Inorganic Compounds with Unusual PropertiesâII - American

17 Novel Cleavage and Oligomerization Reactions

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of Nickel(0) Complexes Applications to Homogeneous Deoxygenation and Desulfurization JOHN

J.

EISCH

and

KYOUNG

R. IM

Department of Chemistry, State University of N e w York at Binghamton, Binghamton, N Y 13901

The ease of interaction of Ni(0) complexes with organic substrates has been shown to depend upon both the ligands on nickel and the solvent. The presence of α,α'-bipyridyl with the Ni(0) complex and the alkyne led to the isolation of a nickelacyclopropene, an observation in accord with the recently proposed metallocyclic pathway for the Ni(0)-catalyzed trimerization of alkynes. Allylic and benzylic ethers and epoxides have been observed to undergo oxidative insertion of Ni(0) into their C-O bonds with solvent (TMEDA > THF > Et O > C H ) and ligand (Et P > 2

6

6

3

Ph P; α,α'-bipy > COD) effects consistent with an electron -transfer attack by Ni(0). With such sulfur heterocycles as dibenzothiophene, phenoxathiin, phenothiazine, and thian threne, a 1:1 admixture of (COD) Ni withα,α'-bipyridylgave as the principal product the desulfurized, ring-contracted cyclic product. 3

2

By

r e p l a c i n g c e r t a i n heterogeneous t r a n s i t i o n m e t a l catalysts b y h o m o geneous o r p o l y m e r - b o n d e d catalysts, m a n y i m p o r t a n t reactions, s u c h as h y d r o g e n a t i o n , u n s a t u r a t e d h y d r o c a r b o n o l i g o m e r i z a t i o n , a n d h y d r o f o r m y l a t i o n , s h o w significant gains i n stereo-, regio-, a n d l o c o - s e l e c t i v i t y (1,2) ( L o c o - is suggested as a prefix t o denote t h e m o l e c u l a r site ( f u n c t i o n a l g r o u p ) at w h i c h a g i v e n r e a c t i o n occurs selectively ( L a t i n , locus: p l a c e o r s i t e ) . T h e t e r m , chemospecific, w h i c h has a l r e a d y b e e n suggested 0-8412-0429-2/79/33-173-195$05.00/0 © 1979 American Chemical Society King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

17 Novel Cleavage and Oligomerization Reactions


of Nickel(0) Complexes Applications to Homogeneous Deoxygenation and Desulfurization JOHN

J.

EISCH

and

KYOUNG

R. IM

Department of Chemistry, State University of N e w York at Binghamton, Binghamton, N Y 13901

The ease of interaction of Ni(0) complexes with organic substrates has been shown to depend upon both the ligands on nickel and the solvent. The presence of α,α'-bipyridyl with the Ni(0) complex and the alkyne led to the isolation of a nickelacyclopropene, an observation in accord with the recently proposed metallocyclic pathway for the Ni(0)-catalyzed trimerization of alkynes. Allylic and benzylic ethers and epoxides have been observed to undergo oxidative insertion of Ni(0) into their C - O bonds with solvent (TMEDA > THF > Et O > C H ) and ligand (Et P > 2

6

6

3

Ph P; α,α'-bipy > COD) effects consistent with an electron -transfer attack by Ni(0). With such sulfur heterocycles as dibenzothiophene, phenoxathiin, phenothiazine, and thian threne, a 1:1 admixture of (COD) Ni withα,α'-bipyridylgave as the principal product the desulfurized, ring-contracted cyclic product. 3

2

By

r e p l a c i n g c e r t a i n heterogeneous t r a n s i t i o n m e t a l catalysts b y h o m o geneous o r p o l y m e r - b o n d e d catalysts, m a n y i m p o r t a n t reactions, s u c h as h y d r o g e n a t i o n , u n s a t u r a t e d h y d r o c a r b o n o l i g o m e r i z a t i o n , a n d h y d r o f o r m y l a t i o n , s h o w significant gains i n stereo-, regio-, a n d l o c o - s e l e c t i v i t y (1,2) ( L o c o - is suggested as a prefix t o denote t h e m o l e c u l a r site ( f u n c t i o n a l g r o u p ) at w h i c h a g i v e n r e a c t i o n occurs selectively ( L a t i n , locus: p l a c e o r s i t e ) . T h e t e r m , chemospecific, w h i c h has a l r e a d y b e e n suggested 0-8412-0429-2/79/33-173-195$05.00/0 © 1979 American Chemical Society King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

196

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

II

f o r this s i t u a t i o n ( 2 ) does n o t seem to c a l l to m i n d t h e i n t e n d e d m e a n i n g . ) A s p a r t of a l o n g - r a n g e , p h y s i c a l o r g a n i c i n v e s t i g a t i o n o f t r a n s i t i o n m e t a l o x i d a t i v e a d d i t i o n s , the present s t u d y has e x a m i n e d t h e i n s e r t i o n reactions of N i ( 0 ) c o m p l e x e s i n t o v a r i o u s r e l a t i v e l y w e a k ir a n d cr b o n d s .

Chosen

f o r p a r t i c u l a r attention w e r e t h e a l k y n e TT b o n d a n d t h e c a r b o n - h e t e r o a t o m a b o n d s ( C - E , w h e r e E = O , S, X , o r a m e t a l l o i d ) . B y u n d e r s t a n d i n g the i n f l u e n c e of l i g a n d s a n d solvents o n t h e rate a n d extent of s u c h Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 8, 2017 | http://pubs.acs.org Publication Date: May 5, 1979 | doi: 10.1021/ba-1979-0173.ch017

s t o i c h i o m e t r i c insertions, w e h o p e to d e v e l o p s u c h reactions i n t o r a t i o n a l l y f o u n d e d c a t a l y t i c processes.

F o r e x a m p l e , t h e c a t a l y t i c scission o f C - S

b o n d s , p r e s e n t l y effected w i t h h y d r o g e n a n d heterogeneous e l e v a t e d temperatures (3,4,5,6,7),

catalysts at

m i g h t b e a c h i e v a b l e at a m u c h l o w e r

temperature w i t h a n appropriate soluble transition metal complex.

Such

m i l d d e s u l f u r i z i n g c o n d i t i o n s m i g h t m e a n savings o f t i m e a n d energy f o r i n d u s t r i a l processes u s e d i n d e s u l f u r i z i n g c o a l - d e r i v e d fuels a n d c h e m i c a l s . I n a d d i t i o n , agents c a p a b l e o f c l e a v i n g C - S b o n d s at l o w temperatures c o u l d b e v a l u a b l e i n selectively d e g r a d i n g t h e macrostructures of v a r i o u s coals themselves i n t o fragments m a n a g e a b l e

f o r s t r u c t u r a l studies. T h e

i n c r e a s i n g r e l i a n c e of the i n d u s t r i a l nations o n c o a l f o r energy a n d f o r chemicals

raises

t h e p r o b l e m of d e s u l f u r i z a t i o n t o n e w p r o m i n e n c e .

I n d e e d , since the days of S o d o m a n d G o m o r r a h , t h e p r e s e n c e o f s u l f u r a n d its oxides i n t h e e n v i r o n m e n t has b e e n r e c o g n i z e d as a serious p r o b lem for human communities. Interaction

of Ni(0)

Complexes with

Alkynes

R e c e n t studies o n t h e a l l y l a t i o n o f alkynes w i t h bis (7r-allyl) n i c k e l h a v e r e v e a l e d that t h e N i ( 0 ) g e n e r a t e d i n this process causes t h e t r i m e r i z a t i o n a n d , m o r e i m p o r t a n t l y , t h e r e d u c t i v e d i m e r i z a t i o n of a p o r t i o n of the a l k y n e ( 8 ) . A d e u t e r o l y t i c w o r k - u p l e d to the t e r m i n a l l y d i - d e u t e r a t e d diene ( 5 ) , s u p p o r t i n g t h e p r e s e n c e of a n i c k e l o l e p r e c u r s o r

(4)

( S c h e m e 1 ) . T h e f u r t h e r i n t e r a c t i o n of 4 w i t h 1, either i n a D i e l s - A l d e r f a s h i o n ( 6 ) o r b y a l k y n e i n s e r t i o n i n a C - N i b o n d ( 7 ) , c o u l d l e a d to the c y c l i c t r i m e r 8 after e x t r u s i o n of N i ( 0 ) , t h e r e b y a c c o u n t i n g f o r t h e t r i m e r i z i n g a c t i o n of N i ( 0 ) o n a l k y n e s . T h i s d e t e c t i o n of d i m e r 5 t h e n p r o v i d e d i m p e t u s f o r t h e synthesis of the u n k n o w n n i c k e l o l e system to l e a r n i f its properties w o u l d a c c o r d w i t h this p r o p o s e d r e a c t i o n Therefore, treated

E,E-l,4-dilithio-l,2,3,4-tetraphenyl-l,3-butadiene

w i t h bis ( t r i p h e n y l p h o s p h i n e ) n i c k e l ( I I )

scheme. (9)

was

chloride or l,2-bis(di-

p h e n y l p h o s p h i n o e t h a n e ) n i c k e l ( I I ) c h l o r i d e to f o r m t h e n i c k e l o l e 10 (9) (Scheme 2 ) . T h e nickelole reacted w i t h d i m e t h y l acetylenedicarboxylate to y i e l d 11 a n d w i t h C O t o p r o d u c e 12. F i n a l l y , i n k e e p i n g w i t h t h e hypothesis offered i n S c h e m e 1, 1 0 a d i d act as a t r i m e r i z i n g catalyst t o w a r d d i p h e n y l a c e t y l e n e ( 1 3 ) to y i e l d 14.

King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

17.

EISCH

Novel Cleavage,

AND I M

Oligomerization

197

Rxns

Scheme 1 R

R — C = C — R -f ( C H = = C H C H ) N i 2

2

2

R

CH =CHCH 2

CH CH^=CH

2

2

2


1

R

R

R \ / C—C // w R—C C—R

\

Ni

R C—C //

DC1

/

x C—R

_ C

R

\

D

D

/

R—GE=C—R

t R R

R or

Ni R

R R 6

T h e p r o f o u n d effect of l i g a n d s o n the course of a l k y n e — N i ( 0 ) interactions w a s o b s e r v e d w i t h b i s ( l , 5 - c y c l o o c t a d i e n e ) n i c k e l ( 0 )

Al-

(15).

t h o u g h h e a t i n g 13 i n hexane w i t h 15 b r o u g h t a b o u t r e d u c t i v e d i m e r i z a t i o n a n d t r i m e r i z a t i o n , a c o m b i n a t i o n of 15 a n d 1 e q u i v of a,«'-t>ipyridyl (cf. i n f r a ) gave a b l a c k s o l i d ( 1 6 , I R b a n d at 1770 c m " ) w h o s e protolysis 1

under a n argon atmosphere w i t h 8 5 % (17).

H P0 3

4

yielded only

cis-stilbene

S i m p l e exposure of a s l u r r y of 16 to a i r r e g e n e r a t e d 13.

O n the

o t h e r h a n d , t r e a t m e n t of 16 w i t h 6N H C 1 u n d e r a r g o n p r o d u c e d a b r i c k c o l o r e d s o l i d (18)

w h o s e protolysis w i t h g l a c i a l a c e t i c a c i d i n a i r p r o -

d u c e d o n l y frans-stilbene

(19).

W h e n the b l a c k s o l i d 16 w a s

i n s t e a d w i t h a sequence of 6 N - D C 1 a n d g l a c i a l o-deuterioacetic «,a'-dideuterio-trans-stilbene

was obtained.

treated acid,

T h e f o r m u l a t i o n of 16 as a

n i c k e l a c y c l o p r o p e n e is s u p p o r t e d b y t h e 1770 c m " b a n d , w h i c h r e s e m 1

bles t h a t characteristic

of other m e t a l l o c y c l o p r o p e n e s

(10).

Thus,


as

198

INORGANIC COMPOUNDS W I T H U N U S U A L PROPERTIES

n

Scheme 2 Ph

Ph //


Ph_C

\ Li

Li

1

Ph

V C—Ph /

L NiCl 2

2

Ph

,c—c Ph—q (MeO,C—C=

C—Ph

' V

\ \

Ni

10a

L„ ,C0 Me

Ph

2

N

10

c-c(

Ph—(5^

CO,Me

V - P h

b a:

12

L=Ph P 3

b: L = ( P h P C H - ) 2

2

2

10a as c a t a l y s t

Ph—C=C—Ph 13

14 p o r t r a y e d i n S c h e m e 3, the p r e s e n c e of b i p y r i d y l seems to arrest t h e a l k y n e - N i ( O ) i n t e r a c t i o n at the 1:1 stage (16). W h e n 16 w a s h e a t e d i n T H F w i t h t w o or m o r e e q u i v a l e n t s of d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e (21), 20 a n d the c y c l o t r i m e r of 21 w e r e i s o l a t e d . F o r the c a t a l y t i c c y c l o t r i m e r i z a t i o n of a l k y n e s , a c c o r d i n g l y , this f i n d i n g supports a stepw i s e passage f r o m a 1:1 (e.g., 16) to a 2 : 1 or n i c k e l o l e a d d u c t ( i n this


17.

EISCH

Novel Cleavage, Oligomerization

AND I M

199

Rxns

Scheme 3

Ph—C=C—Ph

(COD) Ni y 2

(C H N) 5

4

2

Ph \ \

/ .Ni. •NC ';N


13

Ph

Ph—C^C—Ph

°2 y

C = C

7

THF

DCl

Ph

H3PO4

16

'Ar

Ar Ph

Phi

Ph /

\

NiCl—L»

D

17

18 DOAc

D

/

c=c

(Me0 C—C^) 2

\

2

C0 Me

Ph

2

C0 Me

19

2

Ph

Y

1 c

°2Me

C0 Me 2

20 case, 4 , w h e r e R i a n d R = P h a n d R a n d R = C 0 M e ) t o a 3 : 1 a d d u c t (8 a n d 2 0 , v i a 6 or 7 ) . M o r e i m p o r t a n t l y , these results c a n m e a n that b i p y r i d y l fosters o x i d a t i v e a d d i t i o n onto t h e a l k y n e TT b o n d a n d stabilizes the N i ( I I ) - l i k e n i c k e l a c y c l o p r o p e n e i n t e r m e d i a t e ( 1 6 ) , b o t h b y its b a c k b o n d i n g a n d c h e l a t i n g properties. 2

Insertions of Ni(0)

3

4

2

Complexes into Carbons-Oxygen Bonds

F u r t h e r e v i d e n c e f o r t h e f o s t e r i n g effect of d o n o r l i g a n d s o n t h e o x i d a t i v e a d d i t i o n s of N i ( 0 ) w a s g a i n e d f r o m a cleavage s t u d y of ethers a n d epoxides. A l l y l i c ethers, s u c h as a l l y l p h e n y l ether ( 2 2 ) , u n d e r w e n t s m o o t h i n s e r t i o n of N i ( 0 ) w i t h either 15 i n T H F o r t e t r a k i s ( t r i e t h y l p h o s p h i n e ) n i c k e l ( O ) ( 2 3 ) i n b e n z e n e ( S c h e m e 4 ) . T h e f o l l o w i n g react i v i t y trends a r e n o t e w o r t h y : ( 1 ) as to solvent, T M E D A > T H F > >


200

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

II

Scheme 4

.0. CH,

+

0—Ni i CH I CH

L„Ni°


CH M CH,

6

6

2

H C L | ^

+

CH,

CH CH=CHo 3

22

C H ;

OH

15: L„ = 23: L„ =

2C0D 4Et P 3

( 2 ) as to l i g a n d s , ( C O D ) N i + b i p y >

( C O D ) N i ; a n d ( 3 ) as

2

to ether, P h O C H C H — C H 2

2

2

> > Ph-0-CH Ph > > MeOCH Ph (II). 2

2

T h e f o r m a t i o n of s m a l l a m o u n t s ( < 5 % ) of o- a n d p - a l l y l p h e n o l s is c o n sistent w i t h t h e i n t e r m e d i a c y o f a l l y l a n d p h e n o x y r a d i c a l pairs i n these N i ( 0 ) insertions.

[ T h e f o r m a t i o n of c a . e q u a l a m o u n t s of o- a n d p - a l l y l -

p h e n o l s is n o t r e c o n c i l a b l e w i t h a c o m p e t i n g t h e r m a l C l a i s e n rearrangem e n t , w h e r e e x c l u s i v e l y t h e o - a l l y l p h e n o l is p r o d u c e d ( I I ) ] . C o r r o b o r a t i v e e v i d e n c e f o r this m e c h a n i s t i c v i e w w a s a c q u i r e d f r o m a s t u d y of a s p e c i a l case o f ethers, n a m e l y t h e epoxides

( I I ) . I n this

instance, C - O b o n d c l e a v a g e is f o l l o w e d b y e l i m i n a t i o n of N i O ( S c h e m e 5).

T h e scope of t h e r e a c t i o n a n d t h e influence of N i ( 0 ) reagents a r e

i n f o r m a t i v e : (1) s u b s t i t u t e d styrene oxides a n d other epoxides a d j a c e n t TT systems (e.g., d i e t h y l d s - 2 , 3 - e p o x y s u c c i n a t e )

bearing

undergo deoxy-

g e n a t i o n , b u t saturated epoxides (e.g., c i s - l , 2 - e p o x y o c t - l - y l ( t r i m e t h y l s i l a n e ) seem to b e inert; ( 2 ) t h e d e o x y g e n a t i o n appears to b e a stepwise process, f o r either cis- o r £rans-/Mrimethylsilylstyrene

o x i d e (24 o r 25)

e v e n t u a l l y y i e l d t h e same c o m p o s i t i o n o f olefins 26 a n d 27

(~95:5);

h o w e v e r , t h e r a t i o o f o l e f i n i c isomers f r o m 24 at s m a l l c o n v e r s i o n w a s 6 0 : 4 0 (26:27); ( 3 ) a l t h o u g h ( C O D ) N i i n T H F o r ( P h P ) N i i n b e n 2

3

4

zene d o not r e a d i l y react w i t h 24, either a 1:1 m i x t u r e o f ( C O D ) N i a n d 2

b i p y r i d y l i n T H F o r ( E t P ) N i i n b e n z e n e q u a n t i t a t i v e l y f o r m 26 a n d 27 3

4

( 9 5 : 5 ) . N o w , t h e nonstereoselectivity of t h e k i n e t i c a l l y c o n t r o l l e d p r o d u c t c o m p o s i t i o n ( r a n g e of 26:27 =

6 0 : 4 0 to 9 5 : 5 ) i n d i c a t e s a s t e p w i s e

r u p t u r e of t h e C - O e p o x i d e b o n d s , so that intermediates l i k e 28 a n d 29 can interconvert before N i O elimination. Thus, b o t h the smooth deoxyg e n a t i o n o f 24 a n d 25 a n d t h e s l o w e r c o n v e r s i o n o f 27 i n t o 26

seem

most l i k e l y t o o c c u r v i a s i n g l e e l e c t r o n transfer f r o m N i ( 0 ) t o the epoxides o r to t h e o l e f i n 27, r e s p e c t i v e l y .

T h e other observations, s u c h as t h e

a c c e l e r a t i n g effect of e l e c t r o n - a t t r a c t i n g ir systems o n t h e e p o x i d e a n d o f s t r o n g d o n o r l i g a n d s o n n i c k e l ( b i p y r i d y l o r E t P ) , a r e also 3

w i t h s u c h a n electron-transfer

consistent

mechanism.


EISCH

AND

I M

Novel Cleavage,

Oligomerization

Rxns


17.


201

202

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

II

Scheme 6

(C0D) Ni

bipy


2

COD

28

T h e efficacy of a 1:1 c o m b i n a t i o n of ( C O D ) N i ( y e l l o w ) a n d 2

b i p y r i d y l c a n b e a s c r i b e d to t h e f o r m a t i o n of a,c/-bipyridyl ( r ; - l , 5 - c y c l o 2

octadiene)Ni(O)

(28)

(purple i n T H F ) , which

N M R studies

s h o w n to b e f o r m e d u n d e r these c o n d i t i o n s ( 1 2 ) ( S c h e m e 6 ) .

have

Reagent

28 is e v i d e n t l y a m u c h m o r e reactive e l e c t r o n d o n o r . A Japanese research g r o u p has d e m o n s t r a t e d t h e effectiveness of this N i ( 0 ) source i n f o r m i n g c y c l o a l k a n e s f r o m a,

31

) C—CH — > ( C H ) C - C H C H •NiBr 3

2

g

THF

(C H ) C—CH 6

6

5

3

29

2

2

32

THF

3

6

(C H ) CHCH C H 6

s

2

30


2

e

B

5

17.

EISCH

Novel Cleavage,

AND I M

Desulfurization

and

Oligomerization

Hydrodesulfurization

Rxns

of Sulfur

203

Heterocycles

T h e f o r e g o i n g i n s i g h t i n t o the m e c h a n i s m of N i ( 0 ) i n s e r t i o n reactions p r o v e d m o s t h e l p f u l i n d e v e l o p i n g s o l u b l e d e s u l f u r i z i n g agents f o r a r o m a t i c sulfides (16).

A s test substrates f o r N i ( 0 )

desulfurizations,


heterocycles 33, 34, 35, a n d 36 w e r e chosen since these are t y p i c a l of the

35

36

stable o r g a n o s u l f u r c o m p o u n d s f o u n d as contaminants and

organic chemicals

derived f r o m coal.

in liquid

Q u i c k l y it became

that the b i p y ( C O D ) N i reagent w a s a g a i n s u p e r i o r to

fuels

evident

(COD) Ni 2

for

i n s e r t i n g i n t o a C - S b o n d ; b u t a net single C - S i n s e r t i o n l e a d i n g to 37 ( a n d u p o n protolysis to 38) t u r n e d out to b e a m i n o r p a t h w a y ( < 5 % ) (Scheme 8).

W i t h t w o e q u i v of 28 i n T H F at 5 0 ° C , the m a j o r p r o d -

u c t f o r m e d b y treatment (39)

w i t h 6N

H C 1 or w i t h L i A l H

was b i p h e n y l

4

i n a 5 5 - 7 5 % y i e l d . W h e n the r e a c t i o n was c o n d u c t e d f o r shorter

p e r i o d s at l o w e r c o n v e r s i o n , b o t h 39 a n d b i p h e n y l e n e 40 w e r e detected. T h e n a t u r e of i n t e r m e d i a t e ( s )

41 w i l l b e discussed b e l o w w h e n a d d i -

t i o n a l results p e r m i t some g e n e r a l i z a t i o n . T h e b e h a v i o r of heterocycles

34, 3 5, a n d 36 t o w a r d b i p y ( C O D ) N i

a n d was i n s t r u c t i v e ( S c h e m e 9): h e r e c o m p l e t e d e s u l f u r i z a t i o n was the exc l u s i v e course, w i t h r i n g c o n t r a c t i o n ( 4 2 ) c o m e f o r 34 a n d 35. were formed.

b e i n g the p r e p o n d e r a n t out-

O n l y traces of the h y d r o d e s u l f u r i z e d p r o d u c t 43

T h i a n t h r e n e was c o n v e r t e d i n t o d i b e n z o t h i o p h e n e

(33),

w h o s e f u r t h e r reactions f o l l o w e d those d e p i c t e d i n S c h e m e 8. I n the w o r k - u p of s u c h r i n g contractions, i t was f o u n d that a b r i e f (10 m i n ) treatment of the r e a c t i o n m i x t u r e w i t h L i A l H , f o l l o w e d b y 4

h y d r o l y s i s , was a m o r e r a p i d , h i g h e r - y i e l d i n g p r o c e d u r e t h a n w i t h 6N H C 1 . W h e n , o n the other h a n d , 1 e q u i v of L i A l H

4

treatment was a d d e d


204

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES


Scheme 8

55-75%

Scheme 9


II

17.

EISCH

Novel Cleavage,

AND I M

Oligomerization

205

Rxns

to 2 e q u i v of 28 b e f o r e i n t r o d u c i n g the h e t e r o c y c l e substrate,

subsequent

h e a t i n g l e d e x c l u s i v e l y to the h y d r o d e s u l f u r i z e d p r o d u c t f o r 33, 34, a n d 35.

Thianthrene (36)

gave b o t h 33 a n d 39 ( S c h e m e 1 0 ) .

T h e r i n g c o n t r a c t i o n o b s e r v e d w i t h a l l of these heterocycles

(40 and

4 2 ) , t a k e n together w i t h the i n a b i l i t y of ( C O D ) N i alone to effect d e s u l 2

f u r i z a t i o n , indicates that b i p y ( C O D ) N i operates p r i n c i p a l l y b y a n electron-transfer m e c h a n i s m r a t h e r t h a n b y i n s e r t i o n i n a C - S b o n d (cf. l o w Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 8, 2017 | http://pubs.acs.org Publication Date: May 5, 1979 | doi: 10.1021/ba-1979-0173.ch017

y i e l d of 3 8 ) .

S i n c e 2 e q u i v of 28 are m o r e effective, p r i o r c o o r d i n a t i o n

of one N i ( 0 ) at s u l f u r seems to b e i m p o r t a n t ( S c h e m e 11). T h a t b i p h e n y l -

Scheme 11

ene is a k i n e t i c a l l y c o n t r o l l e d p r o d u c t i n the d e s u l f u r i z a t i o n of d i b e n z o thiophene

Scheme 8)

(see

suggested

that

it m u s t

r e c l e a v e d b y the f u r t h e r a c t i o n of N i ( 0 ) complexes.

be

subsequently

This possibility was

v e r i f i e d i n a separate e x p e r i m e n t b y t r e a t i n g samples of b i p h e n y l e n e , i n turn, w i t h LiAlH . 4

(COD) Ni, 2

(LiAlH

4

(Et P) Ni, bipy(COD)Ni, 3

4

alone d i d not attack 4 0 . )

and

(COD) Ni 2

+

A l l of these reagents i n w a r m

T H F cleaved biphenylene and yielded, u p o n hydrolysis, b i p h e n y l

(14).

M o r e i n f o r m a t i v e a b o u t the m a n n e r i n w h i c h these n i c k e l reagents cleave biphenylene ( 4 0 )

w e r e reactions i n w h i c h d e u t e r a t e d h y d r i d e or

p r o t o n sources w e r e u s e d . T h u s , treatment of 4 0 w i t h ( E t P ) N i i n b e n 3

4

zene, f o l l o w e d b y w o r k - u p w i t h 1 2 N D C 1 u n d e r a r g o n , gave a 7 0 : 3 0 m i x t u r e of 2 , 2 ' - d i d e u t e r i o b i p h e n y l ( 4 3 )

and 2-deuteriobiphenyl

(44).

A s i m i l a r r u n c o n d u c t e d i n T H F gave a 3 0 : 7 0 ratio of 43 a n d 4 4 . deuterated

biphenyls presuppose

(Scheme 12),

o r g a n o n i c k e l precursors

w h i c h m u s t also b e the precursors 4 1

45

and

The 46

of the b i p h e n y l


206

INORGANIC

COMPOUNDS

WITH

UNUSUAL

PROPERTIES

II

Scheme 12


40

46

45 DC1

DC1 V

D 44 SH

C H

=

6

6

THF

70%

30%

30%

70%

f o r m e d f r o m d i b e n z o t h i o p h e n e (see

Scheme 8 ) .

T h e l a r g e r a m o u n t of

m o n o d e u t e r a t e d b i p h e n y l ( 4 4 ) i n T H F suggests that r a d i c a l i n t e r m e d i ates m a y b e a t t a c k i n g t h e solvent, a better h y d r o g e n a t o m d o n o r t h a n benzene.

T h a t a s i g n i f i c a n t a m o u n t of 4 4 is f o r m e d , e v e n i n b e n z e n e ,

m a y m e a n that a E t P l i g a n d c a n serve the source of t h e h y d r o g e n 3

(14).

W h e n t h e cleavage of b i p h e n y l e n e w a s c o n d u c t e d w i t h a 2 : 1 ratio of L i A l D 65:35

4

a n d ( C O D ) N i i n T H F at 25 ° C , treatment w i t h H 0 gave a

mixture

2

2

of

biphenyl

(39)

a n d 2,2'-dideuteriobiphenyl

(43)

( S c h e m e 1 3 ) . T h i s result s h o w e d that at least o n e - t h i r d of the h y d r o genolysis of 4 0 h a d o c c u r r e d b e f o r e h y d r o l y s i s . A s i m i l a r r u n that w a s w o r k e d u p w i t h D 0 gave a 3 5 : 6 5 m i x t u r e of 39 a n d 4 3 . A c c o r d i n g l y , 2

another o n e - t h i r d of the b i p h e n y l originates f r o m a m e t a l l o l e ( 4 7 , M

=

N i or A l ) a n d the last o n e - t h i r d of 39 m u s t arise b y h y d r o g e n a b s t r a c t i o n f r o m the solvent ( S c h e m e 13)

(14).

T h e exact n a t u r e of t h e reagents g e n e r a t e d b y a d m i x i n g v a r y i n g ratios of ( C O D ) N i o r b i p y ( C O D ) N i w i t h L i A l H 2

tained.

F o r a 2 : 1 ratio of L i A l H

w o r k suggests (17).

4

4

r e m a i n s to b e ascer-

and ( C O D ) N i ,

some u n p u b l i s h e d

2

t h e f o r m a t i o n of a c o m p o s i t i o n , L i ( A l H 2

3

• N i •A1H ) 3

H o w e v e r , t h e most effective r a t i o of b i p y ( C O D ) N i a n d L i A l H

f o r h y d r o d e s u l f u r i z i n g 3 3 , 3 4 , 3 5 , a n d 36 appears to b e 2 : 1 .

4

F o r the

present, i t seems reasonable to suggest that s u c h c o m b i n a t i o n s c a n i n v o l v e a n i o n i c n i c k e l or A l - N i b o n d s .


17.

EISCH

AND I M

Novel Cleavage,

Oligomerization

207

Rxns

Scheme 13

\ ^

(COD) Ni 2

'


T H F , 25°C

43

39

47

A l t h o u g h t h e f o r e g o i n g results u n a m b i g u o u s l y p r o v e that some of t h e desulfurization

of d i b e n z o t h i o p h e n e

proceeds

v i a biphenylene

as a n

i n t e r m e d i a t e , i t r e m a i n s t o b e established w h e t h e r this is t h e p r i n c i p a l p a t h w a y to 39 ( w i t h 45 a n d 4 6 as p r e c u r s o r s ) .

O n g o i n g studies h o p e

to settle this q u e s t i o n b y t h e d e s u l f u r i z a t i o n of 2 , 7 - d i m e t h y l d i b e n z o t h i o phene ( 4 8 ) ; if the corresponding biphenylene ( 4 9 ) were the p r i n c i p a l p r e c u r s o r of t h e b i t o l y l , o n e m i g h t expect t o o b t a i n a p p r o x i m a t e l y e q u a l a m o u n t s of t h e m,m'~ a n d p - p ' - b i t o l y l s ( 5 0 a n d 5 1 ) . I f d e s u l f u r i z a t i o n w o u l d l e a d d i r e c t l y t o nickeloles ( c f . 4 5 ) a n d b i p h e n y l y l n i c k e l d e r i v a tives ( c f . 4 6 ) , t h e n p , p ' - b i t o l y l s h o u l d b e the p r i n c i p a l o u t c o m e ( S c h e m e 14).

Scheme 14

50

51


208

INORGANIC COMPOUNDS W I T H UNUSUAL PROPERTIES


Prospects for Further

II

Developments

T h e a c h i e v e m e n t o f d e s u l f u r i z i n g r e l a t i v e l y stable a r o m a t i c sulfides w i t h N i ( 0 ) complexes u n d e r s t o i c h i o m e t r i c c o n d i t i o n s n o w sets t h e stage f o r a s t u d y of c a t a l y t i c processes u n d e r a n atmosphere o f h y d r o g e n . A n u n d e r s t a n d i n g of t h e n a t u r e of s u c h homogeneous reagents, w h i c h a r e effective u n d e r m i l d c o n d i t i o n s ( 2 5 ° - 5 0 ° C u n d e r 1 a t m ) , c a n g u i d e t h e d e s i g n of s i m i l a r homogeneous catalysts. A c c o r d i n g l y , n o t o n l y n i c k e l complexes b u t also those s o l u b l e complexes o f i r o n , cobalt, m o l y b d e n u m , t i t a n i u m , a n d tungsten m e r i t close attention i n t h e search f o r n e w , h o m o geneous d e s u l f u r i z i n g catalysts. T h e s e metals a r e e s p e c i a l l y p r o m i s i n g since most o f t h e m h a v e b e e n f o u n d effective as heterogeneous h y d r o d e s u l f u r i z i n g catalysts at e l e v a t e d temperatures ( 3 , 4 , 5 , 6 , 7 ) . A k e y p r o b l e m to b e s o l v e d i n p a s s i n g f r o m t h e s t o i c h i o m e t r i c t o t h e c a t a l y t i c system w i l l b e t h e r e g e n e r a t i o n of t h e m e t a l c o m p l e x f r o m t h e m e t a l sulfide u n d e r m i l d c o n d i t i o n s . E v e n as s t o i c h i o m e t r i c reagents, s u c h n i c k e l complexes as b i p y ( C O D ) N i have already demonstrated their value i n desulfurizing a n d r i n g - c o n t r a c t i n g processes, i n h y d r o d e s u l f u r i z a t i o n , i n selective d e o x y g e n a t i o n of epoxides, a n d i n t h e c o n t r o l l e d cleavage o f a l l y l ethers. T h e i r a b i l i t y to f o r m m e t a l l o c y c l o p e n t a d i e n e s f r o m b i p h e n y l e n e s o r f r o m t h i o phenes c a n d e v e l o p i n t o a v a l u a b l e alternative r o u t e t o s u c h r e a c t i v e m e t a l heterocycles. Finally, the chemistry uncovered i n studying the mode of action of these N i ( 0 ) reagents lends s t r o n g s u p p o r t t o a n electron-transfer v i e w o f t h e i r reactions. I n a d d i t i o n , t h e finding that d i b e n z o t h i o p h e n e divests itself o f s u l f u r , at least p a r t i a l l y , t h r o u g h t h e r e l a t i v e l y s t r a i n e d b i p h e n y l e n e a n d t h e reactive d i b e n z o n i c k e l o l e i n t e r m e d i a t e s , is u n u s u a l . I t demonstrates that nature is o f t e n m o r e tortuous i n its r e a c t i o n paths t h a n the h u m a n m i n d c a n r e a d i l y i m a g i n e . Acknowledgment T h e authors w i s h to a c k n o w l e d g e s u p p o r t o f v a r i o u s aspects o f this research b y t h e N a t i o n a l Science F o u n d a t i o n ( C H E - 7 6 - 1 0 1 1 9 ) a n d t h e E n e r g y Research a n d D e v e l o p m e n t Administration of the Department of Energy (EF-77-G-01-2739).

Literature Cited 1. Forster, D . , Roth, J. F., Eds., "Homogeneous Catalysis—II," ADV. C H E M .

SER. (1974) 132. 2. Trost, B. M., Salzmann, T. N., J. Am. Chem. Soc. (1973) 95, 6840. 3. Wu, W. R. K., Storch, H. H., Bur. Mines Bull. (1968) 633.



17.

EISCH

ANDI M

Novel Cleavage,

Oligomerization

Rxns

209

4. Ivanovskii, F. P., Beskova, G. S., Dontsova, V. A., Khim. Prom. (1966) 42, 845 (Chem. Abstr. (1967) 66, 20788). 5. Novak, V., Cirova, A., Ropa Uhlie (1971) 299 (Chem. Abstr. (1971) 75, 91563). 6. Ishiguro, T., French Pat. 1,466,905 (Chem. Abstr. (1976) 67, 75131). 7. vanKlinken, J., Kouwenhoven, H . W., Van Weeren, P. A., German Pat. 1,951,007 (Chem. Abstr. (1971) 73, 27303). 8. Eisch, J. J., Damasevitz, G. A., J. Organomet. Chem. (1975) 96, c19. 9. Eisch, J. J., Galle, J. E.,J.Organomet. Chem. (1975) 96, c23. 10. Collman, J. P., Acc. Chem. Res. (1968) 1, 141. 11. Eisch, J. J., Im, K. R., J. Organomet. Chem. (1977) 139, c45. 12. Dinjus, E., Gorski, I., Uhlig, E., Walther, H., Z. Anorg. Allg. Chem. (1976) 422, 75. 13. Takahaski, S., Suzuki, Y., Sonogashira, K., Hagihara, N., J. Chem. Soc., Chem. Commun. (1976) 839. 14. Eisch, J. J., Im, K. R., unpublished studies (1977). 15. Curtin, D. Y., Hurwitz, M. J., J. Am. Chem. Soc. (1952) 74, 5381. 16. Eisch, J. J., Im, K. R., J. Organomet. Chem. (1977) 139, c51. 17. House, G., Wilke,G.,unpublished studies, cited in Jolly, P. W., Wilke, G., "The Organic Chemistry of Nickel," Vol. I, pp. 261-262, Academic, New York, 1974. RECEIVED March 3, 1978.


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