The effect of substituents at silicon on the cross-metathesis of trisubstituted vinylsilanes with olefins

Article abstract of DOI:10.1016/j.jorganchem.2005.07.091

Efficient cross-metathesis of vinylsilanes, carrying a large spectrum of different substituents at silicon, with various olefins in the presence of the first and second generation Grubbs catalyst and Hoveyda-Grubbs catalyst is described. On the basis of the results of equimolar reactions of vinylsilanes with ruthenium alkylidene complexes and experiments with deuterium-labelled reagents, a general, metallacarbene mechanism for the cross-metathesis of trisubstituted vinylsilanes with olefins has been suggested. Reaction was proved to be a valuable method for synthesis of unsaturated organosilicon derivatives.

Full text of DOI:10.1016/j.jorganchem.2005.07.091

Journal of Organometallic Chemistry 690 (2005) 5912–5921
www.elsevier.com/locate/jorganchem
The effect of substituents at silicon on the cross-metathesis
of trisubstituted vinylsilanes with olefins
a
b
a
a,
*
Cezary Pietraszuk , Helmut Fischer , Szymon Rogalski , Bogdan Marciniec
a
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan´, Poland
b
Fachbereich Chemie, Universita¨t Konstanz, Fach M 727, 78457 Konstanz, Germany
Received 21 June 2005; received in revised form 22 July 2005; accepted 22 July 2005
Available online 16 September 2005
Abstract
Efficient cross-metathesis of vinylsilanes, carrying a large spectrum of different substituents at silicon, with various olefins in the
presence of the first and second generation Grubbs catalyst and Hoveyda–Grubbs catalyst is described. On the basis of the results of
equimolar reactions of vinylsilanes with ruthenium alkylidene complexes and experiments with deuterium-labelled reagents, a gen-
eral, metallacarbene mechanism for the cross-metathesis of trisubstituted vinylsilanes with olefins has been suggested. Reaction was
proved to be a valuable method for synthesis of unsaturated organosilicon derivatives.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Cross-metathesis; Alkylidene complexes; Vinylsilanes; Ruthenium
1. Introduction
Silylative coupling is not fully regioselective and in spe-
cific systems it is accompanied by double bond migra-
tion and cis–trans isomerization. Moreover, this
method cannot be applied for chlorosubstituted vinylsil-
anes [5]. In the search for new routes of effective synthe-
sis of trisubstituted vinylsilanes, we have directed our
attention to olefin metathesis (Eq. (2)).
Trisubstituted vinylsilanes of the type RCH@
CH(SiR3) constitute a class of unsaturated organosil-
icon compounds of prospective wide applicability in
organic synthesis [1], especially in the fast developing
palladium-catalysed coupling of vinylsilanes with organic
derivatives [2]. The main catalytic routes to silylolefins
involve hydrosilylation of substituted alkynes by hydro-
silanes [3], hydrogenation of alkynylsilanes [4] and
silylative coupling (SC) of vinylsilanes with olefins [5].
Silylative coupling of vinylsilanes with olefins catalysed
by ruthenium, rhodium and cobalt complexes contain-
ing (or generating) M–H and M–Si bonds occurs
through a cleavage of the @C–Si bond of vinylsilane
and @C–H bond of the olefin (Eq. (1)) and is a conve-
nient synthetic route to vinyltrisubstituted silanes [5].
R'
CH2
CH
H C H
H C
R'
CH2
CH2
CH2
C
CH
CH
[Ru]-H or [Ru]-SiR3
+
+
+
SiR3
R'
SiR3
SiR3
ð1Þ
R'
CH2
CH
CH2
CH
R'
CH
[Ru]=CHR
CH2
CH2
+
+
CH
SiR3
SiR3
ð2Þ
*
Corresponding author. Tel.: +48 61 8291 366; fax: +48 61 8291
The olefin metathesis has become an important and
powerful reaction in organic and polymer synthesis [6]
508.
E-mail address: marcinb@amu.edu.pl (B. Marciniec).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.07.091

C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
5913
as a result of development of well-defined functional
group tolerant metal carbene complexes, e.g., I, II or
III, which can act directly as metathesis initiators [7].
tuted olefins such as 1,1-diphenylethene and 1-methyl-
1-phenylethene has been observed.
A significant effect of substituents at the silicon on the
reactivity of vinylsilanes is observed. On the basis of
substantial differences in the reactivity in metathesis,
vinylsilanes can be divided into four general classes
(Scheme 1).
PCy3
N
N
Cl
N
N
Ph
Ru
Cl
Cl
Ph
Ru
Cl
Ru
Cl
PCy3
Cl
O
PCy3
Class 1 consists of the vinylsilanes containing three
identical or different electron withdrawing substituents
such as Cl, OR, OCOR, OSiMe3, C6H4–CF3-4 at silicon.
The cross-metathesis of olefins with the aforementioned
vinylsilanes provides the products with high yields and
selectivities. The CM with olefins is usually accompa-
nied by competitive olefin homo-metathesis. However,
this reaction can be retarded by applying an excess of
vinylsilane. Catalyst I permits an effective course of
the cross-metathesis of olefins with H2C@CHSi(OR)3
or H2C@CHSi(OSiMe3)3 [8a,8b]. Catalyst I, because
of its low catalytic activity in homo-metathesis of sty-
renes, ensures high selectivities in CM of vinylsilanes
with styrenes and permits the use of a small excess of
styrenes, which sometimes facilitates the reaction.
H2C@CHSi(OAc)3 or H2C@CHSiCl3 undergoes effec-
tive cross-metathesis in the presence of II or III. In the
cross-metathesis of vinylsilanes with olefins catalysed
by I or II, the formation of small amounts of E-1-silyl-
2-phenylethene cannot be avoided. It is formed in the
equimolar reaction of benzylidene complex with vinylsil-
anes as presented in Eqs. (4)–(6) and in Scheme 3.
The vinylsilanes containing one or two electron with-
drawing groups at silicon with the remaining substituent
having no electron donor properties, are substantially less
active in CM with olefins. H2C@CHSiF2 Ph in the pres-
ence of catalysts I, II or III and H2C@CHSi(OEt)2Ph or
H2C@CHSiClPh2 in the presence of catalysts II or III,
effectively react with styrene or 1-hexene. However, ex-
tended reaction time is required. H2C@CHSi(OEt)Ph2
and H2C@CHSiFPh2 undergo cross-metathesis with sty-
rene in the presence of II or III, but afford the expected
products with lower yields and selectivities. In this case
competitive olefin homo-metathesis could not be retarded
even when vinylsilane was used in excess.
First generation
Grubbs catalyst
(I)
Second generation
Grubbs catalyst
(II)
Hoveyda - Grubbs
catalyst
(III)
We have previously shown that Grubbs type catalysts
effectively catalyse the cross-metathesis (CM) of trialk-
oxy-, trisiloxy- [8], trichloro- and generally electron
withdrawing group substituted vinylsilanes [9] and vinyl-
silsesquioxanes [10] with styrenes, alkenes and numerous
allyl derivatives. Metathesis of vinylsilanes with dienes
and cycloalkenes catalysed by Grubbs type complexes
has also been demonstrated [11].
Now, we would like to focus on the effect of substit-
uents at silicon on the reaction, discuss advantages and
drawbacks of cross-metathesis of vinylsilanes with ole-
fins as a general synthetic method for the synthesis of
vinyltrisubstituted silanes and finally search for a mech-
anistic scheme of catalysis of the reaction.
2. Results and discussion
2.1. Catalytic examinations
Treatment of a mixture of vinylsilane and olefin in
the presence of 0.5–5 mol% of catalyst I, II or III gives
rise to evolution of ethene and formation of trisubsti-
tuted vinylsilane (Eq. (3)). The reaction permits a syn-
thesis of substituted silylethenes with high yields and
selectivities, under mild reaction conditions. The results
of the catalytic studies are summarised in Table 1.
R1
R1
R1
I, II or III
+
+
R3Si
R1
R3Si
A
B
C
D
ð3Þ
Class 2 consists of the vinylsilanes active both in
homo-metathesis [13] and cross-metathesis with olefins.
Extensive search for reagents representing this type of
reactivity revealed only one ‘‘substituent motif’’ charac-
teristic of this class, that is H2C@CHSiCl2R (where
R = alkyl, aryl, OSiMe3). Cross-metathesis of
H2C@CHSiCl2R with olefins catalysed by II or III gives
the cross-metathesis products with high yields and selec-
tivities. For these silanes, care must be taken to make a
proper choice of the reaction conditions and the vinylsi-
lane/olefin ratio because CM is accompanied by com-
petitive homo-metathesis of vinylsilane and olefin [13].
However, in all reactions with dichlorosubstituted vinyl-
silanes, in the above specified reaction conditions,
The above presented results permit drawing a compari-
son of reactivities of a number of vinylsilanes, olefins
and catalysts used.
High yield of the reaction is obtained for styrene, 4-
substituted styrenes, 1-alkenes and allyl derivatives such
as allyltrimethylsilane and allyl ethers. The reactions
with styrenes lead to selective formation of E-isomer.
The cross-metathesis of vinylsilanes with 1-alkenes,
allylsilanes and allyl ethers gives a mixture of E- and
Z-isomers, with E-isomer in predominant amounts.
Although the synthesis of trisubstituted olefins via
cross-metathesis is possible when using catalyst II [12],
no cross-metathesis of vinylsilanes with 1,1-disubsti-

5914
C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
Table 1
Cross-metathesis of vinylsilanes with olefins
Entry Vinylsilane SiR3 = Olefin R1 =
Cat. Reaction conditions Conv. of B (%) Yield (isolated) of C (%) C E/Z Yield of D (%)
1a
2
3
4
5
6
7
Si(OEt)3
Si(OMe)3
Si(OSiMe3)3
SiCl3
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
I
1:1/6/2/rt.
95
95
97
0
100
40
10
0
3
Trace
100
100
85
80
80
100
100
100
100
80
95
94
95
0
99 (80)
40
7
0
0
0
80
95
83 (70)
75
78 (65)
95
98
95
95
50
88
6
50
5
99
20
0
95
90
98
90 (75)
97 (85)
95 (78)
85
85
70
85
75
72
0
0
99
95
100 (90)
100 (70)
100 (80)
97
95
95
99
75
0
90
0
0
97
97
88
20
100 (92)
100 (70)
100 (80)
92
E
Trace
Trace
Trace
0
Trace
Trace
2
0
0
0
20
5
2
5
Trace
Trace
Trace
Trace
0
30
Trace
2
50
Trace
0
80
0
I
1:1/6/2/reflux
1:1/6/2/reflux
15:1/1/0.5/reflux
1:1/20/5/reflux
1:1/20/5/reflux
1:1/6/2/rt.
1:1/3/5/reflux
1:1/6/2/rt.
1:3/6/2/rt.
E
I
E
I
–
E
SiF2Ph
I
Si(OEt)2Ph
Si(OEt)2Me
Si(OEt)Ph2
Si(OEt)Me2
SiMe3
Si(OEt)3
Si(OEt)3
SiCl3
Si(OAc)3
SiCl2Me
SiCl2(OSiMe3)
SiCl2Ph
SiCl2(C6H4–Me-4) Ph
SiCl2(C6H4–CF3-4) Ph
I
E
I
E
8
9b
I
–
–
–
E
I
10a
11
12
13c
14c
15c
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37d
38b
39b
40c
41c
42
43
44c
45c
46c
47
48
49
50
51
52
53
54c
55
56c
57
58
59
60c
61c
62c
63
I
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
1:1/1/2/reflux
3:1/3/2/reflux
15:1/1/0.5/reflux
15:1/1/0.5/reflux
15:1/1/0.5/reflux
1:1/1/5/reflux
1:1/1/5/reflux
1:1/2/5/reflux
4:1/1/5/reflux
1:1/20/5/reflux
1:1/20/5/reflux
1:1/3/2/reflux
1:1/3/5/reflux
1:1/3/5/reflux
1:1/1/5/reflux
1:1/20/5/reflux
5:1/6/2/reflux
1:1/1/5/reflux
1:1/1/5/reflux
1:1/1/5/reflux
3:1/20/5/reflux
1:1/1/5/reflux
1:1/1/5/reflux
1:1/2/5/reflux
1:1/1/5/reflux
1:1/2/2/reflux
5:1/6/2/reflux
5:1/3/5/reflux
5:1/3/5/reflux
5:1/3/5/reflux
5:1/1/0.5/reflux
5:1/3/5/reflux
5:1/3/5/reflux
5:1/3/5/reflux
5:1/1/0.5/reflux
5:1/1/0.5/reflux
1:1/1/5/reflux
1:1/1/5/reflux
4:1/3/5/reflux
1:1/1/5/reflux
1:1/1/5/reflux
1:1/20/5/reflux
1:1/2/5/reflux
5:1/3/2/reflux
5:1/3/2/reflux
5:1/3/2/reflux
1:1/1/5/reflux
1:1/6/5/reflux
1:1/20/5/reflux
5:1/1/0.5/reflux
5:1/1/0.5/reflux
5:1/1/0.5/reflux
1:1/1/5/reflux
E
E
E
E
E
E
E
E
SiF2Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
E
Si(OEt)2Ph
Si(OEt)2Me
Si(OEt)Ph2
Si(OEt)Me2
SiClPh2
90
10
100
7
E
E
E
–
E
100
100
Trace
100
100
100
95
100
100
100
100
100
90
SiFPh2
SiMe3
E
–
E
SiCl2Me
SiCl2Me
SiCl2Me
Si(OEt)2Ph
SiClPh2
SiCl2Ph
Si(OEt)3
SiCl3
SiCl2Me
SiMe3
Si(OEt)3
Si(OSiMe3)3
SiCl3
SiCl2Me
Si(OEt)3
Si(OSiMe3)3
SiCl3
Si(OAc)3
SiCl2Me
SiCl2(OSiMe3)
SiCl2Ph
C6H4–CH3-4
C6H4–Cl-4
C6H4–CH2Cl-4 II
C6H4–Cl-4
C6H4–Cl-4
C6H4–Cl-4
Ph
Ph
Ph
Ph
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
Trace
10
E
E
Trace
Trace
Trace
Trace
15
15
30
2
12
II
II
II
III
III
III
III
I
E
E
E
E
E
E
E
100
90
0
9/1
10/1
–
I
7
0
0
I
I
0
–
II
II
II
II
II
II
II
II
II
II
II
II
II
II
II
III
III
III
II
II
II
II
100
100
100
100
100
100
100
100
100
90
Trace
100
Trace
Trace
100
99
20/1
20/1
20/1
20/1
20/1
20/1
25/1
22/1
25/1
25/1
–
25/1
–
–
>25/1 Trace
20/1
E
Trace
Trace
0
0
0
Trace
Trace
0
Trace
12
SiCl2(C6H4–CF3-4) C4H9
SiCl2(C6H4–Me-4) C4H9
Si(OEt)2Ph
SiClMe2
SiClPh2
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
0
5
0
0
SiPh3
Si(C6H4–Me-4)3
Si(C6H4–CF3-4)3
SiCl3
SiCl2Me
Si(OEt)2Ph
SiCl3
Si(OAc)3
SiCl2Me
SiCl3
Trace
Trace
80
0
0
90
C4H9
100
100
100
100
100
E
CH2SiMe3
CH2SiMe3
CH2SiMe3
CH2OC4H9
25/1
25/1
22/1
8/1
0
8

C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
5915
Table 1 (continued)
Entry
Vinylsilane SiR3 = Olefin R1 = Cat. Reaction conditions Conv. of B (%) Yield (isolated) of C (%) C E/Z Yield of D (%)
64
65
66
SiCl2Me
SiCl2(OSiMe3)
SiCl2Ph
CH2OC4H9 II
CH2OC4H9 II
CH2OC4H9 II
1:1/1/5/reflux
1:1/1/5/reflux
1:1/1/5/eflux
100
100
100
98 (75)
95
90
25/1
25/1
E
Trace
Trace
Trace
Reaction conditions: [A]:[B]/time (h)/catalyst concentration (mol%)/temp. (ꢁC).
a
See [8a].
See [8b].
See [9].
b
c
d
Proved to be silylative coupling (see text).
R3Si
SiR3 = Si(OR2)3, Si(OAc)3, SiCl3,
Si(C6H4-CF3-4)3
1
2
R1
R3Si
R3Si
SiR3 = SiCl2R3
+
R1
SiR3
I, II or III
R3Si
+
R1
SiR3 = SiMe3 , SiMe2R4, SiMeR4
no metathesis
no conversion
3
4
2
SiPh3
H2C=CR5(SiMe3)
R1 = alkyl, aryl, CH2SiMe3, CH2OBu
R2 = alkyl
R3 = alkyl, aryl, OSiMe3
R4 = alkyl, aryl, OSiMe3, alkoxy
R5 = Br, Ph, SiMe3
Scheme 1. Reactivity of vinylsilanes in the presence of ruthenium alkylidene complexes.
only trace amounts of 1,2-bis(silyl)ethenes have been
detected.
Trimethylvinylsilane, all tested dimethylsubstituted
The effective reaction of trimethylvinylsilane with
styrene observed in the presence of Hoveyda–Grubbs
catalyst III, leading to the effective formation of 1-(tri-
methylsilyl)-2-phenylethene was proved to proceed
according to the non-metallacarbene mechanism.
The vinylsilanes containing substituents at Ca, e.g.
H2C@C(SiMe3)2 and H2C@C(Ph)(SiMe3), belonging
to class 4 do not react with the catalyst. Presumably, a
relevant ruthenacyclobutane intermediate cannot be
formed because of the steric properties of 1,1-disubsti-
tuted olefins. Similarly, no activity was observed for
H2C@CHSiPh3 under the conditions used.
and most monomethyl-substituted vinylsilanes belong
to class 3. They do not undergo cross-metathesis with
olefins in the presence of I, II or III. As we have reported
previously, Grubbs catalyst I undergoes equimolar reac-
tion with trimethylvinylsilane leading to the formation
of substituted propenes and non-alkylidene ruthenium
complexes. This process has been shown to proceed
via formation of putative b-(trimethylsilyl) ruthenacyc-
lobutane complex and its decomposition via b-elimina-
tion of the silyl group (Scheme 2) [14]. The same
process was observed also in the presence of catalyst II.
Comparison of silylative coupling and cross-metathe-
sis of vinylsilanes and olefins [5] revealed that both
Ph
[Ru]
D
Ph
Me3Si
PCy3
Me3Si
D
Ph
SiMe3
Ph
D
SiMe3
D
Cl
+
Ru
Cl
PCy3
β-SiMe3
elimination
[Ru]
Ph
D
Ph
D
[Ru]
Me3Si
SiMe3
main product
Scheme 2. Proposed mechanism of decomposition of catalyst I in the presence of trimethylvinylsilane [14].

5916
C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
methods are important synthetic tools in organosilicon
chemistry and complement each other. Chlorosubsti-
tuted vinylsilanes, being most important monomers in
organosilicon chemistry are effectively transformed by
cross-metathesis (CM), while they are not active in sily-
lative coupling (SC) reactions. Additionally, some vinyl-
silanes containing specific functional groups, e.g.
H2C@CHSiCl2(C6H4–CH2Cl-4), which is an interesting
bifunctional monomer, can be converted only via
metathesis. On the other hand, CM is not applicable
to methylsubstituted vinylsilanes, which are easily trans-
formed by SC.
reaction stoichiometry. Obviously, the methylidene
complexes are not stable under the conditions used. As
illustrated in Fig. 1, the yield of the methylidene com-
plex derived from I is much lower than that derived
from II, suggesting a higher stability of the latter under
the conditions used. In the applied reaction conditions,
only ca. 15% conversion of complex III and no forma-
tion of methylidene complexes were observed by 1H
NMR spectroscopy after 2 h.
The reaction of II with trichlorovinylsilane
H2C@CHSiCl3 leads to the formation of styrene, silyl-
styrene, ethylene and unidentified ruthenium complexes
(Eq. (5)).
2.2. The study of equimolar reactions
N
N
Cl
Both complexes I and II undergo equimolar metathesis
with triethoxyvinylsilane. The reactions lead to selec-
tive formation of respective methylidene complex and
E-1-phenyl-2-(triethoxysilyl)ethene (Eq. (4)). Analo-
gously, the reaction ofcatalyst III withH2C@CHSi(OEt)3
leads to the formation of E-1-[(2-isopropoxy)phenyl]-2-
(triethoxysilyl)ethene.
Ph
SiCl3
+
Ru
Cl
PCy3
N
N
Cl
SiCl3
Ph
Ru
+
+
+
C6D6
Cl
Ph
PCy3
ð5Þ
L
Si(OEt)3
Cl
Ph
Identification of styrene among the reaction products
suggests the formation of (silyl)methylidene complex.
However, all attempts to identify it by H NMR spec-
+
Ru
Cl
1
PCy3
troscopy have failed.
L = PCy3, IMesH2
C6D6, 40oC
Chlorosubstituted vinylsilanes react readily with
complex I to form unidentified non-alkylidene com-
plexes [9]. The decomposition is retarded when at least
one equivalent of free PCy3 is added to the system.
Under the conditions used, the reaction of moisture
traces with chlorosilane has been found to lead to
rapid hydrolysis of the Si–Cl bond and to formation
of HCl. The reaction is catalysed by free phosphine
(which decoordinates from complex I). This catalytic
side-reaction can significantly decrease the product
yield and selectivity. Moreover, the loss of phosphine
due to the reaction with HCl increases the activity
of the catalyst but also accelerates its thermal
decomposition. Such effects caused by ‘‘phosphine
L
Cl
Si(OEt)3
Ru
+
Cl
Ph
PCy3
ð4Þ
1
The course of the reactions was controlled by H NMR
spectroscopy (Fig. 1). Some differences between the reac-
tions of I, II or III with H2C@CHSi(OEt)3 were observed.
The reaction rate of triethoxyvinylsilane with com-
plex I is slightly higher than with complex II. The yields
1
of methylidene complexes (observed by H NMR spec-
troscopy) are lower than expected on the basis of the
100
80
60
40
20
0
uptake of I
uptake of II
uptake of III
yield of [Ru]=CH2 (formed from I)
yield of [Ru]=CH2 (formed from II)
0.0
0.5
1.0
1.5
2.0
time [h]
Fig. 1. Equimolar reactions of I, II or III with triethoxyvinylsilane (C6D6, 40 ꢁC).

C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
5917
scavengers’’ (e.g. CuCl) have been documented in lit-
erature [15]. Catalysts II and III are more stable than
I under these conditions.
ꢀ50 ꢁC failed. Obviously, such complexes are thermally
or, more likely, kinetically unstable under the conditions
used.
Dichlorosubstituted vinylsilanes H2C@CHSiCl2R
(where R = Me, OSiMe3, Ph), undergo equimolar reac-
tions with II, with formation of styrene, silylstyrene, eth-
ylene and methylidene complexes (Eq. (6)).
In order to learn more on the electronic effect of the
substituents at silicon on the reaction rate, a series of
dichlorovinylsilanes containing 4-substituted phenyl
groups H2C@CH[SiCl2(C6H4–X-4)] (where X = H,
Me, OMe, CF3) were tested in equimolar reactions with
II. The results are presented in the form of the Hammett
plot (Fig. 2).
L
SiCl2R
Cl
Ph
+
Ru
The linearity was obtained by using rI parameters
[16]. Slightly higher rates for vinyldichlorosilanes car-
rying more electron withdrawing groups (Fig. 2,
X = CF3, OMe) were observed. This preliminary result
does not allow us to draw reliable conclusions.
According to the mechanistic scheme of metathesis
catalysed by Grubbs catalysts (Eq. (7)) both k1 and
Cl
PCy3
L = IMesH2
L
SiCl2R
Cl
Ph
+
+
+
Ru
Ph
Cl
PCy3
k
ꢀ1/k2 contribute to the overall metathesis activity
[17]. Obviously, in the system studied, the vinylsilanes
containing electron withdrawing substituents compete
more efficiently with phosphine for coordination to
the 14-electron intermediate and in consequence, more
frequently enter the catalytic cycle.
ð6Þ
In the experiments performed in a standard NMR tube,
no or only traces of E-1,2-bis(silyl)ethene were observed.
Except for complex II, only [Cl2(PCy3)(IMesH2)-
Ru(@CH2)] and no other complexes of the type
1
[Ru]@CHR were detected by H NMR spectroscopy.
L
k1
Cl
Ph
On the other hand, effective homo-metathesis of dichlo-
rosubstituted vinylsilanes observed in the presence of II
or III [13] indicates the formation of (silyl)methylidene
complex [Ru]@CH(SiR3) as an intermediate in similar
systems.
Ph
- PCy3
(L)Cl2Ru
Ru
+ PCy3
k -1
Cl
PCy3
L = H2IMes
Efforts were made to confirm the formation of
silylcarbene complex. To this end, the equimolar reac-
tion of [Cl2(PCy3)(IMesH2)Ru(@CH2)] with H2C@
CHSiCl2Me was investigated at different temperatures
(40, room temperature, 0, ꢀ30, ꢀ50 ꢁC) using 1H
NMR spectroscopy. No alkylidene complex except of
the starting [Ru]@CH2 was detected. Also all attempts
to trap the putative (silyl)methylidene complex at
k 2
L
Cl2Ru
SiCl2R
SiCl2R
Ph
catalytic cycle
k -2
RCl2Si
ð7Þ
0.2
log k/k0 = 0.4737σ I - 0.0188
R2 = 0.9705
CF3
0.15
0.1
OMe
0.05
0
H
-0.1
0
0.1
0.2
0.3
0.4
0.5
Me
-0.05
-0.1
σ I
Fig. 2. Effect of the substituent at silicon on the reactions rate in stoichiometric reaction of II with H2C@CHSiCl2(C6H4–X-4) (where X = H, Me,
OMe, CF3) (Hammett plot).

5918
C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
2.3. Labelling studies
which suggests non-metallacarbene mechanism and
indicates H/D exchange.
To distinguish between the non-metallacarbene
mechanism (such as that observed when [RuHCl
(CO)(PPh3)3] or [RuCl(SiR3)(CO)(PPh3)2] was used as
a catalyst), and the metallacarbene mechanism, the reac-
tions of a number of vinylsilanes with styrene-d8 in the
presence of I, II or III were investigated. In the case of
the non-metallacarbene mechanism, the formation of
silylstyrene-d7 and ethylene-d is to be expected (Eq.
(8)). In contrast, the carbene mechanism should afford
silylstyrene-d6 and ethylene-d2 (Eq. (9))
2.4. Mechanistic implications
On the basis of equimolar and catalytic reactions of
vinylsilanes in the presence of ruthenium alkylidene
complexes, a general scheme of reactivity was proposed
(Scheme 3).
According to the scheme proposed (Scheme 3), the
reaction of vinylsilanes with benzylidene complex A gen-
erates methylidene complex
B and E-1-phenyl-2-
(silyl)ethene (pathway a). This metathesis exchange
proceeds via putative b-(silyl)ruthenacyclobutane com-
plex C. In the case of methylsubstituted vinylsilanes
H2C@CHSiR3 (SiR3 = SiMe3, SiMe2R, SiMeR2; R1 =
alkyl, aryl) the metathesis decomposition of b-(silyl)-
ruthenacyclobutane is accompanied by competitive
b-(silyl)elimination, which leads to the loss of alkylidene
moiety and to the formation of species inactive in metath-
esis (Scheme 2 and pathway b in Scheme 3) [14]. In the
presence of olefin, methylidene complex B undergoes
metathesis exchange leading to the formation of alkylid-
ene complex D and ethene (pathway c). Vinylsilane com-
petes with olefin for coordination to alkylidene complex
D. The reaction of alkylidene complex D with vinylsilane
H2C@CHSiR3 (SiR3 = Si(OR1)3, SiCl3, SiCl2R1) affords
organosilicon product and methylidene complex B (path-
way d). Stoichiometric metathesis of olefin with alkylid-
ene complex D affords the olefin homo-metathesis
product and regenerates methylidene complex B (path-
way e). By using an excess of vinylsilanes, the olefin
homo-metathesis can be avoided in most cases.
C6D5
D
D
D
H
H
H
C C
+
C C
SiR3
[Ru]
[Ru] Si
H
or
C6D5
D
H
H
H
D
+
C C
C C
D
SiR3
ð8Þ
ð9Þ
C6D5
D
D
H
H
+
C C
C C
D
H
SiR3
C6D5
D
H
D
D
H
[Ru] CHPh
C C
C C
+
SiR3
H
Analysis of the products formed in the reactions of
styrene-d8 with: H2C@CHSi(OEt)3 in the presence of
I [8a], H2C@CHSiCl2Me in the presence of II, and
with H2C@CHSiCl3 in the presence of II and III
revealed exclusive formation of E-1-phenyl-2-(silyl)eth-
ene-d6, which strongly supports the metallacarbene
mechanism of the reaction [8a]. On the other hand,
the reaction of H2C@CHSiMe3 with styrene-d8 in
the presence of III leads to a mixture of E-1-phenyl-
2-(silyl)ethene-d6 and E-1-phenyl-2-(silyl)ethene-d7,
Additional pathways are available for dichlorosubsti-
tuted vinylsilanes H2C@CHSiR3 (SiR3 = SiCl2R1). They
can react with benzylidene complex A or methylidene
complex B with the formation of putative (silyl)methyl-
idene complex E (pathways f and g, respectively).
Scheme 3. General scheme of reactivity in the system containing Grubbs catalyst, vinylsilane and metathetically active olefin.

C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
5919
Homo-metathesis product [1,2-bis(silyl)ethene] and
3.4. Preliminary kinetic examinations
methylidene complex B are formed in the reaction of
complex E with dichlorovinylsilane (pathway h).
An NMR tube was charged with H2C@CHSiCl2-
(C6H4–X-4) (1.18 · 10ꢀ5 mol), anthracene (0.001 g,
internal standard) and C6D6 (0.6 mL) under argon and
1H NMR analysis was performed at 23 ꢁC. Then the
catalyst (1.18 · 10ꢀ5 mol) was added to the tube under
argon. The tube was inserted into the spectrometer
and the course of the reaction was followed at 23 ꢁC
3. Experimental
3.1. General
1
All manipulations were carried out under dry argon
by H NMR spectroscopy.
1
using standard Schlenk techniques. H- and 13C NMR
spectra were recorded on a Bruker AC250 spectrometer
at 250 and 62.9 MHz, respectively, or on a Varian Gem-
ini at 300 and 75 MHz. GC–MS analyses were made on
Varian Saturn 2100T (DB-1, 30 m capillary column) or
a HP 6890 gas chromatograph (HP-5MS 30 m capillary
column) equipped with a HP 5973 mass selective detec-
tor. The chemicals (complexes II and III, decane, dode-
cane, CH2Cl2, C6D6, H2C@CHSiCl2Me) were obtained
from Aldrich. The other substituted vinylsilanes were
prepared by the literature methods, H2C@CHSiCl2-
(OSiMe3) [18], H2C@CHSiCl2Ph [19]. H2C@CHSiCl2-
(C6H4–X-4) (where X = Me, CF3) were synthesised
using the same methodology as in the case of
H2C@CHSiCl2Ph. Catalyst I was prepared according
to the literature procedure [20].
3.5. Representative procedure for the reaction of
vinylsilane with D2C@C(D)C6D5
In a closed system [Cl2(PCy3)(IMesH2)Ru(@CHPh)]
(II) (0.001 g, 1.18 · 10ꢀ6 mol), C6D6 (0.35 mL), H2C@
CHSiCl2Me (3.0 lL, 2.3 · 10ꢀ5 mol), and styrene-d8
(2.7 lL, 2.3 · 10ꢀ5 mol) were added under argon to an
NMR tube. The sample was heated at 40 ꢁC for 2 h
and the reaction mixture was followed by NMR
spectroscopy.
3.6. Procedure for the synthesis of silylolefins
An oven dried 20 mL Schlenk flask equipped with a
condenser, a bubbler and a magnetic stirring bar was
charged under argon with 10 mL of CH2Cl2, vinylsilane
(4.0 · 10ꢀ2 mol) and olefin. The reaction mixture was
stirred and heated in an oil bath (50 ꢁC) to maintain a
gentle reflux. Then 2.0 · 10ꢀ3 mol of ruthenium benzyl-
idene complex I, II or III was added under argon. Inten-
sive bubbling was observed. A gentle flow of argon was
applied from the top of the column. The course of the
reaction was followed by gas chromatography. After a
given reaction time dichloromethane was distilled off
and the product was obtained by vacuum distillation
with the use of a microdistillation set.
3.2. Catalytic tests
An oven dried 4 mL Schlenk flask with side neck
closed with a septum, equipped with a condenser
and a magnetic stirring bar was charged under argon
with 3 mL of CH2Cl2, vinylsilane (1.18 · 10ꢀ4 mol)
and 10 lL of decane or dodecane (internal standard).
The reaction mixture was stirred and heated in an oil
bath to maintain a gentle reflux (ca. 43 ꢁC). Then
0.005 g (5.89 · 10ꢀ6 mol) of ruthenium benzylidene
complex II was added under argon. A gentle flow of
argon was applied. The reaction was followed by
GC. Before the chromatographic analysis, the sample
of the reaction mixture was treated with an excess
of absolute ethanol in the presence of pyridine in
order to transform chlorosilanes into ethoxy
derivatives.
3.6.1. Analysis of selected products
(a) MeCl2SiCH@CHCH2OC4H9, collected fraction
119–123 ꢁC/1 mmHg, isolated yield 75%; 1H NMR
(C6D6, d, ppm): 0.49 (s, 3H, SiMe), 0.79–0.90 (m, 3H,
CH3), 1.27–1.53 (m, 4H, CH3CH2CH2), 3.15–3.23 (m,
2H,CH3CH2CH2CH2O),3.63–3.68(m,2H,OCH2CH@),
6.06 (dt, 1H, J = 18.5 Hz, 1.9 Hz, @CHSi), 6.33 (dt, 1H,
J = 18.5 Hz, 3.6 Hz, @CHCH2O); 13C NMR (C6D6): 5.4
(SiMe), 14.3 (CH3), 19.9 (CH3CH2), 32.4 (CH3CH2CH2),
70.9 (CH3CH2CH2CH2O), 71.7 (OCH2CH@), 122.8
(@CHSi), 150.4 (@CHCH2O); MS: m/z (rel. intensity) of
ethoxy derivative: 61 (15), 77 (32), 89 (17), 95 (11), 101
(18), 103 (17), 105 (40), 117 (10), 119 (22), 129 (11), 131
(14), 133 (100), 134 (13), 143 (11), 145 (62), 146 (10), 147
(12), 173 (11), 189 (30), 191 (11), 205 (13), 131 (11), 233
(11), 237 (15).
3.3. Equimolar reactions of I, II or III with
triethoxyvinylsilane
An NMR tube was charged with the catalyst
(1.22 · 10ꢀ5 mol), anthracene (0.001 g, internal stan-
1
dard) and C6D6 (0.6 mL) under argon and H NMR
analysis was performed at 40 ꢁC. Then triethoxyvinylsi-
lane (1.22 · 10ꢀ5 mol) was added to the tube under ar-
gon, the tube was inserted into the spectrometer and
1
the course of the reaction was followed at 40 ꢁC by H
NMR spectroscopy.

5920
C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
(b) PhCl2SiCH@CH(C6H4–Cl-4), isolated by crystal-
4. Conclusions
lisation from CH2Cl2, isolated yield 78%; 1H NMR
(C6D6, d, ppm): 6.30 (d, 1H, J = 18.6 Hz, @CHSi),
7.17 (d, 1H, J = 18.6 Hz, @CH), 6.86 (d, 2H,
J = 9.0 Hz, C6H4Cl), 7.10 (d, 2H, J = 9.0 Hz, C6H4Cl),
7.08–7.14, 7.22–7.35, 7.79–7.85 (m, 5H, Ph); 13C NMR
(C6D6): 120.8 (@CHSi), 149.5 (@CH), 134.8, 129.0,
128.9, 135.8 (C6H4Cl), 132.2, 134.1, 128.7, 132.0 (Ph);
MS: m/z (rel. intensity) of ethoxy derivative: 45 (26),
104 (19), 105 (16), 165 (10), 179 (10), 180 (22), 196
(18), 214 (20), 215 (100), 216 (20), 254 (13), 288 (11),
317 (10), 332 (M+, 11).
(c) Ph2ClSiCH@CH(C6H4–Cl-4), isolated by crystal-
lisation from CH2Cl2, isolated yield 85%; 1H NMR
(C6D6, d, ppm): 6.65 (d, 1H, J = 19.3 Hz, @CHSi),
6.77–6.80 (m, 2H, C6H4Cl), 6.97–7.03 (m, 2H,
C6H4Cl), 7.01 (d, 1H, J = 19.3 Hz, @CH), 7.15–7.23,
(m, 6H, Ph), 7.79–7.84 (m, 4H, Ph); 13C NMR (C6D6):
125.3 (@CHSi), 128.3, 128.4, 128.9, 130.4, 134.5,
135.3, 136.1, 136.4 (C6H4Cl, Ph) 147.5 (@CH); MS:
m/z (rel. intensity) of ethoxy derivative: 45 (73), 50 (33),
51 (47), 53 (14), 63 (13), 73 (11), 74 (10), 75 (24), 76
(11), 77 (15), 78 (50), 79 (16), 101 (10), 102 (24), 103
(26), 104 (38), 105 (100), 106 (62), 107 (10), 123 (22),
149 (17), 150 (20), 151 (12), 152 (12), 157 (15), 165
(15), 178 (12), 179 (48), 180 (41), 181 (31), 182 (25),
183 (16), 184 (30), 185 (15), 200 (13), 208 (12), 209
(16), 215 (14), 228 (28), 242 (20), 243 (28), 244 (21),
245 (11), 253 (38), 254 (13), 286 (10), 287 (43), 288
(26), 289 (19), 319 (18), 320 (20), 321 (38), 322 (13),
323 (11), 365(M+, 71), 366 (23), 367 (16).
A variety of vinylsilanes have been tested in equi-
molar and catalytic reactions in the presence of
Grubbs catalysts. Pronounced influence of the proper-
ties of substituents at silicon on the reactivity of vinyl-
silanes in metathesis was demonstrated. Chemo- and
stereoselective course of cross-metathesis of vinylsil-
anes with styrenes, 1-alkenes and numerous allyl deriv-
atives was indicated. In optimised conditions the
products required were synthesised with high yields
and selectivities. The carbene mechanism of the reac-
tion was confirmed. The reaction was proved to be a
valuable method for synthesis of unsaturated organo-
silicon derivatives.
Acknowledgements
We thank the European Commission (Contract Nos.
ICA1-CT-2002-70001 and ICA1-CT-2002-70002) for
the financial support of this investigation.
References
[1] (a) T.H. Chan, I. Fleming, Synthesis (1979) 761;
(b) W.P. Weber, Silicon Reagents for Organic Synthesis, Springer,
Berlin, 1983 (Chapter 7);
(c) E.W. Colvin, Silicon Reagents in Organic Synthesis, Academic
Press, London, 1988 (Chapter 3);
(d) T.-Y. Luh, S.-T. Liu, in: Z. Rappoport, Y. Apeloig (Eds.),
The Chemistry of Organosilicon Compounds, Wiley, Chichester,
1998 (Chapter 30).
(d) Ph(OEt)2SiCH@CH(C6H4–Cl-4) collected frac-
tion 204–207 ꢁC/1 mmHg, isolated yield 75%; 1H
NMR (C6D6, d, ppm): 1.18 (t, 6H, J = 6.8 Hz,
OCH2CH3), 3.81 (q, 4H, J = 6.8 Hz, OCH2CH3), 6.33
(d, 1H, J = 19.2 Hz, @CHSi), 7.12 (d, 1H,
J = 19.2 Hz, @CH), 6.88–7.05 (m, 4H, C6H4Cl), 7.26–
7.34 (m, 3H, Ph), 7.86–7.92 (m, 2H, Ph); 13C NMR
(C6D6): 18.9 (OCH2CH3), 59.1 (OCH2CH3), 122.6
(@CHPh), 147.6 (@CH), 128.3, 128.4, 128.9, 130.6,
134.0, 134.6, 135.2, 136.6 (C6H4Cl, Ph); MS: m/z (rel.
intensity): 45 (17), 104 (12), 105 (13), 165 (10), 178
(11), 179 (19), 195 (17), 214 (100), 215 (45), 216 (44),
217 (16), 254 (18), 255 (15), 288 (10), 317 (16), 332
(M+, 16).
(e) PhF2SiCH@CHPh, isolated by column chroma-
tography, isolated yield 80%; 1H NMR (C6D6, d,
ppm): 6.29 (dt, 1H, J = 19.5 Hz, J = 3.0 Hz, @CHSi),
7.37 (d, 1H, J = 19.5 Hz, @CHPh), 7.10–7.31, 7.41–
7.43, 7.72–7.78, 7.92–7.98 (m, 10H, Ph); 13C NMR
(C6D6): 115.2 (@CHSi), 152.8 (@CHPh), 128.9, 134.5,
128.6, 132.2 (SiPh), 136.8, 127.5, 128.6, 129.9 (Ph); 19F
NMR (C6D6): ꢀ140.3; MS: m/z (rel. intensity): 102
(9), 103 (7), 165 (9), 178 (6), 179 (10), 180 (24),
181 (22), 227 (20), 228 (15), 245 (8), 246 (M+, 100),
247 (21).
[2] For recent reviews on the use of silyl olefins in cross-coupling
reactions see: (a) S.E. Denmark, R.F. Sweis, Organosilicon
compounds, in: A. de Meijere, F. Diederich (Eds.), Metal-
Catalyzed Cross-Coupling Reactions, 2nd ed., Wiley-VCH, Wein-
heim, 2004 (Chapter 4);
(b) S.E. Denmark, M.H. Ober, Aldrichim. Acta 36 (2003)
75.
[3] (a) Hydrosilylation of silylacetylenes B. Marciniec (Ed.), Com-
prehensive Handbook on Hydrosilylation, Pergamon Press,
Oxford, 1992 (Chapter 5.4);
(b) I. Ojima, Z. Li, J. Zhu, in: Z. Rappoport, Y. Apeloig (Eds.),
The Chemistry of Organic Silicon Compounds, vol. 2, Wiley,
Chichester, 1998 (Chapter 29).
[4] (a) L. Hevesi, Vinyl and arylsilicon, germanium and boron
compounds, in: A.R. Katritzky, O. Meth-Cohn, C.W. Rees
(Eds.), Comprehensive Organic Functional Group Transforma-
tions I, Elsevier Science, Oxford, 1995 (Chapter 2.18);
(b) B. Marciniec, C. Pietraszuk, I. Kownacki, M. Zaidlewicz,
Vinyl- and arylsilicon, germanium and boron compounds, in: E.
Katritzky, R.J.K. Taylor (Eds.), Comprehensive Organic Func-
tional Group Transformations II, Elsevier, Amsterdam, 2005
(Chapter 2.18).
[5] (a) B. Marciniec, C. Pietraszuk, Metathesis of silicon-containing
olefins, in: R.H. Grubbs (Ed.), Handbook of Metathesis, Wiley-
VCH, Weinheim, 2003 (Chapter 2.13);
(b) B. Marciniec, C. Pietraszuk, Curr. Org. Chem. 7 (2003)
691.

C. Pietraszuk et al. / Journal of Organometallic Chemistry 690 (2005) 5912–5921
5921
[6] (a) For recent review see: K.J. Ivin, J.C. Mol, Olefin Metathesis and
Metathesis Polymerization, Academic Press, San Diego, 1997;
[9] C. Pietraszuk, B. Marciniec, H. Fischer, Tetrahedron Lett. 44
(2003) 7121.
(b) A. Furstner (Ed.), Alkene Metathesis in Organic Synthesis,
¨
Springer, Berlin, 1998;
[10] Y. Itami, B. Marciniec, M. Kubicki, Chem. Eur. J. 10 (2004)
39.
(c) A. Furstner, Angew. Chem. 112 (2000) 3140;
¨
[11] C. Pietraszuk, B. Marciniec, M. Jankowska, Adv. Synth. Catal.
344 (2002) 789.
[12] A.K. Chatterjee, R.H. Grubbs, Org. Lett. 1 (1999) 1751.
[13] C. Pietraszuk, B. Marciniec, S. Rogalski, H. Fischer, J. Mol.
Catal. A: Chem. (accepted).
[14] C. Pietraszuk, H. Fischer, Chem. Commun. (2000) 2463.
[15] (a) E.L. Dias, S.T. Nguyen, R.H. Grubbs, J. Am. Chem. Soc. 119
(1997) 3887;
(b) M. Ulman, R.H. Grubbs, J. Org. Chem. 64 (1999) 7202.
[16] C. Hansch, H. Leo, R.W. Taft, Chem. Rev. 91 (1991) 165.
[17] M.S. Sanford, J.A. Love, R.H. Grubbs, J. Am. Chem. Soc. 123
(2001) 6543.
(d) Angew. Chem. Int. Ed. 39 (2000) 3012;
(e) M.R. Buchmeiser, Chem. Rev. 100 (2000) 1565;
(f) R.H. Grubbs, S. Chang, Tetrahedron 54 (1998) 4413.
[7] For a review see: (a) T.M. Trnka, R.H. Grubbs, Acc. Chem. Res.
34 (2001) 18;
(b) S.T. Nguyen, T.M. Trnka, The discovery and development of
well-defined, ruthenium based olefin metathesis catalysts, in: R.H.
Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim,
2003 (Chapter 1.6).
[8] (a) C. Pietraszuk, B. Marciniec, H. Fischer, Organometallics 19
(2000) 913;
(b) C. Pietraszuk, H. Fischer, M. Kujawa, B. Marciniec, Tetra-
hedron Lett. 42 (2001) 1175;
[18] N. Auner, C.-R. Heikenwaelder, W. Ziche, Chem. Ber. 126 (1993)
2177.
(c) M. Kujawa-Welten, C. Pietraszuk, B. Marciniec, Organomet-
allics 21 (2002) 840;
[19] R. Tacke, R. Strecker, M. Lambrecht, G. Moser, E. Lachdl,
Liebigs Ann. Chem. 6 (1983) 922.
(d) M. Kujawa-Welten, B. Marciniec, J. Mol. Catal., A: Chem.
190 (2002) 79.
[20] P. Schwab, R.H. Grubbs, J.W. Ziller, J. Am. Chem. Soc. 118
(1996) 100.