Characterization of Novel Antimony Compounds by Antimony-121

16 Characterization of Novel Antimony Compounds by Antimony-121 Mössbauer

Downloaded by UNIV OF MICHIGAN ANN ARBOR on May 18, 2017 | http://pubs.acs.org Publication Date: July 1, 1981 | doi: 10.1021/ba-1981-0194.ch016

Spectroscopy R. V. PARISH and O W E N PARRY Department of Chemistry, University of Manchester Institute of Science and Technology, Manchester, M60 1QD, England

The

products of

R C:N Li +

2

(R

-

reaction of

SbCl

5

with R C:NH

and

2

= phenyl or substituted phenyl) were investi-

gated. Infrared and

Sb Mössbauer spectroscopy suggest

121

that three different types of compounds are formed. type appears to be the ketiminium (δ

ca. 5.7 mm

InSb

s,

e qQ

-1

2

adventitious hydrolysis. most surprisingly, 2

2

The

s ), -1

ca. —8 mm

-1

2

an Sb-C

g

s, -1

but might otherwise have escaped

detection. The final group of compounds has mm s , e qQ

products,

This oxidation state is indicated un-

4

ca. 10 mm

g

6

derivatives, probably

InSb

e qQ

2

second group of

ambiguously by the Mössbauer spectra (δ 2

One

[R C:NH ][SbCl ]

zero), presumably formed by

g

are antimony (III)

[R C:NH ][SbCl ]. 2

salt

δ

InSb

ca. 5.3

ca. 10 mm s , consistent with the presence of -1

bond, and these materials appear to be the first

examples of o-metallated derivatives involving antimony, for example, Ph(C6H4)C:NHSbCl4.

H p h i s i n v e s t i g a t i o n arose f r o m a v i s i t to the U n i v e r s i t y of M a n c h e s t e r I n s t i t u t e of Science a n d T e c h n o l o g y b y D r . K e n W a d e of D u r h a m U n i v e r s i t y , to d e s c r i b e some w o r k h e h a d b e e n d o i n g o n complexes

of

k e t i m i n e s , R C : N H , w i t h m a i n - g r o u p acceptors ( J ) . T h e D u r h a m g r o u p 2

also w a s c o n c e r n e d w i t h the i n t e r a c t i o n of the k e t i m i n e s or t h e i r l i t h i u m derivatives, R C : N L i , w i t h S b C l 2

+

5

(2),

a n d w e suggested t h a t

1 2 1

Sb

M o s s b a u e r spectroscopy m i g h t a i d t h e c h a r a c t e r i z a t i o n of t h e p r o d u c t s . A c c o r d i n g l y , D r . W a d e sent us t e n samples for i n v e s t i g a t i o n , the M o s s b a u e r d a t a for w h i c h w e r e i n d e e d i n v a l u a b l e , as w e d e s c r i b e i n the f o l l o w i n g 0065-2393/81/0194-0361$05.00/0 © 1981 American Chemical Society

Stevens and Shenoy; Mössbauer Spectroscopy and Its Chemical Applications Advances in Chemistry; American Chemical Society: Washington, DC, 1981.

362

M O S S B A U E R S P E C T R O S C O P Y A N D ITS

C H E M I C A L APPLICATIONS

sections. A b r i e f r e v i e w of t h e M o s s b a u e r t e c h n i q u e w i t h

1 2 1

S b is g i v e n

a l s o ; m o r e d e t a i l e d treaments h a v e b e e n p r e s e n t e d b y B o w e n ( 3 ) , c r o f t a n d P i a t t (4), 121

and Greenwood and Gibb

Ban

(5).

Sb Mossbauer Spectroscopy Mossbauer

spectroscopy

with

1 2 1

Sb

is

a

frustrating

experience.

Sources u s u a l l y h a v e o n l y l o w a c t i v i t y , a n d t h e s p e c t r a are c o m p l e x a n d i n h e r e n t l y p o o r l y r e s o l v e d . I t is t e d i o u s to o b t a i n g o o d s p e c t r a .


T h e source m a t e r i a l is t h e 50-year CaSn0 .

T h i s isotope

3

[

1 2 0

Sn(n,y)

1 2 1 m

Sn],

is p r o d u c e d

by

S n , usually i n the f o r m

neutron

of

of

1 2 0

Sn

F r o m t h e h i g h e r - e n e r g y state,

S n decays d i r e c t l y t o t h e 3 7 . 2 - k e V l e v e l of

b a u e r - a c t i v e state.

irradiation

b u t t h e cross section is s m a l l a n d l o w a c t i v i t i e s are

o b t a i n e d e v e n after years of i r r a d i a t i o n . 1 2 1 m

1 2 1 m

1 2 1

S b , w h i c h is t h e M o s s -

T h e source also emits c o n s i d e r a b l e x - r a d i a t i o n , c e n

t e r e d at 26 k e V , a n d t h e n o r m a l m e t h o d of d e t e c t i o n is to m o n i t o r t h e escape p e a k ( 8 k e V )

of a n X e / C 0

2

or X e / C H

4

p r o p o r t i o n a l c o u n t e r or

a N a l ( T l ) scintillator. I n the present w o r k , a high-resolution, h y p e r p u r e g e r m a n i u m L E P S detector

(Ortec)

w a s u s e d to m o n i t o r t h e 37.2-

k e V gamma ray directly. T h e m o d e r a t e l y h i g h e n e r g y of t h e g a m m a r a d i a t i o n results i n r e l a tively small recoil-free

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

compounds.

M e a s u r e m e n t s n o r m a l l y m u s t b e m a d e at l i q u i d - n i t r o g e n t e m p e r a t u r e s or below.

M o s t of t h e d a t a r e p o r t e d h e r e refer to 4.2 K . W e h a v e w o r k e d

w i t h a v e r t i c a l - d r i v e cryostat w i t h b o t h source a n d a b s o r b e r i m m e r s e d i n l i q u i d h e l i u m . T o i m p r o v e b a s e l i n e l i n e a r i t y , t h e source w a s s t a t i o n a r y a n d t h e D o p p l e r m o t i o n w a s a p p l i e d to t h e a b s o r b e r .

kept

Isomer

shifts w e r e m e a s u r e d r e l a t i v e t o I n S b . T h e M o s s b a u e r t r a n s i t i o n is f r o m a g r o u n d state w i t h I = e x c i t e d state w i t h I =

7/2.

5 / 2 to a n

Q u a d r u p o l e i n t e r a c t i o n t h e r e f o r e gives a n

e i g h t - l i n e s p e c t r u m ( T a b l e I ; 12 l i n e s are present i f t h e e l e c t r i c g r a d i e n t is not a x i a l l y s y m m e t r i c , rj =7^ 0 ) .

Table I.

Mossbauer Transitions in

Position (mm s' ) 1

-0.3936 -0.2021 -0.1893 -0.0936 -0.0393 +0.0564 +0.0850 +0.0979

Intensity 0.0119 0.0714 0.0357 0.1191 0.2143 0.1191 0.2500 0.1786

121

field

Unfortunately, the natural

S b for e qQ = 1 . 0 0 2

g

m m s" , TJ = 1

\™i\(s) 5/2 5/2 3/2 3/2 1/2 1/2 5/2 3/2

3/2 5/2 1/2 3/2 1/2 3/2 7/2 5/2


0

16.

Antimony-121

PARISH AND PARRY

Mossbauer

363

Spectroscopy

l i n e w i d t h is l a r g e (2.1 m m s " ) , a n d f u l l y r e s o l v e d s p e c t r a are n e v e r 1

o b t a i n e d (see F i g u r e 1 ) . H o w e v e r , t h e shape of t h e b r o a d

absorption

e n v e l o p e r e a d i l y reveals t h e s i g n of t h e q u a d r u p o l e c o u p l i n g (e qQ ; 2

a

g

Q

g

constant

is t h e q u a d r u p o l e m o m e n t of t h e ground-state n u c l e u s ) , a n d

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

Computer

fitting m u s t b e m a d e w i t h e i g h t lines w h o s e positions a r e c o n s t r a i n e d b y the i s o m e r shift, e qQ ,

a n d t h e r a t i o of g r o u n d - a n d excited-state q u a d r u

pole moments

= 1.34, w h i l e t h e intensities a r e c o n s t r a i n e d t o

2

g

Q x/Q e

g


those f o r a r a n d o m p o w d e r ( T a b l e I ) . I t is therefore necessary t o g r i n d the samples c a r e f u l l y t o a v o i d o r i e n t a t i o n effects.

I f the electric

field

g r a d i e n t is not a x i a l l y s y m m e t r i c , a n a p p r o p r i a t e c a l c u l a t i o n of l i n e p o s i tions a n d intensities m u s t b e m a d e , p r e f e r a b l y b y s o l u t i o n of t h e q u a d r u p o l e H a m i l t o n i a n ( 6 ) . I n t h e present w o r k e qQ 2

is s m a l l (^ 10 m m s ' ) , 1

g

a n d t h e shape of t h e s p e c t r u m is r e l a t i v e l y i n s e n s i t i v e t o m o d e r a t e v a l u e s of t h e a s y m m e t r y p a r a m e t e r ( < c a . 0 . 6 ) ; therefore, w e h a v e u s e d o n l y the e i g h t - l i n e

fitting

procedure.

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

p r e c i s e l y ( c a . ± 0 . 0 5 m m s " ) , b u t , o w i n g t o t h e p o o r r e s o l u t i o n , e qQ 1

2

g

is

m u c h less w e l l d e f i n e d ( c a . ± 0 . 8 m m s ' o r w o r s e ) . 1

T h e shape of t h e s p e c t r u m also c a n b e affected b y t h e thickness of the s a m p l e . T h e o p t i m u m thickness is 5 - 1 0 m g c m " of n a t u r a l a n t i m o n y . 2

For

h i g h e r values, s a t u r a t i o n effects c a n o c c u r , g i v i n g r e l a t i v e e n h a n c e

m e n t of t h e w e a k e r lines. T o o b t a i n a c c u r a t e values of e qQ 2

conditions, the transmission integral described should be used.

g

b y Shenoy

u n d e r these et a l . ( 7 )

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

time, even w i t h Cranshaw's ingenious time-saving modification ( 8 ) , a n d s h o u l d b e a t t e m p t e d o n l y after p r e l i m i n a r y fitting b y t h e n o r m a l m e t h o d . U s i n g t h e t r a n s m i s s i o n i n t e g r a l f o r r e l a t i v e l y s m a l l values of e qQ 2

g

(ca.

10 m m s " ) a n d samples of m o d e r a t e thickness results i n a n a p p r o x i m a t e 1

5%

decrease i n t h e fitted v a l u e ( 9 , 1 0 ) .

T h e transmission integral was

n o t u s e d i n t h e present w o r k . For

1 2 1

S b , SR/R is r e l a t i v e l y l a r g e a n d n e g a t i v e . T h e i s o m e r shift is

v e r y sensitive t o s m a l l e l e c t r o n i c changes, a n d t h e t w o o x i d a t i o n states are w e l l d i f f e r e n t i a t e d . S i n c e &R/R is n e g a t i v e , a n t i m o n y ( I I I ) gives t h e m o r e n e g a t i v e i s o m e r shift, a n d I n S b p r o v i d e s a u s e f u l r o u g h d i v i d i n g point—shifts for antimony ( I I I ) being more negative than for InSb a n d those f o r a n t i m o n y ( V ) m o r e p o s i t i v e . F o r e a c h o x i d a t i o n state t h e i s o m e r shift is sensitive t o t h e n a t u r e of t h e g r o u p s b o n d e d t o t h e a n t i m o n y , normally becoming more positive w i t h increasing electronegativity.

Typi

cal ranges of v a l u e s a r e s h o w n i n T a b l e I I . Q u a d r u p o l e c o u p l i n g is n o r m a l l y s m a l l i n a n t i m o n y ( V )

unless t h e

l i g a n d s differ a p p r e c i a b l y i n e l e c t r o n e g a t i v i t y , a n d s u b s t a n t i a l s p l i t t i n g s are seen p r i m a r i l y i n o r g a n o a n t i m o n y c o m p o u n d s . S b — C b o n d ( o r t w o i n cis p o s i t i o n s )

T h e presence of one

gives e qQ 2

g

equal to 10-14 m m


364

MOSSBAUER

SPECTROSCOPY

A N D ITS

CHEMICAL

APPLICATIONS


V / m m s"

1

i i i i i i i ) i i i i i i i i i i i t i i i i i i i i i i

Figure 1. Calculated Sb Mossbauer spectra for 8 = 0, T = 2.4 mm s' , and e qQ = +30 mm s' (a) and + 20 mm s' (b). In (b) the peak positions are indicated with half intensity. Note the dramatic reduction in resolution as e qQ decreases. 121

2

g

1

1

1

2

g


16.

Antimony-121

PARISH AND PARRY Table II.

T y p i c a l Ranges for

Mossbauer 1 2 1

S b Mossbauer

Parameters e qQ^ (mm s' )

hnsb (mm s' )

2

1

" I n o r g a n i c " antimony (III) "Inorganic" antimony (V) Organoantimony (III) Organoantimony (V)


s"

1

—8 t o —2 + 2 to + 1 2 —2 t o 0 0 to + 6

0 to 0 to + 1 5 to 0 to

( p o s i t i v e i n t h e first case, n e g a t i v e i n t h e second,

1

365

Spectroscopy

+18 ±5 +18 +30

becouse Q

g

is

n e g a t i v e ) , a n d a trans C — S b — C a r r a n g e m e n t gives v a l u e s of 2 2 - 2 7 m m s" . V a l u e s f o r p a r t i c u l a r structures c a n b e e s t i m a t e d b y u s i n g t h e p o i n t 1

c h a r g e t r e a t m e n t ( 4 ) . F o r a n t i m o n y ( I I I ) there is u s u a l l y a l a r g e n e g a t i v e c o n t r i b u t i o n t o t h e e l e c t r i c field g r a d i e n t f r o m t h e l o n e p a i r , w h i c h u s u a l l y o u t w e i g h s t h a t f r o m t h e l i g a n d s , a n d e qQ 2

are f o u n d .

T h e r a n g e reflects differences

v a l u e s of 5 - 1 9 m m s '

g

1

i n t h e h y b r i d i z a t i o n of t h e

a n t i m o n y a t o m a n d t h e w i d e v a r i e t y of structures. I n a f e w c o m p o u n d s c o n t a i n i n g t h e S b C l " i o n t h e a n t i m o n y a t o m o c c u p i e s a site of o c t a 6

3

h e d r a l s y m e m t r y ; t h e l o n e p a i r is n o w f o r c e d t o h a v e 1 0 0 % 55 c h a r a c t e r , e qQ 2

g

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

a b o u t — 1 1 m m s" ( I I ) . 1

Preliminary Investigation T h e t e n samples s u p p l i e d b y D r . W a d e w e r e e x a m i n e d i n i t i a l l y b y i n f r a r e d spectroscopy. C=N cm" , 1

M a r k e d differences w e r e f o u n d i n t h e N — H a n d

s t r e t c h i n g regions of t h e spectra, 3000-34,000 c m " a n d 1550-1700 1

respectively.

O n this basis t h e samples w e r e d i v i d e d i n t o t h r e e

g r o u p s . T h e first ( G r o u p I , t w o s a m p l e s ) shows three a b s o r p t i o n p e a k s i n t h e N — H s t r e t c h i n g r e g i o n , a t a b o u t 1600 a n d 1660 c m " . T h e s e s a m 1

ples w e r e p r e p a r e d b y d i r e c t t r e a t m e n t of S b C l

5

with R C : N H . 2

The

s e c o n d g r o u p ( I I , t h r e e s a m p l e s ) h a s o n l y one s t r o n g N — H s t r e t c h i n g b a n d , b u t f o u r p e a k s i n t h e 1550-1700 c m ' r e g i o n , of w h i c h t h e o n e a t 1

a b o u t 1660 c m " is of m e d i u m - w e a k i n t e n s i t y . T h i s g r o u p , a n d t h e t h i r d , 1

were obtained b y interacting S b C l w i t h R C : N L i . T h e third group ( I I I , 5

2

five s a m p l e s ) shows v e r y b r o a d N — H a b s o r p t i o n a n d t h r e e b r o a d b a n d s i n t h e C = N r e g i o n . T h e shape of t h e N — H b a n d suggests t h e h y d r o g e n b o n d i n g effects seen i n a m i n e salts. T h e s p e c t r a a r e t h u s a l l m o r e c o m p l e x t h a n e x p e c t e d f o r s i m p l e a d d u c t s of t h e t y p e R C : N H • S b C l . 2

5

Repre

sentative s p e c t r a f o r samples d e r i v e d f r o m P h C : N H o r P h C : N L i a r e 2

2

s h o w n i n F i g u r e 2. C h e m i c a l analysis showed that the compounds

of G r o u p I h a d a n

S b : C l r a t i o of 1:6, w h i l e a l l t h e other c o m p o u n d s

g a v e a r a t i o of 1:4

( T a b l e I I I ) . A l t h o u g h analyses f o r h y d r o g e n a r e p r o b a b l y t h e least


366

MOSSBAUER SPECTROSCOPY A N D ITS C H E M I C A L APPLICATIONS

cm -1


3500

3000

1800

1400

Figure 2. Infrared spectra in the N—H and C=N stretching regions for samples derived from (a) Ph CNH/SbCl , Group I; (b) Ph CNLi/SbCl , Group II; and (c) Ph CNLi/SbCl , Group III 2

5

2

2

5

5

r e l i a b l e , t h e a t o m ratios are c o n s i s t e n t l y h i g h e r f o r G r o u p s I a n d I I I , a n d lower for G r o u p I I t h a n expected for the simple adducts R C : N H • S b C l . 2

T h u s , n o n e of t h e c o m p o u n d s

are o f this form, confirming

5

deductions

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

Mossbauer

Spectra

The S b M o s s b a u e r s p e c t r a also s h o w e d differences a m o n g t h e samples, a n d c o n f i r m e d t h e g r o u p i n g d e d u c e d f r o m t h e i n f r a r e d spectra. R e p r e s e n t a t i v e s p e c t r a are s h o w n i n F i g u r e 3. T h e c o m p o u n d s o f G r o u p I s h o w s h a r p , s y m m e t r i c a l s i n g l e t s p e c t r a , c e n t e r e d a r o u n d + 6 m m s" . G r o u p I I gives a s l i g h t l y l o w e r i s o m e r shift, b u t t h e shape o f the a b s o r p t i o n e n v e l o p e c l e a r l y demonstrates a s m a l l b u t definite q u a d r u p o l e 1 2 1

1


16.

Antimony-121

PARISH AND PARRY

splitting, w i t h

positive.

e qQ 2

g

Mossbauer

T h u s , these

367

Spectroscopy

t w o groups

both

contain

a n t i m o n y ( V ) , b u t differ i n t h e s y m m e t r y of t h e a n t i m o n y e n v i r o n m e n t . T h e r e m a i n i n g samples, v e r y s u r p r i s i n g l y , s h o w e d m a j o r resonances about

at

— 8 m m s" , a n d thus are u n a m b i g u o u s l y d e r i v a t i v e s of t r i v a l e n t 1

a n t i m o n y . I n t w o cases a d d i t i o n a l signals w e r e seen also.

Antimony (III) Species (Group III)


A l l five samples of G r o u p I I I s h o w e d resonances i n t h e a n t i m o n y ( I I I ) r e g i o n ( T a b l e I V , F i g u r e 4 ) . A l l h a v e a n e qQ 2

g

of a b o u t + 1 0 m m s" (as 1

e x p l a i n e d e a r l i e r , these values a r e a c c u r a t e t o o n l y a b o u t T h e p o s i t i v e s i g n is consistent w i t h t h e p r e s e n c e of a active lone pair.

± 1 m m s" ). 1

stereochemically

F r o m t h e a n a l y t i c a l d a t a i t seems l i k e l y t h a t

these

c o m p o u n d s c o u l d c o n t a i n S b C l ~ a n i o n s , a n d t h e i n f r a r e d s p e c t r a a r e also 4

consistent w i t h t h e p r e s e n c e of R C : N H 2

2

+

cations.

Comparison w i t h the

( r a t h e r l i m i t e d ) d a t a f o r o t h e r salts of these a n i o n s ( T a b l e I V ) confirms this s u g g e s t i o n a n d r u l e s o u t o t h e r t y p e s o f c o o r d i n a t i o n .

Table

III.

Analytical Data R C:NLi/SbCl 2

R

Group

CeHs p-CH C H 3

C H 6

6

5

p-CH C H 3

CeH

4

6

4

5

p-CH C H 3

P-FC H 6

6

4

4

C H ,m-CH C H 6

5

3

6

4

% C

for R C : N H / S b C l Products 2

5

T h e identifi-

5

and

0

%H

%N

%Cl

%Sb

I

31.6 (14.5

2.5 13.8

2.9 1.1

38.9 6.1

21.9 1.0)

I

39.4 (21.0

3.7 23.7

2.5 1.1

35.1 6.3

18.9 1.0)

II

35.2 (12.9

2.1 9.3

2.8 0.9

32.5 4.0

(27.4) 1.0)

II

38.1 (15.0

3.0 14.2

2.9 1.0

29.9 4.0

25.6 1.0)

II

33.7 (13.0

2.4 11.1

2.9 1.0

33.4 4.4

26.1 1.0)

III

34.9 (12.7

2.7 11.8

3.2 1.0

31.7 3.9

27.8 1.0)

III

37.7 (15.4

3.4 16.7

2.7 0.9

30.1 4.2

24.7 1.0)

III

34.8 (14.4

2.3 11.5

2.8 1.0

27.9 3.9

24.3 1.0)

III

35.9 (14.1

3.2 15.1

2.8 0.9

28.8 3.8

25.6 1.0)

° Figures in parentheses are the atom ratios. By difference. 6


1

368

MOSSBAUER SPECTROSCOPY A N D ITS C H E M I C A L APPLICATIONS

V / m m s10

0

-10

1

>

19C

x


X

29C

Characterization of Novel Antimony Compounds by Antimony-121

Recommend Documents