Catalytic Aspects of Metal Phosphine Complexes - American

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9 Tricyclohexylphosphine Complexes of Ruthenium, Rhodium, and Iridium and Their Reactivity Toward Gas Molecules BRIAN R. J A M E S and M I C H A E L P R E E C E Department of Chemistry, University of British Columbia, British Columbia, Vancouver V 6 T 1Y6, Canada S T E P H E N D. ROBINSON Department of Chemistry, King's College, Strand, London WC2R 2LS, England

Single-stage syntheses from commercially available chlorides and spectroscopic characterization are given for several tricyclohexylphosphine (PCy ) complexes of ruthenium [HRuCl(CO)(PCy ) , Ru(CO) (PCy ) ], rho dium [HRhCl (PCy ) , trans-RhCl(CO)(PCy ) ], and iri dium [HIrCl (PCy ) , trans-IrCl(CO)(PCy ) ]. The iridium (I) precursor [IrCl(C H ) ] has been used to yield HIrCl (PCy ) (dma) (dma = oxygen-bonded Ν,Ν'dimethylacetamide), H IrCl(PCy ) , and deuterated de rivatives, HIr(OH)Cl(CH CN)(PCy ) , IrCl(C H CN)(PCy ) , and IrCl(PCy )2O2. Further data are presented 3

3 2

2

2

3 2

2

3 2

3 2

3 2

8

14 2 2

3 2

2

3 2

3

3 2

on

3

3 2

3 2

6

5

3

previously

reported

complexes

such

as

containing a coordinated hexenyl ring and M(COD)Cl(PCy )(M = Rh COD = 1,5-cyclooctadiene). The carbonyls (PCy ) and two isomers of HIrCl (CO)(PCy ) characterized also. Attempts to isolate PCy containing CO were unsuccessful. 3

3 2

2

3 2

3

cyclo and Ir; H IrCl(CO)are complexes 2

2

T

h e w o r k r e p o r t e d i n t h i s c h a p t e r h a s r e s u l t e d from s t u d i e s i n i t i a t e d b y a N A T O grant a w a r d e d for a project c o n c e r n i n g a c t i v a t i o n o f C 0 b y t r a n s i t i o n - m e t a l c o m p l e x e s (I ). T h e first s t r u c t u r a l 2

0065-2393/82/0196-0145$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.

METAL PHOSPHINE COMPLEXES

146

report of a transition-metal c o m p l e x containing coordinated C 0 s c r i b e d the

bis(tricyclohexylphosphine)nickel(0)

( P C y ) ( 2 ) , a n d this l e d us to investigate the 3

species,

de

2

Ni(C0 )2

tricyclohexylphosphine

2

complexes of ruthenium, r h o d i u m , and i r i d i u m . This basic a n d b u l k y p h o s p h i n e h a s b e e n u s e d w i d e l y (3) to s t a b i l i z e s p e c i e s n o t u s u a l l y i s o l a b l e w i t h less b u l k y p h o s p h i n e s s u c h as t r i p h e n y l p h o s p h i n e , a n d is a l s o a g o o d a n c i l l a r y l i g a n d for a c o o r d i n a t i v e l y u n s a t u r a t e d c o m p l e x l i k e l y to r e a c t w i t h s m a l l gas m o l e c u l e s . T h i s h a d b e e n

well

d o c u m e n t e d for r h o d i u m (4, 5 ) , a n d i n s i t u s o l u t i o n s o f R h C l ( P C y ) , 3

for e x a m p l e , g a v e i s o l a b l e a d d u c t s w i t h 0 , N , C H , C O , a n d H 2

At

the

time

our

studies

were

about ruthenium and i r i d i u m RuCl (CO)(PCy ) , 2

3

initiated little

3

and IrCl(CO)(PCy ) 3

2

2

4

had been

2

(6, 7, 8),

such

Ru(CO) (PCy ) 3

3

as (9),

2

(4) w e r e k n o w n .

Since 1977 several papers on r h o d i u m a n d i r i d i u m systems v a n t to the present w o r k h a v e a p p e a r e d V r i e z e ' s g r o u p (15),

2

(5).

2

reported

species, although carbonyls

HRuCl(CO)(PCy )

2

2

One

(10-16).

rele

o f these

by

w h i c h reported partial dehydrogenation of tricyc

l o h e x y l p h o s p h i n e c o o r d i n a t e d to i r i d i u m ( I ) a n d r h o d i u m ( I ) ,

overlap

p e d w i t h some of our studies w h i c h were reported almost simulta n e o u s l y at a c o n f e r e n c e

(17).

T h i s chapter describes s i m p l e single-stage syntheses of a range o f hydridocarbonyl and hydridocarbonyl tricyclohexylphosphine

com

p l e x e s o f r u t h e n i u m , r h o d i u m , a n d i r i d i u m , a t t e m p t s at f o r m i n g complexes

from rhodium(I) and iridium(I)

precursors, a n d

C 0

2

dehydro

g e n a t i o n o f t h e c y c l o h e x y l r i n g o f t h e p h o s p h i n e . It a l s o r e p o r t s p r e l i m i n a r y data on the formation of a hydrido(hydroxo)

species b y oxida

t i v e a d d i t i o n o f w a t e r to a n i r i d i u m ( I ) c o m p l e x a n d t h e c h a r a c t e r i z a t i o n and chemistry of a dioxygen complex,

IrCl(0 )(PCy ) . 2

W e h a v e p u b l i s h e d a b r i e f r e p o r t (18)

3

2

on some o f the studies de

s c r i b e d i n this chapter. Results and

Discussion

T h e s p e c t r o s c o p i c d a t a for s o m e o f t h e s y n t h e s i z e d c o m p l e x e s g i v e n i n T a b l e I. S e v e r a l o f t h e s y n t h e s e s w e r e o f t h e small-scale

type

developed

tertiary-phosphine-type

by

one

complexes

of

us

(19,

for

20)

are

single-stage, preparing

of G r o u p V I I I p l a t i n u m metals.

T h e m e t h o d involves r a p i d m i x i n g of refluxing ethanolic solutions of a c o m m e r c i a l l y a v a i l a b l e h a l i d e a n d the p h o s p h i n e , sometimes

i n the

presence o f K O H , N a B H , or H C H O . 4

Ruthenium

Complexes.

l i k e the H R u C l ( C O ) P

2

The

HRuCl(CO)(PCy ) 3

2

Complex

a n a l o g u e s ( P = P B u M e , P B u E t ) (21), 2

2

s e n s i t i v e , b u t u n l i k e t h e l a t t e r i t is l i g h t s t a b l e . T h e h i g h - f i e l d N M R is a t r i p l e t i n d i c a t i n g t h e e q u i v a l e n c e

o f the two

1,

is a i r H-l

phosphines,

w h i c h is c o n f i r m e d b y t h e s i n g l e t i n t h e P - 3 1 N M R . T h e h i g h

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

v(Ru-


Z

2

2

2

f l

2

RhCl(COD)P

2

HRhCl P

2

H IrClP*P

2

2

D IrClP HDIrClP H IrCl(CO)P

2

2

2

2

H IrClP

2

2

2

2

HIrCl P (dma) HIrCl (CO)P HIrCl (CO)P

2

2

2

2

2

9

1970

1628 1980 2010 2015

1900 1905 1870 1873

b

v(CO)

2

A

3

a

b

d

—

32.2, 33.6, 30.6, 33.3,

+ + + +

+ 2 6 . 1 (d)'

+ + + +

+ 2 4 . 2 (s)

J

6

—

—

5

12 H z

40.5 (d. o f t ) *

345 342 275

j

1943

4 2 . 4 (t) 30.1 (d. o f t ) ' 18.4 ( d . o f t ) 33.2, 20.5 35.3, 17.2

2

(Ρ

12 H z 13 H z 18 H z

—

Ρ

12 H z 12.5 H z

15 H z 12 H z

—

—

—

+ 4 1 . 4 (s) + 41.9 + 4 1 . 6 (s)

—

4 2 . 3 (t) 43

+ 2 . 3 (s) - 0 . 7 (s)

18.2 (t) 2 6 . 1 (t)

—

250

12.3" 11.5" 14.3* 13.6

11 H z

2210, 2120

+ 2 0 . 9 (s)

255

P

—

+ 6 3 . 5 (s)

C

18 H z 17.5 H z

JiP-H)

2210, 2125

(

C

+ 4 6 . 7 (s)

%P-31)

2300 2105 2275 2276 2230 2240 1605 1605, 2230 2200, 2100

—

4 2 . 3 (t)

3 4 . 5 (t) 3 4 . 6 (t)

295 295

C

T(M-H)

b

v(M-Cl)

317 317 300 310 310, 2 6 0 310, 2 5 5 287 285 287 287 255

not f o u n d

2107 2030

B

v(M-H(D))

S p e c t r o s c o p i c D a t a for S o m e o f t h e S y n t h e s i z e d C o m p l e x e s

TW 13 TW

15

TW

TW

e

TW 6, 8, 23 TW 9 TW 4 TW TW TW 4 TW 15 TW TW

Ref."

fc

/ 2

A

R

-1

0

1

0

e

P

2

2

2

Note: Data for H D I r C l ( C O ) P (11), IrCl(CeH CN)P (13), HIr(OH)Cl(CHî,CN)P (14), IrCl(0 )P (15), and trans-IrCl(CO)P , IrCl(COD)P, and frans-RhCl(CO)P are discussed in the text. Ρ = tricyclohexylphosphine. IR recorded as Nujol mulls on Perkin Elmer Model 457 (centimeters ). N M R data recorded in C D C 1 or C e D solution; H - l (100 M H z ) relative to T M S ; P-31-{H-1} (40.5 M H z ) relative to 85% H3PO4, downfield shifts being positive; s = singlet; d = doublet; t = triplet. T W = this work. Data quoted for I r C l ^ (4). y < H - H ) = 5 Hz. P * = P(CeH )Cy A B quartet; 7 = 336 Hz. * A B quartet; / p - , = 335 Hz. A B quartet; ; - ) = 337 H z . 7(Rh-H) = 30 Hz. i o u i - p ) = 141.9 H z ; olefinic protons detected at τ values of 4.77 and 6.46, trans to phosphorus and chlorine, respectively.

tu P r

-* a a-

met

2

HIrCl P

3

Ru(CO) P

HRuCl(CO)P

Complex"

Table L

148


C l ) , 2 9 5 c m " , is i n d i c a t i v e o f c h l o r i d e t r a n s to C O (22), a n d t h u s t h e 1

s t e r e o c h e m i s t r y s h o w n i n S t r u c t u r e 1 is f a v o r e d , a l t h o u g h a t r i g o n a l b y p y r a m i d a l structure w i t h axial phosphines cannot be r u l e d out The HRuCl(CO)(PCy ) 3

(21).

c o m p l e x p r e p a r e d e a r l i e r (6, 8, 23) a p p e a r s to

2

b e t h e s a m e i s o m e r j u d g i n g f r o m t h e h i g h - f i e l d H - l N M R (23) a n d t h e a n d *>(Ru-Cl) v a l u e s (6, 8 ) , a l t h o u g h o u r *>(Ru-H) at 2 1 0 7 c m "

v(CO)

m u c h h i g h e r than the 2 0 3 0 - c m " v a l u e w h i c h was reported

Ρ

? \

1

1

is

(6).

1

CO /

Ru /

\

Cl

Ρ 1

O n s t a n d i n g i n air, the c a r b o n y l b a n d shifts to 1940 c m " cm"

1

(cf. 1 9 3 5

i n R e f . 6) a n d t h e h y d r i d e b a n d to 2 0 4 0 c m " , w h i l e a b r o a d b a n d

1

1

appears centered a r o u n d 1150 c m

- 1

, t o g e t h e r w i t h a w e a k b a n d at 1 2 2 0

c m " , w h i c h a r e a l m o s t c e r t a i n l y d u e to p h o s p h i n e o x i d e (24). 1

The

b r o w n o x i d a t i o n p r o d u c t h a s n o t b e e n i s o l a t e d i n a p u r e state b u t a h y d r i d o c a r b o n y l c o n t a i n i n g c o o r d i n a t e d p h o s p h i n e o x i d e is i n d i c a t e d strongly. W e have not b e e n a b l e to detect a p o s s i b l e d i o x y g e n inter m e d i a t e e v e n at l o w t e m p e r a t u r e s i n s o l u t i o n , a l t h o u g h t h e o s m i u m analogue H O s C l ( C O ) ( P C y ) 0 3

2

2

is c h a r a c t e r i z e d w e l l

(8).

C o m p l e x 1 is k n o w n (8) to f o r m c o m p l e x e s w i t h C O , S 0 , a n d C S 2

( w h i c h inserts to g i v e a dithioformate), toward C 0

2

but we

found no

2

reactivity

i n toluene solution.

C o m p l e x 1 can b e s y n t h e s i z e d also i n s o m e w h a t l o w e r y i e l d s b y simply refluxing R u C l PPh

3

3

· 3 H 0 a n d P C y i n m e t h a n o l . I n c o n t r a s t to t h e 2

3

reaction w h i c h yields R u C l ( P P h ) 2

3

3

(25), t h e P C y

3

appears basic

e n o u g h to p r o m o t e the b a s e - c a t a l y z e d c a r b o n y l abstraction r e a c t i o n . The

Ru(CO) (PCy ) 3

s t r o n g v(CO)

3

2

complex,

2 , is c h a r a c t e r i z e d b y

a

single,

c e n t e r e d at 1 8 7 0 c m " , a n d t h e s i n g l e t i n t h e P - 3 1 1

shows e q u i v a l e n t p h o s p h i n e s ; l i k e the P P h

a n a l o g u e (26, 27),

3

NMR a tri

g o n a l b i p y r a m i d a l s t r u c t u r e w i t h e q u a t o r i a l C O l i g a n d s is i n d i c a t e d . Iridium Complexes.

The

air-stable, rose-colored

monohydride

H I r C l ( P C y ) , C o m p l e x 3, m a y b e p r e p a r e d d i r e c t l y from a c o m m e r 2

3

2

c i a l l y a v a i l a b l e c h l o r i d e , or b y a d d i n g H C 1 t o a t o l u e n e s o l u t i o n c o n taining

the

cyclooctene

dimer

[IrCl(COT) ] 2

2

and

PCy . 3

The

six-

c o o r d i n a t e , y e l l o w C o m p l e x 4 c o n t a i n i n g o x y g e n - b o n d e d d m a , i>(CO) 1628 c m "

1

(28),

a l s o is i s o l a t e d r e a d i l y .

T h e i>(Ir-H) o f C o m p l e x 3 is n o t o b s e r v e d ; h o w e v e r S h a w ' s g r o u p (29)

h a s n o t e d a l s o t h a t t h e m e t a l h y d r i d e s t r e t c h is w e a k or u n o b s e r v -

able i n

five-coordinate,

square p y r a m i d a l i r i d i u m a n d r h o d i u m h y d -


9.

JAMES E T A L .

Tricyclohexylphosphine

149

Complexes

rides c o n t a i n i n g b u l k y p h o s p h i n e s . B a s e d on the h i g h - f i e l d H - l N M R t r i p l e t , t h e P - 3 1 s i n g l e t , a n d t h e s i n g l e ï>(Ir-Cl), C o m p l e x 3 is a s s i g n e d the

square

p y r a m i d a l structure s h o w n

i n Reaction

1;

a

trigonal

b i p y r a m i d a l s t r u c t u r e w i t h a x i a l c h l o r i d e s satisfies t h e s p e c t r a l d a t a , b u t i t is n o t f a v o r e d o n s t e r i c g r o u n d s o r b y t h e group

findings

of

Shaw's

(29).

C o m p l e x 4 s h o w s t h e i^(Ir-H) at 2 3 0 0 c m "

w h i c h is r e l a t i v e l y

1

h i g h a n d p r e s u m a b l y reflects t h e w e a k t r a n s - i n f l u e n c e o f t h e l i g a n d ; C o m p l e x 4 i n b e n z e n e or C H C 1 2

2

amide

r e a d i l y dissociates to C o m

p l e x 3 a n d free d m a . T h e d e e p r e d solutions o f C o m p l e x 3 react further w i t h g a s e o u s H C l to g i v e y e l l o w s o l u t i o n s . T h i s r e a c t i o n is r e v e r s e d r e a d i l y w h e n H C l is r e m o v e d , b u t t h e n a t u r e o f t h e f o r w a r d r e a c t i o n ( p o s s i b l y o x i d a t i v e a d d i t i o n o r a d d i t i o n o f c h l o r i d e to t h e v a c a n t c o o r d i n a t i o n site) h a s n o t b e e n e l u c i d a t e d . A d i a m a g n e t i c r o s e c o m p l e x f o r m u l a t e d as t h e i r i d i u m ( I I ) s p e c i e s I r C l ^ P C y ^ , V(IT-CI)

317 c m " , prepared from aqueous isopropyl al 1

c o h o l solutions c o n t a i n i n g I r C l

e

3

" and P C y

3

(4), m u s t b e t h e h y d r i d e

c o m p l e x , 3. A d d i n g C O to C o m p l e x 3 g i v e s t h e w h i t e , h y d r i d o c a r b o n y l H I r C l (CO)(PCy ) . 3

The

2

equivalent

phosphines

(P-31

NMR),

2

single

Klr-Cl),

Ρ Ir Cl

Ir

22»

Ρ

Cl

Ir

^

Ρ

CO

^

Cl \

-HCl HC,

/

/ Ir

CO

Ρ

(1)

\

Ρ

a n d d r a m a t i c l o w e r i n g o f t h e τ v a l u e to 1 8 . 2 , i n d i c a t i n g t h e i n t r o d u c t i o n o f a h i g h t r a n s i n f l u e n c e l i g a n d t r a n s to t h e h y d r i d e , a r e a l l c o n s i s t e n t w i t h S t r u c t u r e 5. O n s t a n d i n g i n t h e s o l i d state o r i n s o l u t i o n C o m p l e x 5 i s o m e r i z e s to C o m p l e x 6, a n d t h e r e is a l s o loss o f H C l t o y i e l d t h e k n o w n c o m p o u n d trans - I r C l ( C O ) ( P C y ) 3

the

isomerization, the

changed

2

(4, 15, 3 0 ) . D u r i n g

P-31 c h e m i c a l shift remains essentially u n

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

i>(Ir-Cl) s p l i t s i n t o t w o b a n d s , a n d t h e v(lr-}l)

ligands,

a n d *>(CO) s h i f t s t o

h i g h e r w a v e n u m b e r s . T h e d a t a for C o m p l e x 6 a r e c o n s i s t e n t w i t h t h e g e o m e t r y s h o w n , w h i c h is t h a t p o s t u l a t e d o n I R e v i d e n c e a l o n e for t h e identical

compound

IrCl(CO)(PCy ) 3

2

made

via

addition

of

HCl

to

trans-

(4). O u r s y n t h e s i s o f t h i s V a s k a - t y p e c o m p l e x

from

[ I r C l ( C O T ) ] offers a n a l t e r n a t i v e to t h a t g i v e n i n t h e l i t e r a t u r e ( 4 , 3 0 ) . 2

2

T h e 1,5-cyclooctadiene

complex I r C l ( C O D ) P C y

3

p h o s p h i n e is a d d e d to t h e e a s i l y m a d e a n d h a n d l e d

is f o r m e d w h e n [HIrCl (COD)]


2

2

150


d i m e r (31).

T h e p h o s p h i n e is s u f f i c i e n t l y b a s i c to r e m o v e t h e H C l a n d

a c c o m p l i s h the f a m i l i a r b r i d g e - s p l i t t i n g reaction. T h e

complex

b e e n m a d e p r e v i o u s l y v i a the s o m e w h a t more e l u s i v e

[IrCl(COD)]

c o m p l e x a n d w a s c h a r a c t e r i z e d b y p r o t o n N M R (14).

has 2

The phosphine

a p p e a r s as a s i n g l e t , δ ( Ρ - 3 1 ) + 1 4 . 1 . T h e chemistry of i n situ Ir(I)/PCy interesting dehydrogenation under an H

3

s y s t e m s is c o m p l i c a t e d b y a n

o f a c y c l o h e x y l r i n g (vide infra),

atmosphere [IrCl(COT) ]2/PCy 2

2

3

but

solutions readily y i e l d

t h e d i h y d r i d e c o m p l e x H I r C l ( P C y ) , 7 , as d i s c o v e r e d i n d e p e n d e n t l y 2

by Vrieze's

g r o u p (15).

3

The

2

spectroscopic data indicate a trigonal

b y p y r a m i d a l s t r u c t u r e w i t h a x i a l p h o s p h i n e s (15). W e h a v e m o n i t o r e d f o r m a t i o n o f t h e d i h y d r i d e at 20°C b y f o l l o w i n g a n i r r e v e r s i b l e a b s o r p t i o n o f 1.0 m o l H ^ i r i d i u m , a n d t h e n o t e d h y d r o g é n a t i o n o f t h e c y c l o o c tene

(15)

subsequently

ti

,s

place.

Catalytic

hydrogénation

of

monoenes using C o m p l e x 7 under ambient conditions occurs but very slowly. A n attempted synthesis o f the deuterated analogue o f C o m p l e x 7 using a D

instead of a H

2

2

atmosphere

leads to the e x p e c t e d

di-

deuteride, C o m p l e x 8, together w i t h a p p r e c i a b l e amounts o f the d i h y d r i d e a n d H D c o m p l e x , 9. T h e I R i > ( I r - H a n d I r - D ) c l e a r l y r e v e a l s a h y d r i d e a n d a deuteride, w h i l e the high-field H - l N M R shows

two

d i s t i n c t t r i p l e t s at r 4 2 . 3 a n d r 4 2 . 4 , a s s i g n a b l e to H I r C l ( P C y )

and

2

3

2

H D I r C l ( P C ) , respectively. 3

2

F u r t h e r e v i d e n c e for t h e p r e s e n c e o f t h e H D c o m p l e x c o m e s carbonylation studies. H I r C l ( P C y ) 2

H IrCl(CO)(PCy ) 2

3

3

2

from

reacts w i t h 1 a t m o f C O to g i v e

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

2

r a m e t e r s as C o m p l e x 10. T h e P - 3 1 s i n g l e t i n d i c a t e s e q u i v a l e n t p h o s phines, while

the t w o

d o u b l e t s o f t r i p l e t s at r 3 0 . 1 a n d r l 8 . 4

a s s i g n e d t o H ( t r a n s to c h l o r i n e ) a n d H ( t r a n s t o C O ) , A

A

are

respectively.

C a r b o n y l a t i o n o f the p r o d u c t o b t a i n e d from the deuteration reaction g i v e s S p e c i e s 11 i n w h i c h t h e Jm-m field

c o u p l i n g is l o s t i n t h e t w o h i g h -

r e s o n a n c e s a n d e a c h s i x - l i n e p a t t e r n s i m p l i f i e s to a t r i p l e t (see

Figure

1).

3

seventh

of

11

Species

HDIrCl(CO)(PCy ) . H - H

2

must

be

mainly

the

two

isomers

of

S i n c e H - D c o u p l i n g s are generally about one-

couplings, such

interactions are

not u s u a l l y re

solvable.

,

H(D)

Β

D(H)

Ir /

C Oι

CO 10

\ ι Cl

X

ρ

11


9.

JAMES E T A L .

Tricyclohexylphosphine 18.36 r

H,

B

l

Figure

1.

151

Complexes H

30.11

A

r

Hiah-field H-l NMR for H lrCl(CO)(PCy ) and isomers of HDIrCl(CO)(PCy ) (Complex 2

(Complex 11)

3 2

3 2

10)

T h e m e c h a n i s m of the H D exchange m u s t i n v o l v e the l i g a n d cycl o h e x y l r i n g , p r e s u m a b l y v i a a C - H c l e a v a g e ( o x i d a t i v e a d d i t i o n ; see Refs.

and

32

D IrCl(PCy ) 2

3

within

33)

the

initially

formed

five-coordinate

c o m p l e x . T h e I R o f the d e u t e r a t e d p r o d u c t s h o w s sev

2

eral bands of H I r C l ( P C y ) 2

3

a n d 7 9 5 -> 5 6 6 c m " ) .

s h i f t e d b y a b o u t V 2 (e.g. 8 3 7 -> 6 0 0 c m "

2

1

Treatment o f the d i h y d r i d e w i t h d e u t e r i u m

1

l e a d s to t h e d i d e u t e r i d e ( a n d v i c e v e r s a ) , a l t h o u g h d i h y d r i d e f o r m a t i o n is e s s e n t i a l l y i r r e v e r s i b l e u n d e r t h e s a m e c o n d i t i o n s . T h i s a g a i n s h o w s t h a t t h e e x c h a n g e p r o c e s s m u s t i n v o l v e t h e p h o s p h i n e . T h e r e is n o d i r e c t e v i d e n c e for a n o r t h o - m e t a l l a t e d s p e c i e s s i n c e t h e P - 3 1 N M R o f H IrCl(PCy ) 2

3

tively

2

r e m a i n s as a s i n g l e t e v e n at - 8 5 ° C ( 1 5 ) . T h e c o o r d i n a -

saturated c o m p l e x

H IrCl(CO)(PCy ) 2

3

2

shows

no

exchange

with D . 2

IrCl(PCy ) 3

Ring.

An

Chemistry and Dehydrogenation

2

investigation into the

of

a

Cyçlohexyl

chemistry of I r C l ( P C y ) 3

2

species

s e e m e d w a r r a n t e d i n v i e w o f t h e r e a c t i v i t y o f t h e r h o d i u m a n a l o g u e (5, 12) a n d t h e I r C l ( P P h ) 3

2

s p e c i e s (34)

Treatment of [IrCl(COT) ] 2

2

toward small molecules.

with P C y

3

i n t o l u e n e at 20°C u n d e r

argon yields H I r C Ï Ï Î ^ 6 H ) C y ] ( P C y ) , C o m p l e x 12, i n w h i c h one 2

9

2

3

c y c l o h e x y l r i n g h a s b e e n d e h y d r o g e n a t e d to a c y c l o h e x e n e , t h e d o u b l e b o n d o f w h i c h is c o o r d i n a t e d t o t h e i r i d i u m . T h i s i n t e r e s t i n g r e a c tion was

discovered

independently by Vrieze's

group

(15).

How

e v e r these workers h a d u s e d r e f l u x i n g c o n d i t i o n s a n d this h a d l e d to loss o f

H

2

a n d formation

of four-coordinate

iridium(I)

species

I r C l [ P ( C H ) C y ] ( P C y ) as a m i x t u r e o f i s o m e r s w i t h 4 . 5 - a n d 5.5e

9

2

3


152


membered

rings. Treatment

o f this mixture w i t h H

2

gave the t w o

5 . 5 - m e m b e r e d - r i n g c i s - d i h y d r i d e s s h o w n i n C o m p l e x 1 2 , as w e l l as a d i h y d r i d e o f a 4 . 5 - m e m b e r e d ring. O u r s p e c t r o s c o p i c d a t a for C o m p l e x 12 a r e i n e x c e l l e n t a g r e e m e n t w i t h t h e i r s ; t h e P - 3 1 is w e l l - r e s o l v e d at 20°C, w h e r e a s t h e D u t c h w o r k e r s o b t a i n e d a m o r e c o m p l e x r e a c t i o n m i x t u r e w h i c h r e q u i r e d l o w e r t e m p e r a t u r e s for r e s o l u t i o n . W e a l s o w e r e a b l e t o o b t a i n t h e h i g h - f i e l d b u t p o o r l y r e s o l v e d τ v a l u e s at 2 0 . 5 a n d 3 3 . 2 for t h e d o m i n a n t i s o m e r o f C o m p l e x 1 2 ( 8 0 % ) , a n d at 1 7 . 2 a n d 3 5 . 3 for t h e o t h e r i s o m e r ( 2 0 % ) , t h e h i g h e r τ v a l u e i n e a c h c a s e p r o b a b l y r e f e r r i n g to t h e h y d r i d e w h i c h is trans to c h l o r i d e . C r a b t r e e et a l . (35) h a v e r e p o r t e d r e c e n t l y o n d e h y d r o g e n a t i o n o f c y c l o a l k a n e s using cationic i r i d i u m complexes containing triphenylphosphine. There

i s n o hydrogénation

of the d o u b l e b o n d i n C o m p l e x

(the r e v e r s e o f i t s s y n t h e s i s ) u s i n g a n H although

s u c h hydrogénation

is w e l l

2

atmosphere

documented

12

u p t o 80°C,

for u n s a t u r a t e d

p h o s p h i n e s s u c h as o - v i n y l p h e n y l d i p h e n y l p h o s p h i n e w h e n

coordi

n a t e d at r h o d i u m ( 3 6 ) . D i h y d r o g e n t r a n s f e r w i t h i n s p e c i e s s u c h as [H Ir(diene)(PPh ) ] 2

3

2

+

h a s b e e n d e m o n s t r a t e d (37), b u t h e r e b o t h h y

drogens are cis to a c o o r d i n a t e d o l e f i n i c b o n d , w h e r e a s i n C o m p l e x 12, o n e h y d r o g e n is t r a n s . F o r a n o v e r a l l c i s - a d d i t i o n o f h y d r o g e n s t o a n o l e f i n w i t h i n a n o c t a h e d r a l o l e f i n - d i h y d r i d e i n t e r m e d i a t e , i t is n o t necessary to h a v e b o t h h y d r o g e n s cis to the olefin. T h e h y d r o g e n s are t r a n s f e r r e d s u c c e s s i v e l y a n d i t is c l e a r i n s o m e cases t h a t a n i s o m e r i z a tion w i t h i n an a l k y l - h y d r i d e intermediate

is n e c e s s a r y

to y i e l d a

species w i t h c i s - d i s p o s e d a l k y l a n d h y d r i d e ligands prior to r e d u c t i v e e l i m i n a t i o n o f s a t u r a t e d p r o d u c t (38). I t is p o s s i b l e t h a t a n y s u c h isomerization pathway f o l l o w i n g an initially formed h y d r i d o a l k y l from C o m p l e x 1 2 is d i f f i c u l t . The IrCl(PCy ) 3

2

m o i e t y c o u l d b e s t a b i l i z e d i n t h e s o l i d state b y

i s o l a t i o n as t h e b e n z o n i t r i l e c o m p l e x I r C l ( C H C N ) ( P C y ) , e

5

13, w h i c h was c h a r a c t e r i z e d b y m i c r o a n a l y s i s a n d I R ,

3

2

Complex

^(coordinated

C N ) 2 2 5 0 c m " . N o i n t r a m o l e c u l a r d e h y d r o g e n a t i o n is a p p a r e n t , a l 1

t h o u g h t h e n i t r i l e r e a d i l y d i s s o c i a t e s i n s o l u t i o n a n d C o m p l e x 1 2 is detected b y N M R .


9.

JAMES E T A L .


153

Complexes

Reversible Splitting of Water: H I r ( O H ) C l ( C H C N ) ( P C y ) and I r C l ( 0 ) ( P C y ) . W h i l e a t t e m p t i n g to s y n t h e s i z e I r C l ( C H C N ) ( P C y ) from the cyclooctene precursor, w e i n a d v e r t e n t l y isolated a w h i t e s o l i d t h a t a p p e a r s to b e H I r ( O H ) C l ( C H C N ) ( P C y ) , C o m p l e x 14. T h e *>(CN) is f o u n d at 2 2 8 2 c m " a n d a s t r o n g , s h a r p p e a k at 3 4 9 0 c m " w i t h n o a c c o m p a n y i n g b a n d a r o u n d 1 6 3 0 c m " is a t t r i b u t e d to c o o r d i n a t e d h y d r o x i d e r a t h e r t h a n to w a t e r . A 2 9 0 - c m " b a n d is a t t r i b u t e d t o *>(Ir-Cl). A h y d r i d e b a n d is n o t o b s e r v e d i n t h e I R b e c a u s e i t is e i t h e r t o o w e a k or o b s c u r e d b y t h e y ( C N ) . H o w e v e r h i g h - f i e l d H - l N M R measured immediately on dissolution i n C D sometimes shows a r e s o n a n c e at r 3 4 . 3 t h a t r a p i d l y d e c a y s w i t h t h e a p p e a r a n c e o f o t h e r s at τ v a l u e s o f 19.8 a n d 3 1 . 5 , a t t r i b u t a b l e t o C o m p l e x 12, w h o s e f o r m a tion also was c o n f i r m e d b y P-31 N M R . O n dissolution i n C H C 1 , C o m p l e x 14 a l s o y i e l d s s t o i c h i o m e t r i c a m o u n t s o f C H C N a n d H 0 , as e v i d e n c e d b y gas c h r o m a t o g r a p h y . R e a c t i o n 2 s u m m a r i z e s t h e r e v e r s i b l e f o r m a t i o n o f C o m p l e x 14, w h i c h is t h o u g h t to b e p r o d u c e d b y o x i d a t i v e a d d i t i o n o f t r a c e w a t e r to a n i n s i t u I r C l ( P C y ) species. 3

2

3

3

2

2

3

3

3

3

2

2

1

1

1

1

6

e

2

2

3

2

3

HIr(OH)Cl(CH CN)(PCy ) ^ 3

3

H 0 + CH CN +

2

2

3

IrCl(PCy ) 3

2

2

14

(2) H IrCl[P(C H )Cy ](PCy ) 2

e

9

2

3

12 S u c h o x i d a t i v e a d d i t i o n o f w a t e r to p l a t i n u m ( O ) a n d r h o d i u m ( I ) p h o s p h i n e c o m p l e x e s , i n c l u d i n g c y c l o h e x y l p h o s p h i n e d e r i v a t i v e s , has b e e n d e m o n s t r a t e d b y O t s u k a a n d c o - w o r k e r s (16, 39, 40) a n d s o m e o f t h e s y s t e m s h a v e i n v o l v e d t r a c e w a t e r i n c a r e f u l l y d r i e d s o l v e n t s (16). O n e d i s t u r b i n g r e s u l t c o n c e r n i n g o u r f o r m u l a t i o n o f C o m p l e x 14, h o w e v e r , is t h a t t h e u s e o f C H C N d o p e d w i t h D 0 a g a i n g i v e s t h e h y d r o x o p r o d u c t w i t h o u t any incorporation o f d e u t e r i u m i n the l i g a n d w h i c h is t h o u g h t to b e d e r i v e d f r o m t h e H 0 s p l i t t i n g ! T h e r e c o u l d b e e x c h a n g e w i t h t h e P C y l i g a n d s , a l t h o u g h i t is d i f f i c u l t t o d i s c e r n a n y i s o t o p e shifts i n t h e I R . W h e t h e r a n I r - H or I r - D b o n d is p r e s e n t is m o r e e q u i v o c a l b e c a u s e o f t h e n o n a p p e a r a n c e o f i>(Ir-H) i n t h e I R a n d t h e u n c e r t a i n t y o f its d e t e c t i o n b y N M R . E x c h a n g e v i a c a t i o n i c s p e c i e s s u c h as [ H I r C l ( C H C N ) ( P C y ) ] O H " , i n v o l v i n g C - H c l e a v a g e i n t h e a c e t o n i t r i l e (41), is a p o s s i b i l i t y . F u r t h e r w o r k is n e e d e d t o c l a r i f y t h i s p r o b l e m . T h e formation of H 0 a n d C H C N on dissolution of C o m p l e x 14 a r g u e s s t r o n g l y for t h e s u g g e s t e d f o r m u l a t i o n . 3

2

2

3

3

3

2

2

+

3

F u r t h e r i n d i r e c t e v i d e n c e for f o r m a t i o n o f C o m p l e x 14 v i a I r C l ( P C y ) a n d R e a c t i o n 2 is t h e i s o l a t i o n o f t h e p u r p l e d i o x y g e n a d d u c t I r C l ( 0 ) ( P C y ) , C o m p l e x 15, i n h i g h y i e l d b y treatment o f C o m 3

2

2

3

2


154


p l e x 14 w i t h 0 . O n d i s s o l u t i o n i n C H C 1 , t h e w h i t e s o l i d C o m p l e x 14 2

2

2

y i e l d s a n orange solution (in situ I r C l ( P C y ) ) that u n d e r 0 3

2

s o r b e d p e r m o l e o f i r i d i u m . ) T h e v(0-0)

rapidly

2

a d o p t s t h e p u r p l e c o l o r o f t h e d i o x y g e n c o m p l e x (1.0 m o l 0

is a b

2

at 9 4 0 c m " is u n u s u a l l y h i g h 1

for a G r o u p V I I I m e t a l p e r o x o s p e c i e s (42), b u t t h e r h o d i u m a n a l o g u e RhCl(0 )(PCy ) 2

3

s h o w s t h i s b a n d at t h e e v e n h i g h e r f r e q u e n c y o f 9 9 3

2

c m " . T h i s w a s r a t i o n a l i z e d o n t h e b a s i s o f v e r y w e a k π-back-bonding 1

( R h - O ) w i t h i n a monomeric, square-planar structure containing sideo n c o o r d i n a t e d d i o x y g e n (12). T h e s i n g l e i>(Ir-Cl) at 3 4 0 c m " 328 c m "

(cf. at

1

for t h e r h o d i u m c o m p l e x ) is c o n s i s t e n t w i t h t h e m o n o m e r i c

1

formulation, although w e cannot rule out entirely a d i m e r i c formula tion

containing

bridging

[RhCl(0 )(PPh ) ] 2

3

2

dioxygen

moieties,

as

found

for

(43). W e h a v e n o t b e e n a b l e to g e t N M R d a t a for

2

C o m p l e x 15 because o f l i m i t e d s o l u b i l i t y i n solvents a n d a r a p i d de c o m p o s i t i o n o f s u c h s o l u t i o n s to g i v e p h o s p h i n e o x i d e , S p e c i e s 12 ( v i a I r C l ( P C y ) ) , a n d other u n i d e n t i f i e d products. 3

2

Cl

\

/

/

x

p

Ρ

II

ο 15

T h e dioxygen complex shows oxygen

transfer reactions charac

t e r i s t i c o f s p e c i e s c o n t a i n i n g c o o r d i n a t e d p e r o x i d e (42), a n d , for e x a m p l e , w e have isolated a sulfato c o m p l e x from the reaction w i t h S 0 a carbonato c o m p l e x from a reaction w i t h C 0

2

2

and

i n the presence o f excess

p h o s p h i n e , a n d w e have d e t e c t e d a peroxycarbonato species from the reaction w i t h C 0

(44). A r e a c t i o n w i t h H

2

2

s i m p l y replaces the 0

2

to

y i e l d H I r C l ( P C y ) , C o m p l e x 7 (44). 2

3

2

T h e d i o x y g e n c o m p l e x is l i g h t s e n s i t i v e , b u t i t is o t h e r w i s e s t a b l e i n air. T h e 0

2

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

r e c t s u p p o r t (45) a g a i n s t a w i d e l y a c c e p t e d c o r r e l a t i o n b e t w e e n b o n d strength (and length) a n d 0

2

O-O

l a b i l i t y (46). T h e h i g h y ( O - O ) v a l u e

c o u l d b e a t t r i b u t e d to a w e a k m e t a l - o x y g e n i n t e r a c t i o n a n d a l a b i l e 0

2

m o i e t y (46), b u t s u c h r e a s o n i n g is b a s e d o n t h e i n c o r r e c t a s s u m p t i o n t h a t y ( O - O ) is a p u r e m o d e (45). T h e s o l i d state, l i g h t - s e n s i t i v e r e a c tion (sunlight, 2 - 3 days), w h i c h results i n a color change from p u r p l e t o b r o w n , is a c c o m p a n i e d b y a d e c r e a s e i n i n t e n s i t y o f t h e 9 4 0 - c m "

1

b a n d a n d t h e a p p e a r a n c e o f b a n d s w i t h i n c r e a s i n g i n t e n s i t y at 1 1 3 5 c m " , a l m o s t c e r t a i n l y d u e to p h o s p h i n e o x i d e (24) a n d 7 8 0 c m " . T h e 1

1

l a t t e r c o u l d p o s s i b l y b e a n I r = Ο s t r e t c h (47).

Reactions s h o w n i n


9.

JAMES E T A L .


155

Complexes

E q u a t i o n 3 are i n d i c a t e d a n d are a n a l o g o u s to the o n e r e p o r t e d c e n t l y b y L e d o n e t a l . for a m o l y b d e n u m p o r p h y r i n s y s t e m (see t i o n 4) (48,

re

Reac

49).

IrCl(0 )(PCy ) 2

3

Ο = IrCl(PCy )(OPCy )

2

3

ο—ο

ο ο W

W h

(porp)

Mo

(porp)

or I r C l ( O P C y )

3

3

(3)

2

ο II

pph

Mo

(porp) M o ( O P P h )

(4)

3

°-o S u c h r e a c t i o n s a r e i n t e r e s t i n g as m o d e l s for o x y g e n a t o m t r a n s f e r i n mechanisms of dioxygen activation b y cytochrome P450 enzyme t e m s (49, 5 0 ,

sys

51).

A t t e m p t s to s y n t h e s i z e C o m p l e x 1 5 b y r e a c t i n g 0 situ [ I r C l ( C O T ) ] / P C y 2

2

w i t h either i n

2

s y s t e m s or I r C l ( C H C N ) ( P C y ) 2

3

e

gave

3

5

very

low yields. Rhodium Complexes. 16,

a n d trans-

The complexes H R h C l ( P C y ) , C o m p l e x 2

RhCl(CO)(PCy ) 3

are

2

syntheses i n v o l v i n g solutions o f R h C l

made 3

3

readily

via

2

single-stage

· 3 H 0 and PCy . The hydride 2

3

w a s o b t a i n e d p r e v i o u s l y b y a d d i n g H C l to t h e i s o l a t e d R h C l ( P C y ) 3

c o m p l e x (13).

2

T h e presence of the h y d r i d e h a d b e e n inferred, a l t h o u g h

w e d e t e c t e d this i n the I R a n d i n the N M R . T h e d o u b l e t of triplets o b s e r v e d i n t h e N M R t o g e t h e r w i t h t h e s i n g l e y ( R h - C l ) is c o n s i s t e n t w i t h t h e s q u a r e p y r a m i d a l s t e r e o c h e m i s t r y (cf. C o m p l e x 3) o r i g i n a l l y f o r m u l a t e d (13).

T h e h y d r i d e is p h o t o s e n s i t i v e , b e i n g c o n v e r t e d t o t h e

well-characterized, square-planar, green rhodium(II) species, RhCl (PCy ) 2

3

2

T h e synthesis o f R h C l ( C O ) ( P C y )

(13).

3

trans-

is m o r e

2

conve

n i e n t t h a n t h a t d e s c r i b e d i n t h e l i t e r a t u r e (4), a n d o u r s p e c t r o s c o p i c d a t a a r e t h e s a m e as t h o s e p r e v i o u s l y r e p o r t e d (4, i 5 ) . A s e c o n d c o n v e nient synthesis from C H ^ W m e t h a n o l solutions o f [ R h C l ( C O D ) ] PCy

3

m u s t i n v o l v e a base (phosphine)-promoted

and

2

carbonyl abstraction

reaction, since i n the absence of the m e t h a n o l a s i m p l e b r i d g e - s p l i t t i n g reaction results i n the formation of R h C l ( C O D ) ( P C y ) , 3

C o m p l e x 17.

T h i s C O D c o m p l e x has b e e n s y n t h e s i z e d p r e v i o u s l y b u t s p e c t r o s c o p i c data w e r e not reported

(52).

Forming H RhCl(PCy ) 2

3

2

from Rh(I)/PCy

3

solutions u n d e r H

w e l l d o c u m e n t e d ( 5 , 1 3 , 15), a n d V r i e z e et a l . (15) formation i n the absence

of H

species R h C l [ P ( C H ) C y ] ( P C y ) 6

S t r u c t u r e 12). W e PCy

3

9

find

at 20°C u n d e r

2

3

together

2

w i t h the

c o n t a i n i n g a 4 . 5 - m e m b e r e d r i n g (cf. 2

also

yield

some

of

the

3

2

with

monohydride

HRhCl (PCy ) . 2

is

dehydrogenated

that t o l u e n e solutions o f [ R h C l ( C O T ) ] argon

2

a l s o h a v e n o t e d its

2



156

Formation of C a r b o n Dioxide Complexes.

A s m e n t i o n e d i n the

introduction, o u r i n i t i a l interest i n s y n t h e s i z i n g the P C y

3

complexes

w a s i n t h e i r p o t e n t i a l for b i n d i n g C 0 . H o w e v e r , e x c e p t for t h e f o r m a 2

tion of peroxycarbonate a n d carbonato complexes from IrCl(0 )(PCy )2 3

2

(44),

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

p e r o x i d e c o m p l e x e s (42)

(but, to o u r k n o w l e d g e , not w i t h P C y

t e m s ) , w e h a v e n o t b e e n a b l e to i s o l a t e a n y C 0

2

3

sys

c o m p l e x e s or e v e n

c a r b o n a t e or b i c a r b o n a t e s p e c i e s w h i c h a r e f o r m e d s o m e t i m e s i n t h e presence of adventitious water We

(16).

were hopeful w h e n toluene

solutions o f the

c o m p l e x e s ( M = R h a n d Ir), i n t h e p r e s e n c e o f P C y atm C 0

( p h o s p h i n e : d i m e r = 4) a b s o r b e d 1 m o l C 0

2

[MCl(COT) ] 2

2

at 25°C u n d e r 1

3

2

per metal atom.

T h e r h o d i u m s o l u t i o n , for e x a m p l e , c h a n g e d g r a d u a l l y f r o m y e l l o w t o r e d a n d , i n t h e c o n s t a n t p r e s s u r e a p p a r a t u s u s e d , t h e m e a s u r e d gas u p t a k e a n a l y z e d e x c e l l e n t l y for t h e p s e u d o - f i r s t - o r d e r rate l a w Zc[Rh], w i t h k = 9.3 x 1 0 ~ s . H o w e v e r , 4

only

five

such C 0

_ 1

experiments;

twenty

2

uptake was observed i n

others r e v e a l e d

no reactivity

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

what traced;

water content a n d v i s i b l e l i g h t are not p r o b l e m s . T h e systems c e r t a i n l y are

complicated

by

the

" b l a n k " dehydrogenation

reactions

(vide

supra). Spectroscopic rhodium/C0 [i>(Rh-H)

analysis

solutions

2

1943

of

the

showed

cm" ,

r40.5],

1

2

3

2

3

2

2

obtained

presence

its

RhCl (PCy ) , and RhCl(CO)(PCy ) is f o r m e d i n t h e a b s e n c e o f C 0

products

the

of

from 2

photodecomposition

3

2

product,

1942 c m " ] . T h e

[v(CO)

the

HRhCl (PCy ) 1

hydride

(vide supra), w h i l e the c a r b o n y l c o u l d

b e f o r m e d b y R e a c t i o n s 5 (53, 54) o r 6 (16). M(PCy ) + C 0 3

H M + C 0 2

(Reaction

6 has b e e n

2

2

^ M(CO) + O P C y ^ M(CO) + H 0

2

documented

for

H Rh(0 COH)(PCy )

reactions c o u l d arise from a C 0

complex formed via C 0

2

(6)

2

2

O t h e r I R b a n d s at 1580(s) a n d 1 2 3 5 ( m ) c m " tion C 0

(5)

3

2

1

2

3

2

(16).)

that result from the solu c o m p l e x (54),

i n s e r t i o n i n t o R h - H (16),

a

formate

or e v e n a b i c a r b o

n a t e f o r m e d v i a R e a c t i o n 7, w h i c h h a s b e e n d o c u m e n t e d a g a i n for a rhodium/PCy

3

system

(16).

H M + C 0 The iridium/C0 Complex O(CO)

12

2

2

-2£> H M ( 0 C O H ) 2

(7)

2

reactions gave products i n c l u d i n g the d i h y d r i d e

[v(Ir-H) 2210, 2125, r l 7 , r35]

and

IrCl(CO)(PCy )

1 9 3 0 c m " ] . B a n d s at 1755(s) a n d 1 2 3 5 ( w ) c m " 1

m o r e r e a d i l y to c o o r d i n a t e d C 0

2

3

1

2

are a s s i g n e d

(54, 55) t h a n f o r m a t e or b i c a r b o n a t e

(16).


9.


JAMES E T AL.

157

Complexes

D u r i n g o u r frustrating studies o n the i n situ r h o d i u m / P C y tems, a note a p p e a r e d d e s c r i b i n g isolation of R h C l ( C 0 ) ( P B u 2

the reaction of C 0

2

w i t h i n situ [ R h C l ( C H ) ] / P B u 2

4

2

2

3

3

n

)

sys

3

from

2

solutions

n

(54).

F e w d e t a i l s w e r e r e p o r t e d b u t w e f o u n d n o e v i d e n c e for a n y r e a c t i o n of

[RhCl(olefin) ] /PBu 2

2

3

solutions

n

with

1

atm

C 0

2

at

( o l e f i n = C H , C O T ) ; for e x a m p l e , w i t h [ R h C l ( C H ) ] / 4 P B u 2

4

2

C 0 , 2.0 m o l C H 2

2

4

2

2

3

20°C under

n

are e v o l v e d r a p i d l y per m o l e o f r h o d i u m a n d there

is n o s u b s e q u e n t C 0 The

4

absorption over several hours.

2

study of C 0

2

complexes

of p l a t i n u m metal complexes

re

m a i n s a n e n i g m a , at l e a s t i n o u r h a n d s . Experimental G e n e r a l . D r i e d , degassed reagent-grade solvents were u s e d throughout, a n d d m a was p u r i f i e d as d e s c r i b e d p r e v i o u s l y (56). C o m p l e x e s were made under inert atmospheres u s i n g Schlenk-tube techniques a n d w e r e washed w i t h C 2 H 5 O H / H 2 O / C 2 H 5 O H / hexane before d r y i n g unless stated otherwise. Microanalyses were done b y P. B o r d a of the chemistry department of the U n i v e r s i t y of B r i t i s h C o l u m b i a . T h e constant-pressure apparatus used for m e a s u r i n g rates a n d stoichiometries of gas absorption or e v o l u t i o n has b e e n d e s c r i b e d elsewhere (56). Tricyclohexylphosphine was obtained from Strem Chemicals. R u t h e n i u m , r h o d i u m , a n d i r i d i u m trichlorides were obtained as trihydrates from Johnson, Matthey L i m i t e d . I r i d i u m tetrachloride was obtained from Platinum Chemicals. The precursor complexes [RhCl(COD)] (57), [RhCl(COT) ] (58), [ R h C l ( C H 4 ) ] (59), [ I r C l ( C O D ) ] (14), a n d [ H I r C l ( C O D ) ] (31) were made according to the literature procedures. Ruthenium Complexes. CARBONYLCHLOROHYDRIDOBIS(TRICYCLOH E X Y L P H O S P H I N E ) R U T H E N I U M ( I I ) , H R u C l ( C O ) ( P C y ) , C O M P L E X 1. E t h a n o l solutions of R u C l · 3 H 0 (0.2 g i n 7 m L ) a n d N a B H (0.15 g i n 7 m L ) w e r e a d d e d q u i c k l y a n d successively to a stirring, b o i l i n g ethanol solution of P C y (1.1 g i n 40 m L ) . Refluxing for 10 m i n precipitated a mustard-colored p o w d e r (75%). We found: carbon, 60.8; hydrogen, 9.0. 0 Η Ο Ο ΐ Ρ ^ re quires carbon, 61.2; hydrogen, 9.3. TRICARBONYLBIS(TRICYCLOHEXYLPHOSPHINE)RUTHENIUM(O), Ru(CO) ( P C y ) , C O M P L E X 2. Solutions of R u C l · 3 H 0 (0.07 g i n 5 m L 2-methoxyethanol), H C H O (5 m L , 4 0 % aqueous), a n d N a B H (0.05 g i n 5 m L 2-methoxyethanol) were a d d e d q u i c k l y a n d successively to a stirring, b o i l i n g 2-methoxyethanol solution of P C y (0.4 g i n 15 m L ) . Refluxing for 30 m i n y i e l d e d pale y e l l o w microcrystals (30%). We found: carbon, 62.2; hydrogen, 8.4. C H e e 0 P R u requires carbon, 62.8; hydrogen, 8.8. Iridium Complexes. DICHLOROHYDRIDOBIS(TRICYCLOHEXYLPHOSP H I N E ) I R I D I U M ( I I I ) , H I r C l ( P C y ) , C O M P L E X 3. (a) A solution of I r C l i n 2-methoxyethanol (0.1 g i n 5 m L ) was a d d e d q u i c k l y to a stirring, b o i l i n g 2-methoxyethanol solution of P C y (0.4 g i n 15 m L ) to y i e l d rose-colored crystals (80%). We found: carbon, 52.3; hydrogen, 8.3. C H e 7 C l P I r re quires carbon, 52.4; hydrogen, 8.2. (b) T r i c y c l o h e x y l p h o s p h i n e (0.3 g) a n d [ I r C l ( C O T ) ] (0.22 g) were dissolved i n 5 m L toluene to give an orange solution through w h i c h H C l gas was b u b b l e d ; the solution i m m e d i a t e l y t u r n e d r e d a n d then y e l l o w , but on standing the r e d color returned. We concentrated the solution and a d d e d hexane to i n d u c e d crystallization of the product (65%). 2

2

2

2

2

2

2

2

2

3

3

2

2

4

3

3 7

β 7

3

3

2

3

2

4

3

3 9

3

2

2

3

2

4

3

3 e

2

2


2

2

158


DICHLORO(N,N'-DIMETHYLACETAMIDE)HYDRIDOBIS(TRICYCLOHEXYLP H O S P H I N E ) I R I D I U M ( I I I ) , H I r C l z i P C y a W d m a ) , C O M P L E X 4. T h e d m a · H C l adduct was p r e p a r e d as a w h i t e s o l i d b y b u b b l i n g H C l gas through d m a . T h i s adduct (0.1 g) was a d d e d to a solution o f P C y (0.3 g) a n d [ I r C l ( C O T ) ] (0.15 g) i n 6 m L toluene/dma ( 2 : 1 v/v). T h e y e l l o w product p r e c i p i t a t e d for more than 16 h ; this was w a s h e d w i t h toluene and hexane (95%). W e found: carbon, 54.5; h y d r o g e n , 8.4; nitrogen, 1.9. C 4 o H O N C l P I r requires carbon, 54.9; hydrogen, 8.7; nitrogen, 1.6. D i s s o l u t i o n o f this h y d r i d e i n C H C 1 or benzene y i e l d s the rose color o f C o m p l e x 3, w h i c h is isolated readily b y a d d i n g hexane. CARBONYLDICHLOROHYDRIDOBIS(TRICYCLOHEXYLPHOSPHINE)IRIDIUM (III), H l r C l ^ C O X P C y ^ , C O M P L E X 5. C a r b o n monoxide was b u b b l e d through a C H C 1 solution o f C o m p l e x 3 or 4 (0.1 g i n 3 m L ) . T h e r e s u l t i n g pale y e l l o w solution was concentrated to an o i l to w h i c h hexane (3 m L ) then was added. T h e pale y e l l o w precipitate was w a s h e d l i b e r a l l y w i t h hexane (80%). We found: carbon, 52.3; h y d r o g e n , 8.0. C 7 H 7 0 C l P 2 l r requires carbon, 52.1; hydrogen, 7.8. Trans - C A R B O N Y L C H L O R O B I S ( T R I C Y C L O H E X Y L P H O S P H I N E ) I R I D I U M (I), I r C l ( C O ) ( P C y ) . S o l i d P C y (0.2 g) a n d L I r C l ( C O T ) ] (0.1 g) w e r e p l a c e d u n d e r a C O atmosphere. T h e mixture t u r n e d b l a c k i s h green, but w h e n 10 m L toluene was a d d e d the stirred mixture became lighter a n d after 2 hr it p r e c i p i tated a y e l l o w s o l i d that was c o l l e c t e d a n d washed w i t h ethanol (80%). W e found: carbon, 54.2; hydrogen, 8.2. C H e e O C l P I r requires carbon, 54.4; h y drogen, 8.2. CHLORO(1,5-CYCLOOCTADIENE)(TRICYCLOHEXYLPHOSPHINE)IRIDIUM(I), I r C l ( C O D ) P C y . T h e d i m e r [ H I r C l ( C O D ) ] (0.1 g) a n d P C y (0.2 g) were stirred i n 5 m L benzene for 2 h. T h e b r i g h t y e l l o w solution was concentrated a n d d i e t h y l ether was a d d e d to i n d u c e crystallization (65%). T h e same synthe sis can b e performed u s i n g [ I r C l ( C O D ) ] . W e found: carbon, 50.8; hydrogen, 7.5. C H C l P I r requires carbon, 50.7; hydrogen, 7.4. CHLORODIHYDRIDOBIS(TRICYCLOHEXYLPHOSPHINE)IRIDIUM(III), H IrC l ( P C y ) , C O M P L E X 7. T h i s orange c o m p l e x was prepared according to a literature procedure (15). We found: carbon, 54.9; hydrogen, 8.9. C H 8 C l P I r requires carbon, 54.7; hydrogen, 8.6. CARBONYLCHLORODIHYDRIDOBIS(TRIC Y C L O H E X YLPHOSPHINE) IRIDIUM (III), H I r C l ( C O ) ( P C y ) , C O M P L E X 10. T h i s c o m p l e x was prepared from C o m p l e x 7 b y the same procedure that 5 was prepared from 3. W e f o u n d : carbon, 54.6; h y d r o g e n , 8.3. C H 8 0 C l P I r requires carbon, 54.3; hydrogen, 8.4. CHLORODIHYDRIDO[DICYCLOHEXYL(CYCLOHEX-3-ENYL)PHOSPHINE] Ι 1 (TRICYCLOHEXYLPHOSPHINE)IRIDIUM(III), H IrCl[P(C He)Cy ](PCy ), C O M P L E X 12. T h e d i m e r [ I r C l ( C O T ) ] (0.15 g) and P C y (0.3 g) were stirred together i n 7 m L toluene for 12 h d u r i n g w h i c h time the solution t u r n e d from orange to y e l l o w . T h e solvent was r e m o v e d a n d the resultant o i l was dissolved i n 10 m L hexane a n d refrigerated. T h e product w h i c h precipitated s l o w l y as a pale y e l l o w crystalline s o l i d , was filtered a n d w a s h e d w i t h hexane (45%). W e found: carbon, 55.0; hydrogen, 8.6. C H e C l P I r requires carbon, 54.8; hydrogen, 8.4. BENZONITRILECHLOROBIS(TRICYCLOHEXYLPHOSPHINE)IRIDIUM(I), IrCl( C H C N ) ( P C y ) , C O M P L E X 13. B e n z o n i t r i l e (0.5 m L ) was a d d e d to 5 m L toluene c o n t a i n i n g P C y (0.28 g) and [ I r C l ( C O T ) ] (0.15 g). T h e r e was a n i m m e d i a t e color change from orange to y e l l o w . T h e product precipitated as large pale y e l l o w crystals (70%) on r e d u c i n g the v o l u m e and a d d i n g 5 m L hexane. W e found: carbon, 60.2; hydrogen, 8.1; nitrogen, 1.6. T h e material 3

2

7 e

2

2

2

2

2

2

3

3

2

2

e

3

2

3 7

3

2

2

2

2

3

2

2 e

4 5

2

3

3 e

2

e

2

2

3

2

3 7

6

2

2

2

e

2

3 e

e

5

3

2

3

e

2

2

3

2

2


3

2

9.

JAMES E T A L .


159

Complexes

contains toluene that was not r e m o v e d on p u m p i n g . T h e formula C H N C l P I r plus 1 m o l toluene requires carbon, 61.1; hydrogen, 8.0; nitro gen, 1.4. ACETONITRILECHLOROHYDRIDOHYDROXOBIS(TRICYCLOHEXYLPHOSP H I N E ) I R I D I U M ( I I I ) , H I r ( O H ) C l ( C H C N ) ( P C y ) , C O M P L E X 14. A c e t o n i t r i l e (0.5 m L ) was a d d e d to 5 m L toluene c o n t a i n i n g P C y (0.28 g) a n d [ I r C l ( C O T ) ] (0.15 g). T h e r e s u l t i n g y e l l o w solution was r e d u c e d to an o i l a n d 5 m L hexane was added. Stirring the orange solution for 15 m i n y i e l d s a w h i t e s o l i d w h i c h was filtered a n d washed sparingly w i t h hexane (80%). We found: carbon, 54.1; hydrogen, 8.5; nitrogen, 1.5; c h l o r i n e , 4.2. C H 7 i O N C l P I r requires carbon, 53.8; hydrogen, 8.5; nitrogen, 1.7; c h l o r i n e , 4.2. CHLORO(PEROXO)BIS(TRICYCLOHEXYLPHOSPHINE)IRIDIUM(III), IrCl( 0 ) ( P C y ) , C O M P L E X 15. C o m p l e x 14 (0.3 g) was dissolved i n 7 m L C H C 1 under argon; admission of an 0 atmosphere resulted i n a color change from orange to p u r p l e . H e x a n e (5 m L ) was a d d e d a n d the total v o l u m e was r e d u c e d to about 3 m L . T h e p u r p l e , light-sensitive c o m p o u n d that p r e c i p i t a t e d was w a s h e d w i t h hexane a n d d r i e d (80%). We found: carbon, 52.4; hydrogen, 8.1. C e H e e 0 2 C l P I r requires carbon, 52.4; hydrogen, 8.1. Rhodium Complexes. DICHLOROHYDRIDOBIS(TRICYCLOHEXYLPHOSP H I N E ) R H O D I U M ( I I I ) , H R h C l z i P C y a k C O M P L E X 16. A n ethanol (or H 0 / acetone, 1:4 v/v) solution of R h C l · 3 H 0 (0.07 g i n 5 m L ) was a d d e d to a stirring, b o i l i n g ethanol (or acetone) solution of P C y (0.7 g i n 20 m L ) ; lightsensitive, r e d microcrystals are formed (80%). We found: carbon, 58.7; hydrogen, 9.1. C H C l 2 P 2 R h requires carbon, 58.8; hydrogen, 9.1. TraM5-CARBONYLCHLOROBIS(TRICYCLOHEXYLPHOSPHINE)RHODIUM(I), RhCl(CO)(PCy ) . (a) Solutions of R h C l · 3 H 0 (0.3 g i n 10 m L ethanol), H C H O (5 m L , 4 0 % aqueous), a n d N a B H (0.1 g i n 10 m L ethanol) were a d d e d r a p i d l y a n d successively to a stirring, b o i l i n g ethanol solution of P C y (1.4 g i n 40 m L ) to give the y e l l o w crystalline product (70%). We found: carbon, 60.5; hydrogen, 9.1. C H e e O C l P R h requires carbon, 61.1; hydrogen, 9.2. (b) T r i c y c l o h e x y l p h o s p h i n e (1.6 g) a n d [ R h C l ( C O D ) ] (0.2 g) w e r e stirred i n 4 m L C H C 1 / 1 0 m L M e O H a n d the solution then was r e d u c e d i n v o l u m e . T h e product (85%) p r e c i p i t a t e d on a d d i n g d i e t h y l ether. CHLORO(1,5 - CYCLOOCTADIENE)(TRICYCLOHEXYLPHOSPHINE)RHODIUM(I), R h C l ( C O D ) ( P C y ) , C O M P L E X 17. T h e d i m e r [ R h C l ( C O D ) ] (0.2 g) a n d P C y (1.6 g) were stirred i n 10 m L C H C 1 for 10 m i n . T h e v o l u m e was r e d u c e d a n d d i e t h y l ether was a d d e d to i n d u c e crystallization of the y e l l o w product. We found: carbon, 59.5; hydrogen, 8.4. C e H C l P R h requires carbon, 59.3; hydrogen, 8.6. 4 3

7 1

2

3

3

2

3

2

2

3 8

2

3

2

2

2

2

2

3

2

2

3

2

3

3 e

3

e 7

2

3

2

4

3

3 7

2

2

2

2

3

2

3

2

2

2

Concluding

4 5

Remarks

A l t h o u g h o u r o r i g i n a l o b j e c t i v e to d i s c o v e r p l a t i n u m m e t a l s y s tems that b i n d a n d activate C 0

2

has not b e e n a t t a i n e d , w e f e e l that

some significant c h e m i s t r y has b e e n r e a l i z e d . T h e d e h y d r o g e n a t i o n

of

t h e c y c l o h e x y l g r o u p is i n t e r e s t i n g i n t e r m s o f C - H a c t i v a t i o n . O x i d a t i v e a d d i t i o n o f w a t e r at a t r a n s i t i o n - m e t a l c e n t e r is l i k e l y to b e i m p o r t a n t s t e p i n a r a n g e o f c a t a l y t i c p r o c e s s e s i n v o l v i n g gas cules, particularly C 0

2

a n d C O , a n d the isolation of the d i o x y g e n

p l e x c o u p l e d w i t h its p h o t o a c t i v i t y

could be relevant

for

oxygenations.


an

mole com

catalytic

160


Acknowledgment W e t h a n k N A T O for a g r a n t w h i c h a l l o w e d u s to i n i t i a t e t h i s w o r k and

the

Canada

Natural

Sciences

for s u b s e q u e n t

generously

loaned

us

and Engineering

financial the

Research

support. Johnson,

ruthenium,

rhodium,

Council

of

Matthey, L t d . and

iridium

trichlorides. Literature

Cited

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Tricyclohexylphosphine Complexes

161

9.

JAMES E T A L .

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Parshall, G. W. Acc. Chem. Res. 1975, 8, 113. Webster, D. E . Adv. Organomet. Chem. 1977, 15, 147. van der Ent, Α.; Onderdelinden, A. L. Inorg. Chim. Acta 1973, 7, 203. Crabtree, R. H.; Mihelcic, J. M.; Quirk, J. M. J. Am. Chem. Soc. 1979, 101, 7738. Clark, P. W.; Hartwell, G. E. J. Organomet. Chem. 1977, 139, 385. Crabtree, R. H . Acc. Chem. Res. 1979, 12, 331. James, B. R. Adv. Organomet. Chem. 1979, 17, 319. Yoshida, T.; Ueda, Y.; Otsuka, S. J. Am. Chem. Soc. 1978, 100, 3941. Yoshida, T.; Otsuka, S., Chapter 8 in this book. English, A. D.; Herskovitz, T. J . Am. Chem. Soc. 1977, 99, 1648. Lyons, J. E . In "Aspects of Homogeneous Catalysis"; Ugo, R., E d . ; Reidel: Dordrecht, 1977; Vol. 3, p. 1. Bennett, M. J . ; Donaldson, P. B. J. Am. Chem. Soc. 1971, 93, 3307. James, B. R.; Preece, M., unpublished data. Laing, M.; Nolte, M . J.; Singleton, E. J . Chem. Soc. Chem. Commun. 1975, 660. Cotton, F. Α.; Wilkinson, G. "Advanced Inorganic Chemistry", 3rd ed.; Wiley: New York, 1972; pp. 635, 783. Adams, D. M . "Metal-Ligand and Related Vibrations"; Edward Arnold: London, 1967; Chap. 5. Ledon, H.; Bonnet, M.; Lallemand, J.-Y. J . Chem. Soc. Chem. Commun. 1979, 702. Ledon, H.; Bonnet, M. J. Mol. Catal. 1980, 7, 309. Ullrich, V. J . Mol. Catal. 1980, 7, 159. Groves, J.; Kruper, W. J.; Nemo, T. E . ; Myers, R. S. J. Mol. Catal. 1980, 7, 169. de Waal, D. J. Α.; Robb, W. Inorg. Chim. Acta 1978, 26, 91. Nicholas, K. M . J. Organomet. Chem. 1980, 188, C10. Aresta, M.; Nobile, C. F. Inorg. Chim Acta, 1977, 24, L49. Aresta, M.; Nobile, C. F. J. Chem. Soc., Dalton Trans. 1977, 708. James, B. R.; Rempel, G. L. Discuss. Faraday Soc. 1968, 46, 48. Chatt, J.; Venanzi, L. M . J . Chem. Soc. 1957, 4735. van der Ent, Α.; Onderdelinden, A. L. Inorg. Syn. 1973, 14, 92. Cramer, R. Inorg. Chem. 1962, 1, 722.

36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59.

RECEIVED July 10, 1980.


Catalytic Aspects of Metal Phosphine Complexes - American

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