Ruthenium carbonyl-catalysed Si-heteroatom X coupling (X = S, O, N)

Article abstract of DOI:10.1016/j.jorganchem.2012.07.024

Ru₃(CO)₁₂ has been shown to catalyse the coupling of silanes with thiols, alcohols and amines with turnover number (TON) and turnover frequency (TOF) of up to 200 and 50 h^-1 at 80 °C. IR, NMR and mass spectroscopic studies have identified a ruthenium dimer complex, [Ru(CO)₄(SiEt₃)]₂ as a likely resting state of the catalyst. A mechanism involving this complex has been proposed for the silicon-thiol coupling process.

Full text of DOI:10.1016/j.jorganchem.2012.07.024

Journal of Organometallic Chemistry 717 (2012) 9e13
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Ruthenium carbonyl-catalysed Sieheteroatom X coupling (X ¼ S, O, N)
*
Chun Keong Toh, Hwa Tiong Poh, Ching Si Lim, Wai Yip Fan
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
Ru3(CO)12 has been shown to catalyse the coupling of silanes with thiols, alcohols and amines with
turnover number (TON) and turnover frequency (TOF) of up to 200 and 50 hꢀ1 at 80 ꢁC. IR, NMR and
mass spectroscopic studies have identified a ruthenium dimer complex, [Ru(CO)4(SiEt3)]2 as a likely
resting state of the catalyst. A mechanism involving this complex has been proposed for the siliconethiol
coupling process.
Received 26 March 2012
Received in revised form
9 July 2012
Accepted 16 July 2012
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Ruthenium dodecacarbonyl
Homogeneous catalysis
Siliconeheteroatom coupling
Ruthenium silyl intermediates
1. Introduction
The various couplings of SieN bonds from silanes and amines
resulting in the production of iminosilanes, silazanes and dia-
Organosilanes containing SieH bonds have been used exten-
sively in synthetic organic chemistry for many years. Hydro-
silylation of unsaturated bonds such as alkenes [1], alkynes [2] and
carbonyls [3] is one of the more important processes involving
organosilanes. Transition metal complexes containing iron [4,5],
tungsten [6], molybdenum [7], manganese [8,9]], rhenium [10,11],
rhodium [12], silver [13], nickel [14], and most recently ruthenium
[2,15,16] have been used to catalyse such processes.
Silane hydrolysis and alcoholysis forming silanol, silyl ether and
siloxane [17] demonstrate further the versatility of organosilanes as
valuable substrates. Ruthenium carbonyl complexes have also been
reported to generate hydrogen from a silane/water mixture [17,18]
and from formic acid [19]. The hydrogen gas produced can be used
in a variety of reactions, of which one of the most well-studied
reaction involves the hydrogenation of unsaturated compounds
catalysed by palladium (II) [20] or iridium (I) [21] complexes. These
transformations are made possible because of the relatively weaker
SieH bonds available for activation as compared to CeH bonds.
Silicon coupling with other heteroatoms such as sulphur and
nitrogen are, however, less widely studied. Besides organosilanes,
organosulfur derivatives of silanes can also be used to protect
carbonyl groups selectively [22]. However, methods of their prep-
aration require air-sensitive catalysts such as B(C6H5)3 [23], and in
some cases, sulphur poisoning is observed leading to much lower
efficiency achieved in the catalytic system [24].
minosilanes [16] have also been reported. However, these reactions
were not as extensively explored although they provide much
insight into the role of amine ligands in processes such as alkene
polymerisation [25] and alkene metathesis [26]. Of recent interest
are the formation of direct SieN bonds via the addition of silanes to
metaleimido (M ¼ NR) complexes [27e30], which provides novel
pathways to synthesize potential catalysts for metathesis reactions.
Ruthenium dodecacarbonyl Ru3(CO)12 has been reported to
activate SieH bonds [31] to form dimeric ruthenium silyl complex
of formula (R3Si)RueRu(SiR3). Chatani et al. [32] reported the
activation of benzylic CeH bonds by Ru3(CO)12 in the presence of
silanes to afford benzylsilanes, while Madalska et al. [33] was able
to utilise Ru3(CO)12 to catalyse the silylation of silanols with
vinylsilanes to afford alkenes and siloxanes.
In this work, we have found that Ru3(CO)12 acts as a versatile
and efficient catalyst for Sieheteroatom (S, N and O) coupling with
high turnover numbers. The scope of the catalysis as well as the
kinetics and detection of reactive intermediates have been inves-
tigated using FTIR and NMR spectroscopy. A ruthenium dimer,
[Ru(CO)4(SiEt3)]2, has been identified as the likely resting state of
the catalyst and a mechanism for silaneethiol coupling based on
this dimer has been proposed.
2. Experiment
All chemicals were used as purchased. All reactions were carried
out under vacuum conditions unless otherwise stated. Proton
nuclear magnetic resonance (1H NMR) spectra were obtained on
* Corresponding author. Fax: þ6567791691.
E-mail address: chmfanwy@nus.edu.sg (W.Y. Fan).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.024

10
C.K. Toh et al. / Journal of Organometallic Chemistry 717 (2012) 9e13
Table 2
a Bruker Avance 500 (AV500) spectrometer at room temperature.
The chemical shifts were recorded relative to tetramethylsilane for
spectra taken in CDCl3. Infrared (IR) spectra were obtained on
a Shimadzu IR Prestige-21 Fourier-transformed infrared spec-
trometer (1000e4000 cmꢀ1, 1.0 cmꢀ1 resolution, 4 scans co-added
for spectra averaging) using a 0.05 mm path-length CaF2 cell.
Hydrogen gas was detected using a residual mass analyser (Balzer
Prisma QMS 220) where the signal at m/e ¼ 2 was monitored over
time. The headspace above the reaction mixture was sampled
before and after reaction. 3 ml of the gas was injected directly into
the residual gas analyser using a syringe. A known pressure sample
of pure hydrogen gas was also injected for calibration and hence
used to calculate the amount of hydrogen present in the mixture.
Coupling between silanes and various substrates using 1 mol% Ru3(CO)12 at 80 ꢁC,
4 h.
Entry Silane
Substrate
Producta
TONb
TOF/hrꢀ1c
1
2
3
4
5
6
7
8
Et3SiH
C12H25SH
C8H17SH
PhCH2SH
C12H25SeSiEt3
C8H17SeSiEt3
PhCH2SeSiEt3
100 (73) 25
100 (80) 25
100
100
25
25
o-MeC6H4SH o-MeC6H4SeSiEt3
C2H5OH
iPrOH
C5H11OH
C6H5OH
C8H17NH2
PhNH2
C2H5OeSiEt3
iPrOeSiEt3
C5H11OeSiEt3
C6H5OeSiEt3
C8H17NHeSiEt3
PhNHeSiEt3
PhMeNeSiEt3
C12H25SeSiHPh2
PhCH2SeSiHPh2
100 (82) 25
100
100
100
25
25
25
9
100 (70) 25
10
11
12
13
14
15
16
17
18
19
20
21
22
23
100
100
78
69
73
70
65
58
65
57
62
55
51
35
25
25
13
12
12
12
11
10
9
8
9
8
7
PhMeNH
Ph2SiH2 C12H25SH
PhCH2SH
o-MeC6H4SH o-MeC6H4SeSiHPh2
2.1. Silane coupling reactions using Ru3(CO)12
C2H5OH
C5H11OH
PhNH2
C12H25SH
PhCH2SH
C2H5OeSiHPh2
C5H11OeSiHPh2
PhNHeSiHPh2
C12H25SeSiPh3
PhCH2SeSiPh3
In a typical reaction, Et3SiH (1.56 mmol) and the various
substrates (1.56 mmol) were added to a benzene or toluene solu-
tion containing Ru3(CO)12 (0.01 g, 0.0156 mmol). The mixture was
heated in vacuo at 80 ꢁC for 4 h. For optimization studies, various
conditions as shown in Table 1 have been used. After reaction, NMR
was taken with CDCl3 as the solvent [34]. For isolated yield deter-
mination, the catalytic mixture containing selected products as
Ph3SiH
o-MeC6H4SH o-MeC6H4SeSiPh3
C2H5OH
C5H11OH
PhNH2
C2H5OeSiPh3
C5H11OeSiPh3
PhNHeSiPh3
5
a
Ref. [34].
b
described in Table
2 was concentrated and passed through
NMR integration. Percentage in parentheses represents the isolated yield w.r.t.
NMR yield.
a column of silica gel 60 of dimension Ø14 ꢂ 180 mm using a 1:1
c
Reaction time : Et3SiH (4 h), Ph2SiH2(6 h) and Ph3SiH (7 h).
mixture of hexane and chloroform.
1H NMR of products (CDCl3, 300 MHz): C12H25SeSiEt3
d
2.47
(2H, t); C8H17SeSiEt3 d 2.45 (2H, t); PhCH2SeSiEt3 d 4.88 (2H, s); p-
3. Results and discussion
Me(C6H4)SeSiEt3
iPrOeSiEt3 4.00 (1H, m); C5H11OeSiEt3
1.81 (1H, t); PhNHeSiEt3
2.93 (3H, s); C12H25SeSiPh3
4.82 (2H, s); p-Me(C6H4)SeSiPh3
d
3.10 (3H, s); C2H5OeSiEt3
d
3.69 (2H, q);
3.59 (2H, t);
3.33 (1H, s);
d 2.44 (2H, t);
d
d
A preliminary study using a 1:1 mixture of Et3SiH and dodeca-
nethiol as the substrates has been carried out in order to optimise
the experimental conditions for efficient coupling (see Table 1). A
temperature of 80 ꢁC over 4 h using 1% mol loading of Ru3(CO)12
was sufficient for a full conversion (turnover number TON ¼ 100,
turnover frequency ¼ 25 hꢀ1) of the substrates into the silylth-
ioether, C12H25SeSiEt3 (Table 1, Entry 1). No coupling was observed
in the absence of Ru3(CO)12 while heating the reaction mixture to
more than 80 ꢁC did not increase the coupling rate significantly. Full
conversion can only be achieved after 24 h under lower tempera-
ture conditions (<40 ꢁC). A smaller Ru3(CO)12 mol loading of 0.2%e
0.8% also lengthened the catalysis duration to more than 8 h.
Interestingly the catalysis can be carried out in air or in vacuo with
similar efficiency. However, the efficiency of the coupling reaction
decreases if instead of heating, broadband irradiation was used at
room temperature. A higher silane to thiol ratio of 1.5:1 afforded
better TOF of > 35 hꢀ1 compared to the reverse case of using more
thiol to silane. As depicted in Scheme 1, hydrogen gas is expected to
be generated and indeed, on-line mass spectrometric detection of
the headspace above the solution mixture has recorded its pres-
ence at m/e ¼ 2 (see Fig. 1). By calibration with a known H2 pres-
sure, the yield of the gaseous product has been determined to be
85% ꢃ 20% compared to the silylthioether.
C8H17NHeSiEt3
PhMeNeSiEt3
PhCH2SeSiPh3
d
d
d
d
d
3.10 (3H, s);
C2H5OeSiPh3
PhNHeSiPh3
d
3.87 (2H, q); C5H11OeSiPh3
3.28 (1H, s); C12H25SeSiHPh2
d
4.07 (2H, t);
d
d 2.57 (2H, m);
PhCH2SeSiPh2H
d
4.85 (2H, s); p-Me(C6H4)SeSiPh2H
3.76 (2H, q); C5H11OeSiHPh2 3.88 (2H, m);
d 3.41 (1H, s).
d 3.10 (3H, s);
C2H5OeSiHPh2
d
d
PhNHeSiHPh2
2.2. Synthesis of [(Et3Si)Ru(CO)4]2
Ru3(CO)12 (0.01 g, 0.0165 mmol) was dissolved in benzene and
refluxed with Et3SiH (2.34 mmol) for 2 h until a reddishebrown
solution was obtained.
yCO/cmꢀ1: 2042(m), 2017(s), 2006(w).
Table 1
Optimization of the experimental conditions for the coupling of triethylsilane with
dodecanethiol using [Ru] catalyst. Unless stated otherwise, the reactions were
carried out in air with 1% catalyst mol loading using 1:1 silane/thiol mol ratio in
toluene solvent.
Complex
Experimental conditions
TON
TOF/hrꢀ1
As haloruthenium carbonyls such as Ru2(CO)4(PPh3)2Br4,
Ru2(CO)6Br4 and Ru2(CO)6I4 are known to activate SieH bonds [18],
we have prepared these complexes using reported methods [35] for
the SieS coupling reaction. However the coupling is found to
Ru3(CO)12
80 ꢁC, 4 h
100
65
100
100
32
25
33
25
25
8
80 ꢁC, 2 h
80 ꢁC, 8 h
80 ꢁC, 4 h, vacuum
25 ꢁC, 4 h
proceed less effectively for each of them compare to Ru3(CO)12
.
80 ꢁC, 8 h, 0.5% mol loading
25 ꢁC, 4 h, 300e800 nm photolysis
80 ꢁC, 4 h, silane/thiol ¼ 1.5
80 ꢁC, 4 h, thiol/silane ¼ 1.5
80 ꢁC, 4 h
180
22
100
50
55
52
23
6
25
13
15
13
13
Ru3(CO)12
R'SH
R3Si SR'
R SiH
H2
Ru2(CO)4(PPh3)2Br4
Ru2(CO)6Br4
Ru2(CO)6I4
+
3
+
80 ꢁC, 4 h
Toluene, 80°C, 4hrs
80 ꢁC, 4 h
52
Scheme 1. Silaneethiol coupling catalysed by Ru3(CO)12.

C.K. Toh et al. / Journal of Organometallic Chemistry 717 (2012) 9e13
11
Based on the optimization studies, the catalytic conditions have
been fixed at 80 ꢁC, 4 h and 1% mol loading of Ru3(CO)12 for further
studies with different substrates. Table 2 shows the various
coupling reactions of triethylsilane that have been carried out on
with thiol, amine and alcohol substrates. In general, all three types
of coupling SieS, SieN and SieO take place with similar TOF effi-
ciency under the same conditions. Based on the TOF, it was found
that thiols undergo silane coupling slightly more effectively, fol-
lowed by alcohols and amines, and with the aliphatic substrates
being more reactive than aromatic substrates. When bulkier silanes
were used, a 2e3 times decrease in the rate of coupling with all
three types of substrates was observed. Full conversion can still be
achieved for all substrates upon prolonging the reaction time to 6 h
for Ph2SiH2 and a minimum of 7 h for Ph3SiH.
Fig. 1. Gaseous mass spectra taken of the headspace content of the coupling reaction
between Et3SiH and dodecanethiol catalysed by Ru3(CO)12. The peak labelled ’after
reaction’ corresponds to m/e ¼ 2.
3.1. Reactive intermediates and mechanism
The detection and identification of reactive intermediates
using FTIR, NMR and mass spectroscopic techniques have been
Fig. 2. IR, NMR and ESI spectra of Ru3(CO)12 and Et3SiH reaction in toluene. $Ru2(CO)8(SiEt3)2 nCO (cmꢀ1): 2042, 2017, 2006. *H2Ru3(CO)10 nCO (cmꢀ1) 2082, 2067, 2031, 2013. 1H NMR
(CDCl3): ꢀ14.3 ppm belongs to H2Ru3(CO)10. (Lit Value35 ꢀ13.6 ppm). ESI mass: Ru2(CO)8(SiEt3)2 m/e ¼ 659; H2Ru3(CO)10 m/e ¼ 559.

12
C.K. Toh et al. / Journal of Organometallic Chemistry 717 (2012) 9e13
CO
Ru
CO
OC
OC
CO
Ru
OC
OC
OC
CO
CO
Et3SiH
Ru
Ru3(CO)12
Et3Si
SiEt3
+
+
OC Ru
OC
Ru CO
CO
CO
CO
OC
CO
H
H
Scheme 2. Ru2(CO)8(SiEt3)2 and H2Ru3(CO)10 complexes.
carried out in order to provide some insights into the mechanism
of the coupling reactions. We have chosen the SieS coupling with
dodecanethiol and triethylsilane substrates as the model reac-
tion. For this purpose, the concentration of the ruthenium cata-
lyst has been scaled up in order to generate more intermediates
for characterization. The FTIR spectrum taken of the reaction
Indeed, both the [Ru(CO)4(SiEt3)]2 and H2Ru3(CO)10 complexes
can also be generated in the reaction between Ru3(CO)12 with silane
only, independent of any thiols in the solution. This result would
imply that the hydrogen atoms of the hydride cluster originate from
the silane substrate. The detail mechanism of the formation of both of
these complexes from is probably very complicated but most likely
involves the initial dissociation of Ru3(CO)12 into reactive Ru(CO)4
monomeric units. Both complexes could represent the most
thermodynamically-stable ruthenium silylated and hydride products
upon reactions of Ru(CO)4 with the silane.
While the [Ru(CO)4(SiEt3)]2 could be purified in small yields
(<10%) upon column separation using ethyl acetate as eluant, the
H2Ru3(CO)10 cluster unfortunately decomposed and could not be
recovered. The purified [Ru(CO)4(SiEt3)]2 was then tested as the
catalyst using the same substrates and indeed the silylthioether
product was formed, this time at almost twice the efficiency
compared to Ru3(CO)12. An IR spectrum taken of the mixture upon
completion of catalysis showed that the [Ru(CO)4(SiEt3)]2 bands
mixture containing 5% mol Ru3(CO)12 and
a
1:1
silane:thiol mixture heated for 3 h at 80 ꢁC is shown in Fig. 2. Two
new sets of peaks have appeared at the expense of the initial
Ru3(CO)12 signals at 2061, 2029 and 2009 cmꢀ1. The first set
consisting of a strong nCO band at 2017 cmꢀ1 and 2 weaker peaks
at 2041 cmꢀ1 and 2006 cmꢀ1 has been assigned to a dimeric
ruthenium silyl carbonyl complex, [Ru(CO)4(SiEt3)]2 based on
previous literature [31]. Each ruthenium atom carries a silyl
ligand which is oriented trans to each other (Scheme 2). The
reduced number of carbonyl bands observed in the spectrum is
indicative of the highly-symmetrical nature of the complex. An
ESI mass spectrum recorded of the mixture shows a cluster of
peaks centred at m/e ¼ 659 which matches the molecular ion
mass of the ruthenium dimer.
remained intact albeit at
a lower intensity. Interestingly,
[Ru(CO)4(SiEt3)]2 was able to catalyse silane coupling with amines
and alcohols, also at a higher rate compared to Ru3(CO)12. The
results shown here appear to point to [Ru(CO)4(SiEt3)]2 acting as an
active catalyst or more likely a resting state of the active catalyst in
these coupling processes.
Further studies of the mechanism were carried out whereby
Ru3(CO)12 was allowed to react with dodecanethiol only. The
reaction resulted in the formation of ruthenium thiolate clusters
such as HRu3(CO)9(C12H25S) and HRu3(CO)10(C12H25S) [37] as
The second set of nCO peaks (2082 cmꢀ1, 2067 cmꢀ1, 2031 cmꢀ1
,
2013 cmꢀ1) are due to a ruthenium carbonyl hydride cluster
H2Ru3(CO)10 [36]. A 1H NMR spectrum recorded of the mixture
showed a hydride signal at ꢀ14.3 ppm, which is attributed to the
equivalent bridging hydrides of the cluster. Similarly the mass
spectrum showed the expected molecular ion cluster of peaks at
m/e ¼ 559 together with the fragmentation patterns consistent
with sequential losses of the CO ligands.
CO
OC
OC
OC
HSR
H2
Ru
Ru
Et3Si
SiEt3
CO
CO
CO
OC
Step 1
Step
4
CO
CO
OC
OC
H
SR
Ru
OC
H
SiEt3
Ru
OC
OC
OC
Ru
Et3Si
SiEt3
CO
Ru
Et3Si
H
CO
CO
CO
OC
CO
OC
CO
Step
2
Step
3
CO
OC
OC
Ru
Ru
H
Et3Si
RS SiEt3
CO
HSiEt3
CO
OC
CO
Scheme 3. Proposed mechanism of the silaneethiol coupling reaction.

C.K. Toh et al. / Journal of Organometallic Chemistry 717 (2012) 9e13
13
indicated by the FTIR spectrum obtained after 4 h of reaction at
References
80 ꢁC. However further heating with added silane and the
remaining thiol did not produce any silylthioether, thus indicating
that these complexes are probably not related to the active catalytic
species. It is also reasonable to assume that the active species would
originate from the initial reaction of ruthenium carbonyl with
silanes, since it has to undergo subsequent coupling with all three
different substrates (thiol, amines and alcohol) to generate the
desired product.
[1] J. Tsuji, M. Hara, K. Ohno, Tetrahedron 30 (1974) 2143e2146.
[2] C.S. Yi, J. Organomet, Chem. 696 (2010) 76e80.
[3] Z. Mao, B.T. Gregg, A.R. Cutler, J. Am. Chem. Soc. 117 (1995) 10139e10140.
[4] R.H. Morris, Chem. Soc. Rev. 38 (2009) 2282e2291.
[5] N.S. Shaikh, K. Junge, M. Beller, Org. Lett. 9 (2007) 5429e5432.
[6] A.C. Fernandes, R. Fernandes, C.C. Romão, B. Royo, Chem. Comm. (2005)
213e214.
ꢀ
[7] A. Ga˛dek, T. Szymanska-Buzar, Polyhedron 25 (2006) 1441e1448.
[8] S.U. Son, S. Paik, Y.K. Chung, J. Mol. Catal. A: Chem. 151 (2000) 87e90.
[9] M.D. Cavanaugh, B.T. Gregg, A.R. Cutler, Organometallics 15 (1996)
2764e2769.
[10] M.M. Abu-Omar, G. Du, Organometallics 25 (2006) 4920e4923.
[11] H. Dong, H. Berke, Adv. Synth. Catal. 351 (2009) 1783e1788.
[12] I. Ojima, M. Nihonyanagi, T. Kogure, M. Kumagai, S. Horiuchi,
K.J. Nakatsugawa, J. Organomet. Chem. 94 (1975) 449e461.
[13] B.M. Wile, M. Stradiotto, Chem. Commun. (2006) 4104e4106.
[14] S. Miriam, C. Praesang, S. Inoue, S. Enthaler, M. Driess, Angew. Chem. Int. Ed.
51 (2012) 399e403.
Inspection of the [Ru(CO)4(SiEt3)]2 structure suggests two
possible dissociation pathways namely the RueCO or RueRu bond
cleavage, in order to provide a vacant site for binding. Because of the
trans effect, the RueCO bond is expected to be weaker and hence
likely to undergo thermal dissociation first. However if the RueRu
bond breaks instead, ruthenium-centred radicals will be formed.
This possibility was investigated by adding a radical scavenger
TEMPO (2 mol equivalent of Ru3(CO)12) into a 1:1 silaneethiol
mixture at 80 ꢁC. However the SieS coupling proceeds just as effi-
ciently, hence ruling out a radical pathway in the mechanism.
A mechanism for the siliconesulphur coupling process is
proposed based on the experimental observations (Scheme 3).
Thermal dissociation of one of the RueCO bonds in [Ru(CO)4(-
SiEt3)]2 would allow a thiol molecule to coordinate to the Ru centre
via the lone pair of the sulphur atom. Oxidation addition of the SeH
bond generates an unstable 7-coordinate Ru complex which would
quickly undergo reductive elimination involving the SR and SiEt3
ligand to produce the silylthioether product. The resultant ruthe-
nium hydride complex has a vacant site onto which a silane
molecule coordinates. Another oxidation addition process
involving the SieH bond followed by H2 elimination would
regenerate [Ru(CO)4(SiEt3)]2 to complete the cycle.
[15] D.V. Gutsulyak, S.F. Vyboishchikov, G.I. Nikonov, J. Am. Chem. Soc. 132 (2010)
5950e5951.
[16] (a) M. Jendras, U. Klingebiel, J. Niesmann, Organosilicon Chemistry V, Wiley
VCH, 2000, pp. 264e269;
(b) S. Abele, G. Becker, U. Eberle, P. Oberprantacher, W. Schwarz, Organo-
silicon Chemistry V, Wiley VCH, 2000, pp. 270e276;
(c) A. Oprea, S. Mantey, J. Heinicke, Organosilicon Chemistry V, Wiley VCH,
2000, pp. 277e280.
[17] E.A. Ison, R.A. Corbin, M.M. Abu-Omar, J. Am. Chem. Soc. 127 (2005)
11938e11939.
[18] S.T. Tan, J.W. Kee, W.Y. Fan, Organometallics 30 (2011) 4008e4013.
[19] M. Czaun, A. Goeppert, R. May, R. Haiges, G.K.S. Prakash, G.A. Olah, Chem-
SusChem 4 (2011) 1241e1248.
[20] J.M. Tour, J.P. Cooper, S.L. Pendalwar, J. Org. Chem. 55 (1990) 3452e3453.
[21] D.W. Wang, D.S. Wang, Q.A. Chen, Y.G. Zhou, Chem. Eur. J. 16 (2010)
1133e1136.
[22] D.A. Evans, L.K. Truesdale, K.G. Grimm, S.L. Nesbitt, J. Am. Chem. Soc. 99 (1977)
5009e5017.
[23] D.J. Harrison, D.R. Edwards, R. McDonald, L. Rosenberg, Dalton Trans. 26
(2008) 3401e3411.
[24] B.P.S. Chauhan, P. Boudjouk, Tetrahedron Lett. 41 (2000) 1127e1130.
[25] P.D. Bolton, P. Mountford, Adv. Synth. Catal. 347 (2005) 355e366.
[26] A.H. Hoveyda, R.R. Schrock, Chem. Eur. J. 7 (2001) 945e950.
[27] S.K. Ignatov, N.H. Rees, A.A. Merkoulov, S.R. Dubberley, A.G. Razuvaev,
P. Mountford, G.I. Nikonov, Chem. Eur. J. 14 (2008) 296e310.
[28] T.I. Gountchev, T.D. Tilley, J. Am. Chem. Soc. 119 (1997) 12831e12841.
[29] U. Burckhardt, G.L. Casty, T.D. Tilley, T.W. Woo, U. Rothlisberger, Organome-
tallics 19 (2000) 3830e3841.
[30] R.G. Howe, C.S. Tredget, S.C. Lawrence, S. Subongkoj, A.R. Cowley,
P. Mountford, Chem. Commun. (2006) 223e225.
[31] S.A.R. Knox, F.G.A. Stone, J. Chem. Soc. A (1969) 2559e2565.
[32] F. Kakiuchi, K. Tsuchiya, M. Matsumoto, E. Mizushima, N. Chatani, J. Am. Chem.
Soc. 126 (2004) 12792e12793.
4. Conclusion
Ruthenium complexes, in particular Ru3(CO)12 have been shown
to catalyse the coupling of silanes with thiols, alcohols and amines
with TOF of upto 50 hꢀ1 at 80 ꢁC. IR, NMR and mass spectroscopic
studies have identified a ruthenium dimer complex, [Ru(CO)4
(SiEt3)]2 as a key intermediate and likely resting state of the cata-
lyst. A mechanism involving this complex has been proposed to
account for the experimental data acquired in this work.
[33] B. Marciniec, P. Pawluc, G. Hreczycho, A. Macina, M. Madalska, Tetrahedron
Lett. 49 (2008) 1310e1313.
[34] M.G. Voronkov, N.N. Vlasova, S.A. Bolshakova, S.V. Kirpichenko, J. Organomet.
Chem. 190 (1980) 335e341.
Acknowledgements
[35] B.F.G. Johnson, R.D. Johnston, J. Lewis, J. Chem. Soc. A (1969) 792e797.
[36] N.E. Leadbeater, J. Lewis, P.R. Raithby, J. Organomet. Chem. 543 (1997)
251e253.
The project was supported by a research grant provided by NUS
143-000-430-112. C.K. Toh acknowledges the support of an NUS
scholarship
[37] O. Gambino, E. Sappa, Matematiche e Naturali 3-4 (1974) 305e317.