Silyl and σ-silane ruthenium complexes: Chloride substituent effects on the catalysed silylation of ethylene

Article abstract of DOI:10.1039/c0dt00065e

Silylation of ethylene by the chlorosilanes HSiMe₂Cl and HSiMeCl₂ was catalysed by the bis(dihydrogen) complex RuH ₂(η²-H₂)₂(PCy₃) ₂ (1). Dehydrogenative silylation leading to the formation of the corresponding vinylsilanes was in competition with hydrosilylation. The rate and selectivity of the reactions were influenced by the number of chloro substituents and the ethylene pressure. A comparative mechanistic study was performed in toluene-d₈ with the two chlorosilanes. Reaction of 1 with an excess of HSiMe₂Cl (10 equiv.) produced the σ-silane complexes RuH₂(η²-H₂)(η²- HSiMe₂Cl)(PCy₃)₂ (2Me₂Cl), RuH ₂(η²-HSiMe₂Cl)₂(PCy ₃)₂ (3Me₂Cl) and the silyl complex RuCl(SiMe₂Cl)(η²-H₂)(PCy₃) ₂ (4Me₂Cl), all characterised by multinuclear NMR spectroscopy. Complexes 2Me₂Cl and 3Me₂Cl adopt a cis configuration for the two bulky phosphine ligands as a result of stabilising SISHA (Secondary Interactions between Silicon and Hydrogen Atoms) interactions. Complex 4Me₂Cl resulted from the stoichiometric reaction of HSiMe₂Cl with 1 producing RuHCl(η²-H ₂)(PCy₃)₂in situ which further reacted with evolution of H₂ and formation of 4Me₂Cl. When reacting 1 with 10 equiv. of HSiMeCl₂, the corresponding complexes 3MeCl ₂ and 4MeCl₂ were detected as well as traces of 2MeCl ₂. The reactivity toward ethylene was then examined. Under catalytic conditions (excess silane in toluene-d₈, ethylene atmosphere) only two compounds could be characterised: free PCy₃ and the new (η⁶-aryl)(disilyl) complexes of the general formula Ru(η⁶-C₆D₅CD₃)(SiMe _3-nCl_n)₂(PCy₃) (6Me _3-nCl_n-d₈, n = 1,2). The X-ray structure of 6MeCl₂ was obtained on a single-crystal at 160 K. When only 2 equiv. of HSiMe₂Cl were added, the ethylene(silyl) complex RuH(SiMe ₂Cl)(C₂H₄)(PCy₃)₂ (7Me₂Cl) was obtained in addition to the organic products resulting from catalytic hydrogenation, hydrosilylation and dehydrogenative silylation, i.e. C₂H₆ (major one), C₂H₃SiMe ₂Cl and C₂H₅SiMe₂Cl. In the case of 2 equiv. of HSiMeCl₂, upon ethylene addition, 7MeCl₂ was formed in minority compared to a new disilyl complex Ru(SiMeCl₂) ₂(PCy₃)₂ (8MeCl₂) characterised by NMR spectroscopy and X-ray diffraction on a single crystal at 160 K. In 8MeCl₂, a formal 14-electron species, stabilisation through two agostic C-H bonds of the cyclohexyl groups was ascertained by DFT calculations.

Full text of DOI:10.1039/c0dt00065e

View Article Online / Journal Homepage / Table of Contents for this issue
This article is published as part of the Dalton Transactions themed issue entitled:
Bridging the gap in catalysis via
multidisciplinary approaches
Guest Editors: Christophe Coperet and Rutger van Santen
Université de Lyon, France and Eindhoven University of Technology, The Netherlands
Published in issue 36, 2010 of Dalton Transactions
Image reproduced with the permission of Dieter Vogt
Articles in the issue include:
Molecular understanding of alkyne hydrogenation for the design of selective catalysts
Javier Pérez-Ramírez, Blaise Bridier and Nuria Lopez
Dalton Trans., 2010, DOI: 10.1039/C0DT00010H
Molecular weight enlargement–a molecular approach to continuous homogeneous catalysis
Michèle Janssen, Christian Müller and Dieter Vogt, Dalton Trans., 2010,
DOI: 10.1039/C0DT00175A
Structure Determination of Zeolites and Ordered Mesoporous Materials by Electron
Crystallography
Xiaodong Zou, Junliang Sun, Dalton Trans., 2010, DOI: 10.1039/C0DT00666A
Metal-Catalyzed Immortal Ring-Opening Polymerization of Lactones, Lactides and Cyclic
Carbonates
Noureddine Ajellal, Jean-François Carpentier, Clémence Guillaume, Sophie M. Guillaume, Marion
Helou, Valentin Poirier, Yann Sarazin and Alexander Trifonov, Dalton Trans., 2010, DOI:
10.1039/C001226B
Visit the Dalton Transactions website for more cutting-edge inorganic and organometallic research
www.rsc.org/dalton

PAPER
www.rsc.org/dalton | Dalton Transactions
Silyl and r-silane ruthenium complexes: Chloride substituent effects on the
catalysed silylation of ethylene†
Se´bastien Lachaize,a,b Laure Vendiera,b and Sylviane Sabo-Etienne*a,b
Received 3rd March 2010, Accepted 1st June 2010
DOI: 10.1039/c0dt00065e
Silylation of ethylene by the chlorosilanes HSiMe2Cl and HSiMeCl2 was catalysed by the
2
bis(dihydrogen) complex RuH2(h -H2)2(PCy3)2 (1). Dehydrogenative silylation leading to the formation
of the corresponding vinylsilanes was in competition with hydrosilylation. The rate and selectivity of the
reactions were influenced by the number of chloro substituents and the ethylene pressure. A comparative
mechanistic study was performed in toluene-d8 with the two chlorosilanes. Reaction of 1 with an excess
2
2
of HSiMe2Cl (10 equiv.) produced the s-silane complexes RuH2(h -H2)(h -HSiMe2Cl)(PCy3)2
2
2
(2Me2Cl), RuH2(h -HSiMe2Cl)2(PCy3)2 (3Me2Cl) and the silyl complex RuCl(SiMe2Cl)(h -H2)(PCy3)2
(4Me2Cl), all characterised by multinuclear NMR spectroscopy. Complexes 2Me2Cl and 3Me2Cl adopt
a cis configuration for the two bulky phosphine ligands as a result of stabilising SISHA (Secondary
Interactions between Silicon and Hydrogen Atoms) interactions. Complex 4Me2Cl resulted from the
2
stoichiometric reaction of HSiMe2Cl with 1 producing RuHCl(h -H2)(PCy3)2 in situ which further
reacted with evolution of H2 and formation of 4Me2Cl. When reacting 1 with 10 equiv. of HSiMeCl2,
the corresponding complexes 3MeCl2 and 4MeCl2 were detected as well as traces of 2MeCl2. The
reactivity toward ethylene was then examined. Under catalytic conditions (excess silane in toluene-d8,
ethylene atmosphere) only two compounds could be characterised: free PCy3 and the new
6
6
(h -aryl)(disilyl) complexes of the general formula Ru(h -C6D5CD3)(SiMe3-nCln)2(PCy3) (6Me3-nCln-d8,
n = 1,2). The X-ray structure of 6MeCl2 was obtained on a single-crystal at 160 K. When only 2 equiv.
of HSiMe2Cl were added, the ethylene(silyl) complex RuH(SiMe2Cl)(C2H4)(PCy3)2 (7Me2Cl) was
obtained in addition to the organic products resulting from catalytic hydrogenation, hydrosilylation and
dehydrogenative silylation, i.e. C2H6 (major one), C2H3SiMe2Cl and C2H5SiMe2Cl. In the case of 2
equiv. of HSiMeCl2, upon ethylene addition, 7MeCl2 was formed in minority compared to a new disilyl
complex Ru(SiMeCl2)2(PCy3)2 (8MeCl2) characterised by NMR spectroscopy and X-ray diffraction on
a single crystal at 160 K. In 8MeCl2, a formal 14-electron species, stabilisation through two agostic C–H
bonds of the cyclohexyl groups was ascertained by DFT calculations.
avoiding a change in the oxidation state of the metal center. Such
Introduction
a mechanism has been termed s-CAM mechanism (s-complex
assisted metathesis mechanism) by Perutz and Sabo-Etienne.3
In the specific case of silanes, the establishment of secondary
interactions between silicon and hydrogen atoms around the metal
center (SISHA interactions) allows for isomerisation of various
s-intermediates leading to subsequent functionalization.4 It has
been pointed out that the selectivity in vinylsilanes depends on
different factors, among them ethylene pressure, order of addition
of the reactants. The nature of the silicon substituents is also
a key parameter. In this context, activation of chlorosilanes
deserves a specific attention. Indeed chlorosilanes are good
precursors for a wide variety of reagents in silicon chemistry (silane
coupling agents, silicones, hybrid inorganic–organic materials,
ceramics etc.).1,5 However, when using chlorosilanes one can face
competition between Si–H and Si–Cl bond activation leading in
particular to redistribution reactions.6 It is thus important to gain
mechanistic information on elementary steps involved in catalytic
reactions with chlorosilanes.
Silane activation has attracted a lot of interest in the homogeneous
and heterogeneous communities because of the importance of
the silicon industry.1 Hydrosilylation of alkenes is catalyzed by a
variety of transition-metal complexes, and in some cases dehydro-
genative silylation, a secondary reaction leading to the formation
of the corresponding vinylsilanes, can be quite competitive. The
Chalk–Harrod mechanism and its modified version are often
invoked to explain these processes, with oxidative addition of the
Si–H bond to the metal center being a key elementary step leading
to the formation of the corresponding silyl species (Scheme 1).2
However, in view of the knowledge gained on the properties of
s-complexes, an alternative mechanism involving the intermediacy
of s-silane and s-dihydrogen complexes can take place, thus
aCNRS, LCC (Laboratoire de Chimie de Coordination), 205 Route de
Narbonne, F-31077 Toulouse, France
bUniversite´ de Toulouse, UPS, INPT, F-31077 Toulouse, France. E-mail:
sylviane.sabo@lcc-toulouse.fr
As part of our broad program on H–E bond activation,7
we became interested in ruthenium-catalysed silylation of ethy-
† Electronic supplementary information (ESI) available: DFT data. CCDC
reference numbers 765257 (8MeCl2) and 765258 (6MeCl2). For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c0dt00065e
2
lene. By using the bis(dihydrogen) complex precursor RuH2(h -
H2)2(PCy3)2 (1) (Cy = C6H11) we were able to favour the synthesis
8492 | Dalton Trans., 2010, 39, 8492–8500
This journal is
The Royal Society of Chemistry 2010
©

Scheme 1 The Chalk–Harrod and Chalk–Harrod modified catalytic cycles for alkene hydrosilation.
Table 1 Silylation of C2H4 with HSiMeCl2 and HSiMe2Cl, catalysed by
of vinylsilanes through dehydrogenative silylation. In the case
1 at ambient temperature
of triethylsilane, very high selectivity into the corresponding
vinylsilane was achieved at ambient temperature and under
moderate ethylene pressure (1 to 20 bar).8 Total conversion of
HSiEt3 was achieved in 105 min under 1 bar of ethylene with
a 78% selectivity in triethylvinylsilane. The selectivity increased
up to 97% by introducing ethylene (1 bar) prior to the addition
Selectivity
PC2H4
bar
/
Reaction Conversion (C2H3)SiMenCl3-n
:
b
Entry Silanea
time/h
(%)b
EtSiMenCl3-n
1
2
3
4
5
6
HSiMe2Cl 1.5
HSiMe2Cl
HSiMe2Cl 20
HSiMeCl2 1.5
40
5
2.5
166
96
28
99
80
80
99
94
94
54 : 46
28 : 72
10 : 90
72 : 28
64 : 36
61 : 39
3
3
of HSiEt3. We proved that the ethylene complex RuH[(h -
C6H8)PCy2](PCy3)(C2H4) resulting from the reaction of 1 with
ethylene was the catalyst resting state and that 1 served as
an effective catalyst precursor. The reaction was subsequently
extended to allyldimethylsilane,9 and disilanes.10 We also found an
unexpected tolerance of our system for chlorosilanes.11 However,
in the presence of chloro substituents, the situation was much
more complicated than in the case of triethylsilane. Several findings
derived from our preliminary studies: (i) the catalyst efficiency was
reduced by introduction of an electron-withdrawing group on the
silane; (ii) the ethylene complex, which was the catalyst resting state
in the case of HSiEt3 silylation and led to very high selectivity in
triethylvinylsilane, was not very efficient for HSiMe2Cl activation;
(iii) our studies highlighted the importance of SISHA interactions
and led to the isolation of a wide variety of s-silane complexes.4
In view of these previous results we now report a comparative
study between HSiMe2Cl and HSiMeCl2 with the aim to better
understand the influence of chloro substituents on the catalytic
silylation of ethylene by using 1 as a catalyst precursor. We
present the results of a mechanistic investigation through NMR
monitoring and characterisation of key intermediates.
HSiMeCl2
3
HSiMeCl2 20
a In toluene, with 100 equiv. of silane. b An error of 5% should be
taken into account on the conversion and the selectivity as chlorosilanes
decompose into heavier compounds—most probably polysiloxanes—
along the capillary column. We checked that the reproducibility was not
affected and that this decomposition also occurred when pure chlorosilanes
were injected; less than 5% of decomposition into heavier compounds was
measured in the latter case.
pressurization under ethylene. The experiments were performed
at ambient temperature with ethylene pressure in the range
1.5–20 bar. Toluene was chosen in order to allow mechanistic
investigation through NMR monitoring in toluene-d8. Conversion
and selectivity with respect to vinylsilane vs. ethylsilane are
reported in Table 1. They were determined by gas-chromatography
(GC). Replacing HSiEt3 by HSiMe2Cl had a dramatic effect on
the catalysis with longer reaction times for full conversion and
reduced selectivity in the corresponding vinylsilane.8,11 In the case
of HSiMeCl2, thus replacing one Me group in HSiMe2Cl by a
second chlorine, the reaction rate is even more decreased. However,
this effect can be limited by increasing ethylene pressure which this
time, has a much lower impact on vinylsilane selectivity.
Results and discussion
Silylation of ethylene catalysed by 1 was tested with two chlorosi-
lanes HSiMenCl3-n (n = 1 or 2) (see eqn (1)). The order of
addition of the substrates derives from our preliminary study
showing that selectivity in vinylsilane when using HSiMe2Cl
(1)
3
was reduced when starting from the ethylene complex RuH[(h -
C6H8)PCy2](PCy3)(C2H4) or upon high pressure of ethylene.11
We have thus conducted all our catalytic experiments by first
adding the chlorosilanes to a toluene solution of 1, followed by
The highest selectivities in vinylsilanes were 54% and 72% (en-
tries 1 and 4) for (C2H3)SiMe2Cl and (C2H3)SiMeCl2, respectively.
These values were obtained at low ethylene pressure (1.5 bar). The
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 8492–8500 | 8493
©

Scheme 2 Reactivity of the bis(dihydrogen) complex 1 with an excess of chlorosilanes.
change in selectivity as a function of ethylene pressure is quite
multiplet at -8.55 ppm appeared in the 1H NMR spectrum
which was assigned to RuH3(SiMeCl2)(PCy3)3 (5). This complex
is analogous to the complex RuH3(SiMeCl2)(PPh3)3 previously
reported by Lemke et al.14 This type of complex has already
been extensively studied with Fe, Ru and Os metal centers,
so further characterisation was not carried out. We propose
that 5 results from partial decomposition of the initial mixture:
generation of free phosphine could then lead to substitution of
one s-ligand, H2 in 2MeCl2 or HSiMeCl2 in 3MeCl2, by the free
surprising (entries 1 vs. 3 and 4 vs. 6). For a system in which
hydrosilylation and dehydrogenative silylation are in competition,
a high alkene/silane ratio should favour the dehydrogenative
pathway.1a This was indeed what we had observed previously in
the case of HSiEt3.8 Looking in more details, there is only a slight
influence of the pressure in the case of HSiMeCl2 (entries 4–6)
and the reaction still preferentially produced the corresponding
vinylsilane at 20 bar. In the case of HSiMe2Cl, the selectivity in
vinylsilane dramatically dropped to 10% at high pressure (entry
3). This difference in behaviour is certainly linked to the change in
the electronic properties of the silane when substituting a chlorine
by a methyl group. One can thus postulate that several routes are
possible in this catalytic system as a function of the silane and
the ethylene pressure, especially in the case of HSiMe2Cl. This
prompted us to carry out a comparative mechanistic study with
the two chlorosilanes.
1
phosphine. The 31P{ H} NMR spectrum of the mixture confirmed
the presence of a small amount of free phosphine which resulted
from the formation, in toluene-d8, of an aryl ruthenium complex
6
Ru(h -C6D5CD3)(SiMeCl2)2(PCy3) as it will be discussed below.
Phosphine dissociation was only clearly observed in the case of
HSiMeCl2. The NMR data for 2MeCl2, 3MeCl2 and 4MeCl2, very
similar to those for the corresponding Me2Cl complexes, allow us
to propose the structures shown in Scheme 2. As mentioned above,
we have already reported a detailed experimental and theoretical
study on 4MeCl2 and its analogue 4Me2Cl.13 The relative ratio
of complexes 2 and 3 indicates that, when adding more electron-
withdrawing groups to the silicon atom, silane coordination is
favored over H2, leading thus to the bis(silane) complex as the
major product in the case of HSiMeCl2.
Mechanistic study
We will first describe the reactivity of 1 with the chlorosilanes in
toluene-d8 for NMR analysis, and subsequently, the reaction of the
resulting mixtures with C2H4. This procedure follows the order of
addition of the reactants during the catalytic experiments.
It is interesting to note that the reaction of 1 with 10 equiv
of HSiEt3 gave an equilibrium between 1 and 2Et3 in which no
trace of 3Et3 was detected.8 This difference cannot be explained
by steric considerations alone: the cone angle of HSiEt3 (132◦)
is intermediate between those of HSiMe2Cl, HSiMeCl2 (120◦
and 122◦, respectively) and HSiPh3 (145◦). In the last case,
2Ph3 was quantitatively produced.15 In the case of HSiEt3, the
equilibrium due to competition between s-H2 and s-HSiEt3
coordination agrees with the trend observed with HSiMe2Cl and
HSiMeCl2. The presence of electron-withdrawing groups favours
silane coordination.12b,16
Addition of chlorosilanes to 1
To mimic the catalytic conditions, we have chosen to examine the
reactivity of 1 with 10 equiv. of chlorosilanes (see Scheme 2).
In the case of HSiMe2Cl, we had already reported that the
reaction resulted in the formation of three silicon-containing com-
2
2
2
plexes RuH2(h -H2)(h -HSiMe2Cl)(PCy3)2 (2Me2Cl), RuH2(h -
2
HSiMe2Cl)2(PCy3)2 (3Me2Cl) and RuCl(SiMe2Cl)(h -H2)(PCy3)2
(4Me2Cl) all characterised by NMR spectroscopy.11 Complexes
2Me2Cl and 3Me2Cl adopt a cis configuration for the two bulky
phosphine ligands as a result of stabilising SISHA interactions.4
The chemical shifts (dSi) for the silicon atoms in 2Me2Cl and
3Me2Cl are 38 and 29 ppm, respectively. They are shielded com-
pared to the free silane (dSi = -11.1 ppm) but it remains difficult
to link the variation in chemical shift with the strength of the M–
Si bond.4,12 The formation of complex 4Me2Cl deserves a specific
comment: we had previously shown that easy access to the known
Reaction of the r-silane and silyl complexes with ethylene
Ethylene was bubbled into a toluene-d8 solution of 1 with 10
equiv. of the chlorosilanes. Catalysis proceeded and the organic
compounds could be identified. We observed the elimination of
6
free PCy3 and the formation of a new h -aryl complex of general
2
6
RuHCl(h -H2)(PCy3)2 could be achieved by adding HSiMe2Cl to
formula Ru(h -C6D5CD3)(SiMe3-nCln)2(PCy3) (6Me3-nCln-d8), as
◦
2
1
1 at 0 C. Subsequent reaction of HSiMe2Cl with RuHCl(h -
characterized by 1H and 31P{ H} NMR. In the case of HSiMeCl2,
2
H2)(PCy3)2 resulted in the isolation of RuCl(SiMe2Cl)(h -
other products were formed that remained unidentified. The
1
H2)(PCy3)2 (4Me2Cl) fully characterized by X-ray diffraction.13
It is not thus surprising that we observe 4Me2Cl in our system.
The reaction of 1 with HSiMeCl2 can also be depicted by
Scheme 2. In addition to the hydride multiplets of the 3 complexes,
2MeCl2 (traces), 3MeCl2 and 4MeCl2, a new AA¢A¢¢XX¢X¢¢
31P{ H} NMR spectra gave chemical shifts for 6Me2Cl-d8 and
6MeCl2-d8 of d 48.65 and d 46.4, respectively. Irrespective of
the nature of the silane, it appeared that complexes 6 were quite
stable on the NMR time scale. The X-ray structure of 6MeCl2
was obtained on a single-crystal at 160 K (Fig. 1). The complex
8494 | Dalton Trans., 2010, 39, 8492–8500
This journal is
The Royal Society of Chemistry 2010
©

6
Scheme 3 Addition of chlorosilanes to the bis(dihydrogen) complex 1,
followed by ethylene bubbling.
Fig. 1 X-ray structure of Ru(h -C6H5CH3)(SiMeCl2)2(PCy3) (6MeCl2)
˚
(ellipsoids are at 50% of probability). Selected bond lengths (A): Ru–P
2.4069(9), Ru–Si1 2.3423(9), Ru–Si2 2.3645(9), and angles (◦): P–Ru–Si1
97.30(3), P–Ru–Si2 96.25(3), Si1–Ru–Si2 83.67(3).
6
adopts a classical three legged piano-stool geometry for h -arene
6
complexes in agreement with the Ru(h -C6H6)(SiR3)2(PPh3) series
(R3 = Cl3, MeCl2 and Me3) reported by Lemke et al.17 The
phosphine is in the Si1–Ru–Si2 angle bisector plane. The two
silicon atoms are in a pseudo-tetrahedral environment with Ru–Si1
˚
˚
and Ru–Si2 distances of 2.3423(9) A and 2.3645(9) A, respectively.
Although the two methyl groups are in non-equivalent positions in
the X-ray structure, fast rotation of the silyl groups was observed
at ambient temperature by 1H NMR in solution, as evidenced by
the single resonance observed for the methyl groups.
In order to gain information on the reactivity of species 2–4,
resulting from the reaction of 1 with the chlorosilanes, we have
conducted additional experiments. As previously described, the
reaction of 4 with C2H4 led to the formation of the ethylene(chloro)
complex RuHCl(C2H4)(PCy3)2 and the corresponding organic
compounds.13 With 2Me2Cl preferentially formed upon reaction
of 1 with 2 equiv. of HSiMe2Cl, the ethylene(silyl) complex
RuH(SiMe2Cl)(C2H4)(PCy3)2 (7Me2Cl) was obtained in addition
to the organic products resulting from catalytic hydrogenation,
hydrosilylation and dehydrogenative silylation, i.e. C2H6 (major),
C2H3SiMe2Cl and C2H5SiMe2Cl (Scheme 3). The 1H NMR
spectrum of 7Me2Cl gave a well-resolved triplet at d -5.14 (2JPH
= 32.5 Hz) integrating for one hydride and a broad signal at d
3.17 corresponding to the 4 protons of the coordinated C2H4.
Fig. 2 X-Ray structure of Ru(SiMeCl2)2(PCy3)2 (8MeCl2) (ellipsoids are
at 50% of probability). Only the two hydrogen atoms possibly involved in
an agostic interaction with Ru are represented, for clarity.
In contrast with the bis(silane) species 3MeCl2, the major species
formed upon reaction of 1 with 2 equiv. of HSiMeCl2, 7MeCl2
was formed in minority upon addition of ethylene, compared to
the new species Ru(SiMeCl2)2(PCy3)2 (8MeCl2) characterized as
a disilyl complex (Scheme 3). Ethane was again the main organic
product formed in this reaction, indicating that the Ru–Si bonds
were less reactive than the Ru–H ones. Complex 8MeCl2 was
characterised by NMR spectroscopy and X-ray diffraction on a
single-crystal at 160 K. Its structure showed the ruthenium centre
in a pseudo-octahedral environment with two vacant sites (Fig. 2
and Table 2). The two silyl groups are in a cis position because
of their trans influence. The Ru–Si distances differ insignificantly
1
The 13C{ H} NMR spectrum showed a broad signal at d 44.9,
significantly shielded compared to free C2H4 (d 123.1) and the
31
29Si-1H-{ P} HMQC spectrum showed a correlation between the
2
hydride and the silicon at d 79.7 (d, JSiH = 15 Hz). These data
are in perfect agreement with the formulation of 7Me2Cl as an
unsaturated 16-electron hydrido silyl complex, with the silyl trans
to the vacant site, as a result of it being the strongest trans influence
ligand.18 The analogous complex 7MeCl2 displays similar data
˚
˚
(2.259(2) A and 2.270(2) A) and are in the range reported for
silyl complexes.12b,14,19 These values are shorter than those in
6MeCl2 which is consistent with an unsaturated ruthenium center.
The quality of the data does not allow us to really discuss the
possible stabilisation, of this formally 14-electron complex, by two
agostic C–H bond interactions. However, the two phosphines are
bent away from the pair of silyl ligands with a P–Ru–P angle
of 157.11(7)◦ and two ortho CH2 groups of the PCy3 ligands
except that the silicon atom is more shielded at d 61.2 (d, 2JSiH
=
17.8 Hz). The small JSiH values for the two complexes are consistent
with a formulation as hydrido(silyl) species.4 These unsaturated
complexes are stable over one day in toluene-d8 under a C2H4
atmosphere. Such a stability might be explained by the strong
trans influence of the silyl group trans to the vacant site, which
does not favour the coordination of an additional C2H4 ligand or
any further reaction.
˚
˚
displaying Ru–C and Ru–H distances of ca. 3.01 A and 2.26 A,
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 8492–8500 | 8495
©

◦
˚
with the HSiEt3 system in pentane quite difficult and led to the
formation of arene complexes, but it was a convenient solvent for
the characterization of very unstable species.
Table 2 Relevant distances (A) and angles ( ) for 8MeCl2 (X-ray) and
8MeCl2-a (DFT)
X-Ray
DFT
Ru–P1
Ru–P2
Ru–Si1
Ru–Si2
Ru ◊ ◊ ◊ Ha
Ru ◊ ◊ ◊ Hb
Ru ◊ ◊ ◊ Ca
Ru ◊ ◊ ◊ Cb
2.392(2)
2.424(2)
2.259(2)
2.270(2)
2.28
2.26
3.014(7)
3.008(7)
2.428
2.479
2.279
2.286
2.364
2.373
3.134
3.178
Conclusion
The introduction of chloro substituents on silanes has a strong
effect both on activity and selectivity when using the ruthenium
bis(dihydrogen) complex 1 as a catalyst precursor for ethylene
silylation. At low ethylene pressure, it is still possible to favour
the formation of vinylsilanes, but surprisingly, higher pressures are
detrimental to the dehydrogenative silylation pathway, particularly
in the case of HSiMe2Cl. Our mechanistic investigation shows that
the systems are quite complex with several organometallic species
in competition. The reactivity of chlorosilanes with 1 led to a
mixture of complexes incorporating one or two silane ligands s-
bonded to the metal (complexes 2 and 3, respectively), as well as
chloro(silyl) species resulting from Si–Cl bond cleavage (complexes
4). The ratio of the different species depends on the starting
silane: in HSiMeCl2, the Si–H bond has a better p-acceptor
character than in HSiMe2Cl, thus favouring the formation of
the bis(silane) 3MeCl2. When adding ethylene to the mixture
of products resulting from the reaction of 1 with 2 equiv of
chlorosilanes, different complexes were observed together with the
organic products resulting from catalysis. In the case of HSiMe2Cl,
the unsaturated hydrido(silyl) complex 7Me2Cl was the major
product. In contrast, with HSiMeCl2, the corresponding complex
7MeCl2 became a minor product and the new complex 8MeCl2
was produced and identified as a disilyl species. This formally
14-electron complex was characterised by X-ray diffraction and
convincing evidence came from DFT calculations that agostic C–
H interactions could stabilise the ruthenium centre. Thus, the
addition of electron-withdrawing groups at silicon pushes the
reactions toward the formation of disilyl complexes. In order to
better model the catalytic conditions, we used a large excess of
silanes and subsequent exposure to ethylene led to the observation
of arene species still incorporating two silyl ligands. The arene
complex 6MeCl2 could be characterised by X-ray crystallography.
The formation of arene products is due to the catalytic conditions
involving toluene as the solvent. Such a choice was made to allow
for easy NMR monitoring of the catalysis, but with the drawback
of producing arene species from decomposition of the unsaturated
disilyl complexes. In any case, the presence of disilyl species in
the catalytic cycle, never observed in the case of HSiEt3, might
explain the differences observed in terms of activity and selectivity.
A key factor favouring either hydrosilylation or dehydrogenative
silylation is the competition between ethylene insertion into M–H
vs. M–Si bonds in the Chalk–Harrod or Chalk–Harrod modified
mechanism or in the s-CAM mechanism. In the case of HSiMeCl2,
we form strong Ru–Si bonds within bis(s-silane) and subsequently
disilyl species upon ethylene pressure: long reaction times are
needed to obtain a good conversion but selectivity is in favour
of vinylsilane formation (as a result of ethylene insertion into the
Ru–Si bond), and the influence of ethylene pressure is minimized
(in the absence of Ru–H bonds). In contrast, in the case of tri-
ethylsilane, we had previously shown that a mechanism involving
a partially dehydrogenated phosphine was operating. There, the
formation of disilyl species is not possible as one phosphine
acts as a bifunctional ligand with an allylic coordination to the
P1–Ru–P2
P1–Ru–Si1
P1–Ru–Si2
P2–Ru–Si1
P2–Ru–Si2
Si1–Ru–Si2
157.12(7)
97.35(7)
96.52(8)
101.40(8)
97.37(8)
87.21(8)
156.89
95.60
96.79
102.64
97.93
87.93
respectively. These values are consistent with agostic interactions.
Indeed, 14-electron four-coordinate Ru(II) complexes have already
been disclosed in particular by Caulton, Eisenstein et al. and
shown to be stabilised by double agostic interactions.20 More
recently, an unsaturated Ru(II) complex incorporating a Xantsil
ligand (i.e. disilyl) was shown to be stabilised by an agostic
˚
interaction from the PCy3 ligand (Ru–H distances of 2.89 A and
21
˚
3.06 A). The NMR data of 8MeCl2 are in agreement with a
symmetrical structure in which the silyl groups are free to rotate.
NMR monitoring of a C7D8 solution of 8MeCl2 showed no change
in the presence of dissolved C2H4 in excess.
The structures of three 8MeCl2 rotamers were optimised by
DFT calculations using the B3PW91 functional.22 They differ in
the number of silyl based chloride substituents located in the
equatorial plane, that is to say two, one or none (see ESI).†
Importantly, each structure is stabilised by two C–H agostic
interactions, as inferred by the X-ray crystal structure of 8MeCl2
(keeping in mind the poor quality of the data). The most stable
optimised geometry 8MeCl2-a compares actually very well with
the X-ray data (Table 2). The C–H agostic interactions are
characterised by Ru ◊ ◊ ◊ H contact distances close to 2.4 A, and
Ru ◊ ◊ ◊ C distances around 3.1 A. The impact of the chloride
positions, through silyl rotation (in agreement with NMR data),
on the overall stability of the complex is very limited.
The formation of 7MeCl2 and 8MeCl2 in a ratio close to
the ratio of the silane precursors 2MeCl2 and 3MeCl2 before
C2H4 bubbling and in addition, the absence of any trace of
8Me2Cl when using HSiMe2Cl (2 equiv.), allow for the postulate
that mono(silane) complexes 2 are directly responsible for the
formation of silyl complexes 7, and bis(silane) complexes 3
directly responsible for disilyl complexes 8. Moreover, it should
be noted that the disilyl complex 8MeCl2 can be prepared by
adding an excess of HSiMeCl2 to the ethylene complex RuH[(h -
C6H8)PCy2](PCy3)(C2H4) whereas in the case of triethylsilane we
never observed the formation of a disilyl species.
It is important to note that 8MeCl2 is very air-sensitive and it
was impossible to isolate it in any decent yield, thus preventing
any test as a catalyst precursor. Decomposition occurred leading
to the formation of the arene complex 6MeCl2-d8 as monitored
by NMR in toluene-d8 solution. One can regret the choice of
toluene as a solvent for the catalysis, as it rendered the comparison
˚
˚
3
8496 | Dalton Trans., 2010, 39, 8492–8500
This journal is
The Royal Society of Chemistry 2010
©

Scheme 4 Role of the bis(silyl) species in the catalysed silylation of ethylene
metal center and vinylsilanes are logically preferred with high
prior to use. All reagents were purchased from Aldrich, except
pressures of ethylene. Indeed, assuming that Ru–H bonds are
favourably consumed through ethylene hydrogenation, insertion
of ethylene into a Ru–Si bond and subsequent b-H elimination
can occur, the vinylsilane being then replaced by ethylene (see
Scheme 4). The case of HSiMe2Cl is more puzzling as we observe
a detrimental effect of ethylene pressure on the selectivity towards
vinylsilanes. We have seen that monosilane vs. disilane species are
preferred when using HSiMe2Cl instead of HSiMeCl2. Ethylene
insertion into the M–H bond could now be competitive leading to
hydrosilylation and hydrogenation of ethylene as major processes.
Our study clearly shows that depending on the silicon sub-
stituents, we are facing different catalytic pathways, and it is
thus very difficult to draw a general picture of a mechanism
for homogeneous silylation reactions. Not only can the silane
be either oxidatively added to the metal center leading to the
corresponding M–H and M–Si bonds, but it can also coordinate
to the metal center in a s-bond fashion and mono or bis(silane)
species are then stabilized (and subsequently silyl and disilyl
species), or also the phosphine can interfere and become a “non-
innocent” ligand, complicating even more the situation. However,
it appears that the Ru–Si bond strength, tuned by the silicon
substituents, is a key parameter that guides the reactivity of
the potential intermediates irrespective of whether they contain
s-silane or silyl ligands.
RuCl3·3H2O, which was obtained from Johnson Matthey Ltd.,
2
and were used without further purification. Complex RuH2(h -
H2)2(PCy3)2 (1) was synthesised using a previously published
procedure.23 All NMR solvents were dried using appropriate
methods and degassed prior to use. NMR samples of sensitive
compounds were all prepared in an inert atmosphere glovebox.
1
NMR spectra were recorded on Bruker DPX 300 (with H at
300,13 MHz, 31P at 121,49 MHz and 13C at 75,46 MHz) and
1
AMX 400 (with H at 400,13 MHz, 31P at 161,98 MHz, 13C at
100,71 MHz, 29Si at 79,50 MHz) spectrometers.
Catalyses were performed in a 100 mL stainless steel autoclave
equipped with an anti-vortex mechanical stirring system (1000
tr min-1). The autoclave was equipped with several valves for
liquid and gas introduction and sample withdrawing. All the
catalyses were performed at ambient temperature, using 12 mL of
solvent. GC spectra were recorded on a HP 5890 spectrometer,
and GC-MS spectra (EI, 70 eV) on a HP 6890 spectrometer
coupled with an HP 5970 MSD ion detector. A SE30 column
(50 m, ø 0.32 mm) was used, with a flow of helium (1.5 mL min-1).
Acquisition and treatment of the data were performed using the
GC ChemStation software. To check the reliability of the GC
analysis, we also monitored the reaction by NMR in C6D6 under
analogous experimental conditions as entry #2, Table 1. 1H NMR
spectral integration gave a (C2H3)SiMeCl2 : EtSiMeCl2 ratio of
23 : 77 that compared quite well with the results of entry #2.
It was impossible to isolate the new compounds in a pure
form and get reliable microanalytical data as they were always
contaminated by traces of other species as attested by NMR.
Experimental
General methods
All reactions were performed using standard Schlenk or dry-
box techniques under argon. Solvents were dried and distilled
RuH2(g2-H2)(g2-HSiMe2Cl)(PCy3)2 (2Me2Cl). Addition of
6.7 mL of HSiMe2Cl (0.060 mmol) to a solution of 1 (19.9 mg,
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 8492–8500 | 8497
©

0.030 mmol) in 0.5 mL of toluene-d8, resulted in gas evolution and
total dissolution. 1H NMR (C7D8, 288 K, 400.13 MHz): -8.51 (br,
RuH5), 1.44 (s, SiMe2). T1min (C7D8, 253 K, 300.13 MHz): 32 ms for
the high field resonance. All the hydrides remained in fast exchange
RuH(SiMe2Cl)(C2H4)(PCy3)2 (7Me2Cl). A solution of com-
plex 7Me2Cl was prepared from an NMR sample of 2Me2Cl (see
1
above), by bubbling C2H4 into the solution for 1 min. H NMR
(C7D8, 293 K, 400.13 MHz): -5.14 (t, 2JPH = 32.6 Hz, 1H, RuH),
1
1
from 193 K to 293 K. 31P-{ H} NMR (C7D8, 288 K, 161.97 MHz):
3.17 (br, 4H, RuC2H4), 0.91 (s, SiMe2). 31P-{ H} NMR (C7D8,
1
31
1
57.74 (s). 29Si-{ H}-{ P} NMR (C7D8, 288 K, 79.49 MHz): 38 (s).
293 K, 161.97 MHz): 53.14 (s). 13C-{ H} NMR (C7D8, 293 K,
31
100.62 MHz): 44.9 (br, C2H4). 29Si-{ P} NMR (C7D8, 293 K,
RuH2(g2-H2)(g2-HSiMeCl2)(PCy3)2 (2MeCl2). Addition of
3.1 mL of HSiMeCl2 (0.030 mmol) to a suspension of 1 (20.1 mg,
0.030 mmol) in 0.5 mL of toluene-d8, resulted in gas evolution and
total dissolution. 1H NMR (C7D8, 288 K, 400.13 MHz): -8.37 (br,
RuH5). T1 (C7D8, 253 K, 300.13 MHz): 20 ms for the high field
resonance. All the hydrides remained in fast exchange from 193 K
79.49 MHz): 79.7 (br d, 2JSiH = 15 Hz).
RuH(SiMeCl2)(C2H4)(PCy3)2 (7MeCl2). A solution of com-
plex 7MeCl2 was prepared from an NMR sample of 2MeCl2
1
(see above), by bubbling C2H4 into the solution for 1 min. H
1
to 293 K. 31P-{ H} NMR (C7D8, 253 K, 161.97 MHz): 54.92 (br).
2
NMR (C7D8, 273 K, 400.13 MHz): -4.82 (t, JPH = 30.2 Hz,
The resonance of the silicon atom could not be located in the 29Si
NMR spectrum.
1
1H, RuH), 3.23 (br, 4H, RuC2H4), 1.16 (s, SiMe). 31P-{ H} NMR
1
(C7D8, 273 K, 161.97 MHz): 51.28 (s). 13C-{ H} NMR (C7D8,
31
273 K, 100.62 MHz): 47.5 (br, C2H4). HMQC 29Si-1H-{ P} NMR
RuH2(g2-HSiMe2Cl)2(PCy3)2 (3Me2Cl). Addition of 33.3 mL
ofHSiMe2Cl (0.300mmol)to asolutionof 1 (20.0mg, 0.030mmol)
in 0.5 mL of toluene-d8, resulted in rapid gas evolution and total
dissolution. 1H NMR (C7D8, 233 K, 400.13 MHz): -7.90 (br t, 2JPH
(C7D8, 273 K, 79.49 MHz): 61.2 (br d, 2JSiH = 17.4 Hz).
Ru(SiMeCl2)2(PCy3)2 (8MeCl2). Addition of 17.0 mL of
2
= 10 Hz, 2H, Ru-h -H–Si), -10.69 (AA¢XX¢ pattern, 2JPH = 27 and
3
HSiMeCl2 (0.163 mmol) to
a
suspension of RuH[(h -
1
46 Hz, 2H, RuH), 1.36 (s, SiMe2). 31P-{ H} NMR (C7D8, 233 K,
C6H8)PCy2](PCy3)(C2H4) (27.0 mg, 0.039 mmol, prepared accord-
ing to published procedure)23 in 2 mL of pentane, resulted in slow
dissolution of the solid. The resulting orange solution kept at
ambient temperature for 5 days, gave intense orange/red crystals
suitable for X-ray measurements. NMR spectra were obtained
1
31
161.97 MHz): 50.03 (s). 29Si-{ H}-{ P} NMR (C7D8, 233 K, 79.49
MHz): 29 (s).
RuH2(g2-HSiMeCl2)2(PCy3)2 (3MeCl2). Addition of 6.1 mL
of HSiMeCl2 (0.059 mmol) to a suspension of 1 (18.9 mg, 0.028
mmol) in 0.5 mL of toluene-d8, resulted in rapid gas evolution and
total dissolution. 1H NMR (C7D8, 233 K, 400.13 MHz): -6.56 (br
1
from the crystalline material dissolved in toluene-d8. H NMR
(C7D8, 293 K, 300.13 MHz): 1.81 (s, SiMe), 1.0–2.8 (m, PCy3).
1
31P-{ H} NMR (C7D8, 293 K, 121.49 MHz): 28.3 (s). HMQC
2
t, 2JPH = 9.8 Hz, 2H, Ru-h -H–Si), -9.59 (broad AA¢XX¢ pattern,
31
29Si-1H-{ P} NMR (C7D8, 273 K, 79.49 MHz): 72.2 (br).
1
2H, RuH), 1.79 (s, SiMe). 31P-{ H} NMR (C7D8, 253 K, 161.97
31
MHz): 49.46 (br s). HMQC 29Si-1H-{ P} NMR (C7D8, 193 K,
79.49 MHz): 33 (br s).
X-Ray crystallography
RuH3(SiMeCl2)(PCy3)3 (5MeCl2). Complex 5MeCl2 was ob-
served in an NMR sample of 1 + excess of HSiMeCl2. 1H NMR
(C7D8, 253 K, 400.13 MHz): -8.56 (AA¢A¢¢XX¢X¢¢ pattern, 3H,
Table 3 summarizes the crystal data for 6MeCl2 and 8MeCl2. Data
were collected at low temperature (160 K) on an Xcalibur Oxford
Diffraction diffractometer using a graphite-monochromated Mo-
RuH3), 1.57 (s, SiMe). T1 (C7D8, 400.13 MHz): over 200 ms
˚
Ka radiation (l = 0.71073 A) and equipped with an Oxford
1
from 243 to 283 K for the high field resonance. 31P-{ Hcyclohexyl
}
Instrument Cooler Device. The structures have been solved by
Direct Methods using SIR-92,24 and refined by means of least-
squares procedures on F2 with the aid of the program SHELXL-
9725 include in the software package WinGX version 1.63.26 The
atomic scattering factors were taken from international tables for
X-ray crystallography.27 All hydrogen atoms were geometrically
placed and refined using a riding model. All non-hydrogen atoms
were anisotropically refined, and in the last cycles of refinement
a weighting scheme was used, where weights are calculated from
NMR (C7D8, 253 K, 161.97 MHz): 39.74 (AA¢A¢¢XX¢X¢¢ pattern).
HMQC 29Si-1H-{ P} NMR (C7D8, 193 K, 79.49 MHz): 63 (s).
31
Ru(g6-C6D5CD3)(SiMe2Cl)2(PCy3)
(6Me2Cl-d8). Complex
6Me2Cl-d8 was characterised from an NMR sample of 3Me2Cl
(see above), into which C2H4 was bubbled. 1H NMR (C7D8,
293 K, 300.13 MHz): 1.08 and 1.11 (s, SiMe2), 1.0–2.3 (m, PCy3).
1
31P-{ H} NMR (C7D8, 293 K, 121.49 MHz): 48.6 (s).
Ru(g6-C6H5CH3)(SiMeCl2)2(PCy3) (6MeCl2). Addition of
the following formula: w = 1/[s (Fo2) + (aP)2 + bP] where P =
2
3
2
8.8 mL of HSiMeCl2 (0.084 mmol) to a solution of RuH[(h -
(Fo2+2Fc )/3. Drawing of the molecules was performed with the
C6H8)PCy2](PCy3)(C2H4) (28.7 mg, 0.042 mmol) in 0.7 mL of
toluene, resulted in a colour change from beige to intense orange.
The resulting orange solution kept at ambient temperature for
1 month, gave yellow crystals suitable for X-ray measurements.
NMR spectra were obtained from the crystalline material dis-
solved in toluene-d8. 1H NMR (C7D8, 293 K, 300.13 MHz): 5.0–
5.7 (m, toluene), 2.27 (s, 3H, toluene–Me), 1.46 (s, SiMe), 1.0–2.1
program Mercury with 50% probability displacement ellipsoids
for non-hydrogen atoms.28 The two complexes present statistic
disorders between two Cl and CH3, over two sites. These disorders
have been treated using the PART command of SHELX-97.
Moreover, in the case of 8MeCl2, we were not able to grow superior
single crystals. For this reason, we collected poor quality data,
resulting after data reduction in high Rint and Rs values (13.1 and
1
(m, 33H, PCy3). 31P-{ H} NMR (C7D8, 293 K, 121.49 MHz): 46.3
27.8%, respectively). Indeed, for a 1.49–1.19 A resolution, the Rint
is already at 12.6% and Rs at 19.5%.
˚
(s).
8498 | Dalton Trans., 2010, 39, 8492–8500
This journal is
The Royal Society of Chemistry 2010
©

Table 3 Crystal data for 6MeCl2 and 8MeCl2
6
Compound
Ru(h -C6H5CH3)(SiMeCl2)2(PCy3) (6MeCl2)
Ru(SiMeCl2)2(PCy3)2 (8MeCl2)
1
2
Empirical formula
Formula weight
Crystal size/mm
T/K
C27H47Cl4PRuSi2· C7H8
C38H72Cl4P2RuSi2
889.95
0.2 ¥ 0.12 ¥ 0.05
160(2)
Monoclinic
P21/c
9.7901(8)
44.9570(7)
10.1672(9)
90
105.977(3)
90
747.74
0.25 ¥ 0.17 ¥ 0.07
160(2)
Triclinic
¯
P1
10.1180(8)
11.3620(10)
14.9910(9)
94.278(5)
94.911(3)
92.777(6)
1709.7(2)
2
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
4302.1(5)
4
1.374
Z
rc/cm-3
1.453
Reflections collected/unique
Data/restraints/parameters
GOF on F2
23 632/5653 [Rint = 0.0311]
5653/31/371
1.056
R1 = 0.0391,
wR2 = 0.0954 [I > 2s(I)]
R1 = 0.0409,
wR2 = 0.0971 (all data)
1.96 and -3.06
28 188/7865 [Rint = 0.1095]
7865/0/414
1.137
R1 = 0.0867,
wR2 = 0.1397 [I > 2s(I)]
R1 = 0.133,
wR2 = 0.1532 (all data)
0.82 and -0.815
Final R indices
Largest difference peak and
-3
˚
hole/e A
3 R. N. Perutz and S. Sabo-Etienne, Angew. Chem., Int. Ed., 2007, 46,
2578–2592.
Computational details
4 S. Lachaize and S. Sabo-Etienne, Eur. J. Inorg. Chem., 2006, 2115–2127.
5 (a) S. Calmettes, B. Albela, O. Hamelin, S. Menage, F. Miomandre and
L. Bonneviot, New J. Chem., 2008, 32, 727–737; (b) J. O. Krause, S.
Lubbad, O. Nuyken and M. R. Buchmeiser, Adv. Synth. Catal., 2003,
345, 996–1004; (c) H. Metz, Spec. Chem. Mag., 2007, 27, 38–40; (d) J.
Terao, K. Torii, K. Saito, N. Kambe, A. Baba and N. Sonoda, Angew.
Chem., Int. Ed., 1998, 37, 2653–2656; (e) J. Terao and N. Kambe, Chem.
Rec., 2007, 7, 57–67.
6 (a) M. D. Curtis and P. S. Epstein, Adv. Organomet. Chem., 1981, 19,
213–232; (b) J. Gavenonis and T. D. Tilley, Organometallics, 2004, 23,
31–43.
7 (a) S. Sabo-Etienne and B. Chaudret, Coord. Chem. Rev., 1998, 178–
180, 381–407; (b) G. Alcaraz, M. Grellier and S. Sabo-Etienne, Acc.
Chem. Res., 2009, 42, 1640–1649.
DFT calculations were performed with the GAUSSIAN 03 series
of programs,29 using the hybrid functional denoted as B3PW91.22,30
The structures were fully optimised in the gas-phase without any
symmetry constraints by using the gradient method available in
GAUSSIAN 03. A double-zeta plus polarization valence basis set
(6-31G**) was employed for C and H.31 The energy-consistent
pseudo-potentials of the Stuttgart/Cologne group were used to
represent the core electrons of the other atoms via the SDDALL
keyword in GAUSSIAN 03. The polarization function exponents
for each associate basis set were aRu = 1.235, aSi = 0.287, aP
= 0.387 and aCl = 0.640. Calculations of harmonic vibrational
frequencies were performed to confirm that all the optimised
structures were local minima.
8 M. L. Christ, S. Sabo-Etienne and B. Chaudret, Organometallics, 1995,
14, 1082–1084.
9 F. Delpech, S. Sabo-Etienne, B. Donnadieu and B. Chaudret,
Organometallics, 1998, 17, 4926–4928.
10 F. Delpech, J. Mansas, H. Leuser, S. Sabo-Etienne and B. Chaudret,
Organometallics, 2000, 19, 5750–5757.
11 S. Lachaize, S. Sabo-Etienne, B. Donnadieu and B. Chaudret, Chem.
Commun., 2003, 214–215.
12 (a) G. Alcaraz and S. Sabo-Etienne, Coord. Chem. Rev., 2008, 252,
2395–2409; (b) J. Y. Corey and J. Braddock-Wilking, Chem. Rev., 1999,
99, 175–292.
13 S. Lachaize, A. Caballero, L. Vendier and S. Sabo-Etienne,
Organometallics, 2007, 26, 3713–3721.
Acknowledgements
This work was supported by the CNRS and the European
network IDECAT. S. L. thanks the French Ministery “Education
Nationale, Enseignement Supe´rieur, Recherche” for his AMN
grant. A generous allocation of computer time was given by
CALMIP (Toulouse, France).
14 N. M. Yardy, F. R. Lemke and L. Brammer, Organometallics, 2001, 20,
5670–5674.
15 (a) S. Sabo-Etienne, M. Hernandez, G. Chung, B. Chaudret and
A. Castel, New J. Chem., 1994, 18, 175–177; (b) K. Hussein, C. J.
Marsden, J. C. Barthelat, V. Rodriguez, S. Conejero, S. Sabo-Etienne,
B. Donnadieu and B. Chaudret, Chem. Commun., 1999, 1315–1316.
16 G. J. Kubas, Metal Dihydrogen and s-Bond Complexes, Kluwer
Academic/Plenum Publishers, New York, 2001.
References
1 (a) B. Marciniec, Coord. Chem. Rev., 2005, 249, 2374–2390; (b) T. D.
Tilley, in The chemistry of Organic Silicon Compounds, ed. S. Patai
and Z. Rappoport, John Wiley & Sons, New York, 1989, vol. 3, pp.
1415–1477, 1153–1156; (c) J. Y. Corey, Adv. Organomet. Chem., 2004,
51, 1–52; (d) M. A. Brook, in Silicon in Organic, Organometallic, and
Polymer Chemistry, ed., Wiley, New York, 2000; (e) B. Marciniec, in
Applied Homogeneous Catalysis with Organometallic Compounds, ed.
B. Cornils and W. A. Herrmann, 2nd edn, 2002, p. 491.
17 J. Burgio, N. M. Yardy, J. L. Petersen and F. R. Lemke, Organometallics,
2003, 22, 4928–4932.
18 J. L. Mc Bee, J. Escalada and T. D. Tilley, J. Am. Chem. Soc., 2009, 131,
12703–12713.
19 (a) V. K. Dioumaev, B. R. Yoo, L. J. Procopio, P. J. Carroll and D. H.
Berry, J. Am. Chem. Soc., 2003, 125, 8936–8948; (b) D. V. Gutsulyak,
A. V. Churakov, L. G. Kuzmina, J. A. K. Howard and G. I. Nikonov,
2 (a) S. Sakaki, N. Mizoe and M. Sugimoto, Organometallics, 1998, 17,
2510–2523; (b) A. M. LaPointe, F. C. Rix and M. Brookhart, J. Am.
Chem. Soc., 1997, 119, 906–917.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 8492–8500 | 8499
©

Organometallics, 2009, 28, 2655–2657; (c) D. V. Gutsulyak, A. L.
Osipov, L. G. Kuzmina, J. A. K. Howard and G. I. Nikonov, Dalton
Trans., 2008, 6843–6850.
28 C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock, G. P. Shields,
R. Taylor, M. Towler and J. van de Streek, J. Appl. Crystallogr., 2006,
39, 453–457.
20 (a) D. Huang, W. E. Streib, O. Eisenstein and K. G. Caulton, Angew.
Chem., Int. Ed. Engl., 1997, 36, 2004–2006; (b) D. Huang, W. E. Streib,
J. C. Bollinger, K. G. Caulton, R. F. Winter and T. Scheiring, J. Am.
Chem. Soc., 1999, 121, 8087–8097; (c) W. Baratta, E. Herdtweck and P.
Rigo, Angew. Chem., Int. Ed., 1999, 38, 1629–1631; (d) A. C. Cooper,
E. Clot, J. C. Huffman, W. E. Streib, F. Maseras, O. Eisenstein and
K. G. Caulton, J. Am. Chem. Soc., 1999, 121, 97–106.
21 M. Okazaki, N. Yamahira, J. J. G. Minglana, T. Komuro, H. Ogino and
H. Tobita, Organometallics, 2008, 27, 918–926.
29 M. J. T. Frisch, G. W., H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman, J. A. Montgomery Jr., T. Vreven, K. N. Kudin, J. C.
Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci,
M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji , M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E.
Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth,
P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D.
Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.
Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y.
Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson,
W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, in Gaussian
03Gaussian,Inc.: Wallingford, CT., 2004.
22 J. P. Perdew and Y. Wang, Phys. Rev. B: Condens. Matter, 1992, 45,
13244–13249.
23 A. F. Borowski, S. Sabo-Etienne, M. L. Christ, B. Donnadieu and B.
Chaudret, Organometallics, 1996, 15, 1427–1434.
24 A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi, J. Appl.
Crystallogr., 1993, 26, 343–350.
25 G. M. Sheldrick, SHELX97, Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1998.
26 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837–838.
27 in International tables for X-raycrystallography, Kynoch press, Birm-
ingham, 1974, vol. 4.
30 A. D. Becke, J. Chem. Phys., 1993, 98, 5648–5652.
31 W. J. Hehre, R. Ditchfield and J. A. Pople, J. Chem. Phys., 1972, 56,
2257–2261.
8500 | Dalton Trans., 2010, 39, 8492–8500
This journal is
The Royal Society of Chemistry 2010
©