h e s o l i d c o m p l e x e s a r e

q u i t e s t a b l e t o w a r d s h e a t and m o i s t u r e and a r e i n s o l u b l e in

c o m m o n o r g a n i c s o l v e n t s , e x c e p t for t h o s e of R u ( I I I ) ,

R h d I I ) , P d ( I I ) and A u ( I I I ) w h i c h a r e s o l u b l e in D M S O . T h e

m o l a r c o n d u c t i v i t i e s of t h e s e c o m p l e x e s in D M S O at r o o m

t e m p e r a t u r e i n d i c a t e t h e i r non i o n i c n a t u r e .

On the b a s i s of m a g n e t i c m o m e n t s , i . r . and -electronic

s p e c t r a , an o c t a h e d r a l g e o m e t r y is s u g g e s t e d for a l l b u t t h e

A u ( I I I ) and P d ( I I ) c o m p l e x e s . T h e l i g a n d 2 - m e r c a p t o b e n z o -

t h i a z o l e e x i s t s in the t a u t o m e r i c f o r m t h i o l ( F i g u r e - I I B)

and t h i o n e (Figure - I I C ) . In s o l u t i o n t h e l i g a n d c o n s i s t s

m a i n l y of the t h i o n e f o r m as e v i d e n c e d by t h e p r e s e n c e of

S - H b a n d at 2600 cm ^ w h i c h is n o t p r e s e n t in t h e s o l i d .

S o d i u m 2 - m e r c a p t o b e n z o t h i a z o l e d o e s n o t s h o w a n y a b s o r p t i o n

b a n d in 3 4 0 0 - 3 1 0 0 cm ^ and 2 800-2500 cm ^ r e g i o n a s s i g n e d to

(49)

N - H and S - H b a n d s . A n e w p e a k o b s e r v e d a t 1050 cm is

a s s i g n e d to C = S . T h e c h e l a t i n g l i g a n d 2 - ( 2 ' - m e r c a p t o b e n -

z o t h i a z o l y ) p y r i d i n c (Figure - X X V I I I ) c o n t a i n s a l a r g e

120

n u m b e r of a b s o r p t i o n b a n d s at 1610 cm 1595 cm ^ and 1050

c m ~ ^ a s s i g n e d to i;c=N, iJ C = C and JJ C=S r e s p e c t i v e l y . ^ T h e

s t r o n g b a n d s at 1610 cm ^ and 1595 c m ^ d u e t o V C = N , and

V C=C of the l i g a n d are s h i f t e d to l o w e r r e g i o n in t h e m e t a l

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

the n i t r o g e n a t o m of p y r i d i n e . S u c h a n e g a t i v e s h i f t of t h e

C = N s t r e t c h i n g m o d e to l o w e r f r e q u e n c y on c o m p l e x a t i o n m a y

t e n t a t i v e l y be a t t r i b u t e d t o a l o w e r i n g in t h e C = N b o n d

o r d e r r e s u l t i n g f r o m M - N b o n d f o r m a t i o n . A s t r o n g b a n d at

1050 cm ^ a s c r i b e d to t h e U C = S is s h i f t e d to l o w e r

f r e q u e n c y (10-20 cm i n d i c a t i n g t h e b o n d i n g of the m e t a l

ion t h r o u g h the s u l p h u r a t o m a l s o . In a d d i t i o n , a l l t h e

m e t a l c o m p l e x e s show' b a n d s in the far i . r . r e g i o n ( 4 5 0 - 4 0 0

cm and ( 4 0 0 - 3 0 0 cm w h i c h a r e a s s i g n e d to M - N and M - S

s t r e t c h i n g v i b r a t i o n s , r e s p e c t i v e l y . A n e w b a n d o b s e r v e d in

3 0 0 - 2 0 0 cm ^ r i g i o n is a s s i g n e d to i; M - C l . In c o m p l e x e s of

t r i v a l e n t m e t a l t h e r e a r e t w o b a n d s in 3 0 0 - 2 0 0 cm ^ r a n g e

a s s i g n e d to t e r m i n a l and b r i d g i n g M - C l b a n d s , w h i l e t h o s e

of the d i v a l e n t m e t a l s ions e x h i b i t o n l y o n e M - C l

s t r e t c h i n g f r e q u e n c y .

^H NMR s p e c t r a l d a t a t o g e t h e r w i t h t h e i r a s s i g n m e n t a r e

g i v e n in T a b l e - X X X I I I . T h e ^H N M R s p e c t r a a r e c o m p l i c a t e d

and t h e i r a s s i g n m e n t s of c h e m i c a l s h i f t s w e r e m a d e on t h e

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

by S t e e l and C o n s t a b l e . T h e d o w n f i e l d s h i f t o b s e r v e d in

all the a r o m a t i c p r o t o n s i n d i c a t e s c o o r d i n a t i o n of n i t r o g e n

121

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126

as w e l l as s u l p h u r a t o m of the l i g a n d . T h e l a r g e s t c h e m i c a l

s h i f t o b s e r v e d for the p r o t o n s at p o s i t i o n 6 and 4 of

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

p y r i d i n e (Table - X X X I I I '


T h e C r ( I I I ) c o m p l e x of 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l )

p y r i d i n e s h o w s t h r e e b a n d s a t 16,200 cm 1 9 , 5 0 0 cm ^ and

2 3 , 340 c m " ^ a s s i g n a b l e to '^Tj^g(F) ,, ( F) , ( F ) ( F)

4 4

and Tj^g(P) < A 2 g ( F ) t r a n s i t i o n s r e s p e c t i v e l y for an

o c a t a h e d r a l C r ( I I I ) i o n . T h e ^eff v a l u e of 3.62 BM in

C r ( I I I ) c o m p l e x is s l i g h t l y l o w e r than t h a t e x p e c t e d for an

o c t a h e d r a l g e o m e t r y and is p r o b a b l y d u e to l i g a n d b r i d g i n g .

T h e r e is a s t r o n g c h a r g e t r a n s f e r band at 3 3 , 330 cm ^

in C o ( I I ) c o m p l e x of 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) p y r i d i n e .

T h e o t h e r b a n d s at 1 5 , 2 6 0 2 1 , 3 0 0 c m ~ ^ a s s i g n e d to

^ T 2 g ( F ) < — ^ T j ^ g ( F ) '^T^g(P)-^ ^ T ^ g ( F ) t r a n s i t i o n s r e s p e c -

t i v e l t y , a r e s u g g e s t i v e of an o c t a h e d r a l g e o m e t r y for C o ( I I )

i o n , h o w e v e r t h e /'eff v a l u e of 3.98 BM for t h i s c o m p l e x is

l o w e r tha n t h a t e x p e c t e d for a high spin o c t a h e d r a l C o ( I I ) 1 (123)

c o m p l e x .

B e s i d e s a c h a r g e t r a n s f e r band at 3 4 , 4 3 0 cm ^ in N i ( I I )

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

^^ T h .

(124)

o c t a h e d r a l g e o m e t r y for the N i (II) ion.^^^'^^ T h e ^eff v a l u e

(2.98 B M ) a l s o s u p p o r t s the a b o v e g e o m e t r y .

127

T h e e l e c t r o n i c s p e c t r u m of C u ( l l ) c o m p l e x s h o w s t w o

m a i n b a n d s at 1 3 , 5 0 0 c m ~ ^ and 2 0 , 6 3 0 cm ^ a s s i g n e d to

T 2 2 A , , E < B , t r a n s i t i o n s , r e s p e c t i v e l y . T h e ig g -'•g

"eff v a l u e of 1.82 BM for t h i s c o m p l e x a l s o s u p p o r t s t h e

p r o p o s e d o c t a h e d r a l s t r u c t u r e . ^ ^ ^ ^ ^

T h r e e m a i n b a n d s are o b s e r v e d in the Fe(III) c o m p l e x at

1 6 , 3 6 0 c m ~ ^ , 1 8 , 9 0 0 c m ~ ^ and 25,450 c m ~ ^ a s s i g n a b l e t o

t r a n s i t i o n s for an o c t a h e d r a l g e o m e t r y . T h e ^ e f f v a l u e is

very c l o s e to t h a t e x p e c t e d for an o c t a h e d r a l F e ( l I I ) ion^.^^^^

T h e ^ e f f v a l u e s of 2.12 BM and 2.53 BM for R u ( l I I ) and

R h ( I I I ) c o m p l e x e s as w e l l t h e i r e l e c t r o n i c s p e c t r a a r e

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

i o n s . R u ( I I I ) c o m p l e x d i s p l a y s o n l y o n e b a n d at 1 9 , 3 3 0 c m ~ ^

c o r r e s p o n d i n t to t h e t r a n i s i t i o n h a v i n g an

o c t a h e d r a l g e o m e t r y . The R h ( I I I ) c o m p l e x e x h i b i t s f o u r

a b s o r p t i o n b a n d s a t 1 1 , 5 3 0 1 5 , 6 3 0 c m ~ ^ , 1 8 , 9 5 0 c m ~ ^

and 2 0 , 3 5 0 c m ~ ^ a s s i g n e d to ^"^ig^ ^ ^ I g '

Tj^g-t ^j^g and ^^Ig ' r e s p e c t i v e l y .

128

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Complexes of 2,6-bis(2'mercaptobenzothiazolyl)pyrimidine

132

Experimental

P r e p a r a t i o n o f 2,6 b i s ( 2 - m e r c a p t o b e n z o t h i a z o l y D " p y r i m i d i n e

T o a s o l u t i o n of 8.35 g of 2 - m e c r a p t o b e n z o t h i a z o l e in

100 m L of a n h y d r o u s x y l e n e , 4.18 g of s o d i u m h y d r i d e v/as

a d d e d s l o w l y . T h e r e a c t i o n m i x t u r e w a s s t i r r e d o v e r n i g h t at

r o o m t e m p e r a t u r e . 3.72 g of 2 , 6 - d i c h l o r o p y r i m i d i n e in

a n h y d r o u s x y l e n e w a s a d d e d to the s u s p e n s i o n of s o d i u m s a l t

of 2 - m e r c a p t o b e n s o t h i a z o l e . A f t e r h e a t i n g u n d e r r e f l u x for

32 h o u r s the s o l u t i o n was e v a p o r a t e d u n d e r v a c u u m . T h e

r e s u l t i n g sol id 2,6 b i s ( 2 - m e r c a p t o b e n z o t h i a z o l y l ) p y r i m i d i n e

w a s f i l t e r e d and p u r i f i e d by c o l u m n c h r o m a t o g r a p h y on s i l i c a

g e l u s i n g a c e t o n e as e l u e n t . Y i e l d 5 5 % , m . P . 120°C.


T h e c o m p l e x e s w e r e p r e p a r e d by m i x i n g the l i g a n d

s o l u t i o n in a c e t o n e to the m e t a l h a l i d e s o l u t i o n ( C r C l ^ ,

MnCl2/ F e C l ^ , C 0 C I 2 , N i C l 2 , CUCI2/ Z n C l 2 , H g C l 2 , P d C l 2 ,

RhCl^/ R u C l ^ and H 2 P t C l g in t h e same s o l v e n t in 1:2 and 1:3

(M:L) r a t i o . In each c a s e it w a s r e f l u x e d w i t h s t i r r i n g . A

c o l o u r e d solid p r o d u c t a p p e a r e d a f t e r k e e p i n g the r e a c t i o n

m i x t u r e for a few d a y s , w h i c h w a s t h r o u g h l y w a s h e d w i t h the

same s o l v e n t and d r i e d in v a c u o .

T h e r e a c t i o n may be r e p r e s e n t e d as b e l o w -

t M C I 3

133


T h e a n a l y t i c a l r e s u l t s of t h e c o m p l e x e s (Table-XXXV) a r e

in a g r e e m e n t w i t h t h e i r c o m p o s i t i o n . D u e to t h e i r i n s o l u b i -

lity in o r g a n i c s o l v e n t s , 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 a n d

r e c r y s t a l l i z a t i o n c o u l d n o t b e d o n e . O n l y R u ( I I I ) , R h ( I I I ) ,

P d ( I I ) a n d H g ( I I ) c o m p l e x e s a r e s o l u b l e in o r g a n i c s o l v e n t s

s u c h as w a t e r , D M S O a n d n i t r o b e n z e n e e t c . T h e l o w m o l a r

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

e l e c t o l y t i c n a t u r e .

T h e i . r . s p e c t r u m of s o d i u m s a l t of 2 - m e r c a p t o b e n z o t h i a

z o l e s h o w s b a n d s at 1 5 5 0 cm 1 0 5 0 cm ^ a n d 640 c m ~ ^ w h i c h

m a y be a s s i g n e d t o VC=C, 1/'C=S a n d y c - S v i b r a t i o n s , r e s p e c t i -

v e l y . T h e d i s a p p e a r a n c e of oJN-H a n d V S - H b a n d s at a r o u n d

3300 - 3 1 0 0 c m ~ ^ a n d 2 5 0 0 - 2 3 0 0 c m ~ ^ is d u e t o t h e r e m o v a l

of t h e p r o t o n s f r o m t h e l i g a n d 2 - m e r c a p t o b e n z o t h i a z o l e f o r

t h e f o r m a t i o n of i t s s o d i u m s a l t . O n e a d d i t i o n a l a b s o r p t i o n

b a n d at 1 6 3 0 cm ^ is o b s e r v e d in t h e s p e c t r a o f 2 , 6 - b i s ( 2 ' -

m e r c a p t o b e n z o t h i a z o l y l ) p y r i m i d i n e is a s s i g n e d t o C = N a b s o r p -

t i o n b a n d . A c o m p a r i s o n of t h e s p e c t r a of f r e e c h e l a t i n g

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

i n d i c a t e s t h a t t h e C = N s t r e t c h i n g f r e q u e n c y u n d e r g o e s

s i g n i f i c a n t c h a n g e s . T h e C = S f r e q u e n c y is a l s o s h i f t e d

n e g a t i v e l y d u e to t h e c o o r d i n a t i o n t h r o u g h t h e t h i o c a r b o n y l

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

s p e c t r a of t h e c o m p l e x e s d u e to t h e U M - N , i/M-S a n d ^ M - C l

134

-1 (99)

f r e q u e n c i e s lie in • the r a n g e of 500 - 200 cm r e g i o n .

In d i v a l e n t c o m p l e x e s the p r e s e n c e of only one M - C l band is

i n d i c a t i v e of an o c t a h e d r a l g e o m e t r y . The l i g a n d m u s t be

b i d e n t a t e in all the c o m p l e x e s . The t r i v a l e n t c o m p l e x e s a l s o

have a c h l o r i n e b r i d g e d an o c t a h e d r a n geometry/ w i t h

c o o r d i n a t i o n t h r o u g h the n i t r o g e n atom of p y r i m i d i n e and

s u l p h u r atom of 2 - m e r c a p t o b e n z o t h i a z o l e m o l e c u l e .

The ^H NMR s p e c t r u m of the 2 , 6 - b i s ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l )

p y r i m i d i n e (Figure - XXX. ) d i s p l a y s six p e a k s in the

a r o m a t i c p r o t o n region (Table - X X X V I I ) due to the b e n z e n e

ring of 2 - m e r c a p t o b e n z o t h i a z o l e and p y r i m i d i n e m o l e c u l e . ^ ^ ^ ^ ^

The dov/nfield shift in the a r o m a t i c proton r e g i o n of the

c o m p l e x e s is due to the c o o r d i n a t i o n via the n i t r o g e n a t o m

of p y r i m i d i n e and s u l p h u r atom of 2 - m e r c a p t o b e n z o t h i a z o l e

m o i e t y .

w

2 , 6 - b i s ( 2 - m e r c a p t o b o n z o t h i a z o l y l ) p y r i m i d i n e

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140


T h e o b s e r v e d m a g n e t i c m o m e n t s (3.68 BM 5.80 BM and 5.46

BM) for the C r ( I I I ) , M n ( I I ) and F e ( I I I ) c o m p l e x e s a r e w i t h i n

the r a n g e of an o c t a h e d r a l g e o m e t r y for t h e s e c o m p l e x e s . T h e

e l e c t r o n i c s p e c t r u m of C r ( I I I ) c o m p l e x e x h i b i t s b a n d s at

20,320 c m ~ ^ and 2 4 , 6 8 0 c m ~ ^ w h i c h m a y r e a s o n a b l y be a s s i g n e d

to the ^ t r a n s i -

t i o n s . In a d d i t i o n to the c h a r g e t r a n s f e r b a n d at 3 2 , 2 5 0

cm ^ the M n ( I I ) c o m p l e x a l s o shows two b a n d s a t 1 5 , 3 8 0 cm ^

-1 4 6 and 2 3 , 800 cm a s s i g n a b l e to Tj^g(G).^: A^^^ and

4 6 E (G) A , t r a n s i t i o n s , r e s p e c t i v e l y . T h e F e ( I I I ) g ig

c o m p l e x e x h i b i t s two b a n d s at 1 5 , 3 2 0 cm and 1 8 , 9 0 0 cm ^

4 6 4 6 a s s i g n e d to T ^ ^ « A^^^. and E g ( G ) ^ A ^ ^ t r a n s i t i o n s ,

r e s p e c t i v e l y . An i n t e n s e c h a r g e t r a n s f e r b a n d at 3 2 , 3 4 0

c m ~ ^ is a l s o o b s e r v e d . ^ ^ ^ ^ ' ^

T h e room t e m p e r a t u r e m a g n e t i c m o m e n t v a l u e of C o ( I I )

c o m p l e x is 4.72 BM is s l i g h t l y l o w e r than t h e n o r m a l v a l u e

fo an o c t a h e d r a l g e o m e t r y . T h e r e a r e t w o m a i n b a n d s at

1 6 , 320 c m " ^ and 2 6 , 6 3 0 c m " ^ a s s i g n a b l e to

4 4

and T ^ g ( P ) .f T ^ g ( F ) t r a n s i t i o n s , r e s p e c t i v e l y b e s i d e a

c h a r g e t r a n s f e r b a n d a p p e a r i n g at 3 3 , 3 4 0 cm

T h e N i ( I I ) c o m p l e x s h o w s two s t r o n g band at 18,550 c m ~ ^

and 26 , 320 c m ~ ^ a s s i g n e d to ^ T ^ g ( F ) < ^ A 2 y ( F ) and 3 3 t r a n s i t i o n s , r e s p e c t i v e l y for an

o c t a h e d r a l g e o m e t r y a r o u n d the m e t a l i o n . T h e m a g n e t i c

1 4 1

m o m e n t 3.09 BM is a l s o c o n s i s t e n w i t h the a c c e p t e d v a l u e f o r

an o c t a h e d r a l g e o m e t r y . ^

T h e C u d i ) c o m p l e x s h o w s a s t r o n g band at 1 3 , 3 3 0 c m ~ ^

2 2

a s s i g n a b l e to '^2g * ^g t r a n s x t i o n . T h e m a g n e t i c m o m e n t

v a l u e of 1.85 BM o b s e r v e d for t h e C u ( I I ) c o m p l e x a l s o

s u p p o r t s an o c t a h e d r a l g e o m e t r y . In t h e c a s e of R u ( I I I ) and

R h ( I I I ) c o m p l e x e s the m a g n e t i c m o m e n t s v a l u e of 3.02 BM and

3.06 BM r e s p e c t i v e l y i n d i c a t e s an o c t a h e d r a l g e o m e t r y . T h e

e l e c t r o n i c s p e c t r u m of t h e R u ( I I I ) c o m p l e x e x h i b i t s only o n e -1 2 2

b a n d at 1 9 , 350 cm c o r r e s p o n d i n g to '^2g

t i o n . H o w e v e r t h e R h ( I I I ) c o m p l e x s h o w s t w o b a n d s at 1 6 , 5 5 0

cm ^ and 2 1 , 300 c m ~ ^ a s s i g n e d to ^Îg

^Îg t r a n s i t i o n s for an o c t a h e d r a l s t r u c t u r e

i n v o l v i n g c h l o r i n e b r i d g e s as p r o p o s e d in f i g u r e - X X X I ,

T h e c o m p l e x e s of P d ( I I ) and P t ( I V ) a r e d i a m a g n e t i c as

e x p e c t e d . T h e P t ( I V ) c o m p l e x s h o w s t h r e e m a i n b a n d s at

1 9 , 2 3 0 c m ~ ^ , 2 1 , 5 4 0 c m ~ ^ and 2 6 , 6 6 0 c m " ^ a s s i g n e d to

Âg and t r a n s i t i o n s ,

r e s p e c t i v e l y for an o c t a h e d r a l g e o m e t r y . P d ( I I ) d i s p l a y s

t h r e e m a i n b a n d s (Table X X X V I I ) c h a r a c t e r i s t i c of a s q u a r e

p l a n a r g e o m e t r y a r o u n d P d ( I I ) i o n .

142

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EH EH x: E-I x: < CQ W x; < s: < CO x; Eh EH EH X: u (N u 1—1 rH 1 rH u CO U rH rH U 00 00 , H u

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Complexes of 2-(2'-mercaptobenzothiazolyl)benzoxazole

145

Experimental

P r e p a r a t i o n of 2 - ( 2 ' - m e r c a p t o b e n z o t h i o z o l y l ) b e n z o x a z o l e

T o a s o l u t i o n of s o d i u m s a l t of 2 - m e r c a p t o b e n z o t h i a z o l e

(8.36 g ) ( o b t a i n e d by the m e t h o d d i s c r i b e d in e a r l i e r p a g e s )

in dry e t h a n o l w a s a d d e d 5.25 m L of 2 - b r o m o b e n z o x a z o l e and

the m i x t u r e w a s r e f l u x e d for 25 m i n u t e s . A w h i t e solid w a s

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

T h i s r e a c t i o n m i x t u r e w a s r e f l u x e d w i t h s t r r i n g for a b o u t 6

h o u r s . A f t e r c o m p l e t i o n of the r e a c t i o n t h e b l a c k p r o d u c t w a s

w a s h e d w i t h e t h a n o l and d r i e d in v a c u o . T h e c r u d e p r o d u c t

w a s c h r o m a t o g r a p h c d o v e r a s i l i c a gel c o l u m n ( e l u o n t c h l o r o -

o form and h e x a n e ) for p u r i f i c a t i o n . Y i e l d 40% M . P . 210 C .


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

of the l i g a n d 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) b e n z o x a z o l e (1

m m o l ) in 50 mL dry e t h a n o l w i t h t r i v a l e n t m e t a l c h l o r i d e

( R u ( I I I ) , R h ( I I I ) , C r ( I I I ) , F e ( l I I ) and A u ( I I I ) (0.3 m m o l )

and d i v a l e n t m e t a l c h l o r i d e ( M n ( I I ) , C o ( I I ) , N i ( I l ) , C u ( I I ) ,

Z n ( l l ) , H g ( I I ) and P d ( I I ) (0.5 m m o l ) in the s a m e s o l v e n t .

T h e m i x t u r e s was h e a t e d u n d e r r e f l u x for 10 h o u r s and a f t e r

c o o l i n g to room t e m p e r a t u r e the c o l o u r e d s o l i d p r o d u c t

o b t a i n e d w a s f i l t e r e d w a s h e d w i t h w a t e r and d r i e d in v a c u o .

146


E l e m G n t a l a n a l y s e s , c o l o u r s , d e c o m o s i t i o n t e m p e r a t u r e s

and p e r c e n t yields all the c o m p o u n d s are listed in T a b l e - X X X I X .

They have been f u r t h e r c h a r a c t e r i z e d by i n f r a r e d s p e c t r a ,

^•H.NMR and u v - v i s i b l e spectra and m a g n e t i c m o m e n t m e a s u r e -

m e n t s . The c o m p l e x e s analysed as M X 2 L 2 and M 2 X g L 2 (L=2-(

2 ' - m e r c a p t o b e n z o t h i a z o l y l ) b e n z o x a z o l e , X = c h l o r i d e i o n s ,

M = m e t a l c h l o r i d e s ) and found to be i n s o l u b l e in m o s t common

o r g a n i c s o l v e n t s , but P d ( I I ) R u ( I I I ) and R h ( l I I ) c o m p l e x e s

are soluble in D M S O , w a t e r and a c e t o n i t r i l e .

The p r e s e n c e of C=S band and the a b s e n c e of any

a b s o r p t i o n bands in 3300-3100 cm ^ r e g i o n in t h e , i . r .

s p e c t r u m of s o d i u m salt of 2 ' - m e r c a p t o b e n z o t h i a z o l e

(46-47)

i n d i c a t e s t h a t the ligand is in the t h i o n e f o r m .

Sodium salt of 2 ' - m e r c a p t o b e n z o t h i a z o l e w h e n t r e a t e d with

2 - b r o m o b e n z o x a z o l e y i e l d e d a m u l t i d e n t a t e n o v e l c h e l a t i n g

c o m p o u n d 2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) b e n z o x a z o l e (Figure -

XXXO).

T h e l ; C = N , y c - N , )) C=S, \J C-S and \) C-0 f r e q u e n c i e s are

o b s e r v e d in the region 1640 c m ~ ^ , 1230 c m ~ ^ , 1050 c m ~ ^ , 820

cm ^ and 610 cm ^ in the free ligand 2 - ( 2 - m e r c a p t o b e n z o t h i a -

z o l y l ) b e n z o x a z o l e . The n e g a t i v e shift in C=N s t r e t c h i n g

f r e q u e n c y a f t e r c o m p l e x a t i o n is p r e s u m b l y due to the

c o o r d i nation via the n i t r o g e n atom of b e n z o x a z o l e m o i e t y .

The C=S s t r e t c h i n g frequency at 1050 c m ~ ^ is shifted to low

147

2 - ( 2 - m o r c a p t o b o n z o t h i a z o l y l ) b e n z o x a z o l o

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152

f r e q u e n c y r e g i o n by a b o u t 40-10 cm ^ in all the c o m p l e x e s

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

s h i f t of i)C-0 and C - S f r e q u e n c i e s is a l s o o b s e r v e d in t h e

c o m p l e x e s .

E v i d a n c e for n i t r o g e n c o o r d i n a t i o n in a l l the

c o m p l e x e s is p r o v i d e d by t h e a p p e a r e n c e of a strong new

b a n d s at 4 5 0 - 3 9 0 cm T h e b a n d s o v s o r v e d in the far i . r .

s p e c t r a in t h e r e g i o n 3 9 0 - 3 2 0 cm ^ a r e a s s i g n e d to M - S

s t r e t c h i n g f r e q u e n c i e s . A band of m e d i u m i n t e n s i t y in the

r e g i o n 330-290 cm ^ can be a s s i g n e d to M - C l s t r e t c h i n g m o d e s ,

h o w e v e r in c a s e of F e ( l I I ) , C r ( I I l ) , R u ( I I I ) and R h ( l I I )

c o m p l e x e s t w o b a n d s a t 310 c m " ^ , 290 c m ~ ^ and 320 290

cm ^ and 330 cm 310 cm ^ and 310 cm 280 cm ^ c h a r a c -

t e r i s t i c of t e r m i n a l and b r i d g i n g s t r e t c h i n g f r e q u e n c i e s

o b s e r v e d only. One M - C l m o d e s a r e f o u n d in o t h e r c o m p l e x e s

s u g g e s t i n g an o c t a h e d r a l g e o m e t r y for all the c o m p l e x e s .


T h e e l e c t r o n i c s p e c t r a l b a n d s for M n ( I I ) c o m p l e x at

1 6 , 5 5 0 " c m " ^ 2 1 , 6 3 0 c m ~ ^ and 2 4 , 5 1 0 c m ~ ^ are c o n s i s t e n t w i t h

an o c t a h e d r a l g e o m e t r y (Table - X L I ) .

T h e e l e c t r o n i c s p e c t r a b a n d s of C r ( I I I ) c o m p l e x of

2 - ( 2 ' - m e r c a p t o b e n z o t h i a z o l y l ) b e n z o x a z o l e a r e s u m m a r i z e d in

T a b l e X L I . It can be seen t h a t b a n d s a p p e a r at 1 7 , 5 5 0 cm

19,380 c m ~ ^ and 21,490 c m ~ ^ r e s p e c t i v e l y a s s i g n e d to

153

S ^ g ( F ) ^ A 2 g ( F ) t r a n s i t i o n s

c h a r a c t e r i s t i c of an o c t a h e d r a l g e o m e t r y for the C r ( I I I )

i o n . A c h a r g e t r a n s f e r band is a l s o o b s e r v e d at 3 3 , 3 0 0 cm

T h e "eff v a l u e of 5.82 BM for the F e ( I I I ) c o m p l e x as

1 4 , 3 3 0 c m " ^ , 1 9 , 5 3 0 c m " ^ and 2 4 , 5 0 0 c m " ^ a r e c o n s i s t e n t w i t h

w e l l as its e l e c t r o n i c s p e c t r u m s h o w i n g t h r e e m a i n b a n d s at

w i t h

an o c t a h e d r a l g e o m e t r y a b o u t t h e h i g h spin F e ( I I I ) c o r e . ^ ^ ^ ^ ^

T h r e e is a s t r o n g c h a r g e t r a n s f e r b a n d at 3 3 , 3 4 0 cm ^

in the C o ( I I ) c o m p l e x . O t h e r b a n d s a t 1 5 , 2 6 0 cm ^ and 2 4 , 3 3 0

c m " ^ a s s i g n e d to '^T2g(F) "^T^^CF) and ^Tj^g(F)

t r a n s i t i o n s r e s p e c t i v e l y are s u g g e s t i v e of an o c t a h e d r a l

g e o m e t r y for this c o m p l e x . H o w e v e r , t h e "eff v a l u e (4.66 B M )

for C o ( I I ) ion is very c l o s e to t h a t c a l c u l a t e d for an

o c t a h e d r a l C o ( I I ) c o m p l e x in h i g h spin s t a t e .

T h e N i ( I I ) c o m p l e x s h o w s t h r e e b a n d s at 1 1 , 5 5 0 cm

15,000 c m ~ ^ and 2 1 , 660 c m ~ ^ a s s i g n a b l e to ^ ^ ^ ^ ( F ) ^ —

^ A 2 g { F ) and ^ A ^ ^ t r a n s i t i o n for an

o c t a h e d r a l N i ( I I ) i o n . T h e ^ e f f v a l u e of 3.06 BM for N i ( I I )

in Ni (Cj^^HgN2S20 ) w i t h i n the r a n g e of an o c t a h e d r a l

g e o m e t r y . T h e e l e c t r n i c s p e c t r u m of C u ( I I ) c o m p l e x s h o w s a

s t r o n g b a n d a t 14,530 cm ^ w h i c h can be a s s i g n e d to

2 2

T ^ ^ Eg t r a n s i t i o n of C u ( I I ) in an o c t a h e d r a l c o n f i g u -

r a t i o n . T h e ^eff v a l u e of 1.99 BM (Table - X L I ) is a l s o

c o n s i s t e n t w i t h the a c c e p t e d v a l u e for an o c t a h e d r a l C u ( I I )

c o m p l e x . ^ ^ ^ ^ ^ T h e m a g n e t i c m o m e n t s s h o w s the c o m p l e x e s of

154

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155

P d ( I l ) , R h ( I I I ) and P t ( I V ) to be d i a m a g n e t i c . ^ ^ ^ ^ ^ T h e

P d ( I I ) c o m p l e x d i s p l a y s t h r e e m a i n b a n d s at 1 5 , 5 5 0 cm

1 7 , 390 cm ^ and 2 3 , 440 cm ^ a s s i g n e d to ^Îg

^ B , < Â Ê ^ A , t r a n s i t i o n s in s q u a r e p l a n a r -i-g ig g -Lg

g e o m e t r y a r o u n d P d ( I I ) i o n .

T h e R h ( I I I ) c o m p l e x s h o w t h r e e b a n d s a t 1 4 , 3 8 0 cm

1 7 , 3 3 0 cm ^ and 2 4 , 3 9 0 cm ^ c o r r e s p o n d i n g to t h e t r a n s i t i o n s

f r o m Âg g r o u n d s t a t e to and e x c i t e d s t a t e in

an o c t a h e d r a l g e o m e t r y .

T h e o b s e r v e d m a g n e t i c m o m e n t for R u ( I I I ) c o m p l e x is

3.29 BM w h i c h is n e a r l y the s a m e as t h e c a l c u l a t e d v a l u e for

the low spin R u ( I I I ) in an o c t a h e d r a l e n v i r o n m e n t . T h e

e l c t r o n i c s p e c t r u m e x h i b i t s only o n e band a t 2 0 , 9 4 0 c m ~ ^

2 2 a s s i g n e d to '^2g t r a n s i t i o n c h a r a c t e r i s t i c of an

o c t a h e d r a l g e o m e t r y for R u ( I I I ) i o n .

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CHAPTER - VI

Synthesis and characterization of complexes obtained

from 2,4,6-pyrlmidine trione derived ligand;

1,3-benzoxazolyl (2,4,6-pyrimidine trione)

159

Experimental

Materials and methods

2,4,6 p y r i m i d i n e t r i o n e ( K o c h - L i g h t ) 2 - b r o m o b e n z o x a z o l e

( A l d r i c h ) s o d i u m h y d r i d e (80% s u s p e n s i o n in o i l ) w e r e u s e d

as s u c h . A l l m e t a l c h l o r i d e s BDH A n a l a r and J o h n s o n M a t h e y

w e r e used as r e c e i v e d .

Preparation of sodium salt of 2,4,6 pyrimidine trione

T o a s o l u t i o n - of 12.8 g of 2 , 4 , 6 p y r i m i d i n e

t r i o n e in 150 m L d r y e t h a n o l , 12.0 g of s o d i u m h y d r i d e w a s

a d d e d . T h e r e a c t i o n m i x t u r e w a s s t i r r e d o v e r n i g h t at r o o m

t e m p e r a t u r e . A f t e r h e a t i n g u n d e r r e f l u x for 12 h o u r s a l i g h t

p i n k solid s o d i u m s a l t of 2,4,6 p y r i m i d i n e t r i o n e w a s

o b t a i n e d , w h i c h w a s r e c r y s t a l l i z e d f r o m e t h a n o l . Y i e l d 6 5 % ,

M . P . 320°C.

P r e p a r a t i o n of 1,3 b e n z o x a z o l y K 2 , 4 , 6 p y r i m i d i n e t r i o n e )

An e t h a n o l i c s o l u t i o n of 8.60 g s o d i u m s a l t of 2,4,6

p y r i m i d i n e t r i o n e w a s a d d e d g r a d u a l l y t o a s o l u t i o n of 14.4

m L 2 - b r o m o b e n z o x a z o l e in same s o l v e n t . T h e c o l o u r of the

s o l u t i o n c h a n g e d from l i g h t pink to d a r k y e l l o w . T h i s r e s u l -

ting s o l u t i o n was r e f l u x e d on vv'ater bath for t w e n t y four

h o u r s . On a d d i t i o n of 50 m L w a t e r , p i n k c r y s t a l l i n e solid

a p p e a r e d , w h i c h w a s f i l t e r e d and r e c r y s t a l l i z e d f r o m ethanol.

Yield 35% M . P . 140.° C .

160


T h e c o m p l e x e s of 1,3 b e n z o x a z o l y l ( 2 , 4 , 6 - p y r i m i d i n e

t r i o n e ) w e r e p r e p a r e d by m i x i n g the c o r r e s p o n d i n g m e t a l

h a l i d e and the l i g a n d in a e q u i m o l a r r a t i o (1:2 in c a s e of

M C I 2 and 1:3 in c a s e of M C l ^ ) in dry e t h a n o l . In e a c h c a s e

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

h e a t i n g t h e r e a c t i o n m i x t u r e u n d e r r e f l u x . T h e solid w a s

k e p t o v e r n i g h t and f i l t e r e d . It w a s w a s h e d w i t h e t h a n o l and

d r i e d in v a c u o . T h e c o l o u r s , m e l t i n g p o i n t s and y i e l d s of

the c o m p l e x e s are g i v e n in (Table - X L I I ) .

161


S o d i u m salt of 2,4,u p y r i m i d i n e t r i o n e w a s p r e p a r e d by

h e a t i n g the s t o i c h i o m e t r i c a m o u n t of 2,4,6 p y r i m i d i n e t r i o n e

in e t h a n o l w i t h s o d i u m h y d r i d e . T h e p r o g r e s s of the r e a c t i o n

w a s f o l l o w e d by m e a s u r i n g t h e v o l u m e of • h y d r o g e n gas

e v o l v e d . T h i s s o d i u m s a l t of 2,4,6 p y r i m i d i n e t r i o n e was

f u r t h e r t r e a t e d w i t h 2 - b r o m o b e n z o x a z o l e r e s u l t i n g in the

f o r m a t i o n of 1,3 b e n z o x a z o l y l (2,4,6 p y r i m i d i n e t r i o n e )

l i g a n d (Figure X X X V ) . T h e c o m p l e x e s w e r e p r e p a r e d by

i n t e r a c t i o n of l i g a n d w i t h e q u i v a l e n t a m o u n t of m e t a l ( l l )

and m e t a l ( I I I ) c h l o r i d e s . A c o l o u r e d p r e c i p i t a t e w a s

o b t a i n e d in h i g h y i e l d s . T h e c o m p l e x e s w e r e not s o l u b l e in

c o m m o n o r g a n i c s o l v e n t s . T h e h i g h m e l t i n g p o i n t and i n s o l u -

b i l i t y of the c o m p l e x e s in u s u a l s o l v e n t s s h o w s t h a t they

a r e p o l y m e r i c in n a t u r e .

T h e i . r . s p e c t r u m of s o d i u m s a l t of 2,4,6 p y r i m i d i n e

t r i o n e c o n t a i n s a n u m b e r of a b s o r p t i o n b a n d s b u t it d o e s n o t

s h o w any a b s o r p t i o n b a n d in 3 3 0 0 - 3 1 0 0 c m ~ ^ r e g i o n i n d i c a t i o n

r e m o v a l of h y d r o g e n s from b o t h the N-H g r o u p s . It a l s o s h o w s

t h r e e b a n d s at 1900 cm 1800 cm ^ and 1660 cm ^ i n d i c a t i n g

(129)

p r e s e n c e of C = 0 s t r e t c h i n g f r e q u e n c y . T h e s h i f t of

k e t o n i c g r o u p a f t e r c o m p l e x a t i o n to l o w e r f r e q u e n c y by a b o u t

100 - 50 cm ^ s u g g e s t s the f o r m a t i o n of an o x y g e n m e t a l

b o n d . ^ ^ A s i m i l a r s h i f t was a l s o o b s e r v e d in C=N

f r e q u e n c y d u e to c o o r d i n a t i o n via n i t r o g e n a t o m of b e n z o x a -

162

0 ,0

Na' n 0

Na

Sodium salt of 2,4,6-pyriinidinetrione

2-bromobenzoxazole

Figure XXXIV

1,3 benzoxazolyl(2,4,6-pyrinidino ^^nXone.

F i g u r e X X X V

163

z o l e . E v i d e n c e for n i t r o y c n c o o r d i n a t i o n in b o t h c o m p l e x e s

is p r o v i d e d by the a p p e a r e n c e of a new b a n d a t 4 0 0 - 4 5 0 cm }

O x y g o n c o o r d i n a t i o n is a l s o i n d i c a t e d by the a p p e a r e n c e of a

s t r o n g b r o a d new b a n d at 5 0 0 - 4 5 0 cm ^ in t h e i . r . s p e c t r u m .

T h e s e b a n d s c ould r e a s o n a b l y be a s s i g n e d to the m e t a l o x y g e n

. . u- ^ ( 1 3 1 - 1 3 2 ) -p . and M - N s t r e t c h i n g f r e q u e n c y . In t h e i . r . s p e c t r a

of the t r i v a l e n t c o m p l e x e s b o t h t e r m i n a l a n d b r i d g i n g M - C l

f r e q u e n c i e s are o b s e r v e d at 3 0 0 - 2 5 0 cm T h u s an o c t a h e d r a l

s t r u c t u r e i n v o l v i n g h a l o g e n b r i d g i n g is p r o p o s e d for t h e s e

c o m p l e x e s . T h e a p p e a r e n c e of o n l y o n e M - C l b a n d in d i v a l e n t

c o m p l e x e s a l s o s u g g e s t s an o c t a h c d r a l g e o m e t r y . ^ ^ ^ ^ ^

T h e o b s e r v e d m a g n e t i c m o m e n t s 3.80 BM and 5.82 BM for

t h e C r ( I I I ) and F e ( I I I ) c o m p l e x e s r e s p e c t i v e l y w i t h i n t h e

r a n g e for an o c t a h e d r a l g e o m e t r y . T h e e l e c t r o n i c s p e c t r u m of

C r ( I I I ) c o m p l e x e x h i b i t s b a n d s a:t 1 6 , 330 cm 2 1 , 540 cm ^

and 2 3 , 300 cm ^ w h i c h m a y r e a s o n a b l y be a s s i g n e d to

S ^ ^ ( F ) « S g ^ ^ ) S g ^ ^ )

4 4

Tj g ^ A 2 g ( F ) t r a n s i t i o n s , r e s p e c t i v e l y . In a d d i t i o n to

t h e c h a r g e t r a n s f e r b a n d , t h e F e ( I I I ) c o m p l e x a l s o s h o w s

ligand f i e l d b a n d s at 1 6 , 3 5 0 c m ~ ^ , 1 9 , 5 3 0 c m ~ ^ and 2 6 , 8 6 0 -1 4 6 4 6

cm a s s i g n a b l e to 'îg^^') I g ' Îg

'^T^g(P) < '^Îg t r a n s i t i o n s r e s p e c t i v e l y . ^ ^

T h e m a g n e t i c m o m e n t s 5.70 B M , 4.58 B M , 3.02 BM and 1.90

BM o b s e r v e d for M n ( I I ) , C o ( I I ) , N i ( I I ) and C u ( I I ) c o m p l e x e s

r e s p e c t i v e l y i n d i c a t e an o c t a h e d r a l g e o m e t r y as has b e e n

164

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found in s i m i l a r o t h e r c a s e s . In t h e c a s e of M n ( I I ) c o m p l e x ,

the e l e c t r o n i c s p e c t r u m e x i h i b i t s t h r e e b a n d s at 1 8 , 5 2 0 cm ^

2 1 , 3 3 0 c m " ^ and 2 8 , 990 c m ~ ^ c o r r e s p o n d i n g to ^T^^g (G) ( S)

^ T ^ g C G ) and "Â^^CG) t r a n s i t i o n s ,

r e s p e c t i v e l y . T h e C o ( I I ) c o m p l e x shows t h r e e b a n d s at 1 0 , 5 3 0

cm 1 6 , 950 cm ^ and 1 8 , 8 7 0 cm ^ w i t h a c h a r y e t r a n s f e r

band at 35,330 cm ^ r e s p e c t i v e l y . T h e N i ( l l ) c o m p l e x has

a l s o been fou nd to e x h i b i t o n l y t h r e e b a n d s at 1 3 , 1 6 0 cm

1 5 , 550 c m ~ ^ and 2 1 , 3 3 0 c m ~ ^ a s s i g n e d to ^ T 2 g ( F )

^T^g(F) ^"Îg^^^ transitions

r e s p e c t i v e l y .

The Cu(II) complex shows a strong band at 19,300 cm ^

t o g e t h e r vîth a s h o u l d e r a t 1 3 , 3 3 0 cm ^ a s s i g n e d to

2 2 2 2 Bj^g and E^ Bj^^ transitions respectively for

an o c t a h e d r a l s t r u c t u r e .

T h e êff v a l u e (3.09 B M ) for R u ( I I I ) c o m p l e x lies in

the n o r m a l r a n g e for an o c t a h e d r a l g e o m e t r y . T h e d i f f u s e

r e f l e c t a n c e s p e c t r u m of R u ( I I I ) c o m p l e x e x h i b i t s one m a i n

b a n d at 1 5 , 500 cm ^ a s s i g n a b l e to t r a n s i t i o n .

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

Rh(III), Pd(II) and Pt(IV) to be diamagnetic. The electronic

s p e c t r u m of the R h ( I I I ) c o m p l e x d i s p l a y s t h r e e m a i n b a n d s at

1 4 , 3 0 0 21,330 c m ~ ^ and 25,500 c m ~ ^ a s s i g n e d to

^ ^ I g ' ^"Îg^ ^Îg ^"Îg^^ ^ ^ I g t r a n s i t i o n s

r e s p e c t i v e l y .

203

T h e a b s o r p t i o n b a n d s in the e l e c t r o n i c s p e c t r u m of

P t ( I V ) c o m p l e x is o b s e r v e d at 1 3 , 5 6 0 c m " ^ , 2 1 , 5 3 0 c m ~ ^ and

2 7 , 6 3 0 c m ~ ^ w i t h an i n t e n s e c h a r g e t r a n s f e r at 3 5 , 0 0 0 c m " ^

(Table - X L I V ) i n d i c a t i v e an o c t a h e d r a l g e o m e t r y . ^ ^ ^ ^ ^

T h e P d ( I I ) c o m p l e x d i s p l a y s b a n d s in t h e r e g i o n 2 1 , 3 0 0

cm ^ 2 7 , 5 3 0 cm ^ and 2 9 , 3 0 0 cm ^ c o r r e s p o n d i n g to t h e

t r a n s i t i o n s from t h e ^ A , g r o u n d state- to the , ^ B , Ig ^ 2 g ' Ig

and Eg e x c i t e d states in s q u a r e p l a n a r g e o m e t r y .

170

M = Nn(II), Co(II), Ni(ll), Cu(II), Zn(II) and Ily(II)

M = Cr(III), Fo(III), Rh(lII) and Ru(III)

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P h y s i c a l m e a s u r e m e n t s

T h e e l e m e n t a l a n a l y s e s in a l l the c a s e s w e r e c a r r i e d

out w i t h a T h o m a s and C o l e m a n a n a l y s e r , C a r l o - E r b a 1 1 0 6 .

C h l o r i n e and s u l p h u r w e r e e s t i m a t e d g r a v i m e t r i c a l l y . ^ ^ ^ ^ ^

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

a g a i n s t E D T A . ^ ^ ^ ^ ^ D i f f u s e r e f l e c t r a n c e s p e c t r a w e r e

r e c o r d e d on a C a r l - Z e i s s V S U - 2 p s p e c t r o p h o t o m e t e r . IR

s p e c t r a w e r e r e c o r d e d in K B r and N u j o l in 4 0 0 0 - 2 0 0 c m ~ ^

r e g i o n on a P e r k i n E l m e r g r a t i n g s p e c t r o p h o t o m e t e r m o d e l 621

and F T I R S o m e n M i c h e l s o n - 1 2 0 . ^H NMR s p e c t r a in D M S O { d g )

w e r e o b t a i n e d on a v a r i a n V X R - 2 0 0 M H z F T - N M R s p e c t r o m e t e r ,

M a g n e t i c m o m e n t s w e r e m e a s u r e d by a v i b r a t i n g s a m p l e

m a g n e t o m e t e r m o d e l 155 at r o o m t e m p e r a t u r e . T h e c o n d u c t a n c e s

of the s o l u t i o n of the c o m p l e x e s in D M S O w e r e m e a s u r e d at

room t e m p e r a t u r e e m p l o y i n g a S y s t r o n i c s 321 c o n d u c t i v i t y

b r i d g e .

174

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177

5 0 . B . L o e b , I. C r i v e l l i and C . A n d r a d e , . S y n t h . R e a c t . I n o r g . M e t . - O r g . C h e m . , 2 1 , 331 ( 1 9 9 1 ) .

5 1 . M . A . C i r i a n o , J . J . P e r e z - T o r r e n t e , F . J . L a h o z and L . A . O r o , I n o r g . C h e m . , 3 1 , 969 ( 1 9 9 2 ) .

5 2 . J . B . C o t t o n , I n t . C o n g r . M e t a l C o r r o s i n , 2nd e d . N e w Y o r k , 196 6 P a g e 5 9 0 .

5 3 . J . B . C o t t o n and I . R . S c h o l e s , B r i t . C o r r o s . J., 2 , 1 ( 1 9 6 7 ) .

5 4 . F . A . R o b i n s o n 'The V i t a m i n B C o m p l e x ' , C h a p m a n and H a l l L t d . L o n d o n , 1 9 5 1 p a g e 5 3 3 .

5 5 . S . A . A . Z a i d i , A . S . F a r o o q i and N . S i n g h a l , A c t a . C h i m . A c a d . S c i . H u n g . , 94 5 1 ^ ( 1 9 7 7 ) .

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