Use of the Bulky Alkyl Ligand

21 Use of the Bulky Alkyl Ligand (Me Si) CH 3

2

-to Stabilize Unusual Low Valent Transition Metal Alkyls and Dialkylstannylene Downloaded by MICHIGAN STATE UNIV on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch021

Derivatives MICHAEL F. LAPPERT School of Molecular Sciences, University of Sussex, Brighton BN1 9QJ, England

New kinetically stable homoleptic metal alkyls MR were prepared using principally the ligand (Me Si) CH (R) : (a) low coordination number complexes of GroupIII-VItransi tion metals such as [YR ] and [Ti(η -C H ) CHPh ], and (b) stannylene complexes of transition metals such as trans[Cr(CO) (SnR ) ], [Fe (η -C H ) (CO) SnR ], and [Fe(η C H )(CO) SnR X] (X = Cl or Me). With type b, SnR behaves as a good σ donor, and its coordination chemistry is much like that of tertiary phosphines with the added com plication that, in some reactions, products of insertion may be obtained in which the Sn has increased its oxidation state but it is still attached to the transition metal. Monomeric (cyclo-C H solution), yellow GeR was obtained from Ge{N(SiMe ) } and LiR. He(I) photoelectron data on bivalent Ge, Sn, and Pb alkyls and amides are presented and analyzed. n

-

3

-

2

5

3

5

5 2

2

5

4

5

5

2

2

6

2

5

2

5

5 2

3

2

2

2

12

2

3

2

2

ecently there has b e e n m u c h interest i n the synthesis, s t r u c t u r e , c h a r A

^

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

metal alkyls M R complex

(I).

n

in which

( T h e t e r m h o m o l e p t i c is u s e d to d e s c r i b e a m e t a l

a l l the

S n ( N R ' ) 2 are examples 2

whereas T i ( C l ) R

3

ligands

are

of h o m o l e p t i c

identical

(2),

i.e.

TiR

4

and

metal alkyls a n d dialkylamides

a n d S n ( N R ' ) R are h e t e r o l e p t i c c o m p o u n d s . ) 2

There

are three classes ( 2 ) of these c o m p l e x e s : ( a ) t r a n s i t i o n m e t a l c o m p o u n d s , (b) d i a m a g n e t i c l o w e r v a l e n t m a i n g r o u p element d e r i v a t i v e s s u c h as the

256 In Inorganic Compounds with Unusual Properties; King, R.; Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

21.

257

(Me Si) CH-

LAPPERT

s

3

d i a l k y l s of S n a n d P b ( s

2

complexes), and (c)

paramagnetic m a i n group

c o m p o u n d s , i. e. t h e m e t a l - c e n t e r e d r a d i c a l s s u c h as the «^complexes M R (M =

3

S i , G e , or S n ) . T h e k e y feature is t h a t t h e r m a l s t a b i l i t y is g o v

e r n e d p r i m a r i l y b y k i n e t i c factors.

H e n c e , b y the c h o i c e of

suitable

l i g a n d s R", n o r m a l l y l o w a c t i v a t i o n e n e r g y d e c o m p o s i t i o n p a t h w a y s

be

c o m e e n e r g e t i c a l l y u n f a v o r a b l e . S u c h l i g a n d s are of f o u r t y p e s : ( a ) b u l k y a l k y l s t h a t are free f r o m β - h y d r o g e n atoms, i n c l u d i n g the n e o p e n t y l types ( R M ' ) m C H g-»," (m = 3

Me PCH 3

2

1, 2, o r 3 ) (2)

s u c h as M e S i C H ' (3, 4, 5) 3

and

2

( 6 ) , a n d P h C H - f ( 7 ) ; ( b ) b u l k y a l k y l s t h a t are free f r o m « - H

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atoms s u c h as 1 - n o r b o r n y l ( 8 ) a n d f e r f - b u t y l ( 9 ) ; ( c ) s i m p l e a l k y l s i f the m e t a l is ( n e a r l y ) c o o r d i n a t i v e l y s a t u r a t e d , e.g. M e " i n W M e ( d ) c h e l a t i n g a l k y l s s u c h as o - M e O · C H 6

CH

-

2

CH

Type" (MR). (MR.),

R = Me SiCH 3

3

(CuR) d 4

2

(JO); and and

2

(6).

2

Stable Homoleptic M e t a l M R , , of N e o p e n t y l T y p e R = (Me Si) CH

2

e

· S i ( M e ) C H " (11, 12)

2

Me P^

Table I.

4

Alkyls,

R = Me CCH,

2

3

R = Me SnCH 3

2

1 0

SnR ) PbR» S SiR„ GeR SnR YR TiR VR

,

2

(MR,),

s

3

3

3

3

3

MR

4

TiR ZrR HfR VR ° CrR 4

3

4

4

d° d d

l

4

4

? } )

c

2

d°

d

1

d

2

TiR ZrR HfR

4 4

4

) \ d° )

TiR ZrR HfR

4 4

4

\ d° )

CrR " 4

° For details, see Ref. 2. " T h e degree of molecular aggregation (x) refers to the situation in C e H i solution. "These complexes were first prepared by G . Wilkinson et al., the others by M . F . Lappert et al. (see Ref. 2). 2

In Inorganic Compounds with Unusual Properties; King, R.; Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

258

INORGANIC

COMPOUNDS

WITH

UNUSUAL

A list of s t a b l e ( a t 2 0 ° C i n a n i n e r t a t m o s p h e r e ) complexes

is p r e s e n t e d i n T a b l e I.

PROPERTIES

neopentyl-type

T h e m o s t b u l k y of these l i g a n d s ,

( M e S i ) C H " , c l e a r l y favors t h r e e - c o o r d i n a t i o n f o r the m e t a l . T h i s m a y 3

2

be i l l u s t r a t e d b y reference to Y { C H ( S i M e ) } 3 (H); 3

w i t h t h e less h i n -

2

d e r e d M e S i C H " , the m e t a l a l k y l c a n also b e o b t a i n e d i n presence of a 3

2

d o n o r solvent as w i t h M ( C H S i M e ) 2

3

3

· 2THF (M =

S c or Y ) (12).

i n t e r e s t i n g s t r u c t u r a l f e a t u r e is f o u n d i n [ C u C H S i M e ] 2

3

4

(see

An

Figure 1

for the c r y s t a l a n d m o l e c u l a r s t r u c t u r e ) w h i c h demonstrates t h e u n u s u a l


s i n g l e a l k y l b r i d g e b e t w e e n t w o C u atoms (13).

T h e conventional syn-

Figure 1. The crystal and molecular structure of (CuCH SiMe ) ( 1 3 ) — Cu-Cu, 2.417 A; Cu-C (mean), 2.02 A; < C-Cu-C, 164°; Cu C Si coiplanar; centrosymmetric 2

s â

A

Â

g

t h e t i c r o u t e to a l l a l k y l s , except for t h e s d e r i v a t i v e s , has b e e n f r o m c o r 1

r e s p o n d i n g c h l o r i d e s , or c h l o r o m e t a l c o m p l e x e s , a n d t h e a p p r o p r i a t e a l k y l of L i or M g

(2).

T h e s S n a n d P b complexes M { C H ( S i M e ) } 2

3

stable, m o n o m e r i c i n C H 6

m a g n e t i c (14). complexes

6

2

2

are u n u s u a l i n b e i n g

solution ( b y cryoscopy),

colored, and d i a -

M o r e o v e r , t h e y b e h a v e as g o o d donors a n d g i v e rise to

s u c h as { ( M e S i ) C H } S n - C r ( C O ) ; t h e c r y s t a l a n d m o l e 3

2

2

5

c u l a r s t r u c t u r e of this s t a n n y l e n e c o m p l e x has a n u n u s u a l t r i g o n a l p l a n a r e n v i r o n m e n t for the t i n a t o m ( F i g u r e 2 )

(15).



21.

(Me Si) CH-

LAPPERT

3

259

2

Figure 2. The crystal and molecular structure of {(Me Si) CH} SnCr(CO) ( 1 5 ) — S n - C r , 2.562 A; Sn-C, 2.19 A; < C-Sn-C, 96°; < C-Sn-Cr (mean), 13Γ; C.SnCr(C0) essentially coplanar with Cr in octahedral envi ronment 3

2

2

5

3

Results Synthesis.

A n e w m e t h o d has b e e n d e v i s e d nLiR -»

M(NR' )» 2

MR

n

Reaction 1).

(see

+ nLiNR/

(1)

2

w a s u s e d effectively f o r p r e p a r i n g t h e f o r m e r l y e l u s i v e (14)—i.e. accessible

from

G e C l / L i R ) — G e { C H ( S i M e ) } 2 (16). 2

3

amide was G e { N ( S i M e ) } 3

( b y c r y o s c o p y ) (17).

2

2

3

w h i c h is m o n o m e r i c i n c y c l o - C H i s o l u t i o n e

2

( u s i n g S n C l ) (17)

2

2

(also m o n o m e r s i n C H i ) (18). 6

and F e R

3

2

w h i c h is e x t r e m e l y s o l u b l e

2

alkyl.

c e d u r e w a s u s e d successfully for t h e c o r r e s p o n d i n g S n R

3

not

starting

T h e p r o d u c t s w e r e s e p a r a t e d b y c o n v e r t i n g the L i

a m i d e to S n { N ( S i M e ) }

for C r R

The

2

i n c y c l o - C H i a n d m u c h m o r e so t h a n t h e G e ( I I ) 6

It

2

3

and P b R

2

I t is p r o m i s i n g b u t as y e t i n c o n c l u s i v e

[R' — Me Si, R =

THE B E N Z H Y D R Y L LIGAND (19).

T h e same p r o (16)

2

(Me Si) CH] 3

2

(19).

Reactions w i t h L i C H P h

2

and metal

c h l o r i d e s s u c h as T i C l , H f C l , VCI4, T a C l , N b C l , C r C l , M0CI5, F e C l , 4

4

5

5

3


3

260 and

INORGANIC

SnCl

COMPOUNDS WITH

UNUSUAL

PROPERTIES

h a v e not a t this t i m e afforded c h a r a c t e r i z e d c r y s t a l l i n e p r o d

2

ucts. H o w e v e r , i t w a s n o t e d that this p a r t i c u l a r l i t h i u m a l k y l i s a r a t h e r p o w e r f u l r e d u c i n g agent.

T h e group I V metallocene dichlorides ( R =

P h C H ) m a y b e s u m m a r i z e d b y R e a c t i o n 2. 2

+ 2 R L i ->

M( -C K ) C\ 5

V

5

5 2

2

5

d a r k green ; E S R d o u b l e t a ( H ) ~ 5 G , 0 — 1.98 ( 2 0 ° C Downloaded by MICHIGAN STATE UNIV on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0150.ch021

5

52

(2)

2

5

5 2

inC D ) 6

5

M = Z r : o r a n g e ; dec. > 130°C; r;3.4 (Ph),5.2 ( C H ) , 7.3 ( C H ) M = H f : y e l l o w ; m.p. 1 9 2 - 1 9 4 ° C (dec.) ; r ; 3.4, 5.25, 7.4

Ti(r, -C H ) R 5

M(T7-CH)R

6

5

T H E R M A L D E C O M P O S I T I O N . V a r i o u s p a t h w a y s are a v a i l a b l e for t r a n s i t i o n m e t a l a l k y l d e c o m p o s i t i o n ( J ) . A p p a r e n t l y s m a l l s t r u c t u r a l changes c a n change t o t a l l y the n a t u r e o f t h e p r o d u c t s .

T h i s is i l l u s t r a t e d b y the

t e t r a - a l k y l s of T i , Z r , a n d H f (see R e a c t i o n 3 ) .

M(CH M'Me ) 2

3

heat -> M = C or S i (20)

4

Me M'CH (3) (sole v o l a t i l e p r o d u c t ) 3

3

heat M = S n (21) (Me M'CH ) (principal volatile product) 3

2

2

A Monomeric G e r m a n i u m (II)

Alkyl

methyl]germanium, G e { C H ( S i M e ) } , 3

2

2

(16).

D i [bis ( t r i m e t h y l s i l y l ) -

is a y e l l o w s o l i d , m . p .

179°-

181 ° C ( u n d e r a r g o n ) , t h a t s u b l i m e s a t 1 1 0 ° C a n d 10" m m H g . 3

thermochromic, becoming red when molten.

I t is

I t is a monomer i n C H 6

6

a n d c y c l o - C H i ( b y c r y o s c o p y ) (18). T h e m o n o m e r i c p a r e n t i o n is the 6

2

h i g h e s t p e a k i n the mass s p e c t r u m . T h e R a m a n s p e c t r u m o f the s o l i d has a strong l i n e a t 300 c m "

1

w h i c h m a y arise f r o m a G e - G e s t r e t c h i n t h e

d i m e r i c s o l i d ( b y a n a l o g y w i t h F i g u r e 3 ) (22). T h e Ή N M R s p e c t r u m shows a single s h a r p m e t h y l resonance at 9.55 τ, w h e n c e i t is i n f e r r e d t h a t the m o l e c u l e i n s o l u t i o n is the d i a m a g n e t i c singlet ( p o s s i b l y o f C

2v

sym

metry). The Crystal and Molecular Structure of [ S n { C H ( S i M e ) } ] 3

2

2

2

(23).

T h i s c o m p o u n d c r y s t a l l i z e s as s m a l l r e d plates. T h e m o l e c u l e is c e n t r o s y m m e t r i c a n d p r e l i m i n a r y parameters are s h o w n i n F i g u r e 3. T h e e n v i r o n m e n t a b o u t e a c h t i n a t o m is p e r h a p s best d e s c r i b e d as d i s t o r t e d t e t r a h e d r a l , w i t h the s u m of b o n d angles at t i n as 3 4 1 ° ; for " p u r e " sp S n z

this w o u l d b e ca. 329° a n d f o r " p u r e " sp , 3 6 0 ° . 2

T h e t w o sets o f a l k y l



21.

261

(Me Si) CH-

LAPPERT

3

2

Figure 3. The crystal and molecular structure of [Sn{CH(Sies)i}*]» ( 2 3 ) — S n - S n , 2.76 A; Sn-C, 2.17 A; < Sn-Sn-C (mean), 115°; < C-Sn-C, 112° M

l i g a n d s at e a c h t i n a t o m are d i r e c t e d a w a y f r o m one a n o t h e r as i n S t r u c t u r e I. I t w a s difficult to o b t a i n g o o d q u a l i t y single crystals, b u t n u m e r ous samples w e r e t a k e n for i n d e x i n g a n d e a c h b e l o n g e d to the same space R Sn

R I g r o u p , Fx, as the e v e n t u a l s a m p l e c r y s t a l . W e h o p e to e x a m i n e this p a r t i c u l a r c r y s t a l b y R a m a n spectroscopy; w e expect to locate a l i n e at ca. 1 8 0 - 2 0 0 c m " t h a t is a t t r i b u t a b l e to ν ( S n - S n ) . A t present, h o w e v e r , s u c h 1

attempts w i t h the b u l k s a m p l e h a v e l e d to p h o t o c h e m i c a l d e c o m p o s i t i o n (22).

( W e d e m o n s t r a t e d e a r l i e r t h a t p h o t o l y s i s of S n R i n C H 2

the stable S n R (24). 3

6

e

yields

) T h e S n - S n b o n d l e n g t h is s i m i l a r to t h a t i n S n P h 2

e

a n d s o m e w h a t shorter t h a n t h a t i n t e t r a h e d r a l t i n . T h e r e m a y b e a t e n -


262

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

uous r e l a t i o n b e t w e e n the c r y s t a l s t r u c t u r e of the d i a l k y l s t a n n y l e n e a n d that of the green f o r m of c h l o r o b i s [ l , 2 - b i s ( d i p h e n y l p h o s p h i n o )

ethane]-

c o b a l t ( I I ) t r i c h l o r o s t a n n a t e ( I I ) , i n w h i c h the S n C l " a n i o n is l o c a t e d n e a r 3

a center of s y m m e t r y w h i c h results i n a S n - S n d i s t a n c e of 3 . 5 9 7 ( 4 ) A w i t h t h e three c h l o r i n e atoms b o n d e d to t i n d i r e c t e d a w a y f r o m the S n - S n vector (25).

[I t h a n k a referee f o r d r a w i n g a t t e n t i o n to this a n a l o g y . ]

O u r present t e n t a t i v e i n t e r p r e t a t i o n of the s t r u c t u r a l a n d a n a l y t i c a l data—visible, IR, M S , and Ή

N M R ; magnetism

(diamagnetic

solid b y

the G o u y m e t h o d ; n o E S R s i g n a l i n the s o l i d or i n s o l u t i o n i n the absence


of i r r a d i a t i o n ) ;

1 1 9

S n M o s s b a u e r ; single c r y s t a l x - r a y ; a n d c r y o s c o p i c m o l e

c u l a r w e i g h t — i s t h a t i n s o l u t i o n a n d as a v a p o r the c o m p o u n d exists as t h e m o n o m e r i c b e n t singlet w i t h b o n d i n g f o r m a l i z e d as i n S t r u c t u r e I I , w h e r e a s i n the s o l i d state b e n t b o n d s p r e v a i l as i n S t r u c t u r e I I I . I t is a s s u m e d that, a l t h o u g h the S n - S n b o n d is a d o u b l e b o n d , i t is w e a k ; this accounts for the s o l u t i o n m o l e c u l a r w e i g h t d a t a a n d the r e a d y f o r m a t i o n of stannylene c o m p l e x e s s u c h as that i n F i g u r e 2. T h e p u z z l i n g feature of the x - r a y findings ( F i g u r e 3 ) concerns the angles at t i n . T h e a b o v e i n t e r p r e t a t i o n w o u l d b e m o r e consistent w i t h p l a n a r t r i g o n a l t i n ; d o r b i t a l p a r t i c i p a t i o n i n the b o n d i n g is l i k e l y .

filled

hybrid

sp p x

y

vacant p orbital z

III H e (I)

P h o t o e l e c t r o n S p e c t r a of M o n o m e r i c D i v a l e n t M e t a l A l k y l s

and Dialkylamides (26).

I n k e e p i n g w i t h the g o o d d o n o r p r o p e r t i e s

of

t h e d i a l k y l s t a n n y l e n e (14, 1 5 ) , i t a n d r e l a t e d g r o u p I V c o m p o u n d s h a v e l o w e n e r g y o r b i t a l s that are a t t r i b u t a b l e essentially to n o n b o n d i n g l o n e - p a i r o r b i t a l s . T h e i r p o s i t i o n is c l e a r l y affected b y the t i v i t y of the l i g a n d ( N > the gaseous elements.

metal

electro-nega

C ) , b u t i t is b r o a d l y s i m i l a r to t h a t f o u n d

for

A s e x p e c t e d , the a p p r o p r i a t e b a n d s i n the p h o t o -

e l e c t r o n spectra are sharp. S a l i e n t results are s u m m a r i z e d i n T a b l e I I . T h e C o o r d i n a t i o n C h e m i s t r y o f a D i a l k y l s t a n n y l e n e . I n terms of the s o l u t i o n b e h a v i o r of S n { C H ( S i M e ) } 2 , f o r m a l i z e d as S t r u c t u r e I I , r e a c 3

2

tions m a y be classified as those i n w h i c h i t f u n c t i o n s as a L e w i s a c i d , as a L e w i s base, or as a c a r b e n e - l i k e r e a c t i v e i n t e r m e d i a t e that gives rise to i n s e r t i o n reactions ( 1 4 ) .

F u r t h e r i l l u s t r a t i o n s of this b e h a v i o r are g i v e n

i n Reactions 4 [ R — ( M e S i ) C H ] 3

2

(27).


21.

263

(Me Si) CH-

LAPPERT

3

2

0 II [Fe(, -C H ) (CO) ] 5

5

5

2

R Sn^

C

2

2

^ C

Fe 9


2

-C H 5

brown

Fe

CO

c

5

I W mp 167°-170°C,

II ο

[Cr(CO) (nor-C H )] *• trans- [ C r ( C O ) ( S n R ) ] 4

SnR

5

5

7

8

4

2

(4)

2

m p 2 1 5 ° - 2 1 6 ° C , orange

[Fetf-CHeMCO)^] »·

[Fe(i -C H5)(CO)2(SnR X)] ?

5

5

2

X — C l , m p 1 1 9 ° - 1 2 0 ° C , orange X = M e , mp 141°-142°C, yellow-brown Table II. T h e Highest Occupied Electronic Energy Levels (in eV) of the Monomeric Divalent Metal A l k y l s and Dialkylamides C(N)

Compound

M

M C(N)

Ge{CH(SiMe Sn{CH(SiMe Pb{CH(SiMe Ge{N(SiMe ) Sn{N(SiMe ) Pb{N(SiMe )

3 3

2 2

3

3

2

3

2

3

) ) ) } } }

2

2

} } }

7.75 7.42 7.25 8.68 8.36 8.16

2 2 2

2

"

2 2

ο

^^C(N)

O ' 'C(N)

8.87 8.33 7.98 7.71 7.75 7.92

—

9.50 9.39

8.99 8.85 8.81

" T h i s compound was obtained by us (17) and also independently by Schaeffer and Zuckerman (57). We find it and the other amides in this Table to be mono meric in solution and vapor, but our colleagues formulate it as an iV-bridged dimer. The 1 1 9

1 1 9

S n Mossbauer Spectra of Some of the Complexes

(28).

The

S n M o s s b a u e r spectra of a n u m b e r of the complexes w e r e e x a m i n e d .

D a t a are s u m m a r i z e d i n T a b l e I I I together w i t h r e l e v a n t reports f r o m the literature.

T h e r e are essentially t w o t y p e s :

(a)

the d i a l k y l s t a n n y l e n e

complexes s u c h as R S n C r ( C O ) i n w h i c h d i v a l e n t t i n is t h r e e - c o o r d i n a t e , 2

and (b)

5

dialkylstannylene insertion products into C - H a l , M - H , M - C l ,

M - M e , or M - M b o n d s ( M = is f o u r - c o o r d i n a t e .

(SnR ) 2

2

a transition metal) i n w h i c h tetravalent t i n

a n d C l a s s ( a ) complexes are c h a r a c t e r i z e d b y


264

INORGANIC

Table III.

COMPOUNDS

Data from

1 1 9

Compound 2

5

5

5

2

5

8

5

B

5

1 0

1 0

2

2

u

2


2.16 3.74 3.70 3.69 2.95 4.67 2.21 2.15 2.21 2.13 2.05,1.73 3.79 2.11 2.01 1.73 1.27 1.24 1.48 1.54 1.48 1.39 1.35 1.77 1.35 1.36

2

5

6

5

2

6

5

2

2

2

4

2

4

2

5

5

5

2

2

3

2

5

2

5

2

4

2

6

3

b

3

2

5 5

5

5

5

5

5

5

5

5

5

5

5

8

e

6

2

3

2

B

2

3

2

8

2

3

3

6

2

2

5

5

5

2

3

e

UNUSUAL PROPERTIES

S n Mossbauer Spectra"

Isomer Shift,' mm/sec

(SnR ) » Sn(, -C H ) SnCl(, -C H ) SnBr(, -C H ) Sn(Ph-CB H C) 3-Sn-l,2-C B»H [R SnCr(CO) ] [R SnMo(CO) ] irans-[(R Sn) Cr(CO) ]' frans-[(R Sn) Mo (CO ) ] ' tPtCl(PEts) (SnR Cl)SnR ] » Sn(, -C H ) Br [Bu' (THF)SnCr(CO) ] [Bu' (py)SnCr(CO) ] [SnR {Fe(CO) } ]> SnR Cl SnR Br SnR (Me)I> [Fe(, -C H ) (CO) (SnR Cl)] [Fe(, -C H ) (CO) (SnR Me)] '' [Mo(, -C H ) (CO) (SnR H)] [Mo(, -C H ) (CO) (SnR Me)] » [Fe(, -C H )(CO) SnCl ] tFe(, -C H5)(CO) SnMe ][Mo(, -C H )(CO) SnMe,]

WITH

Quadrupole Splitting, mm/sec

Ref. 28 29,30 31 31 32 33 28 28 28 28 28 30 84 84 28 28 28 28 28 28 28 28 35 36 36

2.31 0.86 1.05 0.99 1.90 3.83 4.43 4.57 4.04 4.24 4.23, 2.66 0.90 4.14 3.44 1.53 2.18 2.05 2.24 2.37 —

0.67 0.71 1.82 >o 1.25

Relative to BaSn03 or S11O2 at ca. 2 0 ° C ; crystalline samples. R = (Me Si) CH. T h e full line width at half-height, Γ, was 1.34 for F e ^ M ^ H s ) ( C O ) ( S n R M e > and 1.16 for F e ( i 7 - C H ) ( C O ) S n M e . a

b

3

2

e

2

5

5

5

2

i s o m e r shifts at 2.15 ± 0 . 1 m m / s e c r e l a t i v e to B a S n 0 r u p o l e s p l i t t i n g s [2.31 f o r ( S n R ) 2

complexes].

2

3

3

a n d large q u a d

a n d 4.25 ± 0.2 m m / s e c f o r C l a s s ( a )

2

C l a s s ( b ) complexes h a v e l o w e r i s o m e r shifts (1.49 ±

m m / s e c ) a n d q u a d r u p o l e s p l i t t i n g s ( < 2.37 m m / s e c ) .

0.25

I t is p e r h a p s s u r

p r i s i n g t h a t f o r t h e n e w t i n ( I I ) complexes, the i s o m e r shifts are r a t h e r l o w a n d n o t b y themselves

d i a g n o s t i c of t h e t i n v a l e n c y .

M o s s b a u e r measurements of ( S n R ) 2

2

Magnetic

a n d R S n C r ( C O ) demonstrate t h a t 2

5

for b o t h complexes the 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 constant and hence V

2 Z

, the p r i n c i p l e c o m p o n e n t

eQV

ZZy

of t h e field g r a d i e n t tensor, is

positive. Acknowledgment T h e a u t h o r t h a n k s h i s c o l l a b o r a t o r s , n a m e d i n t h e b i b l o g r a p h y ; i t has b e e n a p r i v i l e g e to w o r k w i t h t h e m .


21.

LAPPERT

(Me Si),CH3

265


Literature Cited 1. Davidson, J. J., Lappert, M. F., Pearce, R., Chem. Rev. (1976) 76. 2. Davidson, P. J., Lappert, M. F., Pearce, R., Acc. Chem. Res. (1974) 7, 209. 3. Collier, M. R., Kingston, Β. M., Lappert, M. F., Truelock, M. M., British Patent 36021 (1969). 4. Collier, M. R., Lappert, M. F., Truelock, M. M., J. Organomet. Chem. (1970) 25, C36. 5. Yagupsky, G., Mowat, W., Shortland, A. J., Wilkinson, G., Chem. Commun. (1970) 1369. 6. Schmidbaur, H., Franke, R., Angew. Chem. Int. Ed. Engl. (1973) 12, 416. 7. Zucchini, U., Albizzatti, E., Giannini, U., J. Organomet. Chem. (1971) 26, 357. 8. Bower, B. K., Tennent, H. G., J. Am. Chem. Soc. (1972) 94, 2512. 9. Kruse, W., J. Organomet. Chem. (1972) 42, C39. 10. Shortland, A. J., Wilkinson, G., J. Chem. Soc. Dalton Trans. (1973) 872. 11. Barker, G. K., Lappert, M. F., J. Organomet. Chem. (1973) 76, C45. 12. Lappert, M. F., Pearce, R., J. Chem. Soc. Chem. Commun. (1973) 128. 13. larvis, I. Α., Kilbourn, B. T., Pearce, R., Lappert, M. F., J. Chem. Soc. Chem. Commun. (1973) 475. 14. Davidson, P. J., Lappert, M. F., J. Chem. Soc. Chem. Commun. (1973) 317. 15. Cotton, J. D., Davidson, P. J., Goldberg, D. E., Lappert, M. F., Thomas, Κ. M.,J.Chem.Soc.,Chem. Commun. (1974) 893. 16. Harris, D. H., unpublished data. 17. Harris, D. H., Lappert, M. F., J. Chem. Soc. Chem. Commun. (1974) 895. 18. Power, P. P., Miles, S. J., unpublished data. 19. Holton, J., unpublished data. 20. Davidson, P. J., Lappert, M. F., Pearce, R., J. Organomet. Chem. (1973) 57, 269. 21. Webb, M., unpublished data. 22. Gynane, M. J. S., unpublished data. 23. Golberg, D. E., Thomas, Κ. M., unpublished data. 24. Davidson, P. J., Hudson, Α., Lappert, M. F., Lednor, P. L., J. Chem. Soc. Chem. Commun. (1973) 829. 25. Stalick, J. D., Corfield, P. W. R., Meek, D. W., Inorg. Chem. (1973) 12, 1668. 26. Sharp, G. J., unpublished data. 27. Cotton, J. D., unpublished data. 28. Donaldson, J. D., Silver, J., unpublished data. 29. Harrison, P. G., Zuckerman, J. T.,J.Am. Chem. Soc. (1969) 91, 6885. 30. Ibid. (1970) 92, 2577. 31. Bos, K. D., Bulten, E. J., Noltes, J. G., J. Organomet. Chem. (1972) 39, C52. 32. Aleksandrov, A. Yu., Bregadse, V. I., Goldanskii, V. I., Zakharkin, L. I., Okhlobystin, O. Yu., Khrapov, V. I., Dokl. Adak. Nauk SSSR (1965) 165, 593. 33. Rudulph, R. W., Chowdhry, V., Inorg. Chem. (1974) 13, 248. 34. Grynkewich, G. W., Ho, Β. Y. K., Marks, T. J., Tomaja, D. L., Zuckerman, J. J., Inorg. Chem. (1973) 12, 2522. 35. Bird, S. R. Α., Donaldson, J. D., Holding, A. F. LeC, Senior, B. J., Tricker, M. J., J. Chem. Soc. A (1971) 1616. 36. Bird, S. R. Α., Donaldson, J. D., Keppie, S. Α., Lappert, M. F.,J.Chem Soc. A (1971) 1311. 37. Schaeffer, Jr., C. D., Zuckerman, J. J., J. Am. Chem. Soc. (1974) 96, 7160. RECEIVED January 24, 1975.


Use of the Bulky Alkyl Ligand

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