Unusual Carbon Monoxide Activation, Reduction, and Homologation

4 Unusual Carbon Monoxide Activation, Reduction, and Homologation Reactions of 5f-Element Organometallics Downloaded by UNIV OF CALIFORNIA SAN DIEGO on December 16, 2016 | http://pubs.acs.org Publication Date: May 5, 1981 | doi: 10.1021/bk-1981-0152.ch004

The Chemistry of Carbene-Like Dihaptoacyls P A U L J . F A G A N , E R I C A . M A A T T A , and T O B I N J . M A R K S Department of Chemistry, Northwestern University, Evanston, I L 60201 There i s c u r r e n t l y g r e a t i n t e r e s t i n understanding chemistry by w h i c h m e t a l l i c r e a g e n t s t r a n s f o r m c a r b o n monoxide/ e i t h e r c a t a l y t i c a l l y o r s t o i c h i o m e t r i c a l l y , i n t o u s e f u l o r g a n i c com pounds Π,2,3). In t h e case o f Group V I I I t r a n s i t i o n metal c a t a l y s t s , vast q u a n t i t i e s of a c e t i c a c i d , a l c o h o l s , aldehydes, e s t e r s , e t c . , a r e c u r r e n t l y p r o d u c e d from c a r b o n monoxide, h y d r o gen, and v a r i o u s organic feedstocksI n r e g a r d t o mechanism, much o f t h i s c h e m i s t r y i s now r e a s o n a b l y w e l l - u n d e r s t o o d . A key r e a c t i o n i s t h e m i g r a t o r y i n s e r t i o n o f CO (.4/5.) i n t o a m e t a l c a r b o n s i g m a bond ( e q . ( 1 ) ) t o p r o d u c e a m e t a l a c y l , A , f o l l o w e d

Γ

CHo M

ι

CHo +

CO

>

M

M—C=0

(1)

A by s c i s s i o n o f t h e m e t a l - c a r b o n bond v i a a p r o c e s s s u c h a s h y d r o genolysis, reductive elimination, o l e f i n insertion, e t c . A l t h o u g h t h i s c l a s s i c p i c t u r e e v o l v e d from " s o f t , " mononuclear t r a n s i t i o n metal complexes s u f f i c e s t o e x p l a i n a g r e a t d e a l o f c a r b o n monoxide c h e m i s t r y , i t i s n o t c l e a r t h a t i t i s c o m p l e t e o r a c c u r a t e f o r u n d e r s t a n d i n g p r o c e s s e s whereby CO i s r e d u c e d , d e o x y g e n a t e d , and/or p o l y m e r i z e d t o form methane, l o n g - c h a i n hydrocarbons, a l c o h o l s , and other oxocarbons, e s p e c i a l l y i n cases where h e t e r o g e n e o u s c a t a l y s t s o r " h a r d " m e t a l s a r e i n v o l v e d (6,1^,8,9^, W) . T h i s d e f i c i e n c y o f i n f o r m a t i o n h a s l e d t o t h e s e a r c h f o r new modes o f c a r b o n monoxide r e a c t i v i t y and t o a t t e m p t s t o u n d e r s t a n d c a r b o n monoxide c h e m i s t r y i n n o n t r a d i t i o n a l e n v i r o n ments · I n t h e p a s t s e v e r a l y e a r s , i t h a s become a p p a r e n t t h a t w i t h p r o p e r t u n i n g o f l i g a t i o n , i t i s p o s s i b l e t o p r e p a r e organomet a l l i c compounds o f a c t i n i d e e l e m e n t s w i t h v e r y h i g h c o o r d i n a t i v e u n s a t u r a t i o n and very h i g h chemical r e a c t i v i t y ( 1 1 , 1 2 , 1 3 ) . In r e g a r d t o e x p l o r i n g " n o n c l a s s i c a l " modes o f c a r b o n monoxide a c t i -

0097-6156/81/0152-0053$06.50/0 © 1981 American Chemical Society

Ford; Catalytic Activation of Carbon Monoxide ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

CATALYTIC ACTIVATION OF CARBON MONOXIDE

54

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on December 16, 2016 | http://pubs.acs.org Publication Date: May 5, 1981 | doi: 10.1021/bk-1981-0152.ch004

v a t i o n , these f e a t u r e s , combined w i t h the very l a r g e a f f i n i t y which a c t i n i d e s e x h i b i t f o r oxygen, o f f e r the p o s s i b i l i t y o f d r a s t i c a l l y m o d i f y i n g the c l a s s i c a l chemistry and o f m o d e l l i n g i n homogeneous s o l u t i o n , some o f t h e f e a t u r e s o f h e t e r o g e n e o u s CO r e d u c t i o n c a t a l y s t s ( e s p e c i a l l y those i n v o l v i n g a c t i n i d e s ) (12,14-16). The p r o d i g i o u s s t r e n g t h s o f a c t i n i d e - o x y g e n bonds c a n be a p p r e c i a t e d by c o n s i d e r i n g t h e f o r m a t i o n e n t h a l p i e s o f b i n a r y o x i d e s ( T a b l e I) (J_7,JJ3). I t c a n a l s o be s e e n t h a t e a r l y

Table

I.

R e p r e s e n t a t i v e F o r m a t i o n E n t h a l p i e s o f Some B i n a r y d and f - E l e m e n t

Ti0 -112 2

Zr0

V0 -93.9

Cr0 -69.7

2

2

Nb0

-130

-94.5

Oxides. 2

2

Mo0

a

Mn0 -62.0 2

2

-66.5 W0

2

3

Ru0

4

2

-27.3 Os0

2

-67.3 Th0 -143

Fe 0 -64.9

2

-35.2

CoO -56.9 RhO -19.5 Ir0

2

-18.3

U0 -125 2

a In kcal/mole of Ο atoms.

From r e f e r e n c e s

17 a n d 18.

t r a n s i t i o n m e t a l s p o s s e s s s i m i l a r c h a r a c t e r i s t i c s , a n d where mean bond d i s s o c i a t i o n energy d a t a e x i s t f o r both c l a s s e s of m e t a l s ( e . g . , the metal t e t r a h a l i d e s ) t r e n d s i n a c t i n i d e and e a r l y t r a n s i t i o n metal ( e . g . , T i , Zr) parameters are l a r g e l y p a r a l l e l (19). T h e c o n s e q u e n c e s o f t h i s o x y g e n a f f i n i t y f o r t h e m a k i n g and b r e a k i n g o f m e t a l - t o - l i g a n d bonds c a n be r e a d i l y a s s e s s e d i n T a b l e II (2fJ,2λ). E x t r a p o l a t i n g t o t h e a c t i n i d e s , i t c a n be s u r m i s e d t h a t a T h - 0 bond i s s t r o n g e r t h a n a T h - C b o n d by c a . 50 kcal/mole. The p u r p o s e o f t h i s a r t i c l e i s t o r e v i e w r e c e n t r e s u l t s on t h e c a r b o n y l a t i o n c h e m i s t r y o f a c t i n i d e - t o - c a r b o n sigma bonds, b e a r i n g i n mind t h e u n i q u e p r o p e r t i e s o f 5 f - o r g a n o m e t a l l i c s c i t e d above. We f o c u s o u r a t t e n t i o n on t h e p r o p e r t i e s o f bis(pentamethylcyclopentadienyl) actinide acyls. J u s t as t r a n s i t i o n m e t a l a c y l s (A) o c c u p y a p i v o t a l r o l e i n c l a s s i c a l c a r b o n y l a t i o n c h e m i s t r y , i t w i l l be s e e n t h a t many o f t h e u n u s u a l


Table

II.

Mean B o n d D i s s o c i a t i o n E n e r g y D a t a f o r Some E a r l y T r a n s i t i o n Metal Complexes and Estimated Values f o r Thorium and Uranium. 3

MR

n

R CH CH CMe CH Ph 3


2

2

CI NEt OPr-i F 2

In

3

55

Chemistry of Carbene-Like Dihaptoacyls

FAGAN ET AL.

4.

1 3

Ti

Zr

Hf

Nb

Ta

Mo

n=4

4

4

5

5

6

62 45 49

74 54 60

79 54

103 74 106 140

117 82 124 154

119 88 128 155

62

97

73

103 78 105

100

k c a l / m o l e , from r e f e r e n c e s

19,

W

Th

6

4

38

78 53

83 86

117 87 126 153

U 4 b

b

b

b

b

a

73 50

b

b

110 81 118 143

b

b

b

a

20, and 21.

b E s t i m a t e d from t h e p r o p o r t i o n a l i t y Ac-R = M - R ( A c - F / M - F ) , Ac i s t h e a c t i n i d e v a l u e .

where

f e a t u r e s w h i c h a c t i n i d e e l e m e n t s i n t r o d u c e t o CO c h e m i s t r y m a n i f e s t themselves i n the chemical andp h y s i c o c h e m i c a l c h a r a c t e r i s t i c s of the a c y l s . I t w i l l a l s o be s e e n t h a t t h e c o o r d i n a t i v e u n s a t u r a t i o n and oxygen a f f i n i t y o f T h ( I V ) a n d U(IV) i o n s g i v e r i s e t o h i g h l y r e a c t i v e , oxygen-coordinated (dihapto) a c y l s with marked c a r b e n e - l i k e c h a r a c t e r , a n d p a t t e r n s o f c h e m i c a l r e a c t i v i t y never p r e v i o u s l y observed i n s o l u t i o n . We d i s c u s s h e r e the s y n t h e s i s and physicochemical p r o p e r t i e s of a c t i n i d e b i s ( p e n t a m e t h y l c y c l o p e n t a d i e n y l ) d i h a p t o a c y l s , c a r b o n monoxide c o u p l i n g i n v o l v i n g these complexes, rearrangement r e a c t i o n s of t h e d i h a p t o a c y l s , as w e l l as h y d r i d e - c a t a l y z e d i s o m e r i z a t i o n and hydrogénation r e a c t i o n s . Synthesis o f Organoactinide

A c y l s and P r o p e r t i e s

A s d i s c u s s e d e l s e w h e r e (J_2,J[6), t h e c a r b o n y l a t i o n o f b i s (pentamethylcyclopentadienyl) thorium and uranium b i s ( h y d r o c a r b y l s ) , M[(0113)505] R , leads t o r a p i d , i r r e v e r s i b l e formation o f e n e d i o l a t e (B) c o m p l e x e s . Although there i s c i r c u m s t a n t i a l 2

2

/ R

R ^C=:C

0

ο Β


CATALYTIC ACTIVATION OF CARBON MONOXIDE

56


e v i d e n c e (14) t h a t s u c h s p e c i e s c o u l d a r i s e f r o m i n t r a - o r i n t e r m o l e c u l a r c o u p l i n g of d i h a p t o a c y l f u n c t i o n a l i t i e s , the very h i g h r e a c t i v i t y o f t h e o r g a n o a c t i n i d e s has s o f a r p r e c l u d e d t h e o b s e r v a t i o n o r i s o l a t i o n o f i n t e r m e d i a t e s on t h e r e a c t i o n c o o r d i n a t e l e a d i n g to the e n e d i o l a t e . On t h e o t h e r h a n d , s o l u t i o n s o f actinide bis(pentamethylcyclopentadienyl) chlorohydrocarbyls (JJy22y2J3) a n d d i a l k y l a m i d e h y d r o c a r b y l s ( J j l ) a b s o r b an e q u i v a l e n t o f c a r b o n monoxide i n t h e c o u r s e o f 0 . 2 - 1 . 5 h a t low t e m p e r a t u r e s to y i e l d actinide acyls. R e p r e s e n t a t i v e examples are i l l u s t r a t e d in eq.(2). U n l i k e analogous e a r l y t r a n s i t i o n m e t a l systems M [ ( C H ) 5 C 5 ] ( X ) R + *CO 3

> M[(CH ) C ]2(X)(*COR)

2

3

5

1a

M=Th,

X=C1,

R=CH C(CH ) , *C=12

1b

M=Th,

X=C1,

R=CH C(CH ) , *C=13

2a

M=Th,

X=C1,

R=CH C H ,

3a

M=Th,

X=N(CH ) ,

4a

M=U,

X=C1,

R=C H ,

*C=

1 2

C

4b

M=U,

X=C1,

R=C H ,

*C=

1 3

C

2

3

2

2

3

6

6

6

5

5

3

*C=, 1 2

5

R=CH

2

3

3

*C=

3/

(2)

5

C

C

c

1 2

C

(24,25/26/27)/ the i n s e r t i o n i n these o r g a n o a c t i n i d e s i s i r r e versible. T h e new compounds were c h a r a c t e r i z e d by e l e m e n t a l a n a l y s i s , i n f r a r e d a n d nmr s p e c t r o s c o p y . The C - 0 s t r e t c h i n g f r e q u e n c i e s , v e r i f i e d i n s e v e r a l c a s e s by C substitution, p r o v i d e i m p o r t a n t i n f o r m a t i o n on t h e m e t a l - a c y l b o n d i n g . In p a r t i c u l a r , the energies (Table III) are c o n s i d e r a b l y lower than i n c l a s s i c a l t r a n s i t i o n metal a c y l s ( v = c a . 1630-1680 cnT^) and suggest d i h a p t o a c y l l i g a t i o n (C, D ) . 1 3

c o

Λ

M—C—R

C-CH C(CH ) 2

3

\

3

Th

^C—C^C(CH ) 3

à

D

Th

3

> Η


(12)

/

^C(CH ) 3

3

{[(CH3) C ] Th(H)D} a s r e q u i r e d by e q . ( 1 2 ) . I f h y d r o g e n gas i s a d d e d t o t h e r e a c t i o n m i x t u r e o f J , a n d 11^ t h e h y d r o g e n o l y s i s r e a c t i o n o f t h o r i u m - t o - c a r b o n s i g m a bonds (Ιλ'ΖΆ) H ° w s i n t e r c e p t i o n o f s p e c i e s 1^3 a n d t h u s , c a t a l y t i c h y d r o g é n a t i o n o f t h e i n s e r t e d c a r b o n monoxide f u n c t i o n a l i t y . At 5

5

2

2

a

35 C u n d e r 0 . 7 5 atm i n i t i a l H p r e s s u r e w i t h [JJ = 9 . 0 χ 1 0 ~ M a n d [ 1JJ = 6 . 5 χ 1 0 ~ M , h y d r o g é n a t i o n a n d i s o m e r i z a t i o n a r e comp e t i t i v e and both t h e e n o l a t e and the a l k o x i d e r e d u c t i o n p r o d u c t 14 a r e p r o d u c e d ( e q . ( 1 3 ) ) . Under t h e s e c o n d i t i o n s , t u r n o v e r f r e 3

2

4

Λ

N

-

Λ

^«^.

TV.

r

„^

C(CH3>3

> ^ Η ^ThΊ ^ ι Η

Th^:C-CH2C(CH )3 3

r

rf

CH -CH C(CH ) 2

2

3

*/=%*CH >

3

3

per ThH

(initial)

2

moiety

are c a . 8 h "

1

for isomerization and 4 h "

spectrum o f such a r e a c t i o n Reduction product tion

shown

1

If

and hydrogénation

, respectively.

mixture

is

14^ was i n d e p e n d e n t l y

i n eq.(14).

3

IL

14

quencies

(13)

Th-H

the r e a c t i o n

illustrated

A t y p i c a l nmr i n Figure

synthesized v i a the i n eq.(13)

is

4.

reac-

conducted


4.

FAGAN ET AL.

67



WHIP Jifflyipp

-JUL ιI

ι ι ι ι ι ι ι ι ι ι ι ι 19

I I I I

I

(ppm)

Figure 3. A. *H NMR spectrum (90 MHz, FT, C D ) of a mixture of {Th[(CH ) C ] H } and Th[(CH ) C ] [tTîins-OC(H)=C(H)C(CH ) ]Cl, (12); the latter was produced by catalytic isomerization of Th[(CH ) C ] [^-COCH C(CH ) ]Cl, l a . The peak at δ 19.3 is the hydride resonance; the inset shows the oiefinieA Β pattern of 12. B. *H NMR spectrum of the olefinic region of 12 pre pared with an excess of {Th[(CH ) C ] D } i.e., Th[(CH ) C ] [tians-OC(D)=C(H)C(CH ) ]Cl:S = C D H. 6

3

5

5

2

2

2

3

5

5

6

2

3

3

3

3

5

5

2

2

3

3

3

5

5

2

2

2

s

3

6

5

5

2

5

Figure 4. *H NMR spectrum (90 MHz, FT, C D ) of a mixture of Th[(CH ) C ] [trans-OC(H)=C(H)C(CH ) ]Cl, 12(a), and Th[(CH ) C ] (OCH CH C(CH ) Cl, 14(b) prepared by the {Th[(CH ) C ] H } .-catalyzed competitive isomerization and hydrogénation of Th[(CH ) C ] [ -COCH C(CH ) ]Cl. 6

3

6

3

s

3

3

5

5

2

5

5

2

2

2

2

2

3

5

5

2

v

2

s

3


s

5

s

5

2

CATALYTIC

68

/ V / ^ - - /

ACTIVATION

/

Z\

Y

X

T h

• NaOCH CH C(CH )

/

2

2

3

>·

3

85% d e u t e r a t e d

2

2

(by nmr) i n t h e α p o s i t i o n

/ ° \

Th-D 2

κ

0

> Th

Th«-:C-CH C(CH )3 3

χ

X

C(CH ) 3

(eq.(15)).

The

3

Vjj^V Th Η

DyZ-fch-^ ΤΆ

(15)

\θ 0Η 0(0Η )3 2

2

3

15

a c t i v i t y o f { Th [ ( ( ^ 3 ) 5 0 5 ] H } as a hydrogénation c a t a l y s t i s a l s o i l l u s t r a t e d by t h e i n t e r e s t i n g o b s e r v a t i o n t h a t t h e h y d r o g é n a t i o n o f e n o l a t e 12 t o p r o d u c e 14 o c c u r s as a s e c o n d a r y r e a c t i o n i n e q . ( 1 3 ) . Under t h e c o n d i t i o n s c i t e d above, an approximate t u r n - o v e r frequency o f 0.01 h~^ i s c a l c u l a t e d . 2

2

2

T h e c a t a l y t i c h y d r o g é n a t i o n o f i n s e r t e d c a r b o n monoxide i s by n o means l i m i t e d t o n o n c o n j u g a t e d t h o r i u m a l k y l p r e c u r s o r s . T h u s , t h e u r a n i u m b e n z o y l compound 4 i s r e a d i l y h y d r o g e n a t e d ( e q . ( 1 6 ) ) ; i n t h i s c a s e , t h e i n t e r m e d i a t e c a n n o t u n d e r g o B-

h y d r i d e e l i m i n a t i o n , a n d o n l y b e n z y l o x y p r o d u c t 16 i s f o r m e d i n the reaction. An a u t h e n t i c sample o f 16 c o u l d be s y n t h e s i z e d by t h e r e a c t i o n o f U [ ( C H ) 5 C 5 ] C 1 w i t h one e q u i v a l e n t o f C H C H O N a i n diethyl ether. Under c o n d i t i o n s comparable t o t h o s e i n e q . ( 1 2 ) , t h e turnover frequency per T h H u n i t f o r hydrogénation o f 16 i s c a . 1 h ~ . I f Th[(CH )5C5] D / D i s used i n e q . ( 1 6 ) , t h e p r o d u c t i s > 90% d e u t e r a t e d i n t h e α - p o s i t i o n ( e q . ( 1 7 ) ) . 3

2

2

6

2

1

3

2

2

2

2


5

2

4.


FAGAN ET AL.

69

Although not t h e c e n t r a l subject of t h i s review, several thorium d i h a p t o c a r b a m o y l c o m p l e x e s (_14) Th(n -CONR2) # were a l s o e x a m i n e d with respect t o thorium h y d r i d e - c a t a l y z e d reduction. Under 0 . 7 5 atm H2 a n d o v e r t h e c o u r s e o f s e v e r a l d a y s a t t e m p e r a t u r e s as h i g h as 100°C, n o h y d r o g é n a t i o n was o b s e r v e d . These results are i n a c c o r d w i t h o t h e r s p e c t r a l / s t r u c t u r a l / a n d c h e m i c a l d a t a (14) i n d i c a t i n g t h e i m p o r t a n c e o f c a r b a m o y l r e s o n a n c e h y b r i d s 0 a n d P/ and t h a t t h e c a r b e n e - l i k e r e a c t i v i t y i s s i g n i f i c a n t l y r e d u c e d i n comparison t o t h e a c y l s Π 4 ) .


2

Th«-:ONR

Th

Unusual Carbon Monoxide Activation, Reduction, and Homologation

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