f r o m t h c J o t r r n ao
l o c i e t y ,g 1 , 6 5 1 2 ( 1 9 6 9 ) . 1
l f t h e A m e r i c e nC l r c m i c a S
-L o-p_y r ,l g,l l-t Ll y* 6t p9^ . i n t e d
b y t h e A m c r i c a nC h e m i c a S
l o c i c r ya n d r e p r i n t c db y p c r m i s s i o no f r h " . o p y . i g h r o w n e r .
R e a c t ionof Coppe r(I) H y d ri d e w i th
Org a noc opper ( i)C o mp o u n d sI
Sir.'
A n u m b e r o f i m p o r t a n t t r a n s i t i o nm e t a l c a t a l y z e d
o r g a n i c s y n t h e s e sa r e c a r r i e d o u t i n s o l u t i o n sc o n t a i n i n g m i, r t ur es of int e rm e d i a tetra n s i ti o n me ta l h ydri des
a n d a - a l k y l s . 3 T h e r e a c t i v i t yo f t r a n s i t i o n m e t a l h y d r i d e st o w a r d m e t a Ia l k y l s h a s n o t b e e nd e f i n e d . H o w e ve r, t he f ac ilit y w i th w h i c h n o n tra n s i ti o n m e tal hyr i d e s r e a c t w i t h m a n y o - o r g a n o m e t a l l ic o m p o u n d s i , r
s u g g e s t st h a t a n a l o g o u s r e a c t i o n so f t r a n s i t i o n m e t a l
h y d r i d e sm i g h t b e i m p o r t a n t i n t h e c a t a r y t i ct r a n s i t i o n
metal systems.
A s p a r t o f a s t u d y o f t h e m e c h a n i s m ( so) f t h e r m a ld e c o m p o s i t i o no f c o p p e r ( l ) a l k y i s ,w e h a v e p r e p a r e dc o p p e r(l) hy dr ide and e x a mi n e d i ts re a c ti v i ty to w ard oi g a n o c o p p e r ( l )c o m p o u n d s . T h e r e a c t i v i t y o f c o p p e r
h y d r i d e t o w a r d c o p p e r a l k y l s i s o f p a r t i c u r a ri n r e r e s a
ts
a model f or t he r ea c ti v i ty o f o th e r tra n s i ti o n metal hyd r i d e sa n d a l k y l s : s i n c ec o p p e rh y d r i d ed o e s n o t c a t a l yze o lef in is om er iza ti o n o r d e u te ri u m e x c h a n g eunder
t h e c o n d i t i o n s u s e d i n t h i s s t u d y , t h e s t r u c t u r e so f h y d ro car bon pr oduc t s fo rm e d i n th e p re s e n c eo f copper
h y d r i d e c a n b e d e t e r m i n e dw i t h o u t a m b i g u i t y . H e r e
we wish to report that hydridic and o-organometallic
d e r i v a t i v e so f c o p p e r ( t ) r e a c t r e a d i l y w i t h o n e a n o t h e r ,
a n d t h a t t h e m e c h a n i s mo f t h i s r e a c t i o nd o e sn o t i n v o l v e
i n te rmediat eor gani c fre e ra d i c a l s .
-Copper ( t ) hy dr ide w a s p re p a re d b y tre a ti n g I equi v
o f c o p p e r ( l ) b r o m i d e d i s s o l v e di n 1 0 0e q u i v o i p y r i , i i n e
with l.l equiv of diisobutylaluminum
h y d r i A e( j 0 % i n
h e p t a n e )r t - 5 0 o . V i g o r o u s m i x i n g p r o d u c e d a h o m o g e n o u sd
, a r k b r o w n s o l u t i o n ,f r o m w h i c h c o p p e r ( l )
h yd ri de c ould be p re c i p i ta te d b y d i l u ti o n w i th .-300
e q u i vo f e t h e r . c e n t r i f u g a t i o n ,s e p a r a t i o no f t h e s u p e r (l) supported by the Nationar ScienceFoundation,
crant 7266,
a n d b y t h e I n t c r n a t i o n a l C o p p e r R e s e a r c hA s s o c i a t i o n I, n c .
Journal ol'the American Chemical society I 9t;23'I
n a t a n t l i q u i d , a n d r e p e a t e dw a s h i n go f t h e p r e c i p i t a t c
w i t h e t h e r ,a l l a t - 7 8 o , p e r m i t t e di s o l a t i o no f c o p p e r ( l )
h y d r i d e a s a b r o w n s o l i d i n g r e a t e rt h a n 9 0 % y i e l c i . ;
T h e r a t i o o i h y d r i d e t o c o p p e ri n t h i s m a t e r i a li s 0 . 9 6 *
0 . 0 , 1 ;i t c o n t a i n sl e s st h a n 0 . 5 % a l u m i n u m o r b r o m i n e
but retai ns-25 /, pyri di ne,basedon copper.
P u r e , a n h y d r o u s c o p p e r ( l ) h y d r i d e d e c o m p o s e sr o
h y d r o g e na n d m e t a l l i cc o p p e r a b o v e - 2 0 o ; i t i s i n d e f i n i t e l ys t a b l e a t - 7 8 o . S u s p e n s i o n o
sf copper(l)
h y d r i d e i n e t h e r a r e r e l a t i v e l ya i r i n s e n s i t i v e ; t h e d r y
solid is pyrophoric. Tri-rr-butylphosphine
and copp e r ( l ) h y d r i d e f o r m a I : I c o m p l e x ,t h e h i g h s o l u b i l i t y
o f i w h i c h h a s p r e v e n t e di t s i s o l a t i o n . A t t e m p t s t o d e t e c t a m e t a l - h y d r o g e ns t r e t c h i n gv i b r a t i o n i n t h e s o l L r t i o n i r s p e c t r u mo f c o p p e r h y d r i d e ,o r a h y d r i d e r e s o n a n c e i n i t s n m r s p e c t r u m ,h a v e s o f a r b e e n u n s u c c e s ful.3
H y d r i d o ( t r i - n - b u t y l p h o s p h i n e ) c o p p e r r( e
l )d u c e s p r i m a r y , s e c o n d a r y ,a n d t e r t i a r y a l k y l - , v i n y l - , a n d a r y l c o p p e r ( l ) c o m p o u n d s t o t h e c o r r e s p o n d i n gh y d r o c a r -
( 2 ) F o r r e v i e w s o f r c p r e s e n t a t i v er c a c t i o n s , s e e R . H e c k , A d c a n .
O r g a n o m e r aC
l . h e m . , 4 , 2 1 3( 1 9 6 6 ) ; L . R e i c ha n d A . S c h i n d l e r.,. p o l y m _
erization by organometallic compounds," Intersciencepublishers,
N e w Y o r k , N . Y . , 1 9 6 6 ,C h a p t e r I V ; R . C r a m e r , A c c o u n t sC h e m . R e s . ,
I , 1 8 6( 1 9 6 8 ) .
(3) N. G. Gaylord, "Reducrion with Complex N{ctal Hydridcs."
I n t e r s c i c n c eP u b l i s h e r s ,N e w Y o r k , N . y . , 1 9 5 6 , C h a p t e . 4 ; T . C .
T r a y l o r , C h e m .I n d . ( L o n d o n ) , 1 2 2 3 ( t 9 5 9 ) .
( 4 ) D . J . P a s t o a n d J . A . G o n t a r z ,J . A m e r . C h e m .S o c . ,9 1 , 7 1 9
( 1 9 6 9 ) ; L . L Z a k h a r k i n a n d I . M . K h o r l i n a , Z h . O b s h c h .K h i m . , 3 2 ,
2783 (t962).
( 5 ) T h i s p r o c e d u r ei s b a s c do n t h a t d e v e l o p e db y W i b e r g a n d H e n l c , d
b u t y i e l d sc u H o f h i g h c r p u r i t y t h a n t h a t o b t a i n e du s i n g L i A l H , a s a
reducing agent.? The results of our examination of thc material
p r o d u c e db y t h e w i b e r g - H e n l e p r o c c d u r ea r e i n g e n e r a la g r e e m e n w
t irh
t h o s e r e p o r t e d b 7 S h r i v e r ; r i n p a r t i c u l a r ,w e c o n c u r t h a t t h i s m a t e r i a l
r s C u H , h o w b e i t e x t e n s i v e l yc o n t a m i n a t e d .
( 6 ) E . W i b e r g a n d W . H e n l e , Z . N a t u r f o r s c h . , 7 b , 2 5 0( 1 9 5 2 ) .
(7) J. A. Dilrs and D. F. Shriver, !. Amer. Chem. Soc., 90, 5769
( 1 9 6 8 ) ; 9 1 , 4 0 8 8( t 9 6 9 ) .
(8) Scealso ref 7.
Nocember 5, 1969
Scheme I
\
/l----,
MgBr
I
n.cunau,
I
-7r
l E tp,
N
R,
Sc.Heli
N
D
6CHrLi
rn
CuPBu3
J".ta,",r,)n(PBu3),n
4
cH,or,
f
-2go
I
I-'*
lEt,o.
l-8s%
Y
lEtP,
h
CH,
6
b o ns in high y i e l d u n d e r v e ry m i l d c o n d i ti ons.e W e
have explored the intermediacy of free radicals in these
reduc t ions by e x a mi n i n g th e s te re o c h e mi stryof the
products obtained upon reduction of endo-Z-norbornyl(tri-n-butylphosphine)coppe(I) (2) and of cis- and trans2-butenyl(tri-n-butylphosphine)copper(l) with derivati ves of CuH. I n e a c h o f th e re a c ti o n ss tu di ed the resu lt obt ained wa s th a t, w i th i n o u r l i mi ts o f detecti on,
the r educ t ion of th e o rg a n o c o p p e rc o mp o u nd occurred
with complete retention of configuration at carbon.
Under t hes ec on d i ti o n s , H C u P Bu 3d o e s n o t re ducenorb o r nene or 1- or 2 -b u te n e .
Typically, 2 was prepared by reaction of endo-Z-norb o r ny lm agnes iu mb ro m i d e (1 ) t0w i th b ro m o (t ri -n-butyl p h os phine) c opp e r(I) i n e th e r a t -7 8 o (S cheme I).
Th e s t er eoc hem i s tryo f 2 c o u l d b e e s ta b l i s h edby conver s ion t o t he c o rre s p o n d i n gme th y l a te c o m pl ex 3 on
treatment with 3-5 equiv of methyllithium, followed by
o x idat iv e c oupl i n g b y re a c ti o n w i th n i tro benzeneat
-7 8o t o y ield 2 -me th y l n o rb o rn a n e (9 8 % endo, 2%
e x o) . r t T he s am e s te re o c h e mi c are
l s u l t w a s obtai ned
o n nuc leophilicco u p l i n g o f me th y l to s y l a tew i th the ate
co m plex 4 f or m e d o n a d d i ti o n o f 3 -5 e q u i v of n-butyl l i thium t o I equ i v o f 2 .r2 C o n tro l re a c ti o nscarri ed
out using equilibrium mixtures (55-60% endo)\o of
e p im er ic 2- nor b o rn y l Gri g n a rd re a g e n tsy i el ded mi xtur es of 2- m et hyl n o rb o rn a n e sc o n ta i n i n g -6 0 f of the
endo isomer. Taken together, these results establish
(9) Copper(I) hydride and its derivatives also act as reducing agenrs
toward a number of other organic and organometallic substrates.
For example, hydrido(tri-n-butylphosphine)copper(I)reducesiodobenzene to benzene(80%), and benzoyl chloride to benzaldehyde(50%) in
2 hr at 2-{o in ether, and diphenylmercury(Il) to benzenequantitatively
at -50".
( 1 0 ) F . R . J e n s e n a n d K . L . N a k a m a y e , J . A m e r . C h c m . . S o c . ,8 8 ,
3437 (1966).
( l l ) C . M . W h i t e s i d e s ,J . S a n F i l l i p p o , J r . , C . P . C a s e y ,a n d E . J .
Panek, ibid.,E9,5302 ( 1967).
( 1 2 ) E . J . C o r e y a n d G . H . P o s n e r ,i b i d . , 9 0 , 5 6 1 5 ( 1 9 6 8 ) ; G . M .
Whitesides, W. F. Fischer, Jr., J. San Filippo, Jr., R. W. Bashe, and
H . O . H o u s e , i b i d . , 9 l , 4 8 7 1 ( 1 9 6 9 ) ,a n d r e f e r e n c e sr h e r e i n .
N
,//\,
A/!u
^^
|
Cu.(CHrLi)n.(PBu3)^
3
ocueeu,
Ier,No,-7r
--30e
lEr,c.THF,
fv"
rl
7s
N
CH.'
6
that conversi onsof 1 to 2, and o[ 3 and 4 to 6, t ake place
presumabl y w i t h r et ent ion
w i th hi gh stereosel ecti vi ty,
of confi gurati on i n each step.
Treatment of 2 (> 98 f endo)w i th a l i mi t ing am ount
in et her
of deuteri o(tri -n-butyl phosphi ne)copper( l) 13
a t - 3 0 o y i e l d e d n o r b o r n a n e - 2 - d(r9 8 + 5 f e n d o ) . t l
Reduction of a mixture of endo- and exo-2-norbornyl(tri -n-butyl phosphi ne)copper(I)
(60 /, endo ) under sim i l ar condi ti ons produced norbornane-Z- & ( - 607, ,
endo). Thus, reducti on of 2 to 5 takes pl ace wit h r etenti on of stereochemi stry. S i nce the i nte r m ediacy of
a free 2-norbornyl radi cal i n thi s reacti onwould lead t o
products w i th l oss oi stereochemi stry
at the 2 posit ion.
reacti on o[ 2 w i th D C uP B ur rnust take pl ace by a nonradi caI pathw ay.t6
The concl usi on that free organi c radi cals ar e not intermedi atesi n the reducti on of organocop per ( I )com pounds by H C uP B ua i s supported by tw o r elat ed observations: first, reduction of either cis- or trans'2'
i n et her at - 30"
butenyl (tri -n-butyl phosphi ne)copper(t)
yi el ds the correspondi ng2-butenew i th > 97 f r et ent ion
(13) Copper(I) deuteride was prepared using diisobutylaluminum
deuteride synthesizedby a procedure described for the preparation of
diethylaluminum deuteride: G. Wilke and H. Muller, Ann., 629,
222 (1960). Isotopic purity of the CuD was establishedby analysis of
the mixture of Hr O.5%), HD (95.17), and Dt (1.3%) obtained on
p r o t o n o l y s i sa t - 3 0 ' w i t h m e t h a n o l i cH C [ .
( 1 4 ) T h e e p i m e r i c c o m p o s i t i o n so f t h e n o r b o r n a n e - 2 - d frr o m t h e r e '
action mixtures were determined by comparison of their ir spectra with
spectraof mixtures of endo-and exo-norbornane-2-dro[ known epimertc
c o m p o s i t i o n . T h e p r e s e n c e o f n o r b o r n a n e - d oa m o n g t h e r e a c t i o n
products made it impossible to use the fingerprint regiontr for thesc
analyses,and the relative insensitivity of the C-D stretching region to
changes in the ratio of endo- to exo-norbornane-2-dtlimited the accui n s a m p l e sc o n t a i n i n g > 9 0 m o l e l f , e n d o
r a c y o f i r a n a l y s i st o - + 5 [
epimer.
( 1 5 ) A . N i c k o n a n d J . H . H a m m o n s , J . A m e r . C h e m . S o c . ,E 6 ' 3 3 2 2
( r9 6 4 ) .
tl6) The results of Scheme I also exclude free norbornyl radicals as
intermediates in the oxidative or nucleophilic coupling reactions of the
copper(I) ate complexes 3 and 4. By contrast with the conversion ot'
2 to 5, reduction of either exo- or cndo-2<hloronorbornane with tri-nb u t y l t i n d e u t e r i d eu n d e r r a d i c a l c o n d i t i o n s( A I B N , h v , 2 0 " ) y i e l d s m i x tures of the epimers of norbornane-2'drcontaining 84 + 5 ft exo isomcr'
Communications to the Editt.tr
o f c o n fi g u ra ti o n ;17and second,reducti on of neophyl (tri -n -b u ty l p h o s p hi ne)copper(I)under si mi l ar condi ti o n s l e a d s to /-b u tyl benzene,w i th no observabl erearra n g e m e n tto i s o b utyl benzene.
T h e d e ta i l e dn a tu re of the C -H bond formi ng step i n
th e s e re d u c ti o n sh a s not been establ i shed,al though i t
c o u l d p l a u s i b l y p ro ceedby i ntramol ecul ar reacti on of
h y d r i d o a n d a l k y l l i g a n d s c o o r d i n a t e dt o a c o m m o n
c l u s te r o f c o p p e r(l ) atoms.tz'ta S tudi esof the mechan i s m o f th i s a n d re l ated reacti ons,and of the rol e of
c o p p e r h y d ri d e i n the thermal decomposi ti onof al kyl c o p p e r(l ) re a g e n ts,w i l l be di scussedi n l ater papers.
(17) For a discussion of the stereochemicalconsequcncesexpected
from a free 2-butenyl radical in the related thermal decomposition of
these compounds, see G. M. Whitesides and C. P. Casey, J. Amer,
C h e n r .S o c . ,8 8 , 4 5 4 1( 1 9 6 0 .
( 1 8 ) A . C a i r n c r o s sa n d W . A . S h e p p a r d ,A b s t r a c t s , l 5 7 t h N a t i o n a l
Meeting of the American Chemical Society, Minneapolis, Minn.,
A p r i l 1 9 6 9 ,O R G N l l 8 .
( 1 9 ) ( a ) N a t i o n a l I n s t i r u t e so f H e a l t h P r e d o c r o r a F
l ellow, 1966-1969;
( b ) N a t i o n a l I n s t i t u t e s o f H e a l t h P r e d o c r o r a lF e l l o w , 1 9 6 7 - 1 9 6 8 ; ( c )
N a t i o n a l S c i e n c eF o u n d a t i o n P r e d o c t o r a lF e l l o w , 1 9 6 3 - 1 9 6 7 .
George M. Whitesides, Joseph San Filippo, Jr.,re.
Erwin R. Stredronsky,reu Charles P. Caseyteo
Department of Chemisty,
Massachuseus Institute of Technology
Cambridge, Massachuseus 02139
Receioed June 13, 1969
{
Journal of rhe American Chemical Soclety I
9l:23 I Nooember
5, 1969