Efficient synthesis of E-1,2-bis(silyl)ethenes via ruthenium-catalyzed homocoupling of vinylsilanes carried out in ionic liquids

Article abstract of DOI:10.1016/j.apcata.2012.08.038

A series of ruthenium complexes (RuCl₃ × 3H₂O, [C₅H₅Ru(CH₃CN)₃]⁺[PF ₆]^-, [RuCl₂(PPh₃)₃], [RuHCl(CO)(PPh₃)_3<

Full text of DOI:10.1016/j.apcata.2012.08.038

Applied Catalysis A: General 445–446 (2012) 261–268
Contents lists available at SciVerse ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Efficient synthesis of E-1,2-bis(silyl)ethenes via ruthenium-catalyzed
homocoupling of vinylsilanes carried out in ionic liquids
a
a
a
a
a
˙
Szymon Rogalski , Patrycja Zak , Miłosz Mie˛tkiewski , Michał Dutkiewicz , Ryszard Fiedorow ,
Hieronim Maciejewskia,∗, Cezary Pietraszuka,∗∗, Marcin Smiglak , Thomas J.S. Schubert
b
b
´
a Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan´, Poland
b IoLiTec, Ionic Liquids Technologies, GmbH, Salzstrasse 184, 74076 Heilbronn, Germany
a r t i c l e i n f o
a b s t r a c t
series of ruthenium complexes (RuCl3 × 3H2O, [C5H5Ru(CH3CN)3]+[PF6]−, [RuCl2(PPh3)3],
Article history:
Received 26 April 2012
Received in revised form 22 August 2012
Accepted 25 August 2012
Available online 31 August 2012
A
[RuHCl(CO)(PPh3)3], [RuHCl(CO)(PCy3)2]) immobilized in [bmim][Tf2N] were tested in homocou-
pling of vinylsilanes (H2C CHSi(OEt)3, H2C CHSi(OiPr)3, H2C CHSi(OSiMe3)3, H2C CHSiMe(OSiMe3)2,
and H2C CHSiPh(OSiMe3)2) performed in a biphasic system. The highest catalytic activity and selectiv-
ity of homocoupling product was observed for [RuHCl(CO)(PCy3)2]. The complex [RuHCl(CO)(PCy3)2]
immobilized in
a variety ionic liquids ([bmim][PF6], [bmim][BF4], [bmim][Tf2N], [bmim][TfO],
Keywords:
[bmim][HSO4], [bmim][Cl], [trimim][MeSO4], [NBu3Me][MeSO4], [PBu4][Cl], [bpy][PF6], [bpy][BF4],
[bpy][Cl]) exhibits high catalytic activity in homocoupling of H2C CHSiMe2Ph, H2C CHSi(OEt)3 and
H2C CHSiMe(OSiMe3)2 and enables high-yield stereoselective synthesis of the corresponding E-1,2-
bis(silyl)ethenes. The immobilized complex can be easily recycled up to 12 times in the homocoupling
of H2C CHSiMe2Ph and up to 10 times in the homocoupling of H2C CHSiMe(OSiMe3)2 without a
significant drop in activity and selectivity. Results of a split test indicate that the source of catalytic
activity is the catalyst immobilized in ionic liquid phase.
Ionic liquid
Silylative coupling
Vinylsilanes
Ruthenium complexes
Hydride complexes
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
limited to a specific group of reactants [42,43]. From among the
known methods of synthesis, homocoupling seems to be partic-
Vinyl-substituted silanes and siloxanes constitute a class of
unsaturated organosilicon compounds of prospective wide appli-
cability in organic synthesis [1–4]. In particular, Pd-catalyzed
cross-coupling reactions (Hiyama coupling) of vinylsilanes with
various halide partners seem to be processes of high useful-
ness in organic synthesis especially as a reliable alternative to
Suzuki, Stille and Negishi couplings [5–13]. Bis-silyl olefins, partic-
ularly bis(silyl)ethenes, are well-known coupling partners [14–22].
Moreover, E-1,2-bis(triethoxysilyl)ethene was found to be a good
starting compound for the preparation of mesoporous organosili-
cas [23–26]. The main catalytic routes to bis(silyl)ethenes involve
hydrosilylation of silylacetylenes with hydrosilanes [17,27–30],
dehydrogenative silylation of vinylsilanes [31–34], bis-silylation of
acetylenes [35–39], homometathesis [40–42] and homocoupling
of vinylsilanes [32,40–42]. However, most of these methods led to
mixtures of isomers or, as it is in the case of metathesis, they are
ularly interesting [44,21]. Silylative coupling occurs via cleavage
of the C H bond of the olefin and the C Si bond of vinylsilanes,
and is catalyzed by complexes containing or generating hydride or
silyl ligands. It proceeds according to a mechanism that involves
insertion of a vinylsilane molecule into the M H bond, ␤-Si trans-
fer to the metal with elimination of ethylene and generation of
M
Si species, followed by insertion of a second molecule of vinyl-
silane into the M Si bond, and finally a ␤-H transfer leading to
regeneration of the hydride complex and elimination of products
[45–47].
This study was aimed at finding systems and conditions that
would enable ruthenium catalyzed homocoupling of vinylsilanes
with high yield and high selectivity, while using ionic liquids as the
reaction media. We present effective procedures for syntheses and
isolation of 1,2-bis(silyl)ethenes as well as procedures for catalyst
recycling and reusing. There are numerous examples of highly effi-
cient applications of transition metal-catalyzed reactions in ionic
liquids (organic salts usually defined as compounds with the melt-
ing points below 100 ◦C) [48–55]. Reactions proceeding in ionic
liquids catalyzed by ruthenium hydride complexes (or systems in
which hydride complexes are generated) are mainly hydrogena-
tion reactions [48–55] including asymmetric hydrogenation [56].
∗
Corresponding author. Tel.: +48 61 8279753; fax: +48 61 8291508.
Corresponding author. Tel.: +48 61 8291328; fax: +48 61 8291508.
E-mail addresses: maciejm@amu.edu.pl (H. Maciejewski), pietrasz@amu.edu.pl
∗∗
(C. Pietraszuk).
0926-860X/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.apcata.2012.08.038

262
S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
The ruthenium-based complexes employed for olefin hydrogena-
tion performed in ionic liquids involve mainly unmodified classical
catalyst precursors, e.g. [RuCl2(PPh3)3], including a few hydride
complexes [48–55]. For instance [RuHCl(CO)(PCy3)2] was used in
hydrogenation of acrylonitrile butadiene rubber [57,58] and a num-
ber of ruthenium clusters in hydrogenation of arenes [59–61].
2.4.2. Representative procedure for recycling experiment
A 2 mL glass vial equipped with a magnetic stirring bar
was charged under argon with 0.2 g of ionic liquid and 0.02 g
(2.74 × 10−5 mol) of [RuHCl(CO)(PCy3)2] complex, placed
in an oil bath, preheated to 130 ◦C and stirred for 15 min.
Then the mixture of 0.4 mL (1.37 × 10−3 mol) of methyl-
bis(trimethylsilyloxy)vinylsilane and 0.05 mL of dodecane (internal
standard) was added under argon. The mixture was vigorously
stirred and heated for 5 h. After that time, conversion of the
substrate was determined by GC analysis. After each reaction run,
the upper layer was decanted under argon and ionic liquid phase
was reused in a subsequent run.
2. Experimental
2.1. Chemicals
Trimethylimidazolium methylsulphate and tributylmethylam-
monium methylsulphate were purchased from Fluka. Other ionic
liquids were obtained from Ionic Liquid Technologies, GmbH.
All ionic liquids tested were used as received. RuCl3 × 3H2O,
[C5H5Ru(CH3CN)3]+[PF6]−, H2C CHSi(OEt)3, H2C CHSi(OiPr)3,
H2C CHSi(OSiMe3)3, H2C CHSiMe(OSiMe3)2 and xylene were
purchased from Aldrich. H2C CHSiPh(OSiMe3)2 was synthesized
according to procedure reported in the literature [62].
2.4.3. Split test (a test for heterogeneously catalyzed reaction)
A 2 mL glass vial containing catalyst [RuHCl(CO)(PCy3)2] immo-
bilized in IL 3 was charged under argon with the mixture of 0.4 mL
(1.37 × 10−3 mol) of methylbis(trimethylsilyloxy)vinylsilane and
0.05 mL of internal standard (dodecane). The reaction mixture was
heated and stirred for 1 h. Then, the conversion of vinylsilane was
measured by GC and half of the volume of the upper layer (0.15 mL)
was transferred under argon to another vial. Both vials were placed
in the same oil bath and heating was continued for additional 4 h.
Conversion of the substrate was determined by GC analysis.
2.2. Catalyst preparation
2.2.1. Preparation of catalyst precursors
[RuCl2(PPh3)3]
[63],
[RuHCl(CO)(PCy3)2]
[64]
and
[RuHCl(CO)(PPh3)3] [65] were prepared according to the
procedures reported in the literature.
3. Results and discussion
2.2.2. Representative procedure of catalyst immobilization
A 2 mL glass vial equipped with a magnetic stirring bar
was charged under argon with 0.2 g of ionic liquid and 0.02 g
(2.74 × 10−5 mol) of [RuHCl(CO)(PCy3)2] complex, placed in an oil
bath, preheated to 130 ◦C and stirred for 15 min.
3.1. Catalytic tests
While searching for the conditions for effective coupling of
vinylsilanes in ionic liquids a number of catalytic tests was
carried out with the use of (i) vinylsilanes differing in stere-
oelectronic properties of silyl group, (ii) several complexes
and salts of ruthenium, and (iii) several commercially avail-
able ionic liquids. Vinylsilanes employed in the study were
H2C CHSiMe2Ph (1a), H2C CHSi(OEt)3 (1b), H2C CHSi(OiPr)3
(1c), H2C CHSi(OSiMe3)3 (1d), H2C CHSiMe(OSiMe3)2 (1e),
and H2C CHSiPh(OSiMe3)2 (1f). Reactions were conducted
in the presence of ruthenium chloride RuCl3 × 3H2O (2),
tris(acetonitrile)cyclopentadienylruthenium (II) hexafluorophos-
phate [C5H5Ru(CH3CN)3]+[PF6]− (3), selected ruthenium com-
plexes reported to be active for homocoupling of vinylsilanes and
complexes applied to hydrogenation of olefins in ionic liquids, i.e.,
[RuCl2(PPh3)3] (4), [RuHCl(CO)(PPh3)3] (5) and [RuHCl(CO)(PCy3)2]
(6). The catalysts were immobilized using several imidazolium,
pyridinium, phosphonium and ammonium ionic liquids (Fig. 1).
At the first stage of the study, a number of tests was carried out
in order to find the most active and the most selective catalysts
as well as ionic liquids enabling effective conduction of reactions
under biphasic conditions. Salts and complexes of ruthenium at the
used concentrations were fully soluble in ionic liquids tested. For
each test reaction, the components of the reaction system formed
liquid–liquid biphasic systems. Under the reaction conditions (typ-
ically 130 ◦C), the substrates and products were partially miscible
with the ionic liquids, whereas they were practically immiscible at
room temperature. When vinylsilane (in a mixture with internal
standard) was added under argon to preheated solution of a cata-
lyst 3, 5 or 6 immobilized in ionic liquid phase, a slow evolution of
a gas (identified by GC as ethylene) was discerned. Monitoring of
the reaction by gas chromatography and GC–MS revealed gradual
formation of two products, one of which is formed in a consider-
ably greater quantity. Mass spectrum points to the formation of two
bis(silyl)ethene isomers. The analysis of the post-reaction mixture
by 1H and 13C NMR indicates formation of E-1,2-bis(silyl)ethenes
in a mixture with traces of 1,1-bis(silyl)ethene which leads to a
conclusion that vinylsilane homocoupling proceeds in the reaction
2.3. Catalyst characterization
1H and 13C NMR spectra were recorded on a Varian VNMR-S
at 400 and 100 MHz, respectively, or a Varian Gemini at 300 and
75 MHz. IR spectra were recorded on an FTIR spectrometer Bruker
Tensor 27 equipped with SPECAC Golden Gate diamond ATR acces-
sory. In situ FT-IR measurements were performed on a Mettler
Toledo ReactIR 15 instrument equipped with a DS 9.5 mm AgX
DiComp Fiber Probe (1.5 m) with a diamond sensor and a Mer-
cury Cadmium Telluride (MCT) detector. For all the spectra 256
scans were recorded with the resolution of 1 cm−1. HRMS (ESI) was
measured on a Waters Synapt GS-2 (acetonitrile was used as a sol-
vent). Elemental analysis was carried out on a Vario EL III analyzer
(Elementar GmbH).
2.4. Catalytic tests
2.4.1. General procedure
All manipulations were carried out under argon using standard
Schlenk techniques. Mixture of vinylsilane (1.37 × 10−3 mol) and
0.05 mL of dodecane (internal standard) was added by a syringe to
a 2 mL glass vial containing (2.74 × 10−5 mol) of ruthenium com-
plex immobilized in 0.2 g of ionic liquid and preheated to 130 ◦C.
The mixture was vigorously stirred at 130 ◦C for 5 h. Reactions were
monitored by gas chromatography and GC–MS. GC–MS analyses
were carried out on a Bruker 450-GC gas chromatograph (DB-5,
30 m capillary column) equipped with a Bruker 320-MS Triple
Quad mass spectrometer. GC analyses were performed on a Var-
ian CP-3800 or an HP 5890 Series II gas chromatographs (DB-1,
0.53 mm, 30 m megabore column) equipped with TCD detectors.
Ethylene was identified by using HP 5890 Series II gas chromato-
graph equipped with a packed column (6 ft × 1/8 in., Porapak Q) and
a FID.

S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
263
[N(SO2CF3)2]
[PF6]
[BF4]
N
N
N
N
N
N
N
Me
Me
Bu
Bu
Me
Me
Bu
Bu
Me
Me
Bu
Bu
(IL 1)
(IL 2)
(IL 3)
[F3CSO3]
[HSO4]
Cl
N
N
N
N
N
(IL 4)
(IL 5)
(IL 6)
[H3CSO4]
N
N
Me
Me
[NBu3Me] [H3CSO4]
[PBu4] Cl
Me
(IL 7)
(IL 8)
(IL 9)
[PF6 ]
[BF4]
Cl
Bu
Bu
Bu
N
N
N
(IL 10)
(IL 11)
(IL 12)
Fig. 1. Ionic liquids used for immobilization of catalysts.
system (Eq. (1)). Identification of both isomers was performed by
comparing 1H and 13C NMR spectra with the literature data.
investigated. Three vinylsilanes, differing in the character of sub-
stituents at silicon, were chosen for homocoupling tests. For the
sake of comparison, tests were also performed in a homogeneous
system using a small volume of xylene (comparable with the vol-
ume of ionic liquid used) as a catalyst solvent. The results were
summarized in Fig. 2a–c.
On the basis of experiments performed, it has been established
that the reaction in the presence of catalyst 6 proceeds effectively
while maintaining oxygen-free atmosphere. Moreover, since the
reaction proceeded in each case in a biphasic system and phases
were only partially miscible at temperatures applied, it was neces-
sary to stir the reaction mixture vigorously. Inadequate stirring or
the lack of stirring can lead to considerably lower yields and/or the
irreproducibility of results.
The results obtained while using most of ionic liquids were com-
parable to those observed in homogeneous systems. However, in
the case of homocoupling of triethoxyvinylsilane (1b) the reaction
performed in ionic liquid led to higher selectivities. The isomer
ratio [7b]:[8b] for the reaction performed in xylene was equal to
18:1, while for the reactions proceeding in the presence of ionic
liquid-immobilized catalyst the isomer ratio ranged between 21:1
and 45:1. In the presence of ionic liquids IL 6 and IL 8 the reac-
tion proceeds fully selectively and exclusive formation 7b was
observed.
SiR3
SiR3
[Ru] / IL
+
SiR3
1 (a - f)
R3Si
7 (a - f)
SiR3
8 (a - f)
SiR3 = SiMe2Ph (a), Si(OEt)3 (b), Si(Oi Pr)3 (c), Si(OSiMe3)3 (d),
SiMe(OSiMe3)2 (e), SiPh(OSiMe3)2 (f)
(1)
Homocoupling of vinylsilanes
Comparative investigation performed for catalysts (2–6) immo-
bilized in selected ionic liquid (IL 3) enabled identification of
the most efficient catalytic systems under the reaction conditions
tested. Selected results were collected in Table 1.
The highest catalytic activity was observed in the case of the
hydride complex [RuHCl(CO)(PCy3)2] (6) The above complex makes
it possible to obtain almost quantitative conversion of all vinylsi-
lanes tested and to form E-1,2-bis(silyl)ethene with a very high
selectivity. High yields, but lower selectivities, were obtained in
the presence of [RuHCl(CO)(PPh3)3] (5). Other complexes showed
both poor activity and selectivity. To perform further optimization
of catalytic system, the activity of the complex [RuHCl(CO)(PCy3)2]
(6) immobilized in
a large variety of ionic liquids was
Table 1
Catalytic activity of ruthenium complexes (2–6) immobilized in IL 3 in homocoupling of vinylsilanes (1a–f).
Vinylsilane SiR3
Catalyst
Conv. of 1 [%]
Yield of 7 [%]
Yield of 8 [%]
By-products [%]
SiMe2Ph
SiMe2Ph
SiMe2Ph
SiMe2Ph
2
3
4
5
6
6
6
6
6
6
25 (51)a
15 (19)a
13 (15)a
86 (93)a
97
96
93
90
96
Traces
12 (15)a
Traces
69 (74)a
95
92
92
90
92
–
30b
–
2 (3)a
–
8b
–
14 (15)a
SiMe2Ph
2
5
1
0
5
3
–
–
–
–
–
–
Si(OEt)3
Si(OiPr)3
Si(OSiMe3)3
SiMe(OSiMe3)2
SiPh(OSiMe3)2
90
87
Reaction conditions: [RuHCl(CO)(PCy3)2] (2.74 × 10−5 mol), ionic liquid (0.2 g), vinylsilane (1.37 × 10−3 mol), dodecane (internal standard) (0.05 mL), 130 ◦C, 5 h, vigorous
stirring, argon.
a
24 h.
b
PhMe2SiOSiMe2Ph and traces of higher siloxanes.

264
S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
The literature on ionic liquids points to essential importance of
their purity as it substantially affects the course of catalytic reac-
tions [54,66–68]. Ionic liquids used in our study were not subjected
to additional purification. It has been found that the presence from
100 ppm to 1% of water (which is the limit of water content declared
by the manufacturer) does not affect the stability of ruthenium
hydride complex. Ionic liquids IL 1–IL 8 and IL 10–IL 12 used for
immobilization of hydride complex 6 make it possible to obtain
the product of phenyldimethylvinylsilane homocoupling with high
yields and high selectivities.
Homocoupling of silane 1a proceeds with exclusive forma-
tion of bis(silyl)ethenes. No other organosilicon compounds were
detected. It was therefore concluded that the Si Me i Si Ph bonds
are stable in the presence of catalyst 6 and all ionic liquid tested. In
most of ionic liquids used, homocoupling of H2C CHSi(OEt)3 (1b)
and H2C CHSiMe(OSiMe3)2 (1e) proceeded stereoselectively and
lead to high yields of expected products. However, the vinylsilanes
containing Si
O C (1b,c) or Si O Si (1d,e,f) bonds in the presence
of ionic liquid IL 9 and silanes 1b and 1c in the presence of ionic
liquid IL 5 are unstable under the reaction conditions (130 ◦C) and
undergo undesirable processes of condensation with the forma-
tion of di-, tri- and traces of higher siloxanes. The effectiveness of
condensation depends on water content in ionic liquid. Moreover,
[PBu4]Cl (IL 9) can play the role of phase transfer catalyst in conden-
sation of alkoxysilanes [69] and very likely also in condensation of
vinylsiloxane 1e, as this side-reaction does not occur in the absence
of phosphonium salt. When the ionic liquid IL 9 was subjected to
drying by heating at 80 ◦C under dynamic vacuum (1 mmHg) for
72 h, the yield of condensation of 1e (conditions as indicated in
Fig. 2c) considerably decreased from 60% (without drying) to 21%.
To understand the differences in the effectiveness of homocou-
pling in the systems containing different ionic liquids, the process
of immobilization of complex 6 in selected ionic liquids has been
investigated. The experiments were carried out using IR spec-
troscopy, because the complex contains carbonyl ligand that is
characterized by a high intensity of ꢀC stretching vibrations as
O
well as by the known dependence of the frequency of the carbonyl
peaks on the electron density on the metal [70]. We expected that
putative changes in the coordination sphere of catalyst 6 during
its immobilization would result in a frequency shift of the car-
bonyl peak. The investigation was conducted using ionic liquids
that enabled effective performance of the process (IL 3, IL 7) and
ionic liquid that permitted obtaining moderate yields (e.g., IL 11).
Moreover, ionic liquid IL 9 was selected, in the presence of which
no reaction products were formed. The IR (ATR) spectra of com-
plex 6, complex 6 immobilized in 0.2 g of selected ionic liquid and
complex 6 immobilized in the mentioned ionic liquid and heated
at 130 ◦C for 3 h were recorded at room temperature in the absence
of vinylsilane. The obtained data indicate no changes in the band
at 1904 cm−1 assigned to ␯
in the complex 6 and complex 6
(C O)
immobilized in IL 3 (Fig. 3), IL 7 and IL 11 (supplementary data).
The absence of a shift in the band at 1904 cm−1 observed for the
complex 6 immobilized in ionic liquids IL 3, IL 7 and IL 11 indi-
cates that the coordination sphere did not undergo modification.
Therefore, it can be concluded that ionic liquids play only the role
of catalyst solvents in the systems studied.
Measurements carried out using hydride complex (6) immo-
bilized in IL 9 revealed 51% conversion of [RuHCl(CO)(PCy3)2]
(ꢀ(C O) = 1904 cm−1) and the appearance of a new complex charac-
terized by the absorption band at ꢀ(C O) = 1935 cm−1 (Fig. 4) which
suggested the formation of [RuCl2(CO)(PCy3)2] (9) [71].
Fig. 2. Conversion of vinylsilane and yields of products
7 in homocou-
The immobilization of complex 6 in IL 9 was also studied in
similar equimolar experiment performed in DMF and monitored by
1H and 31P NMR. The disappearance of signals at ı = −20.76 ppm (1H
NMR) and ı = 40.4 ppm (31P NMR) was observed, which indicates
a complete decomposition of 6 after 1 h heating at 130 ◦C in the
pling of H2C CHSiMe2Ph (1a) (Fig. 2a), H2C CHSi(OEt)3 (1b) (Fig. 2b) and
H2C CHSiMe(OSiMe3)2 (1e) (Fig. 2c) catalyzed by complex 6 dissolved in xylene
or immobilized in ionic liquids IL 1–IL 12. Reaction conditions: [RuHCl(CO)(PCy3)2]
(2.74 × 10−5 mol), IL (0.2 g), vinylsilane (1.37 × 10−3 mol), dodecane (internal stan-
dard) (0.05 mL), 130 ◦C, 5 h, argon.

S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
265
Fig. 3. IR (ATR) spectra. (1) Complex 6 immobilized in IL 3; (2) Complex 6 immobilized in IL 3 and heated at 130 ◦C for 3 h. Conditions: [RuHCl(CO)(PCy3)2] (2.74 × 10−5 mol),
IL 3 (0.2 g), 130 ◦C, argon.
presence of 20 eq. of IL 9. The formation of complex 9 was confirmed
by the appearance of a new signal at ı = 37.9 ppm in the 31P NMR
spectrum. The above experiments clearly explain why no effective
homocoupling of any reactant used was observed in the presence
of the catalyst 6 immobilized in IL 9.
A significant factor capable of causing differences in the effec-
tiveness of homocoupling carried out in the biphasic system
is the solubility of vinylsilanes in ionic liquid. Therefore, the
solubility of vinylsilanes 1a 1b and 1e in the selected ionic liquids
was investigated. Solubility measurement was performed for IL 3
and IL 7 for which the process proceeded effectively as well for IL
5 and IL 8 for which differences in the process effectiveness were
observed depending on the reactant employed. The solubility was
measured according to the method described in the literature [66].
The obtained results are presented in Fig. 5.
Results of the measurements point to considerable differences
in the solubility of particular vinylsilanes in different ionic liquids
and in the solubilities of different vinylsilanes in a particular ionic
liquid. Moreover, they show that solubility is not the only factor
Fig. 4. IR (ATR) spectra. (1) Complex
6 immobilized in IL 9; (2) complex 6
immobilized in IL 9 and heated at 130 ◦C for 3 h. Conditions: [RuHCl(CO)(PCy3)2]
(2.74 × 10−5 mol), IL 9 (0.2 g), 130 ◦C, argon.
Fig. 5. Solubility of 1a, 1b and 1e in IL 3, IL 5, IL 7 and IL 8 at 130 ◦C.

266
S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
Fig. 7. Homocoupling of phenyldimethylvinylsilane (1a). Recycling of 6 immo-
bilized in IL 3. Conditions: [RuHCl(CO)(PCy3)2] (2.74 × 10−5 mol), IL 3 (0.2 g), 1a
(1.37 × 10−3 mol), dodecane (internal standard) (0.05 mL), 130 ◦C, 5 h, argon.
Fig. 6. Stability of complex 6 immobilized in IL 3, IL 7 and IL 12 under heating at
130 ◦C.
similar in subsequent repetitions, which means that that the cata-
lyst selectivity did not decrease with time on stream.
that decides on the process effectiveness. Despite significant dif-
ferences in the solubility of vinylsilanes in ionic liquids IL 3 and
IL 7, the process proceeds effectively in the presence of both ionic
liquids (see Fig. 2a–c). On the other hand, a very poor solubility of
vinylsilane 1e in IL 5 (0.2 mol%) and in IL 8 (0.1 mol%) can contribute
to the low effectiveness of homocoupling of vinylsilane 1e in the
presence of the above ionic liquids.
To learn more on the stability of catalytic systems used, the
decrease in the catalyst concentration under the reaction condi-
tions (however, in absence of vinylsilanes) was determined for
selected systems. The catalyst concentration was monitored by
observing changes in the intensity of ꢀC O band in IR spectra. Results
shown in Fig. 6 prove a high stability of complex 6 immobilized in
ionic liquids IL 3, IL 7 and IL 12. A particularly high stability was
observed in the presence of IL 3.
To evaluate leaching of the catalyst, post-reaction mixtures were
collected and total content of the metal leached from ionic liq-
uid phase after 10 reaction runs was determined by ICP-MS. The
obtained results show that percentages of ruthenium remaining in
the ionic liquid phase after 10 runs of homocoupling of 1a and 1e
were 87% and 82%, respectively. Therefore, both catalyst leaching
and partial deactivation of the catalyst contribute to the decrease
in the yield.
3.3. Split test
In order to make sure that the catalytic activity origi-
nates from the immobilized catalyst and not from some active
species leached from the ionic liquid, we performed a split
test [72]. The reaction chosen was homocoupling of methyl-
bis(trimethylsiloxy)vinylsilane in the presence of 6 immobilized in
IL 3. One hour after the start of the reaction, half of the upper layer
was decanted under argon (at the conversion of 58%) and trans-
ferred to another reactor. Both reactions were monitored for 5 h
by GC. After 5 h of the reaction, the conversion in the presence of
3.2. Recyclability of the immobilized catalyst
Representative studies on stability of the most active catalytic
system (complex 6 immobilized in IL 3 and IL 7) were per-
formed in a recycling experiment involving the homocoupling of
dimethylphenylvinylsilane. Conversions obtained after 5 h of the
reaction are given in Fig. 7. The values of conversion decrease
slightly in subsequent reaction runs. Conversions obtained after 5 h
of the reaction show that the catalyst 6 can be effectively recycled
up to 12 times without a substantial decrease in the yield of the
reaction product E-1,2-bis(silyl)ethene. The experiment demon-
strated effective recycling of [RuHCl(CO)(PCy3)2] and the total TON
was 554. For catalyst 6 immobilized in IL 7, the total TON was 531
(see supplementary data). For the sake of comparison, the homo-
coupling of 1a was carried out under homogeneous conditions (in
xylene) using 0.17 mol% of complex 6 (i.e. at the concentration
12 times lower than that used in the recycling test). After 24 h
E-1,2-bis(dimethylphenylsilyl)ethene (7a) was observed as the
exclusive product with the yield of 65%, that gives TON equal to 390.
Recycling experiment carried out for the homocoupling of methyl-
bis(trimethylsiloxy)vinylsilane demonstrated effective recycling of
the immobilized catalyst up to 10 times and TON reaching 456 for
IL 3 (Fig. 8) and 435 for IL 7 (see supplementary data).
It is important and worth of emphasizing that in the case
of both reactions for which reproducibility was investigated, i.e.
homocoupling of phenyldimethylvinylsilane and homocoupling
of methylbis(trimethylsiloxy)vinylsilane, the isomer ratio was
Fig. 8. Homocoupling of methylbis(trimethylsilyloxy)vinylsilane (1e). Recycling of
6 immobilized in IL 3. Conditions: [RuHCl(CO)(PCy3)2] (2.74 × 10−5 mol), IL 3 (0.2 g),
1e (1.37 × 10−3 mol), of dodecane (internal standard) (0.05 mL), 130 ◦C, 5 h, argon.

S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
267
[3] E.W. Colvin, Silicon Reagents in Organic Synthesis, Academic Press, London,
1988.
[4] T.-Y. Luh, S.-T. Liu, in: Z. Rappoport, Y. Apeloig (Eds.), The Chemistry of
Organosilicon Compounds, Wiley, Chichester, 1998.
[5] H.F. Sore, W.R.J.D. Galloway, D.R. Spring, Chem. Soc. Rev. 41 (2012) 1845–1866.
[6] Y. Nakao, T. Hiyama, Chem. Soc. Rev. 40 (2011) 4893–4901.
[7] S.E. Denmark, J.H.-C. Liu, Angew. Chem. Int. Ed. 49 (2010) 2978–2986.
[8] S.E. Denmark, J. Org. Chem. 74 (2009) 2915–2927.
[9] S.E. Denmark, C.S. Regens, Acc. Chem. Res. 41 (2008) 1486–1499.
[10] S.E. Denmark, J.D. Baird, Chem. Eur. J. 12 (2006) 4954–4963.
[11] Y. Nakao, A.K. Sahoo, H. Imanaka, A. Yada, T. Hiyama, Pure Appl. Chem. 78 (2006)
435–440.
[12] S.E. Denmark, R.F. Sweis, in: A. de Meijere, F. Diederich (Eds.), Metal-Catalysed
Cross-Coupling Reactions, Wiley-VCH, Weinheim, 2004.
[13] S.E. Denmark, M.H. Ober, Aldrichim. Acta 36 (2003) 75–85.
[14] F. Babudri, G.M. Farinola, V. Fiandanese, L. Mazzone, F. Naso, Tetrahedron 54
(1998) 1085.
[15] S.E. Denmark, S.A. Tymonko, J. Am. Chem. Soc. 127 (2005) 8004–8005.
[16] K. Karabelas, A. Hallberg, Acta Chem. Scand. 44 (1990) 257–261.
[17] C. Thiot, C. Mioskowski, A. Wagner, Eur. J. Org. Chem. 74 (2009) 3219–3227.
[18] Y. Hatanaka, T. Hiyama, J. Org. Chem. 54 (1989) 268–270.
[19] K. Karabelas, A. Hallberg, J. Org. Chem. 54 (1989) 1773–1776.
[20] H.F. Sore, C.M. Boehner, L. Laraia, P. Logoteta, C. Prestinari, M. Scott, K. Williams,
W.R.J.D. Galloway, D.R. Spring, Org. Biomol. Chem. 9 (2011) 504–515.
[21] P. Pawluc, G. Hreczycho, J. Szudkowska, A. Franczyk, B. Marciniec, Appl.
Organomet. Chem. 24 (2010) 853–857.
Fig. 9. Split test. Conditions: [RuHCl(CO)(PCy3)2] (2.74 × 10−5 mol), IL 3 (0.2 g), 1e
(1.37 × 10−3 mol), dodecane (internal standard) (0.05 mL), 130 ◦C, argon.
[22] E. Hagiwara, K.-I. Gouda, Y. Hatanaka, T. Hiyama, Tetrahedron Lett. 38 (1997)
439–442.
[23] X. Meng, T. Yokoi, D. Lu, T. Tatsumi, Angew. Chem. Int. Ed. 46 (2007) 7796–7798.
[24] C. Vercaemst, M. Ide, B. Allaert, N. Ledoux, F. Verpoort, P. Van Der Voort, Chem.
Commun. (2007) 2261–2263.
immobilized complex 6 was 95%, whereas no further progress in
conversion took place in the decanted portion of the upper layer
(Fig. 9). Results of the experiment suggest that catalytic activity
originates from the complex immobilized in ionic liquid.
[25] K. Nakajima, I. Tomita, M. Hara, S. Hayashi, K. Domen, J.N. Kondo, J. Mater. Chem.
15 (2005) 2362–2368.
[26] T. Asefa, M. Kruk, M.J. MacLachlan, N. Coombs, H. Grondey, M. Jaroniec, G.A.
Ozin, J. Am. Chem. Soc. 123 (2001) 8520–8530.
4. Conclusions
[27] B. Marciniec (Ed.), Comprehensive Handbook on Hydrosilylation, Pergamon
Press, Oxford, 1992, pp 192–196.
[28] F. Alonso, R. Buitrago, Y. Moglie, J. Ruiz-Martinez, A. Sepulveda-Escribano, M.
Yus, J. Organomet. Chem. 696 (2011) 368–372.
[29] A. Sato, H. Kinoshita, H. Shinokubo, K. Oshima, Org. Lett. 6 (2004) 2217–2220.
[30] P. Arsenyan, K. Oberte, K. Rubina, S. Belyakov, Tetrahedron Lett. 46 (2005)
1001–1003.
[31] For review see: B. Marciniec, H. Maciejewski, C. Pietraszuk, P. Pawluc, in: B.
Marciniec (Ed.), Hydrosilylation. A Comprehensive Review on Recent Advances,
Springer, Berlin, 2009, pp. 3–51.
[32] B. Marciniec, Coord. Chem. Rev. 249 (2005) 2374–2390.
[33] M. Chauhan, B.J. Hauck, L.P. Keller, P. Boudjouk, J. Organomet. Chem. 645 (2002)
1–13.
[34] R.N. Naumov, M. Itazaki, M. Kamitani, H. Nakazawa, J. Am. Chem. Soc. 134
(2012) 804–807.
[35] M. Suginome, Y. Ito, Chem. Rev. 100 (2000) 3221–3256.
[36] I. Beletskaya, C. Moberg, Chem. Rev. 106 (2006) 2320–2354.
[37] M. Suginome, T. Matsuda, T. Ohmura, A. Seki, M. Murakami, in: R. Crabtree,
D.M.P. Mingos (Eds.), Comprehensive Organometallic Chemistry III, vol. 10,
Elsevier, Oxford, 2007, pp. 725–787.
[38] H.E. Burks, J.P. Morken, Chem. Commun. (2007) 4717–4725.
[39] C. Pubill-Ulldemolins, A. Bonet, C. Bo, H. Gulyas, E. Fernandez, Org. Biomol.
Chem. 8 (2010) 2667–2682.
Comprehensive screening of a number of ruthenium com-
plexes and a variety of commercially available ionic liquids
enabled determination of the optimum conditions for high
yield stereoselective syntheses of E-1,2-bis(silyl)ethenes car-
ried out in ionic liquids as reaction media. [RuHCl(CO)(PCy3)2]
tolerates well ammonium-, pyridinium- and imidazolium-
based ionic liquids tested, including chloride derivatives
even at 130 ◦C. [RuHCl(CO)(PCy3)2] immobilized in 1-butyl-3-
methylimidazolium bis(trifluoromethylsulphonyl)imide (IL 3)
and 1,2,3-trimethylimidazolium methylsulphate (IL 7) exhibit
catalytic activity in regio- and stereoselective homocoupling of
vinylsilanes and can be recycled up to 10 times in homocoupling
of methylbis(trimethylsilyloxy)vinylsilane and up to 12 times in
homocoupling of phenyldimethylvinylsilane without a significant
change in catalytic performance. The effectiveness of the catalytic
system is determined by several factors including stability of the
catalyst and solubility of vinylsilanes in ionic liquids under the
reaction conditions. The developed synthesis procedures enables
a simple separation of products from ionic liquid by decantation.
The source of catalytic activity is the catalyst immobilized in ionic
liquid phase as concluded from results of a split test.
[40] B. Marciniec, C. Pietraszuk, in: R.H. Grubbs (Ed.), Handbook of Metathesis,
Wiley-VCH, Weinheim, 2003, pp. 463–490.
[41] B. Marciniec, C. Pietraszuk, Curr. Org. Chem. 7 (2003) 691–735.
[42] C. Pietraszuk, B. Marciniec, S. Rogalski, H. Fischer, J. Mol. Catal. A: Chem. 240
(2005) 67–71.
[43] A. Keller, R. Matusiak, J. Mol. Catal. A: Chem. 104 (1996) 213–219.
[44] M. Majchrzak, B. Marciniec, Y. Itami, Adv. Synth. Catal. 347 (2005) 1285–1294.
[45] Y. Wakatsuki, H. Yamazaki, M. Nakano, Y. Yamamoto, J. Chem. Soc. Chem. Com-
mun. (1991) 703–704.
Acknowledgement
[46] B. Marciniec, C. Pietraszuk, J. Chem. Soc. Chem. Commun. (1995) 2003–2004.
[47] B. Marciniec, C. Pietraszuk, Organometallics 16 (1997) 4320–4326.
[48] T. Welton, Coord. Chem. Rev. 248 (2004) 2459–2477.
[49] T.J. Geldbach, P.J. Dyson, Metal Catalysed Reactions in Ionic Liquids, Springer,
Berlin, 2005.
Financial support from the Ministry of Science and Higher
Education (Poland) (project No. N N204 165436) is gratefully
acknowledged.
[50] Z.C. Zhang, Adv. Catal. 49 (2006) 153–238.
[51] R. Giernoth, Top. Curr. Chem. 276 (2007) 1–23.
Appendix A. Supplementary data
[52] V.I. Parvulescu, C. Hardacre, Chem. Rev. 107 (2007) 2615–2665.
[53] S. Liu, J. Xiao, J. Mol. Catal. A: Chem. 270 (2007) 1–43.
[54] H. Olivier-Bourbigou, L. Magna, D. Morvan, Appl. Catal. A: Gen. 373 (2010) 1–56.
[55] J.P. Hallett, T. Welton, Chem. Rev. 111 (2011) 3508–3576.
[56] J. Durand, E. Teuma, M. Gomez, C. R. Chim. 10 (2007) 152–177.
[57] L.A. Muller, J. Dupont, R.F. de Souza, Macromol. Rapid Commun. 19 (1998)
409–411.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.apcata.
2012.08.038.
[58] R.F. de Souza, V. Rech, J. Dupont, Adv. Synth. Catal. 344 (2002) 153–155.
[59] P.J. Dyson, D.J. Ellis, D.G. Parker, T. Welton, Chem. Commun. (1999) 25–26.
[60] P.J. Dyson, D.J. Ellis, W. Henderson, G. Laurenczy, Adv. Synth. Catal. 345 (2003)
216–221.
References
[1] T.H. Chan, I. Fleming, Synthesis (1979) 761–786.
[2] W.P. Weber, Silicon Reagents for Organic Synthesis, Springer, Berlin, 1983.
[61] P.J. Dyson, Appl. Organomet. Chem. 16 (2002) 495–500.

268
S. Rogalski et al. / Applied Catalysis A: General 445–446 (2012) 261–268
˙
[62] P. Zak, C. Pietraszuk, B. Marciniec, J. Mol. Catal. A: Chem. 289 (2008) 1–8.
[63] P.S. Hallman, T.A. Stephenson, G. Wilkinson, Inorg. Synth. 12 (1970) 237.
[64] C.S. Yi, D.W. Lee, Y. Chen, Organometallics 18 (1999) 2043–2045.
[65] N. Ahmad, J.J. Levinson, S.D. Robinson, M.F. Uttely, Inorg. Synth. 15 (1974)
45–64.
[68] K.R. Seddon, A. Stark, M.J. Torres, Pure Appl. Chem. 72 (2000) 2275–2287.
[69] H. Wang, Z.J. Duan, S. Raychaudhuri, Yazaki Corporation, US 7,329,716 (2008).
[70] P.S. Braterman, Metal Carbonyl Spectra, Academic Press, New York, 1975.
[71] S.D. Drouin, D. Amoroso, G.P.A. Yap, D.E. Fogg, Organometallics 21 (2002)
1042–1049.
[66] A. Stark, M. Ajam, M. Green, H.G. Raubenheimer, A. Ranwell, B. Ondruschka,
Adv. Synth. Catal. 348 (2006) 1934–1941.
[72] R.A. Sheldon, M. Wallau, I.W.C.E. Arends, U. Schuchardt, Acc. Chem. Res. 31
(1998) 485–493.
[67] Sigma-Aldrich Co., ChemFiles 5 (6) (2005) 8–9.