Cross-metathesis vs. silylative coupling of vinyl alkyl ethers with vinylsilanes catalyzed by a ruthenium-carbene complex (Grubbs catalyst)

Article abstract of DOI:10.1039/b003442h

Grubbs complex, (PCy₃)₂Cl₂Ru=CHPh (I) is a very effective catalyst of the cross-disproportionation of vinyl-trisubstituted silanes H₂C=CHSiR₃ [where R₃ = Me₃, PhMe₂, (OEt)₃] with vinyl alkyl ethers H₂C=CHOR' [where R' = ethyl, propyl, butyl, t-butyl, t-pentyl, 2-(ethyl)hexyl, cyclohexyl, trimethylsilyl] to yield a mixture of (E + Z) 1-silyl-2-alkoxyethenes. The reaction occurs quantitatively under milder conditions (60 °C) than the analogous one catalyzed by Ru-H and/or Ru-Si complexes reported previously (80 °C). The stoichiometric reaction of (I) and (PCy₃)₂Cl₂Ru=CH₂ (III) with vinyl ethyl ether leads to the formation of (PCy₃)₂Cl₂Ru=CH(OEt) (II), inactive in the stoichiometric reaction with vinylsilanes but very active in the catalytic process. Experiments with the use of deuterated vinylsilanes indicate the non-metallacarbene mechanism of the reaction and provide evidence for the initiation of Ru-H bond formation via the hydrovinylation with vinylsilanes.

Full text of DOI:10.1039/b003442h

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Cross-metathesis vs. silylative coupling of vinyl alkyl ethers with
vinylsilanes catalyzed by a ruthenium–carbene complex (Grubbs
catalyst)
Bogdan Marciniec,* Ma¡gorzata Kujawa and Cezary Pietraszuk
Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University,
Grunwaldzka 6, 60-780 Poznan, Poland. E-mail: marcinb=main.amu.edu.pl
Received (in Strasbourg, France) 26th April 2000, Accepted 30th June 2000
Published on the Web 17th August 2000
Grubbs complex, (PCy ) Cl Ru2CHPh (I) is a very e†ective catalyst of the cross-disproportionation of
3 2
2
vinyl-trisubstituted silanes H C2CHSiR [where R \ Me , PhMe , (OEt) ] with vinyl alkyl ethers H C2CHOR@
2
3
3
3
2
3
2
[where R@ \ ethyl, propyl, butyl, t-butyl, t-pentyl, 2-(ethyl)hexyl, cyclohexyl, trimethylsilyl] to yield a mixture of
(E ] Z) 1-silyl-2-alkoxyethenes. The reaction occurs quantitatively under milder conditions (60 ¡C) than the
analogous one catalyzed by RuÈH and/or RuÈSi complexes reported previously (80 ¡C).7 The stoichiometric
reaction of (I) and (PCy ) Cl Ru2CH (III) with vinyl ethyl ether leads to the formation of (PCy ) Cl Ru2CH(OEt)
3 2
2
2
3 2 2
(II), inactive in the stoichiometric reaction with vinylsilanes but very active in the catalytic process. Experiments
with the use of deuterated vinylsilanes indicate the non-metallacarbene mechanism of the reaction and provide
evidence for the initiation of RuÈH bond formation via the hydrovinylation with vinylsilanes.
Many metallacarbenes (Mo, W and Ru) catalyze the meta-
thetical conversion of silicon-containing oleÐns.1 However, the
e†ective self-metathesis as well as acyclic diene metathesis
(ADMET) polymerization of vinyl-substituted organosilicon
oleÐns and dienes (e.g., vinylsilanes and divinyldiorgano-
silanes), even in the presence of well-deÐned Mo, W, Ru com-
plexes, has not been reported yet. The inactivity of
metallacarbene initiators in productive homometathesis of
vinylsilanes is accounted for by steric e†ects and the relative
stability of the silyl-substituted carbenes bonded to the metal.2
However, reports on rutheniumÈcarbene-complex catalyzed
cross-metathesis of vinyl-substituted silsesquioxanes with
alkenes3 and ADMET copolymerization of divinyldimethylsil-
ane with dienes,4 as well as our recent successful experiments
on the cross-metathesis of vinyltrialkoxysilanes and vinyl-
trisiloxysilanes with styrene,5 show the potential utility of
metathetical conversion of vinylsilanes and contribute to
better understanding of the process. Cross-metathesis of vinyl-
silanes with oleÐns can be depicted by the following general
scheme [eqn. (1)] and proceeds according to the metallacarb-
ene mechanism.
silane and the 2CÈH bond of the oleÐn (also vinylsilane in the
self-disproportionation) according to the following equation:
(2)
The mechanism of the latter type of silyloleÐn conversion was
evidenced by stoichiometric reactions including an insertion of
ethylene,6a styrene6c and vinylsilane6b into RuÈSi bonds. Our
recent synthetic examinations conÐrm the non-metallacarbene
mechanism for RuÈH and/or RuÈSi complexes catalyzing the
reaction of vinyl alkyl ethers with vinyl-trisubstituted silanes,
yielding a mixture of (E ] Z) 1-silyl-2-alkoxyethenes.7 Inter-
estingly 1-silyl-1-alkoxyethene was not found among the pro-
ducts.
In view of the above the aim of this work is to check the
catalytic activity of rutheniumÈcarbene complexes (e.g.,
Grubbs catalyst) in the cross-metathesis of vinyl alkyl ethers
with vinylsilanes.
(1)
On the other hand, recent reports on the dispro-
portionation of vinyl-substituted silicon compounds and their
co-disproportionation (trans-silylation) with oleÐns6 catalyzed
by ruthenium, rhodium and cobalt complexes containing (or
generating) MÈH and MÈSi bonds have shown that the reac-
tions occur through the cleavage of the 2CÈSi bond of vinyl-
Results and discussion
The reaction of vinyl-trisubstituted silanes with vinyl alkyl
ethers proceeds in the presence of the Grubbs catalyst,
(PCy ) Cl Ru2CHPh, at 60 ¡C according to eqn (3)
3 2
2
DOI: 10.1039/b003442h
New J. Chem., 2000, 24, 671È675
671
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

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the ethoxycarbene complex (II) and ethene. The reaction of III
with a 100-fold excess of ether results, after 3 h at room tem-
perature, in the formation of II in 40% yield and by 60%
conversion of the methylidene complex.
(5)
However, contrary to catalytic e†ects, an independent stoi-
chiometric study on the reactivity of II with the vinylsilanes
CH 2CHSiR (where R \ Me, OEt) at room temperature and
(3)
where SiR \ SiMe (1a), SiMe Ph (1b) and Si(OEt) (1c),
3
3
2
3
2
3
giving two isomeric products (E and Z)-1-silyl-2-alkoxy-
ethenes and ethylene. The same products were found in an
analogous process catalyzed by RuÈH and RuÈSi complexes.7
Interestingly, in both reactions 1-silyl-1-alkoxyethene was not
formed.
at 60 ¡C showed no expected products of cross-
disproportionation (cross-metathesis). Only unidentiÐed pro-
ducts of decomposition of II were detected.
The results of all catalytic and stoichiometric studies of the
system R SiCH2CH ] R@OCH2CH ] RuÈH (RuÈSi) lead
3
2
2
The catalytic data on the reaction of vinyltrimethylsilane
(1a) with various vinyl alkyl ethers are presented in Table 1.
The yield of the products (two isomers E ] Z) is predomi-
nantly close or equal to the conversion of the vinylsilane used.
Vinyl ethyl ether and vinyl cyclohexyl ether were selected for
the catalytic reaction with two other vinyl-trisubstituted
silanes, vinyldimethylphenylsilane (1b) and vinyltriethoxy-
silane (1c). The obtained results are collected in Table 2.
In order to study the mechanism of the process, the stoi-
chiometric reaction of the Grubbs catalyst (I) with vinyl ethyl
ether was performed. The reaction occurs readily at room
temperature and yields quantitatively the ruthenium complex
with ethoxy-substituted carbene ligand (II).
apparently to ambiguous conclusions.7 Direct insertion of the
ether molecule into RuÈSi as well as catalytic examinations of
CDH2CDSiMe with vinyl ethyl ether provide evidence for
3
the non-metallacarbene mechanism of the reaction.7 On the
other hand, the similar ratios of E/Z isomeric products in pro-
cesses catalyzed by both types of ruthenium complexes (i.e.,
RuÈH or RuÈSi and Ru2CHR) as well as the only slightly
milder experimental conditions (shorter time and lower tem-
perature for the efficient synthetic procedure) required for the
reactions catalyzed by the ruthenium carbene complex I
suggest that in all cases it is actually the cross-
disproportionation of vinyl-trisubstituted silanes with vinyl
alkyl ethers that occurs via the same intermediates.
Stoichiometric metathesis of transition metal carbenes with
vinyl ethers was reviewed by Grubbs et al.8 Complexes of the
type (PPh ) (X) Ru2CHÈCH2CPh can undergo stoichiomet-
(4)
3 2
2
2
ric metathesis with both terminal and internal vinyl ethers,
leading to formation of ethoxy-substituted carbene species
(PPh ) (X) Ru2CH(OR). The complexes generated in such a
Complex II was found to also exhibit high catalytic activity in
an exemplary reaction (Table 1).
Ruthenium methylidene complex (PCy ) Cl Ru2CH (III)
3 2
2
3 2
2
2
way are catalytically inactive in the metathesis polymerization
(ROMP) of norbornene.8
reacts efficiently only with an excess of vinyl ethyl ether, giving
However, 1H NMR experiments showed, at room tem-
perature, a slow decomposition of (TFA) (PPh ) RuCH(OR)
Table 1 The e†ect of the alkyl substituent of vinyl alkyl ether
2
3 2
ROCH2CH in its reaction with vinyltrimethylsilane catalyzed by
(R \ Et, CH Ph) accompanied by the formation of a hydride
2
2
(PCy ) Cl Ru2CHPh (I) on the yield and selectivity of the productsa
complex (resonance at [17.5 ppm in 1H NMR spectrum),8
which also slowly disappeared after several days. In our
3 2
2
R
Yield (%)
E/Z
system [CH 2CHSiMe or CH 2CHSi(OEt) ] II] studied at
2
3
2
3
60 ¡C, a disappearance of the carbene resonance is observed
but there is no RuÈH intermediate detected by 1H NMR and
IR spectroscopy, although the peak at l \ 1993 cm~1
observed in the IR spectrum can be attributed to carbonyl
coordinated to ruthenium.
Ethyl
Propyl
Butyl
t-Butyl
t-Pentyl
2-(Ethyl)hexyl
Cyclohexyl
Trimethylsilyl
99
4
96 (90b) (3c) (90d)
2.5 (2b) (3d)
4
1
1
4
1.5
1
100
100
93
98
100
70
GrubbsÏ et al. proposed two possible decomposition path-
ways consistent with their observations to yield either RuÈCO
or RuÈH complexes.8 Regardless of the type of complex Ðnally
formed, both can be the initiators of the insertionÈelimination
process for cross-disproportionation of vinyl alkyl ethers with
vinylsilanes. Although Ru(CO) (PPh ) contain an RuÈH
a Reaction conditions: 60 ¡C, 24 h, argon, sealed glass ampoules,
[H C2CHSiMe ] : [ether] : [catalyst] \ 1 : 5 : 1 ] 10~2, except for
2
3
b (1 : 5 : 5 ] 10~3) and c (1 : 5 : 2 ] 10~3). d (PCy ) Cl Ru2CH(OEt)
3 2
2
(II) was used as a catalyst.
3
3 2
bond, it appeared to also be a good catalyst for the cross-
coupling of vinylsilanes with vinyl alkyl ethers, presumably
due to ortho-metallation of the ruthenium triphenylphosphine
complex to generate a RuÈH bond.7 The respective cyclo-
hexylphosphine complex (obtained from I) can react in the
same way as the triphenylphosphine complex.9 The previously
observed silylative coupling of oleÐns with vinylsilanes and
vinylsiloxanes catalyzed by RuCl (CO) ,6d,10 Ru (CO) ,11
Table 2 Cross-disproportionation of vinyldimethylphenylsilane (1b)
and vinyltriethoxysilane (1c) with selected vinyl alkyl ethers catalyzed
by Ia
1b
1c
2
3
3
12
Yield (%)
E/Z
Yield (%)
E/Z
Cp*Rh(H C2CHSiMe ) 12 and [(cod)Rh(l-OSiMe )] ,13
2
3 2
3 2
supported by some stoichiometric experiments,12 suggests
that hydrovinylation involving oxidative addition of the vinyl-
silane (or styrene) to the metal can also be regarded as an
initiating step for RuÈH bond formation.
Vinyl ethyl ether
97
11b
99
6
3
4
94
6b
98
1
4
1
Vinyl cyclohexyl ether
a Reaction conditions: 60 ¡C, 24 h, sealed glass ampoules, argon,
In order to check the role of I and II in generating RuÈH
complexes experiments with deuterium-labelled vinylsilane
D C2CDSiMe were performed. In the Ðrst experiment the
[H C2CHSi(OEt) ] : [ether] : [catalyst] \ 1 : 5 : 1 ] 10~2.
b RT,
2
3
24 h.
2
3
672
New J. Chem., 2000, 24, 671È675

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stoichiometric reaction of the ethoxycarbene complex II with
vinylsilane-d was studied by 1H NMR (60 ¡C, 6 h, C D ). No
However, if the reaction occurs according to the metallacarb-
ene mechanism, the cross-metathesis process shown in eqn. (7)
would take place, leading to exclusive formation of 1-
3
6 6
H/D exchange in the vinyl group of the vinylsilanes was
detected after the reaction, which proves that generation of
the RuÈH bond via ortho-metallation (or by decomposition of
ruthenium carbene) did not take place. In another experiment,
trimethylsilyl-2-ethoxyethene-d :
1
the stoichiometric reaction of II with
a mixture of
H C2CHSiMe and D C2CDSiMe (60 ¡C, 24 h) leads to
2
3
2
3
H/D isotopic exchange in all positions of the vinyl groups
(and homocoupling products as well; observed by 1H NMR
spectroscopy), under the same conditions in which II is
decomposed to Ru-carbonyl products. The hydrovinylation
with 2CÈH (2CÈD) of vinylsilane seems to be a key step for
the generation of the rutheniumÈhydrogen intermediates that
initiate the process of the silylative coupling of oleÐns with
this vinylsilane.
(7)
When the reaction is run for a prolonged time, a mixture of
d , d and d products is expected, because H/D exchange in
the vinyl group of ether takes place when RuÈH (RuÈD) com-
plexes are present in the system.
A GC-MS analysis of the reaction mixture after 6 h showed
Moreover, contrary to the very e†ective cross-coupling of
vinyltrimethylsilane with vinyl propyl ether (see Table 1), a
separate study on the catalysis of homocoupling of vinyl-
silanes by II showed only slight conversion (15%, E product).
Apparently, the role of vinylsilane, especially under the cata-
lytic conditions (100-fold excess of vinylsilane over the
catalyst) is just to generate RuÈH and subsequently RuÈSi
bonds but a key step of this process is the insertion of the
oleÐn into the RuÈSi bond. The latter proceeds more readily
with vinyl propyl ether than with vinylsilane.
0
1
2
the formation of 1-trimethylsilyl-2-ethoxyethene-d accompa-
0
nied by traces of d and d products. This strongly conÐrms
the non-metallacarbene mechanism of the process.
1
2
Results of this study have proven the high catalytic activity
of GrubbsÏ complex for the reaction of vinylsilanes with vinyl
ethers. The ruthenium ethoxycarbene complex that is formed
in the reaction of benzylidene or methylidene complexes with
vinyl ethyl ether does not form any organosilicon products in
the stoichiometric reaction with vinylsilanes but reveals high
catalytic activity for the reaction examined. The results of stoi-
chiometric and catalytic experiments with the use of
deuterium-labelled vinylsilanes provide convincing evidence
that instead of cross-metathesis the silylative coupling
(silylation) of vinyl alkyl ethers with vinylsilanes takes place.
On the basis on the previously reported mechanism of the
catalysis by well-deÐned RuÈH and RuÈSi complexes,7 we can
conclude that the reaction occurs via an insertionÈelimination
mechanism initiated by a RuÈH complex generated in situ
from complexes I or II or their decomposition products via
hydrovinylation with vinylsilane. The simpliÐed catalytic
scheme is presented in Scheme 1.
As in previous studies,6c,e,7 the experiment with deuterium-
labelled oleÐn was performed to distinguish between the two
mechanisms. The reaction of HDC2CDSiMe with vinyl ethyl
3
ether catalyzed by I was studied by GC/MS. If the reaction
proceeds according to the non-metallacarbene mechanism
[eqn. (6)] the silylalkoxyethene product formed in the Ðrst
stage of the reaction would contain no deuterium atom:
(6)
Experimental
All manipulations were carried out in argon using standard
Schlenk techniques. 1H and 13C NMR spectra were recorded
in C D on a Varian Gemini 300VT spectrometer (300 and 75
6
6
MHz, respectively). Infrared spectra (KBr plates) were record-
ed using an FT-IR Bruker IFS-113v. The mass spectra of the
products and substrates were determined by GC-MS analysis
(Varian 3300 gas chromatograph equipped with a DB-1, 30 m
capillary column and ITD 800 Finnigan MAT). GC-analyses
were performed on HewlettÈPackard HP 5890 series II with a
HP-1, 30 m megabore column and TCD.
Chemical reagents were received from the following
sources: vinyl alkyl ethers from Aldrich, benzene from
Lachema (Czech Republic), toluene from R&D Center of Pet-
rochemie P¡ock (Poland), benzene-d from Dr. Glaser, A.G.
6
Basel, (PCy ) Cl Ru2CHPh was purchased from Strem
3 2
2
Chemicals. HDC2CDSiMe and (PCy ) Cl Ru2CH were
prepared according to described methods.7,14 Prior to use all
solvents were dried and distilled over CaH in argon.
3
3 2
2
2
2
Catalytic studies
In a typical catalytic test a benzene solution of the ruthen-
ium catalyst was placed in glass ampoules under argon.
Then the reagents (usually used in the ratio
Scheme 1 Cross-metathesis vs. silylative coupling of vinyl alkyl
ethers with vinylsilanes catalyzed by rutheniumÈcarbene complex
(Grubbs catalyst)
New J. Chem., 2000, 24, 671È675
673

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[H C2CHSiR ] : [ether] : [Ru] \ 1 : 5 : 1 ] 10~2)
and
(5.8 ll, 6.06 ] 10~5 mol) was added. The mixture was stirred
for 3 h at room temperature. The contents were evaporated in
vacuum to dryness, followed by work up with 5 ml of meth-
anol. The reddish solid was Ðltered o†, washed 3 times with 5
ml of methanol and dried in vacuum. Yield 0.021 g (44%)
based on Ru carbene complex used. 1H NMR (C D ) d: 1.05
2
3
toluene as an internal standard were added. The sealed
ampoules were heated at the required conditions. The com-
position of the reaction mixture was analyzed by GC. The
yield was calculated by GC using the internal standard
method. The reaction products were identiÐed using authentic
samples synthesized by catalytic reaction in the presence of
6
6
(t, 3H) CH ; 1.10È2.30 (m, 66H) PCy ; 3.82 (q, 2H) OCH ;
3
3
2
RuHCl(CO)(PPh )
described previously.7
and/or RuCl(SiMe )(CO)(PPh ) , as
14.76 (s, 1H)2CH. 31P NMR (C D ) d 34.99.
3 3
3
3 2
6 6
Labelling experiments
Representative procedure for the synthesis of
(Z,E)-1-trimethylsilyl-2-alkoxyethene
Reaction of HDC2CDSiMe with H C2CHOEt catalyzed
3
2
2
by (PCy ) Cl Ru2CHPh. (PCy ) Cl R2CHPh (0.001 g,
(PCy ) Cl Ru2CHPh (0.028.7 g, 3.49 ] 10~5 mol), benzene
3 2
2
3 2
3 2 2
1.22 ] 10~6 mol), benzene (0.3 ml), HDC2CDSiMe (0.012 g,
(0.5 ml), vinyltrimethylsilane (0.35 g, 3.45 ] 10~3 mol) and
vinyl propyl ether (1.48 g, 17.2 ] 10~3 mol) were placed in a
20 ml glass ampoule under argon. The ampoule was sealed
and heated at 60 ¡C for 24 h. The reaction mixture was dis-
tilled to yield (Z/E)-1-trimethylsilyl-2-propoxyethene (bp 110È
120 ¡C, 0.45 g, 82%). 1H NMR (C D ) d 0.12 (s, 9H) SiMe
3
1.17 ] 10~4 mol) and H C2CHOEt 0.044 g, 6.11 ] 10~4 mol)
2
were placed in a 2 ml glass ampoule, which was heated at
60 ¡C for 6 h. The reaction mixture was analyzed by GC-MS.
Two isomers of (EtO)HC\CHSiMe , accompanied by traces
3
of d and d products, were identiÐed.
1
2
6
6
3
(E); 0.29 (s, 9H) SiMe (Z); 0.83 (t, 3H) CH (E), 0.77 (t, 3H)
3
3
Stoichiometric reaction of (PCy ) Cl Ru2CH(OEt) with
3 2
D C2CDSiMe . (PCy ) Cl R2CH(OEt) (0.005 g, 6.32 ] 10~6
3 2
mol) was dissolved in 0.3 ml C D in a 2 ml glass ampoule.
CH (Z); 1.51 (m, 2H) CH (E); 1.34 (m, 2H) CH (Z); 3.42 (t,
2
3
2
2
2H) OCH (E); 3.31 (t, 2H) OCH (Z); 4.52 (d, 1H, J \ 15.0
2
3
2
2
2
Hz) CHSi (E); 4.29 (d, 1H, J \ 8.4 Hz) CHSi (Z); 6.53 (d, 1H,
J \ 15.0 Hz) CHO (E); 6.38 (d, 1H, J \ 8.4 Hz) CHO (Z). 13C
NMR (C H ): 0.24 SiMe (E); 0.63 SiMe (Z); 11.16 CH (E);
6
6
Then D C2CDSiMe (6.5 ] 10~4 g, 6.30 ] 10~6 mol) was
2
3
added with a syringe. The ampoule was sealed and heated at
60 ¡C for 24 h. The reaction mixture was analyzed by 1H
NMR. No signals indicating H/D coupling in the vinyl group
or in any region of the spectrum were observed after reaction.
6
3
6
3
3
3
10.94 CH (Z); 23.17 CH (E); 23.89 CH (Z); 69.56 OCH
(E); 74.11 OCH (Z); 95.44 CHSi (E); 100.36 CHSi (Z); 157.04
CHO (E); 159.32 CHO (Z). MS [m/z (rel. int.)]: 158 (M, 11)
2
2
2
2
(E); 158 (M, 8) (Z); 143 (23) (E); 143 (21) (Z); 118 (17) (E); 118
(14) (Z); 117 (100) (E); 117 (100) (Z); 75 (18) (E); 75 (14) (Z).
Anal. calcd. for C H OSi: C, 60.69; H, 11.46; Found: C,
Reaction of D C2CDSiMe with H C2CHSiMe in the
2
3 2
3
2
3
presence of (PCy ) Cl Ru2CH(OEt). (PCy ) Cl Ru2CH(OEt)
2
3 2 2
8
18
(0.001 g, 1.26 ] 10~6 mol) was dissolved in 0.3 ml C D in a 2
60.01; H, 11.50.
6
6
ml glass ampoule. Then D C2CDSiMe (1.3 ] 10~4 g,
2
3
1.26 ] 10~6 mol) and H C2CHSiMe
(1.3 ] 10~4 g,
2
3
1.30 ] 10~6 mol) were added. The ampoule was sealed and
heated at 60 ¡C for 24 h. 1H NMR analysis of the reaction
mixture shows that all resonances assigned to vinylic protons
of H C2CHSiMe are accompanied by new multiplets of
Acknowledgement
This work was supported by Grant No 13 T09A 074 from the
State Committee for ScientiÐc Research (Poland).
2
3
similar chemical shifts.
Stoichiometric reactions
References
1
(PCy ) Cl Ru2CHPh (I, 0.010 g, 1.22 ] 10~5 mol) and 0.001
3 2
2
For recent reviews on metathesis of silicon-containing oleÐns see:
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g anthracene (internal standard) were dissolved in 0.6 ml of
C D in a NMR tube. Then vinyl ethyl ether (1.2 ll,
6
6
1.25 ] 10~5 mol) was added. The reaction was carried out in
a closed NMR tube at room temperature and monitored by
1H NMR. Quantitative reaction was observed after 3 h.
(PCy ) Cl Ru2CH (III, 0.005 g, 6.69 ] 10~6 mol) and
2
3
3 2
2
2
0.0005 g anthracene (internal standard) were dissolved in 0.6
ml of C D in an NMR tube. Then vinyl ethyl ether (0.64 ll,
6
6
6.69 ] 10~6 mol) was added. The reaction was carried out in
a closed NMR tube at room temperature or at 60 ¡C and con-
trolled by 1H NMR. In another reaction a 100-fold excess of
vinyl ethyl ether was used.
4
5
(PCy ) Cl Ru2CH(OEt) (II, 0.003 g, 3.79 ] 10~6 mol) and
3 2
2
6
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0.0003 g anthracene (internal standard) were dissolved in 0.6
ml of C D in an NMR tube. Then an equimolar amount of
6
6
CH 2CHSiMe or CH 2CHSi(OEt) were added. The reac-
2
3
2
3
tion was carried out in an NMR tube at room temperature (or
at 60 ¡C) and monitored by 1H NMR. No expected metathesis
products were observed. The decomposition of ethoxycarbene
complex II, leading to unidentiÐed products was the only
change observed in the system. IR spectra show the presence
of Ru(CO) (l \ 1933 cm~1) and the absence of RuÈH bonds
in the decomposed complex II.
Synthesis of (PCy ) Cl Ru2CH(OEt)
3 2
2
(PCy ) Cl Ru2CHPh (0.050 g, 6.07 ] 10~5 mol) was dis-
3 2
solved in benzene in a Schlenk tube. Then vinyl ethyl ether
7
B. Marciniec, M. Kujawa and C. Pietraszuk, Organometallics,
2000, 19, 1677.
2
674
New J. Chem., 2000, 24, 671È675

View Article Online
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New J. Chem., 2000, 24, 671È675
675