Chemistry of Alkoxo Complexes, Part III * Synthesis and...

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Chemistry of Alkoxo Complexes, Part III * Synthesis and Characterization of Some Mono(carboxylato)mono (alkoxo)nickel(II) Complexes

B . P . B a r a n w a l , G . K . P a r a s h a r , a n d R . C . M e h r o t r a

Chemical Laboratories, University of Delhi, Delhi-110007, India

Z. Naturforsch. 34b, 459-473 (1979); received November 29, 1978

Nickel Alkoxides, Carboxylic Acids, Nickel A l k o x o Carboxylates, Molecular Weights, I R

A number of mono(carboxylato )mono(a lkoxo)nicke l ( I I ) complexes of the general for-mula, N i ( O R ) ( O O C R ' ) , (with R ' = C13H07, C15H31 and C17H35) have been synthesized (where R = Me and Pr») b y the reactions o f nickel methoxide and isopropoxide with the respective carboxyl ic acids in equimolar ratio and (where R = E t and Bu<) by alcohol interchange reactions. A study of the molecular weight, infra-red and electronic reflect-ance spectra and magnetic susceptibility in addition to elemental analyses has been carried out to throw some light on the probable structure of these derivatives.

E x t e n s i v e s t u d i e s h a v e b e e n c a r r i e d o u t o n m e t a l

c a r b o x y l a t e s a n d s e v e r a l r e v i e w s [ 1 - 4 ] h a v e b e e n

p u b l i s h e d d u r i n g t h e l a s t t w o d e c a d e s . F o l l o w i n g

t h e first s u c c e s s f u l s y n t h e s i s o f a l u m i n i u m tr i -

c a r b o x y l a t e s f r o m a l u m i n i u m i s o p r o p o x i d e [5], t h e

m i x e d a l k o x y c a r b o x y l a t e s o f a n u m b e r o f m e t a l s [6]

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

s t r u c t u r a l p o i n t s o f v i e w . A p e r u s a l o f t h e l i t e r a t u r e

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

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

c a r b o x y l a t e s o f e a r l i e r t r a n s i t i o n e l e m e n t s [viz. T i ,

Z r a n d V ) [ 7 - 9 ] , a l m o s t n o w o r k h a s b e e n d o n e o n

s imi lar d e r i v a t i v e s o f t h e l a t t e r ones .

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

t o i n v e s t i g a t e t h e r e a c t i o n s o f n i c k e l (a t y p i c a l l a t t e r

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

I t h a s b e e n f o u n d t h a t t h e s e r e a c t i o n s a r e q u i t e

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

g e n e r a l f o r m u l a , N i ( O R ) ( O O C R ' ) a n d t h e a n h y d r o u s

d i c a r b o x y l a t e s , N i ( O O C R ' ) 2 a c c o r d i n g t o t h e m o l a r

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

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

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

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

Experimental

A l l g l a s s a p p a r a t u s w i t h i n t e r c h a n g e a b l e q u i c k f i t j o i n t s w e r e u s e d t h r o u g h o u t . E x t r e m e p r e c a u t i o n s w e r e t a k e n t o e x c l u d e m o i s t u r e . B e n z e n e a n d a l c o -

* Part I I : Transition Met. Chem. 3, 220 (1978). Requests for reprints should be sent to Pro f . R . C. Mehrotra, Department o f Chemistry, Delhi University, Delhi-110007, India. 0340-5087/79/0300-0459/$ 01.00/0

hols w e r e d r i e d b y t h e l i t e r a t u r e p r o c e d u r e s [10]. T h e c a r b o x y l i c a c i d s w e r e u s e d a f t e r d i s t i l l a t i o n . N i c k e l a l k o x i d e s w e r e p r e p a r e d f r o m a n h y d r o u s n i c k e l c h l o r i d e a n d t h e a p p r o p r i a t e l i t h i u m a l k o x i d e .

I n f r a - r e d s p e c t r a w e r e r e c o r d e d o n a P e r k i n -E l m e r 621 I R s p e c t r o p h o t o m e t e r u s i n g K B r p e l l e t s . V i s i b l e r e f l e c t a n c e s p e c t r a o f s o l i d c o m p l e x e s (in N u j o l m u l l ) a n d in b e n z e n e s o l u t i o n w e r e r e c o r d e d o n a R u s s i a n c O - l O r e c o r d i n g s p e c t r o p h o t o m e t e r a n d n e a r I R s p e c t r a o n a P e r k i n - E l m e r 4000 A . M o l e c u l a r w e i g h t s w e r e d e t e r m i n e d in a s e m i - m i c r o e b u l l i o m e t e r ( G a l l e n k a m p ) w i t h a t h e r m i s t o r sens-i n g d e v i c e . 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 w e r e m a d e a t r o o m t e m p e r a t u r e b y s t a n d a r d G o u y m e t h o d in b e n z e n e s o l u t i o n .

N i c k e l w a s e s t i m a t e d g r a v i m e t r i c a l l y a s i t s di-m e t h y l g l y o x i m e c o m p l e x a n d a l c o h o l s , b y a n o x i -d i m e t r y m e t h o d [ 1 1 ] .

Reactions of nickel alkoxides with carboxylic acids

T o w e i g h e d a m o u n t s (3 g) o f n i c k e l a l k o x i d e s s u s p e n d e d i n b e n z e n e ( ~ 5 0 m l ) w e r e a d d e d t h e r e q u i r e d p r o p o r t i o n s o f t h e c a r b o x y l i c a c i d s . T h e r e a c t i o n m i x t u r e s w e r e r e f l u x e d f o r 1 0 - 1 2 h w i t h s l o w a n d c o n t i n u o u s f r a c t i o n a t i o n o f t h e l i b e r a t e d a l c o h o l s a z e o t r o p i c a l l y w i t h b e n z e n e . I n c o n t r a s t t o t h e a l k o x i d e s , b o t h t h e m o n o - a s w e l l a s d i c a r b -o x y l a t e d e r i v a t i v e s are s o l u b l e i n b e n z e n e . T h e e x c e s s s o l v e n t w a s r e m o v e d u n d e r r e d u c e d pres-sure . T h e e x p e r i m e n t a l r e s u l t s a r e s u m m a r i s e d in T a b l e I .

Alcohol interchange reactions T h e i n t e r c h a n g e of t h e i s o p r o p o x y in

N ^ O P r ^ O O C R ) b y e t h o x y g r o u p s w a s v e r y f a c i l e a n d c o u l d b e a c h i e v e d b y s t i r r i n g t h e i s o p r o p o x y d e r i v a t i v e w i t h e x c e s s e t h a n o l f o r a b o u t 1 5 m i n a t r o o m t e m p e r a t u r e . T h e c o r r e s p o n d i n g r e p l a c e m e n t o f t h e i s o p r o p o x y b y t e r t i a r y b u t o x y g r o u p s w a s v e r y s l o w a n d c o u l d be a c c o m p l i s h e d o n l y b y con-t i n u o u s f r a c t i o n a t i o n o f a l c o h o l - b e n z e n e a z e o t r o p e f o r a b o u t 5 h f r o m a r e f l u x i n g r e a c t i o n m i x t u r e o f

460 B. P. Baranwal et al. • Chemistry o f A lkoxo Complexes

Table I. React ions of nickel alkoxides with carboxyl ic acids.

A m o u n t o f alcohol Analysis [ % ] .Mnl. Alkoxide Carboxyl ic Molar Product and state in azeotrope [g] nickel a lkoxy Wt.* [g] acid [g] ratio found found found [g] acid [g]

f ound calcd (calcd) (calcd) (calcd)

Ni(OMe)2 CI 3 H 2 7 COOH 1:1 Ni(OMe)(OOC.Ci 3H 2 7 ) 0.93 0.99 18.41 9.58 1246 (3.72) (7.03) light green solid (18.51) (9.80) (317) Ni(OPr*)2 CI 3 H 2 7 COOH 1:1 Ni(OPri)(OOC.Ci3H27) 1.44 1.50 17.42 16.93 1410 (4.43) (5.72) green solid (17.00) (17.12) (345) Ni(OMe)2 C15H31COOH 1:1 Ni(OMe)(OOC.C1 5H3 i ) 0.24 0.26 16.88 8.66 1358 (0.96) (2.04) light green solid (17.00) (9.00) (345) Ni(OPr ' ) 2 C15H31COOH 1 :1 Ni(OPrO(OOC.Ci5H3 i ) 1.27 1.28 15.60 15.80 1461 (3.86) (5.45) light green solid (15.73) (15.84) (373) Ni(OMe)2 C17H35COOH 1:1 Ni(OMe)(OOC.C1 7H3 5 ) 0.36 0.38 15.68 8.12 -

(1.44) (3.39) light green solid (15.73) (8.33) Ni(OPri)2 C17H35COOH 1 :1 Ni(OPri) (OOC.Ci 7H 3 5 ) 0.96 0.99 14.46 14.53 -

(2.91) (4.68) green solid (14.63) (14.72) Ni(OPr»)2 C 1 3 H 2 7 COOH 1 : 2 Ni(OOC.CI3H2 7 )2 1.13 1.15 11.45 1502 (1.70) (4.39) green solid (11.43) (513) Ni(OPr»)2 CISHSICOOH 1 : 2 Ni(OOC.C1 5H3I)2 1.35 1.39 10.21 1676 (2.04) (5.92) light green solid (10.30) (570)

* In boiling benzene (20 ml) .

N i ( 0 P r * ) ( 0 0 C R ) d i s s o l v e d i n b e n z e n e w i t h e x c e s s o f t e r t i a r y b u t a n o l . R e s u l t s are s u m m a r i z e d i n T a b l e I I .

Results and Discussion

R e a c t i o n s o f n i c k e l ( I I ) m e t h o x i d e a n d i soprop-

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

a c i d s h a v e b e e n c a r r i e d o u t in d i f f e r e n t s to ichio-

m e t r i c r a t i o s u s i n g b e n z e n e as s o l v e n t . T h e s e

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

( ~ 1 0 h ) w i t h c o n t i n u o u s f r a c t i o n a t i o n a n d t h e i r

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

a l c o h o l c o n t e n t in t h e a z e o t r o p e c o l l e c t e d . M o n o - as

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

q u a n t i t a t i v e y i e l d s ( T a b l e I) . T h e r e a c t i o n s c a n b e

d e p i c t e d a s f o l l o w s :

b e n z e n e

N i ( O R ) 2 + w R ' C O O H >-

N i ( O R ) 2 _ „ ( O O C R ' ) w + w R O H

( w h e r e R = M e a n d P r * ; R ' = C i 3 H 2 7 , C15H31 a n d C17H35 a n d n= 1 - 2 )

T h e i n c r e a s i n g s t a b i l i t y o f t e r t i a r y b u t o x i d e , iso-

p r o p o x i d e a n d e t h o x i d e ( m e t h o x i d e ) d e r i v a t i v e s

a p p e a r s t o r e s u l t in r e a d y r e p l a c e a b i l i t y o f iso-

p r o p o x y b y e t h o x y ( m e t h o x y ) g r o u p s a t r o o m

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

b y t e r t i a r y g r o u p r e q u i r e d r e f l u x i n g f o r a b o u t 5 h

w i t h c o n t i n u o u s f r a c t i o n a t i o n of i s o p r o p a n o l pro-

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

d e r i v a t i v e s , t h e m e t h o x y a n d e t h o x y d e r i v a t i v e s d o

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

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

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

f o r t h e d i a l k o x i d e s o f n i c k e l [12], i n w h i c h a l so t h e

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

a l k o x y g r o u p s w h e r e a s m e t h o x i d e a n d e t h o x i d e

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

i n t e r c h a n g e . S u c h s h a r p d i f f e r e n c e s i n t h e r e p l a c e -

a b i l i t y o f t h e a l k o x y g r o u p s a p p e a r s t o b e a n u n i q u e

o b s e r v a t i o n i n t h e a l k o x i d e c h e m i s t r y . G e n e r a l

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

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

m e t a l s e.g., g a l l i u m [13] , t i t a n i u m [14] a n d z irco-

n i u m [15] a l k o x i d e s , w h e r e t h e a l c o h o l i n t e r c h a n g e

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

w h a t s i m i l a r o b s e r v a t i o n s [ 15] w e r e f o u n d i n t h e

case o f i n t e r c h a n g e o f Z r ( O M e )4 a n d Z r ( O E t ) 4 w i t h

B u ' O H l e a d i n g f i n a l l y t o Z r ( O M e ) ( O B u ' ) s a n d

Z r ( O E t ) 2 ( O B u < ) 2 ; t h i s w a s e x p l a i n e d o n t h e b a s i s o f

s ter ic f a c t o r s a s t h e m i x e d a l k o x i d e s are inter-

m o l e c u l a r l y a s s o c i a t e d w h e r e a s t h e t e t r a - t e r t i a r y

b u t o x i d e is m o n o m e r i c . I n v i e w o f t h e t e t r a m e r i c

n a t u r e o f a l l t h e m o n o - a l k o x i d e m o n o - c a r b o x y l a t e

d e r i v a t i v e s N i ( O R ) ( O O C R ' ) o f n i c k e l , t h e o n l y

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

t h e a l c o h o l y s i s r e a c t i o n s a p p e a r s t o ar ise f r o m t h e

c o m p a r a t i v e s t r e n g t h s o f N i - O R b o n d s .

A l l t h e d e r i v a t i v e s i s o l a t e d d u r i n g t h e p r e s e n t

i n v e s t i g a t i o n a r e n o n - v o l a t i l e c o l o u r e d sol ids. N i c k e l

461 B. P. Baranwal et al. • Chemistry of Alkoxo Complexes

a l k o x y c a r b o x y l a t e s are s o l u b l e in b e n z e n e a n d

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

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

b e n z e n e so lut ion . O n r e c r y s t a l l i s a t i o n f r o m t h e

b e n z e n e - a l c o h o l m i x t u r e , a d d u c t s w i t h t h e f o r m u l a

N i ( O R ) ( O O C R ' ) . R O H are o b t a i n e d . N i c k e l di-

c a r b o x y l a t e s a lso g i v e a d d u c t s , N i ( O O C R ) 2 . R ' O H

o n r e c r y s t a l l i s a t i o n f r o m b e n z e n e - a l c o h o l m i x t u r e s ,

w h i c h a r e so luble in b e n z e n e b u t i n s o l u b l e in a lco-

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

l o s t a t ~ 1 1 0 ° C / 1 . 0 m m l e a v i n g t h e m o n o - a l k o x y

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

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

Infrared spectra I n f r a r e d s p e c t r a o f a l l t h e d e r i v a t i v e s ,

N i ( O R ) ( O O C R ' ) , N i ( O R ) ( O O C R ' ) . R O H a n d

N i ( O O C R ' ) 2 w e r e r e c o r d e d i n t h e r a n g e 4000 t o

400 c m r 1 w i t h K B r pe l le ts . I n t h e s p e c t r a o f a l l t h e

a b o v e d e r i v a t i v e s n o b a n d w a s o b s e r v e d i n t h e

r e g i o n 3600-3000 c m - 1 i n d i c a t i n g t h e c o m p l e t e

a b s e n c e o f O - H s t r e t c h i n g v i b r a t i o n s [16]. A s t r o n g

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

a p p e a r s a t ~ 9 3 5 c m - 1 in t h e s p e c t r a o f f r e e c a r b -

o x y l i c a c i d s , w a s a lso f o u n d c o m p l e t e l y m i s s i n g in

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

c a r b o n y l s t r e t c h i n g b a n d (ar is ing a t ~ 1 7 1 0 c m - 1 in

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

t h e a p p e a r a n c e o f a n e w s t r o n g b a n d a t ~ 1 5 6 0 c m - 1

w h i c h m a y be a s s i g n e d t o a n t i s y m m e t r i c C - 0

s t r e t c h i n g v i b r a t i o n s (vs) [17] . I t d o e s i n d i c a t e t h e

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

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

w i t h e i t h e r one a n d t h e s a m e m e t a l i o n ( b i d e n t a t e

c o o r d i n a t i o n ) or w i t h a n o t h e r m e t a l ( b r i d g i n g co-

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

a n t i s y m m e t r i c a n d s y m m e t r i c C - 0 s t r e t c h i n g

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

t h a t o f a c e t a t e i o n [18, 19].

I n t h e a c e t a t e ion , C H 3 C < ^ , t h e t w o C - 0 b o n d s

a r e s u p p o s e d t o be e q u i v a l e n t a n d t h e a n d

f r e q u e n c i e s a p p e a r a t ~ 1 5 7 8 a n d ~ 1 4 3 5 c m - 1 [18].

I n c h e l a t i n g c o o r d i n a t i o n , R C ^ q ^ ) M , t h e b o n d i n g

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

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

w i t h t h a t in t h e a c e t a t e ion. C o n s e q u e n t l y t h e a n t i -

s y m m e t r i c C - 0 s t r e t c h i n g f r e q u e n c y (v$) d e c r e a s e s .

O n t h e o t h e r h a n d , t h e b r i d g i n g c o o r d i n a t i o n ,

R

/ C \ ° \

M M , is s u p p o s e d t o i n c r e a s e t h e O C O

a n g l e r e s u l t i n g i n t h e s u b s e q u e n t increase in t h e

a n t i s y m m e t r i c C - 0 s t r e t c h i n g f r e q u e n c y (vs) [20-22],

I n v i e w o f t h i s , t h e b e h a v i o u r o f c a r b o x y l a t e g r o u p s

in t h e p r e s e n t d e r i v a t i v e s m a y t e n t a t i v e l y b e as-

s i g n e d as c h e l a t i n g in n a t u r e . S i m i l a r b a n d s w e r e

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

c a r b o x y l a t e s , w i t h o n e s t r o n g e r b a n d a t ~ 3 0 0 0 c m - 1

w h i c h m a y b e a s s i g n e d t o t h e v O H o f t h e c o o r d i n -

a t e d a l c o h o l m o l e c u l e [17] , S o m e o t h e r v i b r a t i o n s

b e l o w 700 c m - 1 m a y b e a s c r i b e d t o N i - 0 s t r e t c h i n g

v i b r a t i o n s .

Electronic spectra and magnetic moments E l e c t r o n i c s p e c t r a o f a l l t h e d e r i v a t i v e s w e r e

r e c o r d e d i n t h e r a n g e 4000-28000 c m - 1 in N u j o l

m u l l s or i n c h l o r o f o r m a n d n o m a r k e d d i f f e r e n c e

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

n i c k e l i n a n o c t a h e d r a l e n v i r o n m e n t [23] w h i c h

e x h i b i t s t h r e e a b s o r p t i o n b a n d s 3 A 2 g -> 3 T 2 g , 3 A 2 g -> 3 T i g (F) a n d 3 A 2 g -> 3 T i g (P) o b s e r v e d a t

7 0 0 0 - 1 3 0 0 0 ( n ) , 1 1000-20000 (v2) a n d 19000 t o

27000 c m - 1 (i'3), r e s p e c t i v e l y . T h e p o s i t i o n o f t h e

o b s e r v e d a b s o r p t i o n m a x i m a , t h e p r o p o s e d ass ign-

m e n t s , t h e l i g a n d f ie ld p a r a m e t e r ( D q ) , t h e R a c a h

p a r a m e t e r (B) a n d t h e c o v a l e n c y f a c t o r (ß) a r e

s u m m a r i z e d i n T a b l e s I V , V . I t w a s o b s e r v e d t h a t

t h e l i g a n d f ie ld v a l u e i n c r e a s e s a s t h e p o l a r i t y o f

t h e a l c o h o l d e c r e a s e s . T h e p a r a m e t e r B h a s b e e n

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

[24], T h e v a l u e o f B in a l l c a s e s r e d u c e d b e l o w t h e

f r e e i o n v a l u e (1041 c m - 1 ) s h o w i n g c o n s i d e r a b l e

m e t a l l i g a n d i n t e r a c t i o n s .

M a g n e t i c m o m e n t s o f a l l t h e d e r i v a t i v e s h a v e

b e e n m e a s u r e d a t r o o m t e m p e r a t u r e a n d t h e r e s u l t s

( T a b l e s I V a n d V ) i n d i c a t e t h a t a l l t h e c o m p l e x e s

s h o w a m a g n e t i c m o m e n t o f 3 .26 ± 0.05 B . M .

w h i c h a r e n e a r l y 1 5 % h i g h e r c o m p a r e d t o a 'spin-

o n l y ' v a l u e o f 2 .83 B . M . f o r o c t a h e d r a l n i c k e l ( I I )

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

i n t e r a c t i o n i n t h e c l u s t e r [25].

Molecular weight and probable structure M o l e c u l a r w e i g h t s o f t h e a b o v e d e r i v a t i v e s w e r e

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

o r c h l o r o f o r m ( T a b l e s I—III) . T h e r e s u l t s s h o w t h a t

t h e a l k o x y c a r b o x y l a t e d e r i v a t i v e s are t e t r a m e r i c

462 B. P. Baranwal et al. • Chemistry of Alkoxo Complexes

Table II. Alcohol interchanges in alkoxy carboxylates of nickel(II).

Amount of alcohol Analysis [ % ] Mol. Compound Alcohol Product and state in azeotrope [g] nickel alkoxy wt.* [g] [ml] found found found [g] [ml]

found calcd (calcd) (calcd) (calcd)

Ni(OPri)(OOC.Ci3H27) EtOH Ni(OEt)(OOC.Ci3H27) _ _ 17.67 13.20 1341 (2.29) (25) light green solid (17.73) (13.61) (331) Ni(OPrO(OOC.Ci3H27) Bu'OH Ni(OBu<)(OOC.Ci3H27) 0.29 0.31 16.52 - 1420 (1.78) (15) light green solid (16.34) (359) Ni(OPrO(OOC.Ci5H3i) EtOH Ni(OEt)(OOC.Ci5H3i) - - 16.21 12.43 -

(1.72) (25) green solid (16.34) (12.55) Ni(OPrO(OOC.Ci5H3i) Bu<OH Ni(OBu<)(OOC.Ci5H31) 0.26 0.27 15.08 - -

(1.69) (20) green solid (15.16) Ni(OPrO(OOC.Ci7H35) EtOH Ni(OEt)(OOC.Ci7H35) - - 15.04 11.54 -

(1.70) (25) light green solid (15.16) (11.64) Ni(OPrO(OOC.C17H35) Bu<OH Ni(OBu<)(OOC.Ci7H35) 0.28 0.30 14.10 - -

(1.98) (20) green solid (14.14)

* In chloroform (20 ml).

Table III. Recrystallised products of nickel(II)alkoxy carboxylates.

Analysis [ % ] Mol. nickel alkoxy + wt.*

Compound Solvent Product and state alcohol Compound found found found (calcd) (calcd) (calcd)

Ni(OMe)(OOC.Ci3H27) MeOH Ni(OMe)(OOC.Ci3H27).MeOH 16.68 17.79 1070 green solid (16.81) (18.08) (349)

Ni(OEt)(OOC.Ci3H27) EtOH Ni(OEt)(OOC.Ci3H27).EtOH 15.47 24.02 1112 light green solid (15.56) (24.16) (377)

Ni(OEt)(OOC.Ci5H31) EtOH Ni(OEt)(OOC.Ci5H3i).EtOH 14.56 22.66 -

light green solid (14.49) (22.49) Ni(OPri)(OOC.Ci5H31) Pr'OH Ni(OPri)(OOC.Ci5H31).Pr*'OH 13.45 27.31 1276

green solid (13.55) (27.50) (433) Ni(OPri)(OOC.Ci7H35) Pri'OH Ni(OPr*")(OOC.Ci7H35).PriOH 12.81 25.40 -Ni(OPri)(OOC.Ci7H35)

light green solid (12.73) (25.82) Ni(OBu«)(OOC.C17H35) Bu'OH Ni(OBu«)(OOC.Ci7H35).Bu<OH 11.91 - 1440

green solid (12.00) (489)

* In chloroform (20 ml).

Table IV. Electronic spectra* and magnetic moments of nickel(II)alkoxy carboxylates.

Compound 3 A 2 G 3 T 2 g 3 A 2 G - * 3 T L G ( F ) 3 A 2 G - > 3 T L G ( P ) B ß /«eff (10 Dq) (V2) (vs) (B.M.)

Ni(OMe)(OOC.Ci3H27) 8585 14620 24272 687 0.84 3.25 Ni(OEt)(OOC.Ci3H27) 8 620 14705 24155 867 0.83 3.23 Ni(OPr')(OOC.Ci3H27) 8 695 14663 24155 849 0.81 3.22 Ni(OBu<)(OOC.Ci3H27) 8 695 14577 23923 828 0.79 3.25 Ni(OMe)(OOC.Ci5H31) 8 695 14705 23040 777 0.75 3.28 Ni(OEt)(OOC.Ci5H31) 8 735 14837 23474 807 0.77 3.28 Ni(OPri)(OOC.Ci5H31) 8810 14750 24038 824 0.79 3.24 Ni(OBu<)(OOC.Ci5H3i) 8 850 14860 23 923 815 0.78 3.29 Ni(OMe)(OOC.Ci7H35) 8772 14705 24510 860 0.82 3.31 Ni(OEt)(OOC.Ci7H35) 8772 14793 24272 850 0.81 3.31 Ni(OPrO(OOC.Ci7H35) 8 850 14925 24272 840 0.81 3.26 Ni(OBu<)(OOC.Ci7H35) 8 889 14880 24290 840 0.81 3.25 Ni ( 0 0 C . C i 3 H 2 7 ) 2 8 930 15015 23530 784 0.75 3.22 N i ( O O C . C i 5 H 3 I ) 2 9010 14880 23810 777 0.74 3.26

* Transitions and B in cm - 1 .

463 B. P. Baranwal et al. • Chemistry of Alkoxo Complexes

Table V. Electronic spectra* and magnetic moments of alcoholates of nickel(II)alkoxy carboxylates.

Compound 3A2 g->3T2 g 3A2g ->3Tig (F) 3A2g 3T i g (P) B ß ,ie„ (10 Dq) (v2) (vs) (B.M.)

Ni(OMe)(OOC.Ci3H27).MeOH 8 620 14 705 Ni(OEt)(OOC.Ci3H27).EtOH 8695 14837 Ni(OEt)(OOC.Ci5H3i).EtOH 8 810 14 750 Ni(OPri)(OOC.Ci5H3i).PriOH 8 889 14 705 Ni(OPri)(OOC.Ci7H35).PriOH 8 889 14 815 Ni(OBu«)(OOC.Ci7H35).Bu<OH 8 928 14 925

* Transitions and B in cm - 1 .

w h i l e t h e a l c o h o l a t e c o m p l e x e s o f t h e s e d e r i v a t i v e s

are t r i m e r i c i n n a t u r e . N i c k e l d i c a r b o x y l a t e s a r e

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

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

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

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

e n v i r o n m e n t . T h e t e t r a m e r i c n a t u r e o f t h e m o l e c u l e

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

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

24510 890 0.85 3.27 23 390 876 0.84 3.26 23 923 816 0.78 3.29 23810 790 0.76 3.23 24 390 836 0.80 3.22 24 630 851 0.82 3.21

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

t h a t s u g g e s t e d f o r t h e [ N i 4 ( O H ) 4 ] 4 + i o n [26], w i t h

t h e p o s s i b i l i t y o f n i c k e l - n i c k e l i n t e r a c t i o n s . H o w -

e v e r , t h e t r i m e r i c s t i u c t u r e s u g g e s t e d f o r t h e n i c k e l

b i s - a c e t y l a c e t o n e c o m p l e x [27], a p p e a r s t o b e m o s t

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

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

p e r n i c k e l a t o m .

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[16] L. J. Bellamy, Infrared Spectra of Complex Molecules, p. 190, Methuen, London 1975.

[17] K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, Willey-Inter Science, New York 1970.

[18] A. I. Grigorev, Russ. J. Inorg. Chem. 8, 409 (1963).

[19] E. Spinner, J. Chem. Soc. 1964, 4217. [20] N. Nakamura, J. Chem. Soc. Jpn. 79, 1411 (1958). [21] C. A. Agamber and K. G. Orrell, J. Chem. Soc. (A)

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