Catalytic Aspects of Metal Phosphine Complexes - ACS Publications

2

P-31, Sn-119, and Pt-195 NMR Studies on Platinum-Tin Homogeneous Hydrogenation Catalysts K. A . O S T O J A S T A R Z E W S K I and P. S.

PREGOSIN

Downloaded by CORNELL UNIV on August 10, 2016 | http://pubs.acs.org Publication Date: June 1, 1982 | doi: 10.1021/ba-1982-0196.ch002

Laboratorium für Anorganische C h e m i e , E T H - Z e n t r u m , Universitätstrasse 6, C H - 8 0 9 2 Zürich, S w i t z e r l a n d

P-31, Sn-119, and Pt-195 NMR spectroscopic methods have been used to identify the products of the reaction of SnCl2 with phosphine complexes of platinum(II). These complexes are of the type [Pt(SnCl3)L(PR )2], L = Cl-, SnCl3-, H-, or alkyl, and are of interest, spectroscopically, in that the one-bond platinum-tin coupling 1J(195Pt,1 1 9 S n )can exceed 30,000 Hz and therefore represents the largest known nuclear spin-spin coupling constant. The two-bond interaction in the poly-SnCl complex J(119Sn, 117Sn) at > 18,000 Hz is also exceedingly large. 3

3

2

P

l a t i n u m p h o s p h i n e c o m p l e x e s a r e r e c o g n i z e d t o f u n c t i o n as h o m o geneous

hydrogénation

c o m b i n e d w i t h a n excess

a n d hydroformylation

catalysts

o f a c o - c a t a l y s t s u c h as t i n ( I I )

when

chloride

(1, 2, 3 ) . S p e c i f i c a l l y , α-olefin h y d r o f o r m y l a t i o n p r o c e e d s b o t h w i t h high y i e l d a n d selectivity SnCl

2

using the combination [PtCl (PPh ) ] + 2

3

2

as s h o w n i n E q u a t i o n 1 (4):

CH (CH ) CH=CH 3

d V

2

Z

/

4

4

2 A

— PtCUPPhak + n-SnClj

• 9 0 % 1-octanal

(1)

66° T h e h o m o g e n e o u s hydrogénation a n d h y d r o f o r m y l a t i o n r e a c t i o n s are k n o w n to i n v o l v e m e t a l h y d r i d e , m e t a l olefin, a n d m e t a l a l k y l c o o r d i n a t i o n c o m p l e x e s ( 5 ) ; h o w e v e r , t h e r e is r e l a t i v e l y l i t t l e i n t h e literature c o n c e r n i n g the function o f S n C l i n this connection. T h e w o r k t h a t h a s b e e n d o n e s u g g e s t s (6, 7, 8, 9) t h a t S n C l r e a c t s w i t h p l a t i n u m c o m p l e x e s c o n t a i n i n g a P t - C l b o n d a c c o r d i n g to E q u a t i o n 2. 2

2

0065-2393/82/0196-0023$05.00/0 © 1982 American Chemical Society Alyea and Meek; Catalytic Aspects of Metal Phosphine Complexes Advances in Chemistry; American Chemical Society: Washington, DC, 1982.

24

METAL PHOSPHINE COMPLEXES

Pt-Cl + SnCl

Pt-SnCl

2

(2)

3

I n s u p p o r t o f the d i r e c t p l a t i n u m - t i n b o n d are structural

determinations

(SnCl )(PPh )] (ii), 3

3

for

[Mn(SnCl )(CO) ] 3

5

[ A u ( S n C l ) ( P M e P h ) ] (12), 3

2

2

crystallographic

(10),

[Pd(w-allyl)-

a n d the

cycloocta-

d i e n e cluster [ P t ( S n C l ) ( C H ) ] w h i c h has a triangle o f p l a t i n u m 3

3

2

8

1 2

3

a t o m s c a p p e d a b o v e a n d b e l o w b y t w o S n C l " g r o u p s (13). 3

In addition

to t h e m e t a l - m e t a l b o n d t h e r e a r e t w o f u r t h e r p o s s i b l e i n t e r a c t i o n s o f the S n C l " l i g a n d w i t h the p l a t i n u m . T h e

m o s t t r i v i a l is n o n a s s o -

3

ciative, w i t h the S n C l trichlorostannate

2

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

counterion, and

indeed

t h e s o l i d state for [ C o C l ( d p p e ) ] S n C l


2

phino)ethane recent

(14).

this has

(dppe =

3

been

of

in

l,2-bis(diphenylphos-

T h e last a n d most i n t r i g u i n g option, stems

structural determination

the

found

[Ag(SnCl )(PP)] 3

where

2,ll-bis(diphenylphosphinomethyl)benzo[c]phenanthrene,

a

from

a

PP

=

chelat

i n g d i p h o s p h i n e that m a y s p a n the trans positions o f a s q u a r e p l a n a r c o m p l e x (15).

I n t h i s m o l e c u l e , a b b r e v i a t e d as I, t h e S n C l ~ c o o r d i 3

nates to the t r a n s i t i o n m e t a l v i a the h a l o g e n .

CI

SnCl

2

I

T h e p r o b l e m o f e s t a b l i s h i n g the solution structure o f p l a t i n u m tin complexes

is c o m p l i c a t e d b y t h e l a b i l i t y o f t h i s s y s t e m . W e

f o u n d (16,

( a n d w i l l refer to this later) that these c o m p l e x e s

17)

have are

o f t e n d y n a m i c o n t h e N M R t i m e s c a l e . D e s p i t e t h e s e d i f f i c u l t i e s i t is p o s s i b l e to c h a r a c t e r i z e s u c h m o l e c u l e s u s i n g N M R T h i s means that w e

u s e (a)

P-31 N M R

methods.

both qualitatively,

for

information o n the orientation o f the tertiary p h o s p h i n e ligands, a n d a n a l y t i c a l l y t o d e t e r m i n e t h e n u m b e r o f c o m p l e x e s i n s o l u t i o n (this is a very receptive nucleus a n d 1-2% readily);

(b)

S n - 1 1 9 (I = i

o f i m p u r i t i e s often are

n a t u r a l a b u n d a n c e = 8.6%)

detected

NMR

p r o b e for t h e i d e n t i t y o f t h e t r i c h l o r o s t a n n a t e m o i e t y ; a n d (c) (I = i , n a t u r a l a b u n d a n c e = 3 3 . 7 % ) N M R

as

a

Pt-195

for m u l t i p l i c i t y d a t a c o n

c e r n e d w i t h the n u m b e r of coordinated phosphines (and N M R spins i n g e n e r a l ) . T h e v a l u e o f H - l N M R i n m e t a l h y d r i d e c h e m i s t r y is so w e l l e s t a b l i s h e d (18)

t h a t n o f u r t h e r j u s t i f i c a t i o n is r e q u i r e d h e r e .

Alyea and Meek; Catalytic Aspects of Metal Phosphine Complexes Advances in Chemistry; American Chemical Society: Washington, DC, 1982.

2.

STARZEWSKi A N D P R E G O S I N

Pt-Sn

Hydrogénation

25

Catalysts

W e b e g i n b y c o n s i d e r i n g the products o f E q u a t i o n 3 a n d f o l l o w b y d i s c u s s i n g t h e c o m p l e x e s t h a t r e s u l t from a d d i n g m o l e c u l a r h y d r o g e n and eventually an acetylene. PtCl P 2

? -SSi* ?

2

(3)

Experimental P-31, Sn-119, and Pt-195 N M R spectra were measured using B r u k e r H X - 9 0 ( P only) a n d W M - 2 5 0 (101.27, 93.28, and 53.77 M H z ) spectrometers. T h e samples were measured as solutions i n rotating 10-mm tubes u s i n g ~40°-45° pulse angles for P , S n , and P t w i t h acquisition times of —0.7, 0.2, and 0.2 s, respectively. Spectral widths were routinely (WM-250) 10,000, 50,000 and 50,000 H z for these same n u c l e i . C h e m i c a l shifts are i n parts per m i l l i o n relative to external H P 0 , M e S n , a n d N a P t C l a n d ± 1 p p m for the two metals. A positive sign indicates a shift to a lower field (higher frequency) relative to the reference. C o u p l i n g constants are i n hertz a n d are ± 3 H z for Ρ and ±12 H z for S n a n d P t . T h e variable-temperature spectra were mea sured u s i n g the commercially p r o v i d e d controller whose accuracy is ~ ±1°C. T h e temperatures a n d solvents for the i n d i v i d u a l measurements are given i n the tables. Sample concentrations were of the order of 5 x 10~ M . 31


31

119

195

3

4

4

2

e

31

1 1 9

195

2

Results and

Discussion

[PtCl(SnCl )P ] Complexes. T h e r e a c t i o n o f cis- [ P t C l ( P E t ) ] (or t h e t r i p r o p y l or t r i - n - b u t y l a n a l o g s ) i n e i t h e r C D C 1 o r C D C 1 d o e s n o t afford s i m p l e i n s e r t i o n o f S n C l i n t o a P t - C l b o n d to y i e l d t h e c i s i s o m e r , b u t g i v e s d i r e c t l y trans- [ P t C l ( S n C l ) ( P E t ) ] . T h e trans i s o m e r is s u g g e s t e d b y t h e a p p e a r a n c e o f a s i n g l e P r e s o n a n c e , δ = 13.6, flanked symmetrically by P t (7( Pt, P ) = 2 0 4 2 H z ) a n d - Sn (7( Sn, 3 i ) = 227 H z , / ( S n , P) = 2 3 7 H z ) satellite lines. (In the p r o c e e d i n g p a g e s o n l y v a l u e s for t h e S n isotope w i l l b e given). T h e S n s p e c t r u m reveals t r i p l e t structure from the t w o P E t groups a n d P t s a t e l l i t e s w h o s e s p a c i n g is s t r o n g l y s u g g e s t i v e o f a o n e - b o n d c o u p l i n g constant; the P t spectrum shows a 1 : 2 : 1 structure confirming t h e p r e s e n c e o f t w o e q u i v a l e n t P E t g r o u p s (δ P t = - 4 7 9 0 r e l a t i v e to N a P t C l ) . W e reserve further c o m m e n t o n these c o u p l i n g constants u n t i l t h e d e s c r i p t i v e c h e m i s t r y is finished. T h e s a m e c o m p l e x is o b t a i n e d d i r e c t l y f r o m trans- [ P t C l ( P E t ) ] . T h e a n a l o g o u s d i c h l o r i d e c o m p l e x c o n t a i n i n g t h e trans s p a n n i n g c h e l a t e , C o m p l e x II, w h i c h is e l e c t r o n i c a l l y s i m i l a r to P E t , c l e a n l y affords £ r a n s - [ P t C l ( S n C l ) ( E t P P E t ) ] (19). 3

2

2

3

2

3

2

2

2

3

3

2

3 1

1 9 5

117

2

P

195

1 1 9

31

1 1 7

1 1 9

31

1 1 9

1 1 9

3

1 9 5

1 9 5

1 9 5

3

2

e

2

3

2

3

2

3

2

T h e c o m p l e x e s cis-[PtCl(SnCl )P ] m a y be obtained starting from either a c i s - b i s - p h o s p h i n e c o m p l e x o f a tertiary aryl p h o s p h i n e or a c h e l a t i n g d i p h o s p h i n e , e.g. P P h or D I O P c o m p l e x e s (20), ( a l t h o u g h careful e x a m i n a t i o n o f the P-31 spectra o f the monodentate systems s u g g e s t s t h a t t h e t r a n s i s o m e r is a l s o p r e s e n t ) . 3

2

3



26

= Et PPEt 2

CH

CH

2

Et P

2

PEt

2

= bis(diethylphosphinom e t h y l ) b e n z o [ c]phenanthrene

2

2

II

[Pt(SnCl ) P ] Complexes.


3

2

Further addition of S n C l

2

t i o n c o n t a i n i n g trans- [ P t C l ( S n C l ) ( P E t ) ] l e a d s 3

3

s h o w n i n E q u a t i o n 4. U n f o r t u n a t e l y , S n C l

2

2

to a solu

to the e q u i l i b r i u m

2

is o n l y s p a r i n g l y s o l u b l e i n

c h l o r i n a t e d h y d r o c a r b o n s ; h o w e v e r , sufficient tin(II) d i c h l o r i d e c a n b e d i s s o l v e d i n a c e t o n e s u c h that t h e e q u i l i b r i u m lies far to the right. fran5-[PtCl(SnCl )(PEt ) l 3

3

trans-[Pt(SnCl ) (PEt ) ]

2

3 2

(4)

3 2

A t t h i s p o i n t i t is w o r t h m e n t i o n i n g t h a t t h e r e a r e t w o w a y s

to

detect the presence o f a poly-trichlorostannane derivative u s i n g N M R s p e c t r o s c o p y : (1) v i a t h e r e l a t i v e i n t e n s i t i e s o f t h e

1 1 7

Sn and

1 1 9

S n satel

l i t e s i n t h e P - 3 1 (or P t - 1 9 5 ) N M R s p e c t r u m a n d (2) f r o m t h e o b s e r v a tion o f a y( 2

1 1 7

Sn,

1 1 9

S n ) c o u p l i n g constant i n the Sn-119 spectrum.

P o i n t 2 is t h e m o r e o b v i o u s a n d c a n b e d e m o n s t r a t e d for a c o m p l e x s u c h as III. C l e a r l y t h e t w o m a g n e t i c a l l y i n e q u i v a l e n t t i n a t o m s PEt Cl

3

1 1 7

3

Sn—Pt— PEt

1 1 9

SnCl

3

3

III w i l l superimpose a n additional s i m p l e c o u p l i n g pattern o n the Sn-119 spectrum, thereby u n e q u i v o c a l l y establishing the presence o f more t h a n o n e S n C l " l i g a n d (see F i g u r e 1). 3

P o i n t 1 is l e s s o b v i o u s b u t e q u a l l y i m p o r t a n t . I n t h e P - 3 1 s p e c t r u m o f a m o n o - t i n c o m p l e x , the ratio o f the

1 1 9

S n (or

1 1 7

S n ) satellites to the

m a i n - b a n d ( P not c o u p l e d to N M R - a c t i v e tin) w i l l b e approximately 3 1

1 : 2 0 d u e to the r e l a t i v e l y d i l u t e s p i n I = i t i n isotopes ([—84% not c o u p l e d to I = \ S n ] / [ ~ 8 %

3 1

P c o u p l e d t o e.g.

1 1 9

d u e to c o u p l i n g ] ) . I n a c o m p l e x c o n t a i n i n g t w o S n C l molecules

having only one

1 1 7

S n or

1 1 9

3 1

P

Sn, divided by 2 3

groups there are

S n (-13%) and a few


(

2

2

CD CU/RT CD C1 /-30°C CD Cy-80°C CDCl3/-50°C

e

d

b

3

t

3

2

117

2

3

3

3

119

2

3

3

2

2

e

3

8

2

(+4.0) (-7.9) (-5.4) (-5.3)

(+0.1)

(-2.7)

(-1.1) (+1.4) (-7.2) (-2.3)

(Δδ)»

2493 2503 2640 2625

2650

2713

( -301) ( -311) ( -297) (-294)

( -369)

( -339)

(•- 6 3 3 ) ( -356) ( -363) ( -347)

2102 2041 2372 2363

6

(Δ/)

/ΐββρα»

8

3

(CI complex)], e.g. (values for [PtCl(SnCl )(PEt ),])

9.8 10.1 18.3 18.0

+28.5

+24.6

+ 17.1 + 13.6 + 18.8 +20.5

3 1

δ Ρ

P-31N M R Data"

T + irons-[PtCHSnCljKPEt^]' T + trans- [ P t C * ( S n C l ) ( P B z P h ) ] + T trans- [ P t C ( S n C l ) ( P P h ) ] + T trans- [ P t C ( S n C l ) ( P P h ) ] Λ experimental for details The Δ sign refers to the following difference: [(SnCl complex) [PtCl (PEt ) ]). ' Et^PP = Complex II. Average of S n and S n . MeO,C = C H C 0 M e . C = phenyl; C = E t 0 C = C H C O E t ; C

3

2

[PtH(SnCl )(PPh ) ]

3

trans-

c

[PtH(SnCl )(PBzPh ) ]

2

2

trans-

3

3

3

3

3

[PtCUSnClaXEtfT)]' [PtCl(SnCl )(PEt ) ] [PtH(SnCl )(Et4PP)] [PtH(SnCl )(PEt ) ]

transtranstranstrans-

T a b l e I.


34

METAL PHOSPHINE COMPLEXES o q ^ T t r - i o c s j i o o o

(M CM

«-H i-H

β 00

Ν Η Ν 05 Ο ι>

Ο Ο (Ν CO CO Œ>

»

Η

C

* ^

i-H i-H ©

i-H

χ J (Μ

11

ce

^

J

^

S ο ίο σ ί ο

00 ΙΟ

+ + +

Η

+

©

CO CO ^ b00 b- l> ic

-Η 00 ο Η Φ ι—1


+ ++

ce

I>t^ co

1

I I

ce 15 Q

Τ3

ΙΟ 00 ^t co ο œ co oq

OOOOCO^^COiO^

ι ι

I

I

I

^ 2 S

O CO CO CD 00 l> t> Tjî + + -h -h

as

t> 00 ^ ci ai oô ai

I I cb

fi

s

oo

«D

ΙΟ

S

ϋ ϋ ϋ υ b b b I OObNr, ι ι ι ε a.

ϋ ϋ ϋ ϋ ϋ b b b b b

^ ^ ^ ^ Ν

f2

Ν

Ν

Ν

M

M W

N U

Q Q Q Û Û Û Û Û Û ϋ ϋ ϋ ϋ ϋ ϋ ϋ ϋ ϋ

ϋ ϋ ϋ Π Ν

M

M

Il

W

Q Q Q Q ϋ ϋ ϋ ϋ

PH PH

§ S ai « «S ce 5

PH PH PH

CO

u

UUPQ α -g fi fi fi fi fi fi fi 00 00 00 00 52,00 00 00 00^ o

«!

co


2.

STARZEWSKi A N D P R E G O S I N

Pt-Sn

Hydrogénation

PEt

35

Catalysts

3

I [Cl Sn—Pt—CI] 3

I PEt 7(

195

Pt,

119

3

Sn) = 28954 H z VIII

C o m p l e x VIII; a l t h o u g h t h e s a m e o p e r a t i o n ( p l u s a s e c o n d factor o f ~ 2 d u e t o t h e p r e s e n c e o f e t h y l g r o u p s i n s t e a d o f c h l o r i n e (39)) s e e m s s a t i s f a c t o r y w h e n c o m p a r i n g C o m p l e x e s IX a n d X . P e r h a p s t h e π t e r m is m o r e i m p o r t a n t i n o n e c a s e t h a n i n a n o t h e r and/or a c o m p a r i s o n w i t h a Ρ c o u p l i n g is u n s u i t a b l e . T h e t r i c h l o r o s t a n n a t e g r o u p is t h o u g h t t o b e a g o o d π-acceptor d u e t o t h e e l e c t r o n - w i t h d r a w i n g properties o f the halogens, a n d this c o n c e i v a b l y c o u l d favor larger s coefficients i n a m o l e c u l a r o r b i t a l i n v o l v e d w i t h t h e p l a t i n u m - t i n bond.


Α Β

3 1

PEt

PEt

3

I [Et P—Pt—H] 3

+

3

I PEt P t , P ) = 2,515 H z (37) IX 3

7(

195

3

I [Cl Sn—Pt—H] I PEt S n ) = 9,067 H z X 3

7(

31

195

Pt,

119

I n s u m m a t i o n , t h e 7( Pt> S n ) c a n b e u s e d to assign structure w h e r e t h e m o d e o f b i n d i n g o f t h e t i n is i n q u e s t i o n a n d l a r g e o n e - b o n d p l a t i n u m - t i n / values are to b e e x p e c t e d a n d seem m a n a g e a b l e w i t h i n the context o f the F e r m i contact term. O V E R T W O B O N D S . A S mentioned, the splitting /( Sn, Ή ) = 1 7 4 0 H z (see F i g u r e 3) is s o m e w h a t l a r g e for a t w o - b o n d t r a n s c o u p l i n g c o n s t a n t (40) a n d i n fact is t h e l a r g e s t k n o w n t w o - b o n d c o u p l i n g i n v o l v i n g a p r o t o n (17). 195

1 1 9

2

1 1 9

This k i n d of coupling-constant information c a n have diagnostic v a l u e for other transition-metal h y d r i d e c o m p l e x e s . T h e V a s k a a n a l o g trans- [ I r C l ( C O ) P P ] r e a c t s w i t h S n C l t o g i v e a n i r i d i u m h y d r i d e c o m p l e x w h o s e s t r u c t u r e m a y b e e i t h e r X I or X I I (41 ). T h e o b s e r v a t i o n o f a / ( S n , Ή ) c o u p l i n g c o n s t a n t o f 1 5 7 0 H z s u g g e s t s t h a t S t r u c t u r e X I is correct a n d vibrational spectroscopic data support this assignment. 2

2

1 1 9

/

P

H

-

ΛO C - K i r —

, Cl

P

-

OC-(-Ir —

Cl

P P = 2,11bis(diphenylphosphinomethyl)-

CljSn"

N

XPI

^

" '

v

~

benzo[c]phenanthrene


36


A

two-bond

V ("•Sn

3 1

c o u p l i n g constant

>1.5

K H z is l a r g e ;

? ) ^ i n t h e c o m p l e x e s cis- [ P t C l ( S n C l ) P ] , P 3

2

2

however,

= 2 x PPh

3

or

D I O P , i s l a r g e r y e t w i t h v a l u e s e x c e e d i n g 4 K H z . T h i s k n o w l e d g e is also v a l u a b l e a n d has assisted i n d i s t i n g u i s h i n g b e t w e e n the isomeric p o s s i b i l i t i e s for t h e [ P t ( S n C l ) P 2 ] c o m p l e x e s , w h i c h for m o n o d e n t a t e 3

2

phosphorus ligands are a l l trans: J ( 2

1 1 9

Sn,

4 K H z is n o t t h e l a s t w o r d ! W e find J ( 2

1 1 9

P)

3 1

c i s

~ 200 - 250 Hz). B u t

S n , " ' S n ) ^ to b e >

16,000

a n d w e p l a n to s u b m i t these, a n d y e t larger t w o - b o n d c o u p l i n g c o n s t a n t s , s e p a r a t e l y for p u b l i c a t i o n . Additional Physical Measurements.

I n a l l o f the complexes

we


have e n c o u n t e r e d to d a t e — a n d s u c h m o l e c u l e s are reasonable m o d e l s for i n t e r m e d i a t e s

i n t h e hydrogénation c y c l e — t h e

SnCl

g r o u p is

3

p r e s e n t as a c o o r d i n a t e d l i g a n d a n d f o r m s d i s t i n c t m e t a l - m e t a l b o n d s in solution. F u r t h e r , b o t h t h e hydrogénation a n d h y d r o f o r m y l a t i o n reactions are r e p o r t e d to r e q u i r e a n excess o f tin(II) d i c h l o r i d e w i t h a Sn/Pt ratio o f m o r e t h a n 2 ( o f t e n 5 is o p t i m a l ) . O u r N M R s t u d i e s s u g g e s t S n / P t > 1 affords trans-

an appreciable

increase

[Pt(SnCl ) (PEt ) ] a n d higher S n C l 3

more complete tial relevance

2

3

2

2

that

i n the concentration

of

concentrations support a

formation o f poly-tin species. I n v i e w o f the poten o f these c o m p l e x e s

it w o u l d b e v a l u a b l e to further

characterize them. T h i s w i l l require not only additional

complexes

b u t also a d d i t i o n a l p h y s i c o c h e m i c a l information c o n c e r n i n g the elec t r o n i c s t r u c t u r e o f t h e g r o u n d a n d l o w - l y i n g e x c i t e d states. W e h a v e therefore

measured some X-ray photoelectron E S C A spectra i n the

hope o f o b t a i n i n g a fuller picture o f the charge distribution. I n con trast to U V p h o t o e l e c t r o n

spectroscopy,

(UV-PES),

where

orbital

interactions p l a y a d o m i n a n t role, E S C A b i n d i n g energies, B E s , are recognized

(42, 43) t o d e p e n d p r i m a r i l y o n t h e c h a r g e o f t h e a t o m

a n d t h e charges o f t h e s u r r o u n d i n g a t o m s ; i.e., t h e h i g h e r t h e p o s i t i v e c h a r g e t h e m o r e e n e r g y is n e e d e d t o e j e c t a c o r e e l e c t r o n ( a s s u m i n g that there are s i m i l a r relaxation

energies).

I n T a b l e I I I w e g i v e B E s for s o m e o f o u r c o m p l e x e s a n d n o t e t h e f o l l o w i n g p o i n t s : (a) t h e S n ( 3 d

5 / 2

) values o f 4 8 6 . 7 - 487.2 e V are larger

t h a n t h a t f o r t h e m o d e l t i n ( I I ) c o m p l e x ( E t 4 N ) S n C l at 4 8 5 . 7 e V 3

s u g g e s t i n g a n i n c r e a s e d p o s i t i v e c h a r g e o n t i n d u e to S n C l t i o n t o t h e p l a t i n u m , a n d (b) t h e P t ( 4 f

7/2

) values, 72.7-73.3 eV, do not

deviate significantly from those o f K P t C l 2

c o m p l e x e s (see T a b l e

3

4

= 73.4 e V or other m o d e l

III).

δ+ ;Sn:

(44)

coordina

—^Sn

— Pt

—


2.

STARZEWSKi

Pt-Sn

A N D PREGOSIN

Hydrogénation

These data m a y b e interpreted u s i n g a classical complex

model

i n w h i c h w e have

37

Catalysts

donor-acceptor

a d i m i n i s h e d positive

platinum

charge a n d a n e n h a n c e d p o s i t i v e charge o n t i n . T h e c o o r d i n a t i o n o f the S n C l " u n i t decreases the P t B E o n o n e h a n d ; h o w e v e r , the presence o f 3

a positively charged neighboring t i n compensates BE

b y increasing the

w i t h the n e t result b e i n g little or n o significant change

i nthe

ionization potential o f the p l a t i n u m core electrons. T h e t i n core re sponds to the donation o f the lone p a i r b y s h o w i n g a n e n h a n c e d poten t i a l w h i c h is i n c r e a s e d f u r t h e r b y i n t r o d u c i n g a p o s i t i v e l y

charged

n e i g h b o r i n g p l a t i n u m . T h e e n d effect at t i n is a r e l a t i v e l y h i g h c o r e


p o t e n t i a l t h a t c r e a t e s t h e i m p r e s s i o n o f a h i g h p o s i t i v e c h a r g e at t h i s metal ((Et N) SnCl 4

The

2

e

= 4 8 7 . 1 e V (45)).

p i c t u r e is a t l e a s t q u a l i t a t i v e l y i n a g r e e m e n t w i t h

S n - 1 1 9 m Môssbauer m e a s u r e m e n t s trichlorostannate

complexes

earlier

for a v a r i e t y o f t r a n s i t i o n - m e t a l

b y Fenton

a n d Z u c k e r m a n (46) w h o

more rigorously c o n c l u d e d that the t i n i n M - S n C l

3

units should be

c o n s i d e r e d as t i n ( I V ) . F r o m T a b l e I I w e note that t h e P t - 1 9 5 N M R c h e m i c a l shifts o f the platinum-tin complexes

f a l l i n a n d e v e n at h i g h e r

classical Pt(0) c o m p l e x e s ppm,

field

than the

(e.g. [ P t ( C F - t e C - C F ) ( P E t ) ] = - 4 7 1 2 3

3

[ P t ( f r a n s - s t i l b e n e ) ( P E t ) ] = - 5 1 2 2 (47)). 3

2

3

2

Accordingly

i t is

t e m p t i n g to seek a r e l a t i o n s h i p b e t w e e n t h e Pt-195 N M R c o o r d i n a t i o n c h e m i c a l shift Δδ = ô(complex w i t h tin)-6(related c o m p l e x w i t h o u t tin) a n d the e l e c t r o n d e n s i t y at t h e m e t a l . H o w e v e r , t h e f e w E S C A data for t h e c h o s e n test c o m p o u n d s d o n o t i n d i c a t e a s i m p l e c h a r g e

depen

dence o f the N M R shielding. A m o r e q u a n t i t a t i v e a t t e m p t at i n t e r p r e t i n g p l a t i n u m c h e m i c a l s h i f t s r e q u i r e s t h a t w e c o n s i d e r s o m e f o r m o f t h e R a m s e y (48) e q u a tion, w h i c h describes

the resonance

p a r a m a g n e t i c s c r e e n i n g t e r m , σ>· Q

A

frequency,

v, i n t e r m s o f t h e

is a c h a r g e - d e n s i t y ,

B

bond-order

m a t r i x , Δ Ε is t h e a v e r a g e e x c i t a t i o n e n e r g y , a n d r r e p r e s e n t s a d i s t a n c e f r o m t h e n u c l e u s for, i n t h i s c a s e , a g i v e n d e l e c t r o n . voz8H (l 0

-

σ )\ π Ρ

a oc(lME)(l/r )XQ P

3

(8)

2

A B

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

1 9 5

Pt chemi

c a l shifts m a y b e u n d e r s t o o d q u a l i t a t i v e l y i f the Δ Ε t e r m c a n b e esti m a t e d from v i s i b l e U V d a t a (49), t h e r e is a n e x p e r i m e n t a l d i f f i c u l t y i n o u r c o m p l e x e s i n t r o d u c e d b y t h e fact t h a t m i n o r i m p u r i t i e s w i t h h i g h extinction coefficients

m a y distort considerably the U V curves. W e

have f o u n d that o u r n e a r l y colorless h y d r i d o - t i n , a n d c h l o r o - t i n d e r i v a t i v e s a l s o c a n b e i s o l a t e d as y e l l o w - o r o r a n g e - c o l o r e d c o m p l e x e s t h a t , from

3 1

P m e a s u r e m e n t s , are > 9 5 % p u r e . It seems that c a u t i o n w i l l b e

r e q u i r e d i n interpreting the U V spectra. Nevertheless, a future study



4

2

2

3

2

3

3

3

c

2

2

2

3

73.3 73.3 — 72.7 c l s

6

6

(73.2) (73.0) (73.2) — 6

ESCA

Data"

e

0

Ref. 51. Data are in electron volts relative to a carbon Is B E of 285.0 eV. * Values for the complexes where S n C l is replaced by chlorine. Ref. 52.

3

3

3

trans- [ P t C l ( S n C l ) ( P E t ) ] frans-[PtH(SnCl )(PPh ) ] cis- [ P t C l ( S n C l ) ( P P h ) ] cis-[Bu N] [PtCl (SnCl ) ]

m

Pt(4f )

T a b l e III.

487.2 487.0 486.8 486.7

m

Sn(3d )


131.6 132.0 132.5 —

(131.7) (131.9)

P(2p)

2.

Pt-Sn

A N D PREGOSIN

STARZEWSKi

T a b l e IV.

Hydrogénation IR Data" (Δί>)" [cm ']

»>PtH

[cm trans- [ P t C l ( S n C l ) ( E t P P ) ] trans- [ P t C l ( S n C l ) ( P E t ) ] trans-[PtH(SnCl )(Et PP)] trans- [ P t H ( S n C l ) ( P E t ) ] trans-[PtH(SnCl )(PBzPh ) ] trans-[PtH(SnCl )(PPh ) ] trans- [ P t C H S n C l a X P E t , , ) ^ trans- [ P t C ( S n C l ) ( P B z P h ) ] ° Measured as K B r discs. Δν = (i/Pt-H in the tin complex) - (v See Table I for abbreviations. 3

3

3

3

3

2

2 2

3

2


2

4

3

3 2

3

2

2

']

— — 2112 2120 2154 2200 _ —

4

3

c

39

Catalysts

î-SnCU

[cm

— — (93) (-108) (66) (45) _ —

']

353,335,320 352,329,316 342,320 332,306 337,317,308 332,315,306 329,305 340,320

Pt-Η in the chloro complex).

b

c

i n this d i r e c t i o n c o u l d p r o v e h e l p f u l , a l t h o u g h the k n o w l e d g e

of a

s i n g l e , l o w - e n e r g y U V t r a n s i t i o n b y i t s e l f is n o t n e c e s s a r i l y s u f f i c i e n t to c l a i m a f u l l u n d e r s t a n d i n g o f t h e Δ Ε s u m m a t i o n . T h e 1/r t e r m m a y n o t 3

b e v a r y i n g s i g n i f i c a n t l y as o u r E S C A d a t a s h o w n o m a r k e d c h a n g e i n t h e c h a r g e o n p l a t i n u m . S i n c e w e h a v e n o s a t i s f a c t o r y m e t h o d o f es t i m a t i n g c h a n g e s i n Q B , o t h e r t h a n o u r I R d a t a w h i c h is far t o o c r u d e A

(see

Table

IV), a n d since an interpretation of ΔΕ

deeper understanding of our δ

1 9 5

is p r o b l e m a t i c , a

P t data m u s t await further support,

perhaps i n the form o f m o l e c u l a r orbital calculations. O n e c o u l d seek a d d i t i o n a l h e l p from the values δ

1 1 9

S n ; however,

i n a d d i t i o n t o t h e p r o b l e m s a l r e a d y m e n t i o n e d w e n o t e t h a t t h e r e is a considerable dependence

of δ

1 1 9

S n on both solvent a n d temperature

(50). I n v i e w o f t h e d i f f e r e n t s a m p l e c o n d i t i o n s i n d i c a t e d b y b o t h t h e s o l u b i l i t y a n d the d y n a m i c characteristics o f o u r c o m p l e x e s , a d e t a i l e d interpretation o f these values w o u l d b e p r e s u m p t u o u s . I n s u m m a t i o n , t h e r e is r e a s o n t o b e l i e v e , N M R studies, that the c o o r d i n a t i o n o f S n C l

2

from the E S C A

and

bestows interesting prop

e r t i e s o n o u r c o m p l e x e s ; h o w e v e r , t h e r e is as y e t i n s u f f i c i e n t d a t a t o p e r m i t d e f i n i t i v e c o n c l u s i o n s r e l e v a n t to t h e h o m o g e n e o u s

hydrogéna

tion reaction. Acknowledgments W e t h a n k H . R u e g g e r for e x p e r i m e n t a l a s s i s t a n c e a n d L . M . V e n a n z i for m a n y h e l p f u l d i s c u s s i o n s . Literature

Cited

1. Itatani, H.; Bailar, J. C. Jr. Ind. Eng. Chem. Prod. Res. Dev. 1972, 11, 146. 2. Cramer, R. D.; Jenner, E . L.; Lindsey, R. V. Jr.; Stolberg, U. G. J. Amer. Chem. Soc. 1963, 85, 1691.


40 3. 4. 5. 6. 7. 8. 9.


10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46.

M E T A L PHOSPHINE COMPLEXES

Knifton, J. F. J. Org. Chem. 1976, 41, 793. Schwager, I.; Knifton, J. F. J. Catal. 1976, 45, 256. Parshall, G. W. J. Mol. Catal. 1978, 4, 243. Young, J. F.; Gillard, R. D.; Wilkinson, G. J. Chem. Soc. 1964, 5176. Baird, M . C. J. Inorg. Nucl. Chem. 1967, 29, 367. Cramer, R. D.; Lindsey, R. V. Jr.; Prewitt, C. T.; Stolberg, U. G. J. Amer. Chem. Soc. 1965, 87, 658. Lindsey, R. V.; Parshall, G. W.; Stolberg, U. G. J. Amer. Chem. Soc. 1965, 87, 658. Onaka, S. Bull. Chem. Soc. Jpn. 1975, 48, 319. Mason, R.; Robertson, G. B.; Whimp, P. O. Chem. Comm. 1968, 1655. Clegg, W., Acta Crystallogr. 1978, B34, 278. Guggenberger, L. J . Chem. Comm. 1968, 512. Stalick, J. K.; Corfield, P. W. R.; Meek, D. W. J. Amer. Chem. Soc. 1972, 94, 6194. Bürgi, H . B.; Johnson, D. K.; Venanzi, L. M., unpublished results. Pregosin, P. S.; Sze, S. N. Helv. Chim. Acta 1978, 61, 1848. Starzewski, Ostoja Κ. Α.; Ruegger, H.; Pregosin, P. S. Inorg. Chim. Acta 1979, 36, L445. Jesson, J. P. In "Transition Metal Hydrides", Muetterties, E . , E d . ; Marcel Dekker: New York, 1971; p. 75. Baumgartner, E . ; Venanzi, L. M., unpublished data. Pregosin, P. S.; Sze, S. N. Helv. Chim. Acta 1978, 61, 1848. Starzewski, Ostoja Κ. Α.; Pregosin, P. S., unpublished data. Hsu, C. C.; Geanangel, R. A. Inorg. Chem. 1980, 19, 110. Hsu, C. C.; Geanangel, R. A. Inora. Chem. 1977, 16, 2529. Kauffman, J. W.; Moor, D. H.; Williams, R. J. J. Inorg. Nucl Chem. 1977, 39, 1165. Ruegger, H.; Pregosin, P. S., unpublished data. Kunz, R. W.; Pregosin, P. S. In " N M R Basic Principles and Progress"; Springer-Verlag: Heidelberg, 1979; Vol. 16. Butler, G.; Eaborn, C.; Pidcock, A. J. Organomet. Chem. 1979, 181, 47. Eaborn, C.; Pidcock, Α.; Steele, B. R. J. Chem. Soc. Dalton 1976, 767. Eaborn, C.; Pidcock, Α.; Steele, B. R. J. Chem. Soc. Dalton 1975, 809. Starzewski, Ostoja Κ. Α.; Pregosin, P. S. Angew. Chem. Int. Ed. 1980, 19, 316. Nelson, J. H.; Cooper, V.; Rudolph, R. R. Inorg. Nucl. Chem. Lett. 1980, 16, 263. Pidcock, Α.; Richards, R. E . ; Venanzi, L. M . J. Chem. Soc. A 1966, 1707. Appleton, T. G.; Clark, H . C.; Manzer, L. E . Coord. Chem. Rev. 1973, 10, 335. Pople, J. Α.; Santry, D. P. Mol. Phys. 1964, 8, 1. Ibid, 1965, 9, 311. Crocker, C.; Goggin, P. L.; Goodfellow, R. J. J. Chem. Soc. Dalton 1976, 2494. Allen, F. H.; Pidcock, Α.; Waterhouse, C. R. J. Chem. Soc. A, 1970, 2087. Dingle, T. W.; Dixon, K. R. Inorg. Chem. 1974, 13, 846. Mather, G. G.; Pidcock, Α.; Rapsey, G. J . N. J.C.S. Dalton 1973, 2095. Verkade, J. G. Coord. Chem. Rev. 1972-73, 9, 1. Baumgartner, E . ; Starzewski, Ostoja Κ. Α.; Venanzi, L. M., unpublished data. Riggs, W. M. Anal. Chem. 1972, 44, 830. Cook, C. D.; Wan, K. Y.; Gelius, U.; Hamrin, K.; Johansson, G.; Olsson, E . ; Siegbahn, H.; Nordling, C.; Siegbahn, K. J. Amer. Chem. Soc. 1971, 93, 1904. Parshall, G. W. Inorg. Chem. 1972, 11, 433. Swartz, W. E . ; Watts, P. H.; Lippincott, E. R.; Watts, J. C.; Huheey, J. E . Inorg. Chem. 1972, 11, 2632. Fenton, D. E . ; Zuckerman, J. J. Inorg. Chem. 8, 1771.


2.

STARZEWSKI A N D PREGOSIN

Pt-Sn Hydrogénation Catalysts

41

47. Browning, J . ; Green, M.; Spencer, J. L.; Stone, F. G. A. J. Chem. Soc. Dalton, 1977, 278. 48. Ramsey, N . F. Phys. Rev. 1950, 78, 699. 49. Goggin, P. L.; Goodfellow, R. J.; Haddock, S. R.; Taylor, B. F.; Marshall, I. R. H. J. Chem. Soc. Dalton 1976, 459. 50. Smith, P. J.; Smith, L. Inorg. Chim. Acta Rev. 1973, 7, 11. 51. Starzewski, Ostoja Κ. Α.; Pregosin, P. S.; Sawatsky, G., unpublished data. 52. Grutsch, P. Α.; Zeller, M . V.; Fehlner, T. P. Inorg. Chem. 1973, 12, 1431.


R E C E I V E D August 15, 1980.


Catalytic Aspects of Metal Phosphine Complexes - ACS Publications

Recommend Documents