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Tungsten—carbene—alkene complexes
.ro,,rr~lof Molecular CatcJys~s, 8 (19S0) 1 - 13
1
~) ElsevierSequoia S_A.. La,,=---e --Printed in the Netherlands
TUNGSTF_,_N--CARBENE -ALKENE
CO~LEXE~
C H A R L E S P. C A S E v and A L A N J. S H U S T E R M A N D e p a r t m e n t o f Chemistry, Univenzity o f Wiaco.~in, Madison, Wfa. 5 3 706 ( U . S . A . )
S-mmary Reaction c_-f(CO) s W [ C ( O C ~ 3 }C6H~ ~ C H z ] w i t h 3-buten-l~ol gives a butenyloxy carbene complex ( C O ) s W [ C ( O C H z C H z C H = C H z ) C s H 4 - P ~ H a ], 2. O n heating to 38 q[3 in benzene, 2 decomposes to l-(4-methylpbenyl)-2oxabicyclo[3.1.0]hexane, 4. A n intermediate tetracarbonyltungstencarbene-alkene complex 5 was detected b y N M I ~ during the course of the decomposition of 2 to cyclopropane 4. In the decomposition of 2 an init~' induction period fol£owed by an autocetalytic decomposition was observed. R e a c t i o n o f ( C O ) s W [ C ( O C H s ) C e H ¢ - p - C H 3 ] w i t h a]lyT-m~ne p r o d u c e d a 1:1.2 m~ztui-e of isomers of ( C O ) s W [ C ( N H C H 2 C H = C H ~ ) C B H 4 - P - C I - I a ], 9 Z and 9.~..Thermolysis of the mixture of 9 Z and 9 E produced a steble tetracazbonylt,.tngsten-cezbene--alkene complex, II.
Introduction T h e o l e f m m e t a t h e a i s r e a c t i o n [ I ] h a s b e e n p r o p o s e d t o p r o c e e d via interconversion of mefel-carbene-~l~ene complexes and metaIlacyclolx,£anes [ 2 ] . T h i s p r o p o s a l is s u p p o r t e d b o t h b y s t u d i e s o f t h e r e a c t i o n s o f m e t a l r~rbene complexes with ~}~enes [3] and by labelling experiments which s h o w t h a t t h e o l e 5 v m e t a t h e s i s r e a c t i o n p r o c e e d s in a non-pakw;_se m ~ n n e r
(4). O u r inf._rest i n t h e mefmth~,~s r e a c t i o n h a s l e d u s t o s t u d y t h e p r e p a r a t i o n o f m e t a l c o m p l e x e s c o n f ~ i n / n g b o t h c a r b e n e a n d ~ e n e l i ~ d s a n d :-,he the_rm~1 r e a c t i o n s o f t h e s e c o m p l e x e s . P r i e s f e r a n d R o s e n b I , , m h~ve r e p o r t e d t h e s y n t h e s i s o f a n i r o n - c a r b e n e - e l k e n e c o m p l e x , ( C s H s ) F e ( C O ) ( C H 2 = CH2)[ C ( O C H 3 ) ( O C s H , I ) ] ÷ b u t t h e c o m p o u n d d o e s n o t r e a c t t o give e i t h e r c y c / o p r o p a n e s o r m e ~ a t h e s i s 4 i k e p r o d u c t s [ 5 ] . We h a v e a t t e m p t e d t o p r e p a r e tungsten-cazbene-alkene complexes ~m~,ar to ( C O ) s W [ C ( O C H ~ ) C s H s ] and ( C O ) s W [ C ( C a H s ) 2 ] w b / c h h a v e b e e n u s e d in m o d e l s t u d i e s o f t h e oI~t~. metath~.ci~ reaction [3] and which are catalyst precursors for o I ~ - metathesis [6]. T, an effort to m a k e stable m e t a l - c a r b e n e - ~ e h e complexes, w e have studied c o m p o u n d s in w h i c h the earbene and ~Irene ligand are joined together to form a bidentate che/ating ligand.
Results
Preparation of metal c~rbene complexes P e n t a c a x b o n y l [ a l l y l o x y { p - t o l y l ) c a t b e n e ] h m g s t e n ( O ) , 1, p e n t a c a r b o n y l [ b u t - 3 ~ e n y l - l - o x y ( p - ~ l y l ) c a r b e n e ] hLngsten(O), 2, a n d p e n t a c a r b o n y l [ p e n t ~ 4 ~ e n y l - l ~ x y ( p - t o l y l ) c a r b e n e ] h m g s t e n ( O ) , 3, w e r e p r e p a r e d f r o m p e n t a carbonyl[meth.oxy(p-tolyl)carbene] tungsten(0) by base catalyzed alcohol e x c h a n g e r e a c t i o n s . F o r e x a m p l e , { C O ) s W [ C ( O C H a ) C 6 H ~ - p - C H a ] ( 0 . 5 0 g, 1.09 mmol), 3-buten-l~l (2.40 ml, 27.8 retool) and sodium 3-buten-l,glate ( ~ 0 . 5 r e t o o l ) w e r e ~ i r r e d f o r 4 h in E t 2 0 a t 0 c~ Gver m o l e c u l a r s/eves ( 4 A ) . I t w a s n e c e s s a r y t o u s e a 2 0 - 3 0 f o l d e x c e s s o f 3 - b u t e n - l - o l an," __- e m p l o y m o l e c u l a r sieves t o s e l e c t i v e l y b i n d m e t h a n o l t o d r i v e t h e e q - i ~ , 0 r i u m reaction to virtual completion. The ether solution was filtered and concentrated u n d e r v a c u u m a t 2 5 ~C. T h e o i l y r e s i d u e w a s di~c~olved in h e x a n e , a n d f-rite_red t h r o u g h a s h o r t c o l u m n o f silica gel, c o n c e n t r a t e d u n d e r vacuu.m, a n d c r y s t a l l i z e d ~-om h e x a n e aL - - 7 8 ~ t o give o r a n g e - r e d cry~-.~'l~ o f ( C O ) s W [ C ( O C H 2 C H 2 C H = C H 2 ) C e H 4 _-p-CHa], 2, ( 0 . 3 6 7 g, 6 8 ~ ) , m . p . 5 3 ~ ( d e c . ) . S o l i d 2 d e c o m p o s e s a t r o o m t e m p e r a 0 a r e o v e r several h o u r s b u t h a s b e e n s t o r e d f o r m o n t h s a t - - 2 0 2:. T h e i n f r a r e d s p e c t r u m o f 2 h a s c a r b o n y l band~ a*. 2 0 6 8 ( m ) , 1 9 8 3 ( w } , 1 9 5 4 ( s ) , a n d 1 9 4 3 ( v s ) c m - I t y p i c a l o f a ~ n g s t e n p e n t a c a r b o n y l c o m p l e x [ 7 ] . T h e I H NMI~ o f 2 is given in T a b l e 1. T h e l a c N M R o f 2 ( t e t r a h y d r o f u r a n < l s , 0 . 0 7 M Cr(acac~3, p r o t o n - d e c o u p l e d ) is 5 2 1 . 6 ( C H 3 ) , 3 4 . 5 ( O C H ~ C H , ) , 8 4 . 4 ( O C H z ) , 13 8 . 7 ( = C H z ) , 1 2 9 . 8 , 1 3 0 . 1 ( o r t h o , m e t a ) , 1 3 5 . 4 (_CH=CH2), 1 4 5 . 3 , 1 5 3 . 2 (i ~so, p a r a ) , 1 9 9 . 1 (c/s C O ) , 2 0 5 . 0 (t=ans C O ) , 3 1 9 . 0 ( c a r b e n e ) . OCH] [CO.~:~V= C/
base .
CH 3
CH2=CH-[CHZ]n-0H
/ 0-[ "HI]nCH:CH2 . [CO}sW=C
2 3
n=2 n=3
"C,'~
S i m i l a r l y , r e a c t i o n o f ( C O ) s W [ C ( O C H 3 ) C s H 4 - p - C H a ] w i t h allyl a l c o h o l gave 1, m . p . 8 5 ¢C ( d e c . ) , w h i c h w a s s t a b l e a t r o o m t e m p e r a t u r e . F o r 1: I R ( h e x a n e ) ~ (CO}: 2 0 6 4 ( m ) , 1 9 8 6 ( w ) , 1 9 5 8 ( s ) , 1 9 4 6 ( v s ) ; 1H N M R ( b e n z e n e - d s ) : 5 1 . 9 1 (s, 3 H ) , 5 . 0 0 (din.. J = I 0 H z , 2 H ) , 5 . 0 9 - 5.14= ( m , 2 H ) , 5.6 - 5.8 ( m , I_H), 6 . 7 9 ( d , J = 8 H z , 2 H ) , 7 . 5 5 (d, J = 8 H z , 2 H ) ; l a C N ~ I R ( p r o t o n - d e c o u p ! e d , a c e t o n e - d s , 0 . 0 7 M CY(ae~e)a): 6 2 1 . 6 ( C H a ) , 8 5 . 2 (OCH2) , 120.4 (-CH=C_H2) , 128.3, 129.6 (ortho, meta), 132.2 (-~_H=CH2), 1 4 4 . 2 , 1 5 3 . 0 ( i p s o , p a r a ) , 1 9 7 . 9 (c/s C O ) , 2 0 4 . 0 ( t r a n s C O ) , 3 1 8 . 6 ( c a r b e n e ) ; m . p . 8 5 ¢C ( d e c . ) . R ~ a c t i o n o f ( C O ) s W [ C ( O C H a } C e H , - p < ~ H 3 ] w i t h 4 - p e n t e n - l ~ l gave 3 w h i c h w a s c r y ~ n i T C d f r o m h e x a n e a t - - 2 0 ¢C b u t w h i c h f o r m s a t h e r m a l l y s t a b l e oil a t r o o m ~ e m p e x a t u r e . F o r 3: I R ( h e x a n e ) v ( C O ) : 2 0 6 8 ( m ) , 1 9 8 6 ( w ) , 1 9 5 6 ( s ) . 1 9 4 4 { v Q c m - 1 ; I H N M R ( b e n z e n e ~ l ~ ) : ~ 1 . 3 9 ( q , , i n t e t , J = 6 . 9 I-Iz, 2 H ) , 1 . 7 2 (s, 3 H ) , 1 . 6 - 1 . 9 ( m , 2 H ) , 4 . 4 3 ( t , J = 6 . 0 H z , 2 H ) , 4 . 5 - 4 . 9 ( m , 2 H ) , 5 . 1 5 - 5 . 6 0 ( m , 1 H ) , 6 . 6 5 (d, J = 8 . 1 H z , 2 H ) , 7 . 3 4 (d, J = 8 . 3 H z , 2 H ) ;
TABLE
1
2 7 0 ~ f H z 1 H IqM.R
spec.~-ao f tungsten-cs~hene-alkeneintermediates
S~rtir~
m t ~
Major
intermediatez
Minor ~ - ~ - m e ~
Compound Solvent
2
2
5e b
5a b
6a b
5b
C6D 6
CDzC12
CeD 6
CD2t.,'~ 2
C6D 6
C6D6
6b C6D6
HI
4.67
3.95 4.25 2.02 0.61 3.59 3.09 2.73
c
2.22 2-22 5.6 5.0 5.0 1.96
4.77 5.10 3.10 1.61 4.32 c 3.42 2.37
e
H3 H4 H5 He H7 CH 3 Aromatic Aromatic
c 4.30 c 0.61 3.59 3.14 2.73 1.93
c
4.67
5.05 5.05 2.84 2.84 5.98 5.21 5.27 2.40
4.46
H~_
2.60 c c c 2.78
2.56 c 3.84 2.79 2.73
-
1.92
-
6.83
7 -25
6.89
7 24
c
6.81
c
7.56
7.63
7.90
7.80
c
7.56
e
a
a A . r b i t r s . t ~ ~ s ~ i g n m e n t of' r e l a t i o r , ~ h i p o f c a r h e n e a n d s / k e n e ] / g a n d s ; s e e ~,ext, h J 1 2 = 1 1 . 3 , g13 = 7 . 3 , J 1 4 = 3 . 6 , J z 3 = 3 . 6 , J z 4 = 6 . 6 , J 3 4 = 1 4 . 4 , J s 5 = 6 . 6 , J 4 s = 8 . 5 , Js6 = 8.7, Js7 = 12.7, J67 = 0.
CNot observabledue to ~nCerferences.
XSC Nq~IR (proton decoupled, acetonitrfle-ds, 0.07 M Cr(acac)s): 5 21 (CH~), 28 (CH2), 30 (CH2), 84 (OCHz), 115 (CH= _CHz), 127, 129 (ortho, meta), 137 (_CH=CHz), 143, 152 (ipso, para), 197 (c~s CO), 204 (trans CO), 318 (carbene).
Thermolysis of (CO )sW[ C(OCHzCIIzCH= CIIz]Cell4-p-CH~ ], 2 T h e butenyloxy carbene complex 2 rapidly d e c o m p o s e d at 40 ~C in b e n z e n e ~ e producing the cyclopropane l~4-nlethylphenyl)-2~:~xabicyc[o[3.1.0] hexane, 4, in quantitative yield as d e f i n e d by NICIR. T h e stricture of 4 was assigned on the basis of its I H N - M R spectrum (benzene-de): 6 0.91 (ddd, J = 9 [q_z,6 Hz, 1 Hz, He), 1.13 (dd, J = 6 Hz, 5 ~iz, Hv), 1.42 (dr, J = 9 Hz, 5 Hz, Hs), 1.5% (dddd, J = 11.9 Hz, 7.~_Hz, 2.5 I/z, 0.6 Hz, H4), 1.80 (m, H3), 2.13 (s, CHs), 3.40 (ed, J = 9 Hz, 7.4 [-Iz,H z ] , 3.95 (td, J = 9 Hz,
2.5 Hz, H~), 7.02 (d, J = 8 Ha, aromatic), 7.32 (d, J = 8 Ha, aromatic). Coupling constant ~ m e n t s were made with the afd of decoupling experiments. T h e ~ S C N M R i n ~ e t o n i t : r / I e - . d . ~ c o - f ~ r m e d t h e s t r u h ~ l r e o f 4 : & 1 6 . 7 (cyclopropyl CHz), 19.9 (cyc/opropyI CH), 24.7 (CI-Is),28.7 (OCH~CI-Iz), ~6.5 (OC[-Iz}, 69.0 (cyclopropy[ CO}~ 124.5 an d 1~¢8.5 (ortho and meta), 135.6 and 138.0 (ipso and para).The measured exact mass of 4 was 174.1041 (calcd for C ~ z H z 4 0 : 174.1045).
4
,
0
W h e n t h e t/~ermolysis o f b u t e n y l o x y carbene c o m p l e x 2 in benzene
"W'H~..~ a
"'W'- 'V "" H7
0 HS~-"-H7 5_~c X=C.~.3
5bb x=CH~
5.,.~..~ X = H
6.~b X=,-I
In £he s p e c ~ u m of the major intermediate 5, the diastereotopic relationship of methylene protons H z and H z (Jl2 = II.3 Hz) and H s and H ~ (Js4 = !4.4 Hz) indicates that the butenyl group is part of a rigid asymmetric f r a m e w o r k such as fJlat of a chelating ligand. T h e lack of any observable coupling between f~/~inal ~/nyl protons H s and H 7 and f,he large values for c/s (J56 = 8.7 Hz) a n d trurts ( J 5 7 = 1 3 . 7 Hz) c o u p l i n g c o n s t m a l t s t o t h e s e c o n d e_ry v~myl proton H s indicates that the p]~-ar ~_nyl group is stillpresent. T h e
c h e m i c a l s h i f t s o f v i n y l p r o t o n s H 5 , H 6 , a n d H7 in f/le m a j o r i n t e r m e d i a t e 5 a r e s h i f t e d 2 . 0 - 2 . 5 p p m u p f i e l d f r o m t h e i r p o s i t i o n s in s ~ g m a t e r i a l 2. T h e s e u p f i e l d c h e m i c a l .~bi,~s e s t a b l i s h t h a t t h e a l k e n e is c o m p l e x e d t o ~ n g s t e n . ~n~ne m e t h y l e n e p r o t o n s n e x t t o o x y g e n in m a j o r i n t e r m e d i a t e 5 are e x c e p t i o n a l l y d e s h i e l d e d ( H 1 , 5 4 . 7 7 ; H 2 , 6 5 . I 0 ) j u s t as Lhey are in starting material 2. This deshieldw, g is aLt~ihuted to the strongly electron w i t h d r a w i n g o x y g e n a t o m o f t h e a l k o x y c a r b e n e m o i e t y a n d e s t a b l i s h e s that the carbene ligand is intact irm 5. T h e intermediaries generated in the decomposition of butenyloxy carbene complex 2 to cyclopropane 4 in h-~ane at r o o m temperature were observed and characterized by infrared spectroscopy. ~j~]ly, only the four carbonyl bands of s~-V~ug complex 2 were observed. A s reaction began, n e w bands were observed a~ 2 0 3 0 ~_d 1 9 1 0 c m -I (shoulder), in addition, f~he band at 1 9 8 2 c m -z i n c r e ~ i due to formation of W(CO)~. After ~ver~d hours, the band at 2 0 6 2 cm-* had disappeared indica~dng that all of 2 had decomposed. A t this point, the I R spec~-~m consisted of a ~band at 1 9 8 2 c m -z d u e t o W ( C O ) s a n d f o u r e q u a l l y i n t e n s e b a n d s a t 2 0 3 0 , 1 9 4 7 , I 9 2 8 , a n d 1 9 0 8 c m -~ . U p o n f u r t h e r stand~=g a t r o o m ~ r n p e r a k L r e all o f *.he h a n d s d i s a p p e a r e d e x c e p t f o r t h e 1 9 8 2 c m -1 b a n d d u e t o W ( C O ) 6 . T h e o b s e r v a t i o n o f f o u r e q u a l inten~t--y' c a r b o n y l b a n d s is in a g r e e m e n t w i t h t h e f o r m u l a Z i o n o f 5 as a ci~ d i ~ b s t i 0 a t e d m e t a l t e t r a c a r b o n y l c o m p l e x [ 7 ] . T h e i n t e r m e 4 ~ t e tungsten-carbene-~IIcene c o m p l e x 5 w a s t r a p p e d with fxiethylphosphine. A s a m p l e of 2 in benzene-d 6 was allowed t o d e c o m m pose at 38 =C until the mixture contained leas than ~ % 2, 3 5 ~ intermediate 5, and 6 0 % cyclopropane 4 as deterr-~ned by I ~ . A t f~hi~point, the solution was cooled to 6 ~[~, I.I equivalents of ~-ie~,_7~.hosphine were added, a n d t h e s o l u t i o n w a s w a r m e d t o 3 8 ~ f o r 5 m}n. G ~ - z t e r t h a n 9 0 ~ o f t h e t u n g s t e n - - c a r b e n e - ~ l ~ r e n e c o m p l e x w a s c o a v e r t e d i-n=o ci~-tetr;,c-~-rbonyl( t r i e t h y l p h o s p h i n e ) [ b u t - Z - e n y l - l - o x y ( p - t o l y l } c a z b e n e ] "..:ngsten(0), 7. T h e i n f r a r e d s p e c t r u m o f 7 h a s f o u r c a r b o n y l b a n d s a t 20170.-'). 1 9 2 g ( s ) , 1 9 1 8 ( s ) , a n d 1 8 9 0 ( s ) Cn1-1 a s e x p e c t e d f o r a e/~ d.isu~ti~..~ted m e t e ! f ~ b ' ~ _ ~ r b o n y I c o m p l e x . T h e XH N_-MH.s p e c t x - m o f t h e c a r b e n e l i g a n d o f "7 elo.cely r e s e m b l e d t h a t o f 2. A c o n t r o l e x p e r i m e n t d e m o n s t r a t e d Zhat 7 is _n:,~ f o r m e d b y r e a c t i o n o f t r i e t / ~ y l p h o s p h i n e w i t h 2 a t 3 8 ~C. F o r 7: 1H NMP-_ ( b e n z e n e - d 6 ) : 6 0 . 6 9 (dr, J = 1 5 . 4 I-l.z, 7.7 I-iz, 9 H ) , 1 . 3 4 ( q u i n t e t , J = 7.7 I-iz, 6 ~ ) , 1 . 9 7 (s, 3 H ) , 2 . 3 5 (q, J = 6 H z , 2 H ) , 4 . 6 0 (t, J = 6 H z , 2 H ) , 5 . 0 2 ( m : 2/-1), 5 . 7 3 ( m , 1 H ) , 6 . 8 9 (d, J = 8 H z , 2 H ) , 7 . 5 2 (d, J = 8 H z , 2 H ) .
~-----~.0
PEt,,j
T h e r a t e o f d e c o m p o s i t i o n o f b u t e n y l o x y c a r b e n e c o m p l e x 2 in b e n zene-d6 a t 3 8 ¢C w a s meamzred b y N M R a n d f o u n d t o b e u n u s u a l (Fig. 1). a n i n d u c t i o n p e r i o d o f a b o u t 2 0 rain, a n a u t o c a t a l y f / c d e c o m p e ~ J t i o n
6 LOT [0 ~CL-7.
Fi:~CT'.CN
0
o
[ I
I! o = 2
O.S~ c
o=--
!
L
I,"
,-.
•
i °
6
•
_9.
£
o
C .- : XJ. -- [..--.in]
F i g . 1 . Th.=.rmal d e c o m p o s i t i o n
of ~ in benzene-d
6 =_t 3 8 ~:~.
o f 2 was o b s e r v e d . A f t e r 50 m i n , all o f t h e s t a r t i n g mate_da] 2 h a d d e a o m po.~ed= t h e t u n g s t e n - c a r b e n e - a l k e n e c o m p l e x 5 h a d r e a c h e d its m a x i m u m level o f a b o u t 35%, a n d a b o u t 65% y i e l d o f c y c l o p r o p a n e 4 h a d b e e n f o r m e d . I n t e r m e d i a t e 5 t h e n d e c o m p o s e d s m o o t h l y t o c y c l o p r o p a n e 4 w i t h a half-life o f a b o u t 1 0 - 15 rain. T h e s o l v e n t was f o u n d t o h a v e a m a j o r e f f e c t o n t h e t h e r m a l d e c o m p o s i t i o n s o f 2. I n b e n z e n e ~ l s , t h e t i m e f o r h a l f d e c o m p o s i t i o n o f 2 was 3 7 r a i n a n d aun i n d u c t i o n pem:od was o b s e r v e d . I n b e n z e n e - d 6 , t r i e t h y l p h o s p h i n e i n h i b i t e d t h e d e c o m p o s i t i o n o f 2; a f t e r 1 h less t h a n 10% c o n v e r s i o n t o 4 was o b s ? r v e d . I n t e r m e d i n t e 5 w a s n o t o b s e r v e d in t h e p h o s p h i n e inh i b i t e d r e a c t i o n . L-i c l ! c h l o r o m e t h a n e - d 2 , t h e t i m e f o r h a l f d e c o m p o s i t i o n w a s 18 r a i n , t h e i n t e r m e d i a t e t u n g s t e n - c a x b e n e - a l k e n e c c m p l e ~ 5 w a s o b s e r v e d a n d a s h o r t i n d u c L i o n p e r i o d w a s seen. I n c a r b o n d i s u l f i d e , t h e decomposition of 2 to cyclopropane 4 followed first-order kinetics with a half-life o f g r e a t e r t h a n 5 0 0 rain. N o i n t e r m e d i a t e w a s o b s e r v e d , a n d n o i n d u c t i o n p e r i o d w a s seen.
Therrno;ysi.s o f p e n t e n y l o x y carbene c o m p l e x 3 T h e p e n t e n y l o x y carb~.ne c o m p l e x 3 was m u c h m o r e t h e r m a l l y s t a b l e t h a n t h e b u t e n y l o x y c a r b e n e c o m p l e x 2. N o o b s e r v a b l e d e c o m p o s i t i o n o f 3 o c c u r r e d o n h e a t i n g t o 4 0 ~C in b e n z e n e f o r 1 2 h . C o m p l e t e d e c o m p o s i t ~ o a o t 3 o c c u r r e d o n h e a t i n g t o 7 0 ¢C in b e n z e n e - d 6 f o r several h o u r s . T h e o n l y obse~-ved p r o d u c t s w e r e W(CO)6 a n d t h e c y c l o p r o p a n e , 1 - ( 4 d m e t h y i p h e n y l ) 2 - o x a b i c y c l o [ 4 . 1 . O ] i-,eptane, 8, w h i c h was f o r m e d in g r e a t e r t h a n 80% y i e l d as d e t e r m i n e d b y N ~ I R . T h e c y c l o p r o p a n e 8 w a s i s o l a t e d ip_ 54% y i e l d b y t h i n l a y e r c h r o m a t o g r a p h y (silica g e l ] h e x r n e ) . F o r 8: "-H NMI~. ( b e n z e n e < i s ) : 6 1.0 - 1.6 ( m , ? H ) , 2 . 1 5 (s, 3 H ) , 3 . 1 8 ( d d d , J = 11.6 H z , 1 0 . 7 I-Iz, 2.0 H z , 1H), 3.61 ( d i d , J = 1 0 . 7 H z , 3 . 2 H z , 1 . 0 H z , 1 H ) , 7 . 0 4 (d, J = 8 H z , 2 H ) , 7 . 2 1 (d, J = 8 H z , 2 H ) ; l a c N M R ( p r o t o n - d e c o u p l e d , acetoniCrile~13): 8 1 9 . 7 , 19.9, 20.4, 21.3. 21.8. 60, 64, 123 a n d 129 (ortho, m e t a ) , 135 a n d 142 (ipso, p a r a ) ; e x a c t m a s s : 1 8 8 . 1 1 9 8 , ( c a l c d f o r C13H1eO: 1 8 8 . 1 2 0 1 ) .
0
~
When the thermal decomposition of 3 at 70 ~ was monitored at inte~-als b y NrMR, n o i n t e r m e d i a t e tungsten--carbeue--al~rene c o m p l e x wa-~ detected; only the spectra of staring material 3 and cyctopropane 8 were seen. A n induction period followed by autz~.atalytie decomposition of 3 was observed. T h e thermal stabili~] o f 3 was greatly decreased w h e n solul/ons o f 3 w e r e Ln-adiatad p r i o r t o t h e r m o l y s i s . P h o t o l y s i s o f a 0 . 1 5 94 b e n z e n e ~ s o ! u l / o n o f 3 (e = 6 0 0 0 a t 3 5 0 sin) in a S r i n i v ~ n - - G r ~ f f i n p h o t o c h e m i c a l r e a c t o r w i t h G e n e r a l E l e c t r i c F S T S / B L R l a m p s (ma~r~rn,m e r n i . ~ o n a t 3 5 0 n m ) f o r 3 h a t SO - 4 0 ~D re~.,Ited in a p p r o x i m a t e l y 4% c o n v e r s i o n o f c a r b e n e c o m p l e x 3 i n t o c y c l o p r o p a n e 8. S u b s e q u e n t h e a I / n g o f t h e s o l u t i o n t o 4 0 5C f o r 1 0 h in t h e d a r k r e s u l t e d in 7 5 % c o n v e r s i o n o f 3 t o 8.
"fTzermolysis o f a l l y l o x y carbene c o m p l e x 1 T h e t h e r m a l s¢,~bi]it-j o f t h e a l l y l o x y c a r b e n e c o m p l e x 1 is i n t e r m e c l h t e b e t w e e n t h a t o f 2 a n d :-'. C o m p l e t e d e c o m p o s i t i o n o f I o c c u r r e d u p o n heat~ ing t o 41 ~C in benzene ds for 13 h. A n induction period followed by an autoeatalytic decompomtior, was observed. T h e major o r g a n i c product we_s p-tolyl allyl ketone formed in 40c7o yield as determined by NIVIi9..In adddt/on, singlets d o e t o t h e t o l y l [ ' , e t h y l g r o u p o f five a d d i t i o n a l m i n o r p r o d u c t s w e r e o b s e r v e d . F o r p - t o l y l allyl k e t o n e : 1H NMR; ( b e n z e n e - d s ) : 5 1 . 9 9 (s, 3II), 3 . 3 2 (de, J = 6 . 8 H z , 1.5 H z , 2 H ) , 5 . 0 3 ( m , 2 H ) , 6 . 1 0 ( d d t , J = 1 7 . 1 H z , 1 0 . 3 H z , 6 . 7 I£z, 1 H ) , 6 . 8 7 (d, J = 8 H z , 2 H ) , 7 . 7 4 (d, J = 8 H z , o H ) ; [ ~ 1 6 8 6 ( v s ) , 1 6 1 3 ( m ) era-* [ 8 ] . ~
0
Preparation o f pentaearbonyl[allylamino(p-tolyl}earbene] ~'ungsten(O}. 9 I n a n a t t e m p t t o m a k e a m o r e t h e r m a l l y s t a b l e £u_ng~ten-eaxbenealkene complex, we initiated studies of ~mi~o-substituted carbene complexes. A d d i t i o n o f 1 0 e q u i v a l e n t s o f a / / y l a m i n e t o a r e d e t h e r s o I u t i o n o f (CO)~W[C(OCH3)C6H4-'P-C'H3] (0.458 g, 1.0 retoOl) msult, e d in an ~mmec'ii:~te r e a c t i o n p r o d u c i n g a y e l l o w s o l u l / o n . E v a p o r a l / o n o f s o l v e n t gave 0 . 4 6 g (95?5) o f a y e l l o w oil w h i c h c o - ~ t e d o f a 1 : 1 . 2 m i r ~ t r e o f t w o i s o m e r s o f pentaeazhonyl[ad/yl~m;no(p-tolyl)cazbene] tungsten(O), 9Z and 9E.
8
OCHz
0
N-H
e
F o r 9E: ZH N M R (benzene-ds): ~ 1.98 (s, 3H), 2.84 (tin J = 5.7 Hz, 2I-I), 4.6S (din, J = 9.0 Hz, I H ) , 4.70 (rim, J = 18.2 Hz, 1H), 4.91 (ddt, J = 16.5 FIz', 10.7 ~z, 5.1 Hz, 1H), 6.52 ( d , J = 8.1 Hz, 2H), 6.83 ( d , J = 7.5 Hz, 1H), 7.27 (bd s, 1H). For 9Z: ZH N M R (benzene-d6): ,5 2.02 (s, 3H), 3.94 (tin, J = 5.7 Hz, 2R), 4.79 (din, J = 17.0 Hz, 1H), 4.87 (din, J = 10.3 Hz. 1H), 5.3_4 (ddt, J = 17.1 Hz, 10.3 Hz, 5.7 Hz, 1H), 6.57 (d, J = 8.1 Hz, 2H), 6.83 ( d , J = 7.5 Hz, 2Z-I), 8.29 (bd s, 1 H ) . F o r 9 Z : 9 E (1:1.2):I~t (dichloromethane) v (CO): 2064(m), 1 9 7 0 ( w ) , 1928(vs) cm -z. T h e i s o m e r i c a s s / g n m e n t o f 9 E a n d 9 Z was m a d e o n the b ~ i ~ o f N_MR c h e m i c a l shifts. M o s e r a n d F i s c h e r h a v e r e p o r t e d t h a t t h e N - m e t h y l r e s o n a n c e o f 1 0 E in b e n z e n e - d s a p p e a r s a t 5 1 . 7 9 w h i l e t h a t o f 1 0 Z a p p e a r s a t 5 2 . 6 8 [ 9 ] . T h e m e t h y l e n e p r o t o n s o f t h e a l l y l g r o u p a p p e a r a t ~ 2 . 8 4 in t h e i s o m e r assigned =-L~cture 9 E while the methylene protons of the ~llyl ~roup appear at 5 3.94 in the isomer assigned "=he :true.ire 9Z. Isomers 9 E and 9 Z are configu_rationally stable and d o not interconvert at r o o m temperature. T h e barrier to rotation about the carbene carbon-nitrogen b o n d of penT._~earbonyl[dknethyi~mino(methyl)carbene] tungsten(0) was estimated '~o be greater t h a n 26 k c a l mo1-1 [ 1 0 ] . T h e v i n y l p r o t o n s o f 9E ~ d 9 Z a p p e a r b e ~ e e n 4.5 - 5.5 i n d i c a t i n g t h a t t h e d o u b l e b o n d is n o t c o m p l e x e d t ~ t~;ngsten.
H,C,:..~. ;coh_~'--~ I0~ CH~
H~..CH~ (co]s?,'--/~ 10E
CH3
Heating a mixture of 9 E and 9 Z in benzene
-1
(C0]s~'V--~
T h e 1H NI~fP~ s p e c t ~ m o f isolat_=cl 11 w a s identical t o th~ spectr,)m o f t h e m a t e r ~ l being fo_~aed d u r i n g t h e c o u r s e o f t h e thermoly:~is. F o r I 1 : I R ( N u j o l ) v ( C O ) : 2 0 2 0 ( s ) , 1 9 3 4 ( s ) , I 9 0 3 ( s ) , 1 8 - ~ 0 ( s ) c m - z ; zH N'~IR ( b e a z e n e d s ) : 5 2 . 0 0 ( s , CH3), 2.81 ( d , J = 1 3 . 2 Hz, H s ) , 2 . 9 4 ( b d d , J = 1.4.1 H z , H I ) , 3 . 0 6 (d, J = 8.6 Hz, H e ) , 3 . 3 1 ( d d d , J = 14.1 Hz, 5.1 Hz, 1.6 Hz, H2), 4 . 0 9 (ddddd, J = 1 3 . 1 H.-~-, 8.8 Hz, 4.8 Hz, 4 . 0 Hz, 0.7 Hz, Hz), 6 . 8 2 ( d , J = 8 . 0 Hz, 2H), 6 . 9 2 (d, J = 8.0 Hz, ~_&I), 7.26 ( b d s, N - H ) ; Z~C N-MP• ( p r o t o n - . l e c o u p l e d , acetonitrile
10
Decreased carbene c a z b o n - n i t r o g e n b o n d order in the excited state would fac'fiitate isome_~_zation o f *due a l l y l g r o u p . T , - m g s t e n - - c a r b e n e - a l k e n e c o m p l e x 11 h a s h i g h t h e r m a l s t a b i l i t y . N o d e c o m p o s i ~ o n was o b s e r v a b l e b y N M R a f t e r a b e n z e n e , ! 6 s o l u t i o n o f 1 1 w a s h e a t e d t o 9 2 ~ f o r 23 h. A f t e r a n a d d i t i o n a l 2 2 h a t 1 2 5 ~C, a b o u t 8 5 % d e c o m p o s i t i o n o f 1 ! to a n u n i d e n t i f i e d m i x t u r e o f p r o d u c t s h a d o c c u r r e d . W h e n a b e n z e n e < t 6 s o l u t i o n o f 11 w a s h e a t e d t o 9 8 ¢C f o r 6 6 h u n d e r 1. 9 a r m CO, s o m e carbonylation occurred to regenerate alIyl~mino carbene complexes 9 Z and 9E; in addition, s o m e formation of the allyl ir-ine of p-tolualdehyde was ,a~so observed. T h e ratio of ll:9Z:9E:allyl imine of p-tolualdehyde determined by N ' M R was 2:2:1:1. Hea~/ng a 1.2:1 mixture of 9 E : 9 Z it,. t o l u e n e f o r 3 9 h a t 6 5 - 8 5 ¢C u n d e r 1 4 a r m o f CO gave a m i x t u r e o f 9 Z , 9F~ a n d t h e al l yl i m i n e o f p - t o l u a l d e h y d e i n a r a t i o o f 1 : 6 : 6 .
Discussion T h e k e y i n t e r m e ~ i n t e s in t h e olet-m m e t a t h e s i s r e a c t i o n a n d i n c y c l o p r o p a n a t i o n s ar e m e t o J l l a c y c l o b u t a n e s a n d m e t a l - c a r b e n e - a l k e n e c o m p l e x e s . I t is n o t k n o w n w h i c h o f t h e s e t w o i n t e r m e d i a t e s is t h e m o s t s t a b l e f o r a given metathesis catalyst. T h e t r a n s f o r m a t i o n b e t w e e n a m e t a l - c a r b e n e alkene c o m p l e x and a me*~_llacyclobutane involves a f o r m a l o x i d a t i o n at the m e t a l c e n t e r a n d t h e c r e a t i o n o f o n e a d d i t i o n a l c o o r d i n a t i o n site. T h u s t h e equilibrilJm b e t w e e n a m e t a l - c a r b e n e - - a l k e n e c o m p l e x and a m e ~ _ t a c y c l o b u t a n e slaeuld d e p e n d s t r o n g l y o n t h e o x i d a t i o n s t a t e a n d c o o r d i n a t i o n n u m b e r ~f t h e m e t a l . T h e 6 ~ : o o r d i n a t e t u n g s t e n ( 0 ) - c a r h e n e - a l k e n e c o m p l e x e s r e p o r t e d h e r e a r e sta[~le e n o u g h t o b e o b s e r v e d a n d axe c e r t a i n l y m o r e stable than th-unobserved coordinatively unsaturated 6~oordinate tungstencyciobutanes. The stability of the tungsten-carbene-alkene complexes repo=eted h e r e is p r o b a b l y d u e t o t w o spc-ci~li~ed e f f e c t s . F i r s t , t h e c_belation o f t h e c a r b e n e a n d a l k e n e l i g a n d s p r o m o t e s t h e f o r m a t i o n o f a tungs~_en c a r b e n e - - a l k e n e s y s t e m a n d r e t a r d s f o r m a t i o n o f a s t r a i n e d b i c y c l / c metaledcycle. S e c o n d , 6 - c o o r d i n a t e tungsten(0) c a r b o n y l c o m p o u n d s are very stable w h e r e a s a t t e m p t s t o p r e p a r e t u n g s t e n ( H ) c a r b o n y l c o m p o u n d s s u c h as ( C O ) s W R 2 o r (CO)sWI~.H h a v e f a i l e d [ ! 2 ] . T h e c o n v e r s i o n o f b u t e n y l o x - y c e x b e n e c o m p l e x 2 t o c y c l o p r o p a n e 4 is t h e fin-st c y c l o p r o p a n a t i o n i n w h i c h a m e t a l - - c a r b e n e - - a l k e n e c o m p l e x w a s o b s e r ¢ ~ d as a n interm,_~di~te. In t h e r e a c t i o n s o f ( C O ) s W C ( C a H s ) 2 w i t h a l k e n e s b o t h c y c l o p r o p a n e s a n d a l k e n e s cis s i on p r o d u c t s w e r e o b t a i n e d [ 3 ] . E a r l i e r , w e h a d s u g g e s t e d that 7~oordipate met~ll~cyc!es were cyclopropane precursors and that 6~coordL-uate m e t a l l a c y c l e s w e r e p r e c u r s o ~ o f m e ~ t h e s i s 4 i k e a l P e n e sci . ~i on p r o d u c t s [ 1 3 ] . T h e f a c t t h a t C O d i s s o c i a t i o n is r e q u i r e d in t h e r2aetioru~ o f (CO)sWC(C~Hs)o_ pro~cides e v i d e n c e t h a t m e t a t h e s i s - l i k e p r o d u c t s a r e d e r i v e d from 6~oordirmted metal-alkene -ca~bene complexes. The obse.vation that t e t r a c a r b o n y l t t m g s t e n - c a r b e n e - a l k e n e c o m p l e x 5 is c o n v e r t e d t o c y c ! o -
11
p r o p a n e 4 d e m o n s t r a t e s t h a t c y c l o p r o p a n e s c a n also b e d e r i v e d f r o m 6 - c o o r d i n a t e t u n g s - t e n - - c ~ b e n e - ' a l ~ e n e c o m p l e x e s . All o f t h e r e a c t i o n s o f ( C O ) s W C ( C 6 H s ) 2 w i t ~ a l k e n e s c a n b e e x p l ~ - e d as p r o c e e d i n g tb.rough t h e s ~ m e 6 - c o o r d i n a b e mef~nllacycle i n t e r m e d i a t e . T h i s is s u p p o r t e d b y t h e o b s e r v a t i o n that the ratio of cyclopcopane:~kene s c ~ o n s products in the reaction of alkenes with ( C O ) s W C ( C 6 H ¢ - p 4 ~ H z ) 2 does not depend on external C O pres_~ntre [14]. [_niN~lly w e thought that metal--carbene-alkene compiexes could be formed by uD~molecnlar fl~cociation of C O from a carbene complex followed by inCramolecular trapping to form a chelated metal-cazbene-alkene c o m plex. However, t w o observations indicate that the loss of C O from 2 cA-not be the rate deterr-~-/ng step h-* the formation of tungsten-caxbene- 'alkene complex 5. FL-st, the rate of C O dJ~¢ociation from ( C O ) s W [ C ( O C H ~ ) C s H ~ p-CH3] is m u c h slower than the rate of decomposition of 2. T h e Firstorder rate constant for " 3 C O exchange with ( C O ) 5 W [ C = ( O C H ~ ) C s H s in toluene at 77 °C is 2.8 -+ 0.6 × I0 -s s-* (ill2 ~ 7 h) [15] while the half-~me for decomposition of 2 at 38 ~C in benzene was about 37 m}n. Second, rate determining loss of C O from 2 cannot explain either the induction pe_m~od o b ~ r v e d in the conversion of 2 to metel-carbene-alkene compiex 5 or the accelerating rate of convermon of 2 to 5. T h e observed idnetic behavior of 2 indicates tha~ while i.rJLi~l decomposition of 2 was slow, at least one c o m p o n e n t of the product mizture was capable of catalyzing the ,further decomposition of 2. W e propose that coordinatively unsaturated tungsten carbonyl species are the c o m p o n e n t s responsible for catalyzing the decomposition of 2. W ( C O ) 6 is the only observed eaxbonyl containing species at the end of the rp~etion hut the ratio of C O : W in the s ~ g material is ot~Jy 5:1. Therefore, s o m e scaven~ng of C O either from solution or from metal complexes m u s t be occun~_'ng. Conversion of metal-esxbene-alkene complex 5 to cyclopropane 4 would produce %V(CO)4. W e propose that W ( C O ) 4 abstracts C O from starting material 2 to generate 5 and W ( C O ) s and that W ( C O ) s then abstracts C O from 2 to generate a second equlwalent of metal-carbene-alkene compZex 5. Thus every, time 5 decomposes to cyelopropane 4 and W ( C O ) 4 , the W(CO)~ reacts with t w o molecules of 2 to generate inc_rea~in_g concen~%eations of metal-carbene-alkene c o m p l e x 5. A s long as the eff,_'ciency of C O abstraction from 2 by W ( C O ) 4 and W ( C O ) s is high enough to produce m o d e than one equivalent of 5 per equivalent of 5 destroyed, an accelerating autocat~ylic rate of decomposition of 2 w o u l d be observed. %r"ne autocataly~dc mechanist- for the decomposition of 2 also explains inhibition of the decomposition by added triethy|phosphine and slow" rate of decomposition in carbon di~,lIWde. Roth £riethylphosphine and carbon disulfide are capable of react~.'ngwith W ( C O ) s and W ( C O ) 4 to int~-rupt the catalytic ch~-. S~m*~rly, the autocataly~/c mechsnis~/c scheme also expl~rts the photochon~ical ird~tion of autocatalytic decomposition of pentenyloxy cazbene complex 3. It should be emphasized that w e are proposing an active attack of W ( C O ) ~ and W ( C O ) s on carbene c o m p l e x 2 and not ~r-ply scaven~-g of
12
C O fzom solution. PreviouLsly, in order to e~plain carbene ligand transfer between ch.ronzium and tungsten, we suggested that, coordinat~cely unsaizlrated metal compl~-~-~ were capable of attacking metal complexed C O
[13, Z61.
(C01sw~
-cOslow "
(CG}4W
CH3 (CC}&W~
CH-
=
~1CO).~
CHa w(c0)~
+
z(c0~sw
~O
~
CH~
CH a
fast
• ~c%
+
2
{CC]&W~ CHm -
Experimenta!
Reactions Lnvolv~ng org~nometallic c o m p o u n d s were carried out in fl~me-dried glassware under u nitrogen atmosphere. N-bIR ~ m p l e s were prepared on a v a c u u m ],'heby distillingdegassed solvent onto the organomet~lic c:ompoonds and se~llng the tubes under vacuum. 1H NMR were o b t a i n e d o n B r u c k e r W H - 2 7 0 a n d J E O L M H - 1 0 0 s p e c t r o m e t e r s . ~3C _ ~ I I ~ w e r e o b t a i n e d o n J E O L F X ~ 5 0 a n d Var~-n X L - 1 0 0 s p e c t r o m e t e r s . F o u r i e r transform infrared spectra were obtahaed on a Digilab FTS-20 interferometer High resolution mas~ spectra were obtained on a AEI-MS-902 mass spectrom e t e r . U V - v i s i b l e s _ t ~ c t r a w e r e me2_m_red o n a C a r y 1 1 8 s p e c t r o p h o t o m e t ~ . r .
AeI~nowledo-men*.
Financial support from the National Science Foundation is grateCn~lly acknowledged.
References F o r r e c e n t r e v i e w s o f t h e olef'm m e t a t h e s / s r e a c t / o n see R . H. G r u b b s , Prog. I n o r g . Chem., 2 4 ( 1 9 7 8 ) 1. T . J. l~,.a~.z,Ado. (~h'ganomeL Chem., 1 6 ( 1 9 7 7 ) 2 8 3 . J. C . M o l a n d J. A. Mor_lijn, Ado. CataL, 2 4 ( 1 9 7 5 ) 1 3 1 .
13
2 3 4
5 6 7 S 9 10 11 12 13
14 15 16
N. C a l d e m - , J. P. Lawrenc= a n d E. A_ OEstead, A d v . OrEanome~. C h e m . , 1 7 ( 1 9 7 9 ) 4~19. J. L. H6_rrisson a n d Y. C h a u v i n , , ' 6 c ~ o m o L CherrL. 141 ( 1 9 7 0 ) 1 6 1 . C. P. Casey and 'r. J. ]~[r~b~rdt,, =r. A m . Chem. Soc., 9 6 ( 1 9 7 4 ) 7 808. C. P. Ca.sey, H. E. ='l~nc~"a and M. C. S a p m , - , J ' . A,'w.. Ghent. Sot., 98 ( I 9 7 6 ) 608. R . H. G r u h b s , P. L. B u r k an,~ D. D. Cazr, J. Am_ C h e m . S o t . , 9 7 ( 1 9 7 5 ) 3 2 6 5 . R . H. G m h h s , D. D. C a n ' , C. H o p p / n a n d P. L . B u r k , ,r. A m . C h e m . Soc., 9 8 ( 1 9 7 6 . ~ 3 4"78. T . J. K a t z a n d J. L. McG~--~% J. A m . Chent. S o t . , 9 7 ( 1 9 7 5 ) 1 5 9 2 . T. J. K a t z a n d R . R o t h e h , q d , J. A m . C h e m . Soc., 9 8 ( 1 9 7 6 ) 2 5 1 9 . W. Pr~ester a n d i%[. R o s e n b l u m . J. C h e m . Soc., Chero_ C o m m u n . , (19"/6) 9 2 6 . T . J . K a t z , S. J. L e e a n d N. A c t o R , T e t r u h e d r u n L e f t . , ( 1 9 7 6 ) 4 2 4 7 . T. J. K a t z a n d N. A c t o r . : T e i r a h e d r u n Le~T., ( 1 9 7 6 } 4 2 5 i . F. A. Cotton and C. S. Kra~enzet, J. A m _ Chem. Soc.. 8 4 (1962) 4432. M. ~=kosza and T. Goetzer, OrE. Prep. Proc. [nt, 5 (1973) 203. E. Moser and E. O. Fischer, J. O r ~ a , t o m e t Chem., 16 (1969) 275. E. I~[oserand E. O. Fischer, g. O r g a n o m e L Chem_, 13 (IS68) 387. C. Kreit~r and V. Form~cek, Angew. CherrL, [nt Ed. E~gL, II (1972)141. C. P. Casey and S. W . PoIichnowski, J. Ar~. Chem._ Soc., I00 (1978) 7 565. C. P. C a s e y , in H. A / p e r ( e d . ) , ~r~u~sition M e t n l OrEanometaH'~zc.s in Organ.~c S y n t h e s i s , V o l . I, CI-.~ptar 3, _~cademic Press, N e w Y o r E , 1 9 7 6 . C. P. C a s e y a n d H. E . Tuinsf;ra, u n p u b ] ~ ' , e d o h s e r v a t / o n s 1 9 7 7 . H. E. Tuhzstra, Ph.D. Thes~s, Uni~,ersity o f W ' t s c o n ~ - , 1 3 7 8 . C . P . Casey a n d l~d. C. Ce.~. u n p u b l i s h e d o ~ t i o n s 1979. M. C. Cesa, Ph.D. T~zesia. University_ o£ W-moon~-, 1 9 7 9 . C. P. Case~- and R. L. Anderson, J. Chem. Soc., Chero- Comrn,,rL, (~975) 895.
1
~) ElsevierSequoia S_A.. La,,=---e --Printed in the Netherlands
TUNGSTF_,_N--CARBENE -ALKENE
CO~LEXE~
C H A R L E S P. C A S E v and A L A N J. S H U S T E R M A N D e p a r t m e n t o f Chemistry, Univenzity o f Wiaco.~in, Madison, Wfa. 5 3 706 ( U . S . A . )
S-mmary Reaction c_-f(CO) s W [ C ( O C ~ 3 }C6H~ ~ C H z ] w i t h 3-buten-l~ol gives a butenyloxy carbene complex ( C O ) s W [ C ( O C H z C H z C H = C H z ) C s H 4 - P ~ H a ], 2. O n heating to 38 q[3 in benzene, 2 decomposes to l-(4-methylpbenyl)-2oxabicyclo[3.1.0]hexane, 4. A n intermediate tetracarbonyltungstencarbene-alkene complex 5 was detected b y N M I ~ during the course of the decomposition of 2 to cyclopropane 4. In the decomposition of 2 an init~' induction period fol£owed by an autocetalytic decomposition was observed. R e a c t i o n o f ( C O ) s W [ C ( O C H s ) C e H ¢ - p - C H 3 ] w i t h a]lyT-m~ne p r o d u c e d a 1:1.2 m~ztui-e of isomers of ( C O ) s W [ C ( N H C H 2 C H = C H ~ ) C B H 4 - P - C I - I a ], 9 Z and 9.~..Thermolysis of the mixture of 9 Z and 9 E produced a steble tetracazbonylt,.tngsten-cezbene--alkene complex, II.
Introduction T h e o l e f m m e t a t h e a i s r e a c t i o n [ I ] h a s b e e n p r o p o s e d t o p r o c e e d via interconversion of mefel-carbene-~l~ene complexes and metaIlacyclolx,£anes [ 2 ] . T h i s p r o p o s a l is s u p p o r t e d b o t h b y s t u d i e s o f t h e r e a c t i o n s o f m e t a l r~rbene complexes with ~}~enes [3] and by labelling experiments which s h o w t h a t t h e o l e 5 v m e t a t h e s i s r e a c t i o n p r o c e e d s in a non-pakw;_se m ~ n n e r
(4). O u r inf._rest i n t h e mefmth~,~s r e a c t i o n h a s l e d u s t o s t u d y t h e p r e p a r a t i o n o f m e t a l c o m p l e x e s c o n f ~ i n / n g b o t h c a r b e n e a n d ~ e n e l i ~ d s a n d :-,he the_rm~1 r e a c t i o n s o f t h e s e c o m p l e x e s . P r i e s f e r a n d R o s e n b I , , m h~ve r e p o r t e d t h e s y n t h e s i s o f a n i r o n - c a r b e n e - e l k e n e c o m p l e x , ( C s H s ) F e ( C O ) ( C H 2 = CH2)[ C ( O C H 3 ) ( O C s H , I ) ] ÷ b u t t h e c o m p o u n d d o e s n o t r e a c t t o give e i t h e r c y c / o p r o p a n e s o r m e ~ a t h e s i s 4 i k e p r o d u c t s [ 5 ] . We h a v e a t t e m p t e d t o p r e p a r e tungsten-cazbene-alkene complexes ~m~,ar to ( C O ) s W [ C ( O C H ~ ) C s H s ] and ( C O ) s W [ C ( C a H s ) 2 ] w b / c h h a v e b e e n u s e d in m o d e l s t u d i e s o f t h e oI~t~. metath~.ci~ reaction [3] and which are catalyst precursors for o I ~ - metathesis [6]. T, an effort to m a k e stable m e t a l - c a r b e n e - ~ e h e complexes, w e have studied c o m p o u n d s in w h i c h the earbene and ~Irene ligand are joined together to form a bidentate che/ating ligand.
Results
Preparation of metal c~rbene complexes P e n t a c a x b o n y l [ a l l y l o x y { p - t o l y l ) c a t b e n e ] h m g s t e n ( O ) , 1, p e n t a c a r b o n y l [ b u t - 3 ~ e n y l - l - o x y ( p - ~ l y l ) c a r b e n e ] hLngsten(O), 2, a n d p e n t a c a r b o n y l [ p e n t ~ 4 ~ e n y l - l ~ x y ( p - t o l y l ) c a r b e n e ] h m g s t e n ( O ) , 3, w e r e p r e p a r e d f r o m p e n t a carbonyl[meth.oxy(p-tolyl)carbene] tungsten(0) by base catalyzed alcohol e x c h a n g e r e a c t i o n s . F o r e x a m p l e , { C O ) s W [ C ( O C H a ) C 6 H ~ - p - C H a ] ( 0 . 5 0 g, 1.09 mmol), 3-buten-l~l (2.40 ml, 27.8 retool) and sodium 3-buten-l,glate ( ~ 0 . 5 r e t o o l ) w e r e ~ i r r e d f o r 4 h in E t 2 0 a t 0 c~ Gver m o l e c u l a r s/eves ( 4 A ) . I t w a s n e c e s s a r y t o u s e a 2 0 - 3 0 f o l d e x c e s s o f 3 - b u t e n - l - o l an," __- e m p l o y m o l e c u l a r sieves t o s e l e c t i v e l y b i n d m e t h a n o l t o d r i v e t h e e q - i ~ , 0 r i u m reaction to virtual completion. The ether solution was filtered and concentrated u n d e r v a c u u m a t 2 5 ~C. T h e o i l y r e s i d u e w a s di~c~olved in h e x a n e , a n d f-rite_red t h r o u g h a s h o r t c o l u m n o f silica gel, c o n c e n t r a t e d u n d e r vacuu.m, a n d c r y s t a l l i z e d ~-om h e x a n e aL - - 7 8 ~ t o give o r a n g e - r e d cry~-.~'l~ o f ( C O ) s W [ C ( O C H 2 C H 2 C H = C H 2 ) C e H 4 _-p-CHa], 2, ( 0 . 3 6 7 g, 6 8 ~ ) , m . p . 5 3 ~ ( d e c . ) . S o l i d 2 d e c o m p o s e s a t r o o m t e m p e r a 0 a r e o v e r several h o u r s b u t h a s b e e n s t o r e d f o r m o n t h s a t - - 2 0 2:. T h e i n f r a r e d s p e c t r u m o f 2 h a s c a r b o n y l band~ a*. 2 0 6 8 ( m ) , 1 9 8 3 ( w } , 1 9 5 4 ( s ) , a n d 1 9 4 3 ( v s ) c m - I t y p i c a l o f a ~ n g s t e n p e n t a c a r b o n y l c o m p l e x [ 7 ] . T h e I H NMI~ o f 2 is given in T a b l e 1. T h e l a c N M R o f 2 ( t e t r a h y d r o f u r a n < l s , 0 . 0 7 M Cr(acac~3, p r o t o n - d e c o u p l e d ) is 5 2 1 . 6 ( C H 3 ) , 3 4 . 5 ( O C H ~ C H , ) , 8 4 . 4 ( O C H z ) , 13 8 . 7 ( = C H z ) , 1 2 9 . 8 , 1 3 0 . 1 ( o r t h o , m e t a ) , 1 3 5 . 4 (_CH=CH2), 1 4 5 . 3 , 1 5 3 . 2 (i ~so, p a r a ) , 1 9 9 . 1 (c/s C O ) , 2 0 5 . 0 (t=ans C O ) , 3 1 9 . 0 ( c a r b e n e ) . OCH] [CO.~:~V= C/
base .
CH 3
CH2=CH-[CHZ]n-0H
/ 0-[ "HI]nCH:CH2 . [CO}sW=C
2 3
n=2 n=3
"C,'~
S i m i l a r l y , r e a c t i o n o f ( C O ) s W [ C ( O C H 3 ) C s H 4 - p - C H a ] w i t h allyl a l c o h o l gave 1, m . p . 8 5 ¢C ( d e c . ) , w h i c h w a s s t a b l e a t r o o m t e m p e r a t u r e . F o r 1: I R ( h e x a n e ) ~ (CO}: 2 0 6 4 ( m ) , 1 9 8 6 ( w ) , 1 9 5 8 ( s ) , 1 9 4 6 ( v s ) ; 1H N M R ( b e n z e n e - d s ) : 5 1 . 9 1 (s, 3 H ) , 5 . 0 0 (din.. J = I 0 H z , 2 H ) , 5 . 0 9 - 5.14= ( m , 2 H ) , 5.6 - 5.8 ( m , I_H), 6 . 7 9 ( d , J = 8 H z , 2 H ) , 7 . 5 5 (d, J = 8 H z , 2 H ) ; l a C N ~ I R ( p r o t o n - d e c o u p ! e d , a c e t o n e - d s , 0 . 0 7 M CY(ae~e)a): 6 2 1 . 6 ( C H a ) , 8 5 . 2 (OCH2) , 120.4 (-CH=C_H2) , 128.3, 129.6 (ortho, meta), 132.2 (-~_H=CH2), 1 4 4 . 2 , 1 5 3 . 0 ( i p s o , p a r a ) , 1 9 7 . 9 (c/s C O ) , 2 0 4 . 0 ( t r a n s C O ) , 3 1 8 . 6 ( c a r b e n e ) ; m . p . 8 5 ¢C ( d e c . ) . R ~ a c t i o n o f ( C O ) s W [ C ( O C H a } C e H , - p < ~ H 3 ] w i t h 4 - p e n t e n - l ~ l gave 3 w h i c h w a s c r y ~ n i T C d f r o m h e x a n e a t - - 2 0 ¢C b u t w h i c h f o r m s a t h e r m a l l y s t a b l e oil a t r o o m ~ e m p e x a t u r e . F o r 3: I R ( h e x a n e ) v ( C O ) : 2 0 6 8 ( m ) , 1 9 8 6 ( w ) , 1 9 5 6 ( s ) . 1 9 4 4 { v Q c m - 1 ; I H N M R ( b e n z e n e ~ l ~ ) : ~ 1 . 3 9 ( q , , i n t e t , J = 6 . 9 I-Iz, 2 H ) , 1 . 7 2 (s, 3 H ) , 1 . 6 - 1 . 9 ( m , 2 H ) , 4 . 4 3 ( t , J = 6 . 0 H z , 2 H ) , 4 . 5 - 4 . 9 ( m , 2 H ) , 5 . 1 5 - 5 . 6 0 ( m , 1 H ) , 6 . 6 5 (d, J = 8 . 1 H z , 2 H ) , 7 . 3 4 (d, J = 8 . 3 H z , 2 H ) ;
TABLE
1
2 7 0 ~ f H z 1 H IqM.R
spec.~-ao f tungsten-cs~hene-alkeneintermediates
S~rtir~
m t ~
Major
intermediatez
Minor ~ - ~ - m e ~
Compound Solvent
2
2
5e b
5a b
6a b
5b
C6D 6
CDzC12
CeD 6
CD2t.,'~ 2
C6D 6
C6D6
6b C6D6
HI
4.67
3.95 4.25 2.02 0.61 3.59 3.09 2.73
c
2.22 2-22 5.6 5.0 5.0 1.96
4.77 5.10 3.10 1.61 4.32 c 3.42 2.37
e
H3 H4 H5 He H7 CH 3 Aromatic Aromatic
c 4.30 c 0.61 3.59 3.14 2.73 1.93
c
4.67
5.05 5.05 2.84 2.84 5.98 5.21 5.27 2.40
4.46
H~_
2.60 c c c 2.78
2.56 c 3.84 2.79 2.73
-
1.92
-
6.83
7 -25
6.89
7 24
c
6.81
c
7.56
7.63
7.90
7.80
c
7.56
e
a
a A . r b i t r s . t ~ ~ s ~ i g n m e n t of' r e l a t i o r , ~ h i p o f c a r h e n e a n d s / k e n e ] / g a n d s ; s e e ~,ext, h J 1 2 = 1 1 . 3 , g13 = 7 . 3 , J 1 4 = 3 . 6 , J z 3 = 3 . 6 , J z 4 = 6 . 6 , J 3 4 = 1 4 . 4 , J s 5 = 6 . 6 , J 4 s = 8 . 5 , Js6 = 8.7, Js7 = 12.7, J67 = 0.
CNot observabledue to ~nCerferences.
XSC Nq~IR (proton decoupled, acetonitrfle-ds, 0.07 M Cr(acac)s): 5 21 (CH~), 28 (CH2), 30 (CH2), 84 (OCHz), 115 (CH= _CHz), 127, 129 (ortho, meta), 137 (_CH=CHz), 143, 152 (ipso, para), 197 (c~s CO), 204 (trans CO), 318 (carbene).
Thermolysis of (CO )sW[ C(OCHzCIIzCH= CIIz]Cell4-p-CH~ ], 2 T h e butenyloxy carbene complex 2 rapidly d e c o m p o s e d at 40 ~C in b e n z e n e ~ e producing the cyclopropane l~4-nlethylphenyl)-2~:~xabicyc[o[3.1.0] hexane, 4, in quantitative yield as d e f i n e d by NICIR. T h e stricture of 4 was assigned on the basis of its I H N - M R spectrum (benzene-de): 6 0.91 (ddd, J = 9 [q_z,6 Hz, 1 Hz, He), 1.13 (dd, J = 6 Hz, 5 ~iz, Hv), 1.42 (dr, J = 9 Hz, 5 Hz, Hs), 1.5% (dddd, J = 11.9 Hz, 7.~_Hz, 2.5 I/z, 0.6 Hz, H4), 1.80 (m, H3), 2.13 (s, CHs), 3.40 (ed, J = 9 Hz, 7.4 [-Iz,H z ] , 3.95 (td, J = 9 Hz,
2.5 Hz, H~), 7.02 (d, J = 8 Ha, aromatic), 7.32 (d, J = 8 Ha, aromatic). Coupling constant ~ m e n t s were made with the afd of decoupling experiments. T h e ~ S C N M R i n ~ e t o n i t : r / I e - . d . ~ c o - f ~ r m e d t h e s t r u h ~ l r e o f 4 : & 1 6 . 7 (cyclopropyl CHz), 19.9 (cyc/opropyI CH), 24.7 (CI-Is),28.7 (OCH~CI-Iz), ~6.5 (OC[-Iz}, 69.0 (cyclopropy[ CO}~ 124.5 an d 1~¢8.5 (ortho and meta), 135.6 and 138.0 (ipso and para).The measured exact mass of 4 was 174.1041 (calcd for C ~ z H z 4 0 : 174.1045).
4
,
0
W h e n t h e t/~ermolysis o f b u t e n y l o x y carbene c o m p l e x 2 in benzene
"W'H~..~ a
"'W'- 'V "" H7
0 HS~-"-H7 5_~c X=C.~.3
5bb x=CH~
5.,.~..~ X = H
6.~b X=,-I
In £he s p e c ~ u m of the major intermediate 5, the diastereotopic relationship of methylene protons H z and H z (Jl2 = II.3 Hz) and H s and H ~ (Js4 = !4.4 Hz) indicates that the butenyl group is part of a rigid asymmetric f r a m e w o r k such as fJlat of a chelating ligand. T h e lack of any observable coupling between f~/~inal ~/nyl protons H s and H 7 and f,he large values for c/s (J56 = 8.7 Hz) a n d trurts ( J 5 7 = 1 3 . 7 Hz) c o u p l i n g c o n s t m a l t s t o t h e s e c o n d e_ry v~myl proton H s indicates that the p]~-ar ~_nyl group is stillpresent. T h e
c h e m i c a l s h i f t s o f v i n y l p r o t o n s H 5 , H 6 , a n d H7 in f/le m a j o r i n t e r m e d i a t e 5 a r e s h i f t e d 2 . 0 - 2 . 5 p p m u p f i e l d f r o m t h e i r p o s i t i o n s in s ~ g m a t e r i a l 2. T h e s e u p f i e l d c h e m i c a l .~bi,~s e s t a b l i s h t h a t t h e a l k e n e is c o m p l e x e d t o ~ n g s t e n . ~n~ne m e t h y l e n e p r o t o n s n e x t t o o x y g e n in m a j o r i n t e r m e d i a t e 5 are e x c e p t i o n a l l y d e s h i e l d e d ( H 1 , 5 4 . 7 7 ; H 2 , 6 5 . I 0 ) j u s t as Lhey are in starting material 2. This deshieldw, g is aLt~ihuted to the strongly electron w i t h d r a w i n g o x y g e n a t o m o f t h e a l k o x y c a r b e n e m o i e t y a n d e s t a b l i s h e s that the carbene ligand is intact irm 5. T h e intermediaries generated in the decomposition of butenyloxy carbene complex 2 to cyclopropane 4 in h-~ane at r o o m temperature were observed and characterized by infrared spectroscopy. ~j~]ly, only the four carbonyl bands of s~-V~ug complex 2 were observed. A s reaction began, n e w bands were observed a~ 2 0 3 0 ~_d 1 9 1 0 c m -I (shoulder), in addition, f~he band at 1 9 8 2 c m -z i n c r e ~ i due to formation of W(CO)~. After ~ver~d hours, the band at 2 0 6 2 cm-* had disappeared indica~dng that all of 2 had decomposed. A t this point, the I R spec~-~m consisted of a ~band at 1 9 8 2 c m -z d u e t o W ( C O ) s a n d f o u r e q u a l l y i n t e n s e b a n d s a t 2 0 3 0 , 1 9 4 7 , I 9 2 8 , a n d 1 9 0 8 c m -~ . U p o n f u r t h e r stand~=g a t r o o m ~ r n p e r a k L r e all o f *.he h a n d s d i s a p p e a r e d e x c e p t f o r t h e 1 9 8 2 c m -1 b a n d d u e t o W ( C O ) 6 . T h e o b s e r v a t i o n o f f o u r e q u a l inten~t--y' c a r b o n y l b a n d s is in a g r e e m e n t w i t h t h e f o r m u l a Z i o n o f 5 as a ci~ d i ~ b s t i 0 a t e d m e t a l t e t r a c a r b o n y l c o m p l e x [ 7 ] . T h e i n t e r m e 4 ~ t e tungsten-carbene-~IIcene c o m p l e x 5 w a s t r a p p e d with fxiethylphosphine. A s a m p l e of 2 in benzene-d 6 was allowed t o d e c o m m pose at 38 =C until the mixture contained leas than ~ % 2, 3 5 ~ intermediate 5, and 6 0 % cyclopropane 4 as deterr-~ned by I ~ . A t f~hi~point, the solution was cooled to 6 ~[~, I.I equivalents of ~-ie~,_7~.hosphine were added, a n d t h e s o l u t i o n w a s w a r m e d t o 3 8 ~ f o r 5 m}n. G ~ - z t e r t h a n 9 0 ~ o f t h e t u n g s t e n - - c a r b e n e - ~ l ~ r e n e c o m p l e x w a s c o a v e r t e d i-n=o ci~-tetr;,c-~-rbonyl( t r i e t h y l p h o s p h i n e ) [ b u t - Z - e n y l - l - o x y ( p - t o l y l } c a z b e n e ] "..:ngsten(0), 7. T h e i n f r a r e d s p e c t r u m o f 7 h a s f o u r c a r b o n y l b a n d s a t 20170.-'). 1 9 2 g ( s ) , 1 9 1 8 ( s ) , a n d 1 8 9 0 ( s ) Cn1-1 a s e x p e c t e d f o r a e/~ d.isu~ti~..~ted m e t e ! f ~ b ' ~ _ ~ r b o n y I c o m p l e x . T h e XH N_-MH.s p e c t x - m o f t h e c a r b e n e l i g a n d o f "7 elo.cely r e s e m b l e d t h a t o f 2. A c o n t r o l e x p e r i m e n t d e m o n s t r a t e d Zhat 7 is _n:,~ f o r m e d b y r e a c t i o n o f t r i e t / ~ y l p h o s p h i n e w i t h 2 a t 3 8 ~C. F o r 7: 1H NMP-_ ( b e n z e n e - d 6 ) : 6 0 . 6 9 (dr, J = 1 5 . 4 I-l.z, 7.7 I-iz, 9 H ) , 1 . 3 4 ( q u i n t e t , J = 7.7 I-iz, 6 ~ ) , 1 . 9 7 (s, 3 H ) , 2 . 3 5 (q, J = 6 H z , 2 H ) , 4 . 6 0 (t, J = 6 H z , 2 H ) , 5 . 0 2 ( m : 2/-1), 5 . 7 3 ( m , 1 H ) , 6 . 8 9 (d, J = 8 H z , 2 H ) , 7 . 5 2 (d, J = 8 H z , 2 H ) .
~-----~.0
PEt,,j
T h e r a t e o f d e c o m p o s i t i o n o f b u t e n y l o x y c a r b e n e c o m p l e x 2 in b e n zene-d6 a t 3 8 ¢C w a s meamzred b y N M R a n d f o u n d t o b e u n u s u a l (Fig. 1). a n i n d u c t i o n p e r i o d o f a b o u t 2 0 rain, a n a u t o c a t a l y f / c d e c o m p e ~ J t i o n
6 LOT [0 ~CL-7.
Fi:~CT'.CN
0
o
[ I
I! o = 2
O.S~ c
o=--
!
L
I,"
,-.
•
i °
6
•
_9.
£
o
C .- : XJ. -- [..--.in]
F i g . 1 . Th.=.rmal d e c o m p o s i t i o n
of ~ in benzene-d
6 =_t 3 8 ~:~.
o f 2 was o b s e r v e d . A f t e r 50 m i n , all o f t h e s t a r t i n g mate_da] 2 h a d d e a o m po.~ed= t h e t u n g s t e n - c a r b e n e - a l k e n e c o m p l e x 5 h a d r e a c h e d its m a x i m u m level o f a b o u t 35%, a n d a b o u t 65% y i e l d o f c y c l o p r o p a n e 4 h a d b e e n f o r m e d . I n t e r m e d i a t e 5 t h e n d e c o m p o s e d s m o o t h l y t o c y c l o p r o p a n e 4 w i t h a half-life o f a b o u t 1 0 - 15 rain. T h e s o l v e n t was f o u n d t o h a v e a m a j o r e f f e c t o n t h e t h e r m a l d e c o m p o s i t i o n s o f 2. I n b e n z e n e ~ l s , t h e t i m e f o r h a l f d e c o m p o s i t i o n o f 2 was 3 7 r a i n a n d aun i n d u c t i o n pem:od was o b s e r v e d . I n b e n z e n e - d 6 , t r i e t h y l p h o s p h i n e i n h i b i t e d t h e d e c o m p o s i t i o n o f 2; a f t e r 1 h less t h a n 10% c o n v e r s i o n t o 4 was o b s ? r v e d . I n t e r m e d i n t e 5 w a s n o t o b s e r v e d in t h e p h o s p h i n e inh i b i t e d r e a c t i o n . L-i c l ! c h l o r o m e t h a n e - d 2 , t h e t i m e f o r h a l f d e c o m p o s i t i o n w a s 18 r a i n , t h e i n t e r m e d i a t e t u n g s t e n - c a x b e n e - a l k e n e c c m p l e ~ 5 w a s o b s e r v e d a n d a s h o r t i n d u c L i o n p e r i o d w a s seen. I n c a r b o n d i s u l f i d e , t h e decomposition of 2 to cyclopropane 4 followed first-order kinetics with a half-life o f g r e a t e r t h a n 5 0 0 rain. N o i n t e r m e d i a t e w a s o b s e r v e d , a n d n o i n d u c t i o n p e r i o d w a s seen.
Therrno;ysi.s o f p e n t e n y l o x y carbene c o m p l e x 3 T h e p e n t e n y l o x y carb~.ne c o m p l e x 3 was m u c h m o r e t h e r m a l l y s t a b l e t h a n t h e b u t e n y l o x y c a r b e n e c o m p l e x 2. N o o b s e r v a b l e d e c o m p o s i t i o n o f 3 o c c u r r e d o n h e a t i n g t o 4 0 ~C in b e n z e n e f o r 1 2 h . C o m p l e t e d e c o m p o s i t ~ o a o t 3 o c c u r r e d o n h e a t i n g t o 7 0 ¢C in b e n z e n e - d 6 f o r several h o u r s . T h e o n l y obse~-ved p r o d u c t s w e r e W(CO)6 a n d t h e c y c l o p r o p a n e , 1 - ( 4 d m e t h y i p h e n y l ) 2 - o x a b i c y c l o [ 4 . 1 . O ] i-,eptane, 8, w h i c h was f o r m e d in g r e a t e r t h a n 80% y i e l d as d e t e r m i n e d b y N ~ I R . T h e c y c l o p r o p a n e 8 w a s i s o l a t e d ip_ 54% y i e l d b y t h i n l a y e r c h r o m a t o g r a p h y (silica g e l ] h e x r n e ) . F o r 8: "-H NMI~. ( b e n z e n e < i s ) : 6 1.0 - 1.6 ( m , ? H ) , 2 . 1 5 (s, 3 H ) , 3 . 1 8 ( d d d , J = 11.6 H z , 1 0 . 7 I-Iz, 2.0 H z , 1H), 3.61 ( d i d , J = 1 0 . 7 H z , 3 . 2 H z , 1 . 0 H z , 1 H ) , 7 . 0 4 (d, J = 8 H z , 2 H ) , 7 . 2 1 (d, J = 8 H z , 2 H ) ; l a c N M R ( p r o t o n - d e c o u p l e d , acetoniCrile~13): 8 1 9 . 7 , 19.9, 20.4, 21.3. 21.8. 60, 64, 123 a n d 129 (ortho, m e t a ) , 135 a n d 142 (ipso, p a r a ) ; e x a c t m a s s : 1 8 8 . 1 1 9 8 , ( c a l c d f o r C13H1eO: 1 8 8 . 1 2 0 1 ) .
0
~
When the thermal decomposition of 3 at 70 ~ was monitored at inte~-als b y NrMR, n o i n t e r m e d i a t e tungsten--carbeue--al~rene c o m p l e x wa-~ detected; only the spectra of staring material 3 and cyctopropane 8 were seen. A n induction period followed by autz~.atalytie decomposition of 3 was observed. T h e thermal stabili~] o f 3 was greatly decreased w h e n solul/ons o f 3 w e r e Ln-adiatad p r i o r t o t h e r m o l y s i s . P h o t o l y s i s o f a 0 . 1 5 94 b e n z e n e ~ s o ! u l / o n o f 3 (e = 6 0 0 0 a t 3 5 0 sin) in a S r i n i v ~ n - - G r ~ f f i n p h o t o c h e m i c a l r e a c t o r w i t h G e n e r a l E l e c t r i c F S T S / B L R l a m p s (ma~r~rn,m e r n i . ~ o n a t 3 5 0 n m ) f o r 3 h a t SO - 4 0 ~D re~.,Ited in a p p r o x i m a t e l y 4% c o n v e r s i o n o f c a r b e n e c o m p l e x 3 i n t o c y c l o p r o p a n e 8. S u b s e q u e n t h e a I / n g o f t h e s o l u t i o n t o 4 0 5C f o r 1 0 h in t h e d a r k r e s u l t e d in 7 5 % c o n v e r s i o n o f 3 t o 8.
"fTzermolysis o f a l l y l o x y carbene c o m p l e x 1 T h e t h e r m a l s¢,~bi]it-j o f t h e a l l y l o x y c a r b e n e c o m p l e x 1 is i n t e r m e c l h t e b e t w e e n t h a t o f 2 a n d :-'. C o m p l e t e d e c o m p o s i t i o n o f I o c c u r r e d u p o n heat~ ing t o 41 ~C in benzene ds for 13 h. A n induction period followed by an autoeatalytic decompomtior, was observed. T h e major o r g a n i c product we_s p-tolyl allyl ketone formed in 40c7o yield as determined by NIVIi9..In adddt/on, singlets d o e t o t h e t o l y l [ ' , e t h y l g r o u p o f five a d d i t i o n a l m i n o r p r o d u c t s w e r e o b s e r v e d . F o r p - t o l y l allyl k e t o n e : 1H NMR; ( b e n z e n e - d s ) : 5 1 . 9 9 (s, 3II), 3 . 3 2 (de, J = 6 . 8 H z , 1.5 H z , 2 H ) , 5 . 0 3 ( m , 2 H ) , 6 . 1 0 ( d d t , J = 1 7 . 1 H z , 1 0 . 3 H z , 6 . 7 I£z, 1 H ) , 6 . 8 7 (d, J = 8 H z , 2 H ) , 7 . 7 4 (d, J = 8 H z , o H ) ; [ ~ 1 6 8 6 ( v s ) , 1 6 1 3 ( m ) era-* [ 8 ] . ~
0
Preparation o f pentaearbonyl[allylamino(p-tolyl}earbene] ~'ungsten(O}. 9 I n a n a t t e m p t t o m a k e a m o r e t h e r m a l l y s t a b l e £u_ng~ten-eaxbenealkene complex, we initiated studies of ~mi~o-substituted carbene complexes. A d d i t i o n o f 1 0 e q u i v a l e n t s o f a / / y l a m i n e t o a r e d e t h e r s o I u t i o n o f (CO)~W[C(OCH3)C6H4-'P-C'H3] (0.458 g, 1.0 retoOl) msult, e d in an ~mmec'ii:~te r e a c t i o n p r o d u c i n g a y e l l o w s o l u l / o n . E v a p o r a l / o n o f s o l v e n t gave 0 . 4 6 g (95?5) o f a y e l l o w oil w h i c h c o - ~ t e d o f a 1 : 1 . 2 m i r ~ t r e o f t w o i s o m e r s o f pentaeazhonyl[ad/yl~m;no(p-tolyl)cazbene] tungsten(O), 9Z and 9E.
8
OCHz
0
N-H
e
F o r 9E: ZH N M R (benzene-ds): ~ 1.98 (s, 3H), 2.84 (tin J = 5.7 Hz, 2I-I), 4.6S (din, J = 9.0 Hz, I H ) , 4.70 (rim, J = 18.2 Hz, 1H), 4.91 (ddt, J = 16.5 FIz', 10.7 ~z, 5.1 Hz, 1H), 6.52 ( d , J = 8.1 Hz, 2H), 6.83 ( d , J = 7.5 Hz, 1H), 7.27 (bd s, 1H). For 9Z: ZH N M R (benzene-d6): ,5 2.02 (s, 3H), 3.94 (tin, J = 5.7 Hz, 2R), 4.79 (din, J = 17.0 Hz, 1H), 4.87 (din, J = 10.3 Hz. 1H), 5.3_4 (ddt, J = 17.1 Hz, 10.3 Hz, 5.7 Hz, 1H), 6.57 (d, J = 8.1 Hz, 2H), 6.83 ( d , J = 7.5 Hz, 2Z-I), 8.29 (bd s, 1 H ) . F o r 9 Z : 9 E (1:1.2):I~t (dichloromethane) v (CO): 2064(m), 1 9 7 0 ( w ) , 1928(vs) cm -z. T h e i s o m e r i c a s s / g n m e n t o f 9 E a n d 9 Z was m a d e o n the b ~ i ~ o f N_MR c h e m i c a l shifts. M o s e r a n d F i s c h e r h a v e r e p o r t e d t h a t t h e N - m e t h y l r e s o n a n c e o f 1 0 E in b e n z e n e - d s a p p e a r s a t 5 1 . 7 9 w h i l e t h a t o f 1 0 Z a p p e a r s a t 5 2 . 6 8 [ 9 ] . T h e m e t h y l e n e p r o t o n s o f t h e a l l y l g r o u p a p p e a r a t ~ 2 . 8 4 in t h e i s o m e r assigned =-L~cture 9 E while the methylene protons of the ~llyl ~roup appear at 5 3.94 in the isomer assigned "=he :true.ire 9Z. Isomers 9 E and 9 Z are configu_rationally stable and d o not interconvert at r o o m temperature. T h e barrier to rotation about the carbene carbon-nitrogen b o n d of penT._~earbonyl[dknethyi~mino(methyl)carbene] tungsten(0) was estimated '~o be greater t h a n 26 k c a l mo1-1 [ 1 0 ] . T h e v i n y l p r o t o n s o f 9E ~ d 9 Z a p p e a r b e ~ e e n 4.5 - 5.5 i n d i c a t i n g t h a t t h e d o u b l e b o n d is n o t c o m p l e x e d t ~ t~;ngsten.
H,C,:..~. ;coh_~'--~ I0~ CH~
H~..CH~ (co]s?,'--/~ 10E
CH3
Heating a mixture of 9 E and 9 Z in benzene
-1
(C0]s~'V--~
T h e 1H NI~fP~ s p e c t ~ m o f isolat_=cl 11 w a s identical t o th~ spectr,)m o f t h e m a t e r ~ l being fo_~aed d u r i n g t h e c o u r s e o f t h e thermoly:~is. F o r I 1 : I R ( N u j o l ) v ( C O ) : 2 0 2 0 ( s ) , 1 9 3 4 ( s ) , I 9 0 3 ( s ) , 1 8 - ~ 0 ( s ) c m - z ; zH N'~IR ( b e a z e n e d s ) : 5 2 . 0 0 ( s , CH3), 2.81 ( d , J = 1 3 . 2 Hz, H s ) , 2 . 9 4 ( b d d , J = 1.4.1 H z , H I ) , 3 . 0 6 (d, J = 8.6 Hz, H e ) , 3 . 3 1 ( d d d , J = 14.1 Hz, 5.1 Hz, 1.6 Hz, H2), 4 . 0 9 (ddddd, J = 1 3 . 1 H.-~-, 8.8 Hz, 4.8 Hz, 4 . 0 Hz, 0.7 Hz, Hz), 6 . 8 2 ( d , J = 8 . 0 Hz, 2H), 6 . 9 2 (d, J = 8.0 Hz, ~_&I), 7.26 ( b d s, N - H ) ; Z~C N-MP• ( p r o t o n - . l e c o u p l e d , acetonitrile
10
Decreased carbene c a z b o n - n i t r o g e n b o n d order in the excited state would fac'fiitate isome_~_zation o f *due a l l y l g r o u p . T , - m g s t e n - - c a r b e n e - a l k e n e c o m p l e x 11 h a s h i g h t h e r m a l s t a b i l i t y . N o d e c o m p o s i ~ o n was o b s e r v a b l e b y N M R a f t e r a b e n z e n e , ! 6 s o l u t i o n o f 1 1 w a s h e a t e d t o 9 2 ~ f o r 23 h. A f t e r a n a d d i t i o n a l 2 2 h a t 1 2 5 ~C, a b o u t 8 5 % d e c o m p o s i t i o n o f 1 ! to a n u n i d e n t i f i e d m i x t u r e o f p r o d u c t s h a d o c c u r r e d . W h e n a b e n z e n e < t 6 s o l u t i o n o f 11 w a s h e a t e d t o 9 8 ¢C f o r 6 6 h u n d e r 1. 9 a r m CO, s o m e carbonylation occurred to regenerate alIyl~mino carbene complexes 9 Z and 9E; in addition, s o m e formation of the allyl ir-ine of p-tolualdehyde was ,a~so observed. T h e ratio of ll:9Z:9E:allyl imine of p-tolualdehyde determined by N ' M R was 2:2:1:1. Hea~/ng a 1.2:1 mixture of 9 E : 9 Z it,. t o l u e n e f o r 3 9 h a t 6 5 - 8 5 ¢C u n d e r 1 4 a r m o f CO gave a m i x t u r e o f 9 Z , 9F~ a n d t h e al l yl i m i n e o f p - t o l u a l d e h y d e i n a r a t i o o f 1 : 6 : 6 .
Discussion T h e k e y i n t e r m e ~ i n t e s in t h e olet-m m e t a t h e s i s r e a c t i o n a n d i n c y c l o p r o p a n a t i o n s ar e m e t o J l l a c y c l o b u t a n e s a n d m e t a l - c a r b e n e - a l k e n e c o m p l e x e s . I t is n o t k n o w n w h i c h o f t h e s e t w o i n t e r m e d i a t e s is t h e m o s t s t a b l e f o r a given metathesis catalyst. T h e t r a n s f o r m a t i o n b e t w e e n a m e t a l - c a r b e n e alkene c o m p l e x and a me*~_llacyclobutane involves a f o r m a l o x i d a t i o n at the m e t a l c e n t e r a n d t h e c r e a t i o n o f o n e a d d i t i o n a l c o o r d i n a t i o n site. T h u s t h e equilibrilJm b e t w e e n a m e t a l - c a r b e n e - - a l k e n e c o m p l e x and a m e ~ _ t a c y c l o b u t a n e slaeuld d e p e n d s t r o n g l y o n t h e o x i d a t i o n s t a t e a n d c o o r d i n a t i o n n u m b e r ~f t h e m e t a l . T h e 6 ~ : o o r d i n a t e t u n g s t e n ( 0 ) - c a r h e n e - a l k e n e c o m p l e x e s r e p o r t e d h e r e a r e sta[~le e n o u g h t o b e o b s e r v e d a n d axe c e r t a i n l y m o r e stable than th-unobserved coordinatively unsaturated 6~oordinate tungstencyciobutanes. The stability of the tungsten-carbene-alkene complexes repo=eted h e r e is p r o b a b l y d u e t o t w o spc-ci~li~ed e f f e c t s . F i r s t , t h e c_belation o f t h e c a r b e n e a n d a l k e n e l i g a n d s p r o m o t e s t h e f o r m a t i o n o f a tungs~_en c a r b e n e - - a l k e n e s y s t e m a n d r e t a r d s f o r m a t i o n o f a s t r a i n e d b i c y c l / c metaledcycle. S e c o n d , 6 - c o o r d i n a t e tungsten(0) c a r b o n y l c o m p o u n d s are very stable w h e r e a s a t t e m p t s t o p r e p a r e t u n g s t e n ( H ) c a r b o n y l c o m p o u n d s s u c h as ( C O ) s W R 2 o r (CO)sWI~.H h a v e f a i l e d [ ! 2 ] . T h e c o n v e r s i o n o f b u t e n y l o x - y c e x b e n e c o m p l e x 2 t o c y c l o p r o p a n e 4 is t h e fin-st c y c l o p r o p a n a t i o n i n w h i c h a m e t a l - - c a r b e n e - - a l k e n e c o m p l e x w a s o b s e r ¢ ~ d as a n interm,_~di~te. In t h e r e a c t i o n s o f ( C O ) s W C ( C a H s ) 2 w i t h a l k e n e s b o t h c y c l o p r o p a n e s a n d a l k e n e s cis s i on p r o d u c t s w e r e o b t a i n e d [ 3 ] . E a r l i e r , w e h a d s u g g e s t e d that 7~oordipate met~ll~cyc!es were cyclopropane precursors and that 6~coordL-uate m e t a l l a c y c l e s w e r e p r e c u r s o ~ o f m e ~ t h e s i s 4 i k e a l P e n e sci . ~i on p r o d u c t s [ 1 3 ] . T h e f a c t t h a t C O d i s s o c i a t i o n is r e q u i r e d in t h e r2aetioru~ o f (CO)sWC(C~Hs)o_ pro~cides e v i d e n c e t h a t m e t a t h e s i s - l i k e p r o d u c t s a r e d e r i v e d from 6~oordirmted metal-alkene -ca~bene complexes. The obse.vation that t e t r a c a r b o n y l t t m g s t e n - c a r b e n e - a l k e n e c o m p l e x 5 is c o n v e r t e d t o c y c ! o -
11
p r o p a n e 4 d e m o n s t r a t e s t h a t c y c l o p r o p a n e s c a n also b e d e r i v e d f r o m 6 - c o o r d i n a t e t u n g s - t e n - - c ~ b e n e - ' a l ~ e n e c o m p l e x e s . All o f t h e r e a c t i o n s o f ( C O ) s W C ( C 6 H s ) 2 w i t ~ a l k e n e s c a n b e e x p l ~ - e d as p r o c e e d i n g tb.rough t h e s ~ m e 6 - c o o r d i n a b e mef~nllacycle i n t e r m e d i a t e . T h i s is s u p p o r t e d b y t h e o b s e r v a t i o n that the ratio of cyclopcopane:~kene s c ~ o n s products in the reaction of alkenes with ( C O ) s W C ( C 6 H ¢ - p 4 ~ H z ) 2 does not depend on external C O pres_~ntre [14]. [_niN~lly w e thought that metal--carbene-alkene compiexes could be formed by uD~molecnlar fl~cociation of C O from a carbene complex followed by inCramolecular trapping to form a chelated metal-cazbene-alkene c o m plex. However, t w o observations indicate that the loss of C O from 2 cA-not be the rate deterr-~-/ng step h-* the formation of tungsten-caxbene- 'alkene complex 5. FL-st, the rate of C O dJ~¢ociation from ( C O ) s W [ C ( O C H ~ ) C s H ~ p-CH3] is m u c h slower than the rate of decomposition of 2. T h e Firstorder rate constant for " 3 C O exchange with ( C O ) 5 W [ C = ( O C H ~ ) C s H s in toluene at 77 °C is 2.8 -+ 0.6 × I0 -s s-* (ill2 ~ 7 h) [15] while the half-~me for decomposition of 2 at 38 ~C in benzene was about 37 m}n. Second, rate determining loss of C O from 2 cannot explain either the induction pe_m~od o b ~ r v e d in the conversion of 2 to metel-carbene-alkene compiex 5 or the accelerating rate of convermon of 2 to 5. T h e observed idnetic behavior of 2 indicates tha~ while i.rJLi~l decomposition of 2 was slow, at least one c o m p o n e n t of the product mizture was capable of catalyzing the ,further decomposition of 2. W e propose that coordinatively unsaturated tungsten carbonyl species are the c o m p o n e n t s responsible for catalyzing the decomposition of 2. W ( C O ) 6 is the only observed eaxbonyl containing species at the end of the rp~etion hut the ratio of C O : W in the s ~ g material is ot~Jy 5:1. Therefore, s o m e scaven~ng of C O either from solution or from metal complexes m u s t be occun~_'ng. Conversion of metal-esxbene-alkene complex 5 to cyclopropane 4 would produce %V(CO)4. W e propose that W ( C O ) 4 abstracts C O from starting material 2 to generate 5 and W ( C O ) s and that W ( C O ) s then abstracts C O from 2 to generate a second equlwalent of metal-carbene-alkene compZex 5. Thus every, time 5 decomposes to cyelopropane 4 and W ( C O ) 4 , the W(CO)~ reacts with t w o molecules of 2 to generate inc_rea~in_g concen~%eations of metal-carbene-alkene c o m p l e x 5. A s long as the eff,_'ciency of C O abstraction from 2 by W ( C O ) 4 and W ( C O ) s is high enough to produce m o d e than one equivalent of 5 per equivalent of 5 destroyed, an accelerating autocat~ylic rate of decomposition of 2 w o u l d be observed. %r"ne autocataly~dc mechanist- for the decomposition of 2 also explains inhibition of the decomposition by added triethy|phosphine and slow" rate of decomposition in carbon di~,lIWde. Roth £riethylphosphine and carbon disulfide are capable of react~.'ngwith W ( C O ) s and W ( C O ) 4 to int~-rupt the catalytic ch~-. S~m*~rly, the autocataly~/c mechsnis~/c scheme also expl~rts the photochon~ical ird~tion of autocatalytic decomposition of pentenyloxy cazbene complex 3. It should be emphasized that w e are proposing an active attack of W ( C O ) ~ and W ( C O ) s on carbene c o m p l e x 2 and not ~r-ply scaven~-g of
12
C O fzom solution. PreviouLsly, in order to e~plain carbene ligand transfer between ch.ronzium and tungsten, we suggested that, coordinat~cely unsaizlrated metal compl~-~-~ were capable of attacking metal complexed C O
[13, Z61.
(C01sw~
-cOslow "
(CG}4W
CH3 (CC}&W~
CH-
=
~1CO).~
CHa w(c0)~
+
z(c0~sw
~O
~
CH~
CH a
fast
• ~c%
+
2
{CC]&W~ CHm -
Experimenta!
Reactions Lnvolv~ng org~nometallic c o m p o u n d s were carried out in fl~me-dried glassware under u nitrogen atmosphere. N-bIR ~ m p l e s were prepared on a v a c u u m ],'heby distillingdegassed solvent onto the organomet~lic c:ompoonds and se~llng the tubes under vacuum. 1H NMR were o b t a i n e d o n B r u c k e r W H - 2 7 0 a n d J E O L M H - 1 0 0 s p e c t r o m e t e r s . ~3C _ ~ I I ~ w e r e o b t a i n e d o n J E O L F X ~ 5 0 a n d Var~-n X L - 1 0 0 s p e c t r o m e t e r s . F o u r i e r transform infrared spectra were obtahaed on a Digilab FTS-20 interferometer High resolution mas~ spectra were obtained on a AEI-MS-902 mass spectrom e t e r . U V - v i s i b l e s _ t ~ c t r a w e r e me2_m_red o n a C a r y 1 1 8 s p e c t r o p h o t o m e t ~ . r .
AeI~nowledo-men*.
Financial support from the National Science Foundation is grateCn~lly acknowledged.
References F o r r e c e n t r e v i e w s o f t h e olef'm m e t a t h e s / s r e a c t / o n see R . H. G r u b b s , Prog. I n o r g . Chem., 2 4 ( 1 9 7 8 ) 1. T . J. l~,.a~.z,Ado. (~h'ganomeL Chem., 1 6 ( 1 9 7 7 ) 2 8 3 . J. C . M o l a n d J. A. Mor_lijn, Ado. CataL, 2 4 ( 1 9 7 5 ) 1 3 1 .
13
2 3 4
5 6 7 S 9 10 11 12 13
14 15 16
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