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
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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.
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
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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,
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
as
198
INORGANIC COMPOUNDS W I T H U N U S U A L PROPERTIES
n
Scheme 2 Ph
Ph //
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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
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
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
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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 > >
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
200
INORGANIC
COMPOUNDS
WITH
UNUSUAL
PROPERTIES
II
Scheme 4
.0. CH,
+
0—Ni i CH I CH
L„Ni°
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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.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
EISCH
AND
I M
Novel Cleavage,
Oligomerization
Rxns
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17.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
201
202
INORGANIC
COMPOUNDS
WITH
UNUSUAL
PROPERTIES
II
Scheme 6
(C0D) Ni
bipy
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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
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
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,
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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
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
204
INORGANIC
COMPOUNDS
WITH
UNUSUAL
PROPERTIES
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Scheme 8
55-75%
Scheme 9
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
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
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
206
INORGANIC
COMPOUNDS
WITH
UNUSUAL
PROPERTIES
II
Scheme 12
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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 .
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
17.
EISCH
AND I M
Novel Cleavage,
Oligomerization
207
Rxns
Scheme 13
\ ^
(COD) Ni 2
'
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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
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
208
INORGANIC COMPOUNDS W I T H UNUSUAL PROPERTIES
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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.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
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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.
King; Inorganic Compounds with Unusual Properties—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.