Activation of chlorosilanes at ruthenium: A route to silyl σ-dihydrogen complexes

Article abstract of DOI:10.1021/om700295g

The hydrido σ-dihydrogen complex RuClH(η²-H ₂)(PCy₃)₂ (2) reacts with the chlorosilanes HSiMe_3-nCl_n (n = 1-3) to form the corresponding silyl σ-dihydrogen complexes RuCl(SiMe_3-nCl_n) (η²-H₂)(PCy₃)₂ (3Me _3-nCl_n). These complexes display a 16-electron configuration, as shown by NMR, by X-ray data in the case of 3MeCl₂, and by theoretical calculations. The σ-H₂ ligand in 3MeCl ₂ has been located by X-ray diffraction, and the H-H distance of 1.05(3) A compares well with the value obtained by DFT/ B3PW91 (1.073 A) as well as with the value of 1.08 ± 0.01 A derived from the measurement of the J_HD coupling constant of 17.5 Hz for the deuterated isotopomer RuCl(SiMeCl₂)(η²-HD)(PCy ₃)₂. The series of model complexes RuCl(SiMe _3-nCl_n)(η²-H₂)(PMe ₃)₂ (S3Me_3-nCl_n) was investigated by DFT at the B3PW91 level. The most stable isomers have a structure that resembles the X-ray structure of 3MeCl₂: i.e., a silyl σ-dihydrogen formulation. In the case of S3Me₂Cl and S3MeCl₂ a second minimum very close in energy was optimized and formulated as a hydrido σ-silane species. The influence of the number of Cl substituents on Si and their location have been analyzed. The difference between 3Me₂Cl on one side and 3MeCl₂ and 3Cl₃ on the other side is highlighted both by NMR and DFT data and by their reactivity toward ethylene. No reaction was observed for the latter complexes, whereas reaction with 3Me₂Cl produces the hydrido η²-ethylene complex RuClH(C₂H₄)(PCy ₃)₂ (4). In the case of styrene, the arene complex RuCl(SiMe₂Cl)(η⁶-C₈H₁₀)(PCy ₃) (5) was isolated.

Full text of DOI:10.1021/om700295g

Organometallics 2007, 26, 3713-3721
3713
Activation of Chlorosilanes at Ruthenium: A Route to Silyl
σ-Dihydrogen Complexes
Se´bastien Lachaize, Ana Caballero, Laure Vendier, and Sylviane Sabo-Etienne*
Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne,
31077 Toulouse Cedex 04, France
ReceiVed March 27, 2007
The hydrido σ-dihydrogen complex RuClH(η2-H2)(PCy3)2 (2) reacts with the chlorosilanes HSiMe3-nCln
(n ) 1-3) to form the corresponding silyl σ-dihydrogen complexes RuCl(SiMe3-nCln)(η2-H2)(PCy3)2
(3Me3-nCln). These complexes display a 16-electron configuration, as shown by NMR, by X-ray data in
the case of 3MeCl2, and by theoretical calculations. The σ-H2 ligand in 3MeCl2 has been located by
X-ray diffraction, and the H-H distance of 1.05(3) Å compares well with the value obtained by DFT/
B3PW91 (1.073 Å) as well as with the value of 1.08 ( 0.01 Å derived from the measurement of the JHD
coupling constant of 17.5 Hz for the deuterated isotopomer RuCl(SiMeCl2)(η2-HD)(PCy3)2. The series
of model complexes RuCl(SiMe3-nCln)(η2-H2)(PMe3)2 (S3Me3-nCln) was investigated by DFT at the
B3PW91 level. The most stable isomers have a structure that resembles the X-ray structure of 3MeCl2:
i.e., a silyl σ-dihydrogen formulation. In the case of S3Me2Cl and S3MeCl2 a second minimum very
close in energy was optimized and formulated as a hydrido σ-silane species. The influence of the number
of Cl substituents on Si and their location have been analyzed. The difference between 3Me2Cl on one
side and 3MeCl2 and 3Cl3 on the other side is highlighted both by NMR and DFT data and by their
reactivity toward ethylene. No reaction was observed for the latter complexes, whereas reaction with
3Me2Cl produces the hydrido η2-ethylene complex RuClH(C2H4)(PCy3)2 (4). In the case of styrene, the
arene complex RuCl(SiMe2Cl)(η6-C8H10)(PCy3) (5) was isolated.
σ-complexes are formed. It is also distinct from the well-known
σ-bond metathesis mechanism, which involves a four-centered
transition state but does not require any intermediates. In silane
chemistry, the hypervalence property of silicon favors such a
mechanism by allowing the formation of secondary interactions
with neighboring atoms (secondary interactions between silicon
and hydrogen atoms: SISHA interactions).6-8 It is thus obvious
that the nature of the silicon substituents will play a major role.
As part of our broad research program on silane activation
by ruthenium complexes, we have considered the effect of the
introduction of chlorine atom(s). Silane activation by the bis-
(dihydrogen)ruthenium complex RuH2(η2-H2)2(PCy3)2 (1) is
dominated by substitution reactions of the dihydrogen ligands,
Introduction
Oxidative addition of a Si-H bond to a metal center has long
been considered as the pathway of choice in silane activation
by transition-metal complexes.1 The formation of the corre-
sponding hydrido silyl complex represents a key step in
hydrosilylation, a process with wide industrial applications.2,3
However, the formation of a σ-silane complex as an intermediate
of this elementary step is very often invoked.4 Perutz and Sabo-
Etienne have recently published a review on a mechanism
highlighting the role of σ-H-E complexes (E ) H, C, B, Si) in
the functionalization of various substrates.5 This process, called
σ-complex assisted metathesis or σ-CAM, is based on the
possibility of interconverting σ-ligands without a change in
oxidation state. In the case of silane activation, addition of a
silane to a metal center produces a hydrido σ-silane complex
which can be converted to a silyl σ-dihydrogen complex and
ultimately a silyl complex can be formed ready for subsequent
functionalization (see eq 1).
leading to the corresponding silane complexes RuH2(η2-H2)2-x
-
(η2-HSiR2R′)x(PCy3)2 (x ) 1, 2; R, R′ ) alkyl, alkoxy, aryl)
with one or two σ-silane ligands.7,9,10 We have recently reported
some preliminary studies concerning the catalytic activation of
dimethylchlorosilane.11 Stoichiometric experiments showed that,
in addition to the expected mono- and disubstitution products
RuH2(η2-H2)(η2-HSiMe2Cl)(PCy3)2 and RuH2(η2-HSiMe2Cl)2-
(PCy3)2, a third complex, RuCl(SiMe2Cl)(η2-H2)(PCy3)2 (3Me2Cl),
MH + HSiR3 f MH(η2-H-SiR3) f
M(η2-H-H)(SiR3) f M(SiR3) + H2 (1)
(6) Atheaux, I.; Delpech, F.; Donnadieu, B.; Sabo-Etienne, S.; Chaudret,
B.; Hussein, K.; Barthelat, J. C.; Braun, T.; Duckett, S. B.; Perutz, R. N.
Organometallics 2002, 21, 5347-5357.
As opposed to the addition-reductive elimination sequences,
no change of oxidation state is required and at least two discrete
(7) Lachaize, S.; Sabo-Etienne, S. Eur. J. Inorg. Chem. 2006, 2115-
2127, ibid 4697-4699.
* To whom correspondence should be addressed. Tel: + 33 5 61 33 31
77. Fax: +33 5 61 55 30 03. E-mail: sylviane.sabo@lcc-toulouse.fr.
(1) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175-292.
(2) Marciniec, B. Coord. Chem. ReV. 2005, 249, 2374-2390.
(3) Marciniec, B. In Applied Homogeneous Catalysis with Organometallic
Compounds, 2nd ed.; Cornils, B., Herrmann, W. A., Eds.; Wiley: New
York, 2002; p 491.
(4) Kubas, G. J. Catal. Lett. 2005, 104, 79-101.
(5) Perutz, R. N.; Sabo-Etienne, S. Angew. Chem., Int. Ed. 2007, 46,
2578-2592.
(8) Lin, Z. Chem. Soc. ReV. 2002, 31, 239-245.
(9) Delpech, F.; Sabo-Etienne, S.; Daran, J. C.; Chaudret, B.; Hussein,
K.; Marsden, C. J.; Barthelat, J. C. J. Am. Chem. Soc. 1999, 121, 6668-
6682.
(10) Hussein, K.; Marsden, C. J.; Barthelat, J. C.; Rodriguez, V.;
Conejero, S.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret, B. Chem.
Commun. 1999, 1315-1316.
(11) Lachaize, S.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret, B. Chem.
Commun. 2003, 214-215.
10.1021/om700295g CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/16/2007

3714 Organometallics, Vol. 26, No. 15, 2007
Lachaize et al.
Scheme 1. Formation of RuCl(SiMe3-nCln)(η2-H2)(PCy3)2
(3Me3-nCln, n ) 1-3)
Table 1. NMR Data (C7D8) for Compounds 3Me3-nCln (n )
1-3)
3Me2Cl
3MeCl2
3Cl3
δ(σ-H2)
-13.75
-12.14
-12.02
T1(min)a (253 K, 300 MHz), ms
T1(min)a (263 K, 400 MHz), ms
δ(PCy3)
29
23
27
45.5
72.6
46.7
85.7
46.0
14.8
δ(SiMe3-nCln)
a T1(min) values are given with an error range of 1 ms.
resulting from Si-Cl bond breaking, was detected. 3Me2Cl
could be better isolated by reacting HSiMe2Cl with the known
chloro complex12 RuClH(η2-H2)(PCy3)2 (2). Herein we describe
the reactivity of 2 with the series of chlorosilanes HSiMe3-nCln
(n ) 1-3) leading to the isolation of a family of silyl
σ-dihydrogen complexes RuCl(SiMe3-nCln)(η2-H2)(PCy3)2
(3Me3-nCln). NMR, X-ray, and DFT data are analyzed to
evaluate how the number of chlorine atoms influences the silane
activation and dihydrogen coordination.
Results
Silyl σ-Dihydrogen Complexes. Complex 2 easily reacts in
THF with the chlorosilanes HSiMe3-nCln (n ) 1 - 3) to form
the corresponding silyl σ-dihydrogen complexes RuCl-
(SiMe3-nCln)(η2-H2)(PCy3)2 (3Me3-nCln) (see Scheme 1). Di-
hydrogen is released, according to the observed gas evolution
Figure 1. X-ray structure of 3MeCl2 with a projection view along
the P1-Ru-P2 axis (50% probability ellipsoids). Protons of methyl
and cyclohexyl groups are omitted for clarity. Distances (Å) and
angles (deg): Ru-P1 ) 2.3919(5), Ru-P2 ) 2.3822(5), Ru-Cl1
) 2.3819(4), Ru-Si ) 2.2727(5), Ru-H1 ) 1.59(2), Ru-H2 )
1.62(2), H1-H2 ) 1.05(3), Si‚‚‚H1 ) 2.25(2), Si-C1 ) 1.864-
(2), Si-Cl3 ) 2.1100(7), Si-Cl2 ) 2.1140(7); P1-Ru-P2 )
160.31(2), Cl1-Ru-H1 ) 163.6(8), Cl1-Ru-H2 ) 158.3(8),
Cl1-Ru-Si ) 94.85(2), H1-Ru-H2 ) 38.1(8), H1-Ru-Si )
68.8(7), C1-Si-H1 ) 153.2(8).
1
and to the signal detected at 4.6 ppm in the in situ H NMR
spectra. These species slowly decompose in presence of an
excess of chlorosilane. However, dilute NMR toluene-d8 solu-
tions of 3 are stable over a few days. Relevant NMR data
concerning this series of complexes are given in Table 1. In
the case of 3MeCl2, the σ-H2 ligand resonates as a broad peak
at δ -12.14 in the 1H NMR spectrum. The peak remained broad
in the range 298-193 K. The T1(min) value of 27 ms at 253 K
(400 MHz) confirms a σ-dihydrogen formulation (see below
for more details). The 31P{1H} spectrum consists of a single
resonance at δ 45.5 corresponding to the equivalent phosphanes.
The 29Si{1H,31P} spectrum reveals a signal at δ 72.6, in the
classical range for silyl complexes.1,7 Complexes 3Me2Cl and
3Cl3 exhibit similar NMR data. All of these NMR data and the
observation of H2 evolution are consistent with the formulation
of 3Me3-nCln as 16-electron silyl σ-dihydrogen complexes.
We were able to determine the structure of 3MeCl2 by X-ray
diffraction of a single crystal at 100 K (see Figure 1). The
ruthenium center is in a pseudo-octahedral environment, with
a vacant site trans to the SiMeCl2 group. Such an arrangement
is in agreement with the trans effect of the silyl.13 The Ru-Si
bond length of 2.2727(5) Å is in the classical range for silyl
ligands.1,7 The phosphanes are almost trans to each other with
a P1-Ru-P2 angle of 160.31(2)°. The Ru-Cl1 distance of
2.3819(4) Å is unchanged compared to that in 2 (2.380(2) Å).14
The quality of the data allowed the location of the σ-dihydrogen
ligand, although it still has to be discussed cautiously. The H1-
H2 distance of 1.05(3) Å reveals a slightly elongated dihydrogen
ligand located in the equatorial plane, trans to the chlorine
(13) Zhu, J.; Lin, Z.; Marder, T. B. Inorg. Chem. 2005, 44, 9384-9390.
(14) Lachaize, S. Thesis, Universite´ Toulouse III-Paul Sabatier, Toulouse,
France, 2004.
(12) Christ, M. L.; Sabo-Etienne, S.; Chaudret, B. Organometallics 1994,
13, 3800-3804.

ActiVation of Chlorosilanes at Ruthenium
Organometallics, Vol. 26, No. 15, 2007 3715
Table 2. Selected Bond Distances and Angles for the
DFT/B3PW91 Optimized Geometries of
RuCl(SiMe3-nCln)(η2-H2)(PMe3)2 (S3Me3-nCln, n ) 1-3) and
RuHCl(η2-H2)(PMe3)2 (S2)a
S3Me2Cl
S3MeCl2
S2
R1 )
(Si ≡
R1 ) Me
Cl R1 ) Me R1 ) Cl S3Cl3 H3)
Ru-Cl1
2.409
2.412 2.392
2.3819(4)
2.398
2.378 2.411
Cl1···R1
Ru-P1
3.758
2.345
4.095 3.664
2.355 2.360
2.3919(5)
2.355 2.359
2.3822(5)
1.625 1.623
1.59(2)
1.558 1.617
1.62(2)
4.148
2.368
3.823
2.368 2.334
Ru-P2
Ru-H1
Ru-H2
Si-R1
Si-R2
Si-R3
2.356
1.600
1.575
1.893
2.359
1.620
1.558
2.120
2.368 2.334
1.633 1.592
1.616 1.592
2.090
Figure 2. Optimized geometries of S3MeCl2 isomers.
2.145 1.881
1.864(2)
(S2). Extended Hu¨ckel calculations carried out on the related
analogous iodo complex was previously reported by Eisenstein
et al.17 Two local minima were found on the potential energy
surface for both S3Me2Cl and S3MeCl2. Their structures differ
from the nature of the σ-ligand, either a σ-dihydrogen or a
σ-silane formulation. These isomers depend on the silyl group
rotation imposing either a methyl or a chloro group in the
equatorial plane (this group will be referred to as R1). No
geometry with a σ-ligand orthogonal to the equatorial plane has
converged. The energies and relative stabilities of the various
isomers will be discussed later. The calculated geometry of
S3MeCl2 (R1 ) Me) matches quite well the X-ray crystal
structure of 3MeCl2. The Ru-Si distance is 2.286 Å by DFT
studies, compared to 2.2727(5) Å by X-ray studies, and the
σ-dihydrogen bond length is 1.073 Å, compared to 1.05(3) Å.
The formulation as a silyl σ-dihydrogen complex is thus well
reproduced by the calculations. Moreover, a SISHA interaction
is detected by both DFT and X-ray with comparable Si‚‚‚H
distances of 2.204 and 2.25(2) Å, respectively. Such an inter-
action could be the result of an overlap with the σ* Si-C orbital
of the methyl substituent. Similarly, an interaction between CO
and SiR3 has been evidenced by Roper et al. in the series OsCl-
(SiR3)(CO)(PPh3)2.18 The rotamer of S3MeCl2 with R1 ) Cl
is a σ-silane complex with an elongated Si-H bond of 1.897
Å. The H1‚‚‚H2 distance (1.561 Å) is now higher than what
can be found for a very stretched dihydrogen complex (limit
ca. 1.4 Å).19-21 The switch between the silyl σ-dihydrogen and
the hydrido σ-silane isomers is also evidenced by the variation
of the Cl1-Ru-H2 and Cl1-Ru-Si angles. These angles are
always above 100° as a result of chloride π-donation to the
ruthenium.22 The Ru-Si distance is only elongated by +0.005
Å in the σ-silane isomer compared to the silyl species. In the
case of S3Me2Cl and S3MeCl2 the existence of two rotamers,
resulting from the nature of the R1 ligand, leads to the
optimization of σ-dihydrogen and σ-silane species. As a result
of the three identical substituents (Cl) on S3Cl3, only one isomer
was optimized in that case. It displays a σ-dihydrogen structure
with a H1-H2 bond distance of 1.063 Å. Again, a SISHA
interaction is evidenced with a Si‚‚‚H distance of 2.172 Å.
1.891 (Me) 1.888 2.129
2.1100(7)
2.147 (Cl) 1.889 2.129
2.1140(7)
4.365 3.673
2.320 2.286
2.2727(5)
2.124 (Cl) 2.110
1.879 (Me) 2.110
Si···Cl1
Ru-Si
3.903
2.318
4.268
2.291
3.790 3.233
2.270 1.555
2.172 1.609
1.063 1.221
Si-H1
H1-H2
2.009
1.878 2.204
2.25(2)
1.659 1.073
1.05(3)
1.897
1.561
1.387
H1-Ru-H2
H1-Ru-Si
R1-Si-H1
P1-Ru-P2
Cl1-Ru-H2
Cl1-Ru-H1
Cl1-Ru-Si
51.8
62.8 38.7
38.1(8)
53.4 66.1
68.8(7)
135.6 156.5
153.2(8)
164.4 167.1
160.31(2)
109.3 151.8
158.3(8)
58.8
38.2 45.1
65.3 61.5
154.3
58.3
54.8
149.2
165.8
138.7
169.5
111.3
141.5
166.0
115.3
174.1
131.0
167.5 176.8
147.4 146.1
174.4 168.8
109.2 107.3
172.1 169.6
163.6(8)
134.5 103.4
94.85(2)
H2-Ru-Si-H1 3.6
R1-Si-Ru-H1 176.9
0.0
1.0
-1.5
177.7
2.0
0.4
179.7 179.0
179.9
∆Eisom
0.0
+6.6 0.0
+8.4
a R1 is the silicon substituent which is in the equatorial plane of the S3
complexes; R2 and R3 are the others. Distances are given in Å, angles in
deg, and relative energies in kJ mol-1. The corresponding X-ray data for
3MeCl2 are given in italics for comparison.
ligand. The crystal structure is in perfect agreement with the
NMR data and confirms also a 16-electron formulation for
3MeCl2.
In species incorporating hydride and σ-ligands, it is very often
difficult to propose arrested well-defined structures. In such
cases, DFT studies can greatly improve the understanding of
the coordination modes of the various ligands.8,15,16 Thus, in
addition to the experimental work, we have performed a theor-
etical study on the new family of complexes using DFT at the
B3PW91 level. PMe3 was selected to model the behavior of the
PCy3 phosphanes. The main data for the RuCl(SiMe3-nCln)-
(η2-H2)(PMe3)2 (S3Me3-nCln) series (n ) 1-3) are depicted
in Table 2 (see also Figure 2). For comparative purpose, a DFT
study was also performed on the model RuClH(η2-H2)(PMe3)2
(17) Chaudret, B.; Chung, G.; Eisenstein, O.; Jackson, S. A.; Lahoz, F.
J.; Lopez, J. A. J. Am. Chem. Soc. 1991, 113, 2314-2316.
(18) Hu¨bler, K.; Hunt, P. A.; Maddock, S. M.; Rickard, C. E. F.; Roper,
W. R.; Salter, D. M.; Schwerdtfeger, P.; Wright, L. J. Organometallics 1997,
16, 5076-5083.
(19) Heinekey, D. M.; Lledos, A.; Lluch, J. M. Chem. Soc. ReV. 2004,
33, 175-182.
(20) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes; Kluwer
Academic/Plenum Publishers: New York, 2001.
(15) Maseras, F.; Lledos, A.; Clot, E.; Eisenstein, O. Chem. ReV. 2000,
100, 601-636.
(16) Bader, R. F. W.; Matta, C. F.; Corte´s-Guzma´n, F. Organometallics
2004, 23, 6253-6263.
(21) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789-805.
(22) Gerard, H.; Eisenstein, O. Dalton Trans. 2003, 839-845.

3716 Organometallics, Vol. 26, No. 15, 2007
Lachaize et al.
Scheme 2. Synthetic Route to
RuCl(SiMe3-nCln)(η2-HD)(PCy3)2 (3Me3-nCln-d, n ) 1-3)
Scheme 3. Reactivity of 3Me2Cl with Ethylene and Styrene
Reactivity of the Silyl σ-Dihydrogen Complexes. Dihydro-
gen was bubbled into NMR samples of 3Me3-nCln (n ) 1 -
We have looked for the transition states (TS) connected to
the isomerization process from the silyl σ-dihydrogen to the
hydrido σ-silane species. In the case of S3Me2Cl (R1 ) Me)
we found a TS at 16.0 kJ mol-1 with a geometry resembling
that of the starting material, the SiR3 group being rotated by
ca. 60°. An increased delocalization is observed with the H1-
H2 distance elongated to 1.43 Å and the Si-H1 distance reduced
to 1.94 Å (the corresponding values for the minimum were 1.38
and 2.09 Å). In the case of S3MeCl2 (R1 ) Me) we found a
TS at 20.4 kJ mol-1 with a geometry again resembling that of
the starting complex, the SiR3 group being rotated by ca. 60°.
In contrast, very small variations of the key parameters, H1-
H2 and Si-H1 distances, are observed: 1.03 Å versus 1.07 Å
for the H1-H2 distance and 2.20 Å for the Si-H1 distance
both in the TS and in the starting minimum. In the two systems,
such a pathway allowing the isomerization of the σ-dihydrogen
to the σ-silane structure has a low cost in energy. It occurs by
simple rotation of the SiR1R2R3 group, with a fine tuning of
the various interactions: H‚‚‚H, Si‚‚‚H, and Ru‚‚‚SiR1R2R3.
An alternative pathway involving silane dissociation cannot be
excluded, however, regarding the flatness of the potential energy
curve and the facility of redistribution reactions at Si (see also
Discussion).
Deuteriation of the Silyl σ-Dihydrogen Complexes. In order
to get more information on the dihydrogen ligand activation
degree within this new family, we measured the JHD coupling
constant of the partially deuterated species RuCl(SiMe3-nCln)-
(η2-HD)(PCy3)2 (3Me3-nCln-d, n ) 1-3). The NMR samples
were all prepared in the same way. The deuterated isomer of 2
was first prepared by exposing 2 under a D2 atmosphere. Total
H/D exchange of the hydrido σ-dihydrogen ligands was
observed within 3 min. Two equivalents of chlorosilane was
then added (see Scheme 2). The hydride signal for 3Me3-nCln-
d now appears as a triplet of triplets resulting from the coupling
with the two phosphorus atoms and the deuterium. No signifi-
cant isotopic effect was detected at room temperature. A
maximum chemical shift variation of ∆δ ) -0.06 ppm was
measured for 3Me2Cl. The JHD coupling constant values are
12.0, 17.5, and 18.9 Hz for n ) 1-3, respectively. Measure-
ments of the JHD values in the range 193-293 K did not lead
to any significant variation.23 The JHD values increase with the
number of chlorine substituents, meaning that the HD ligand is
more elongated in 3Me2Cl than in 3MeCl2 and 3Cl3. The
methyl/chlorine replacement has apparently more influence on
the HD activation between the two former complexes than
between the two latter species.
1
3) in toluene-d8. H and 31P NMR monitoring showed that the
starting complex immediately disappeared, leading to the
formation of new species characterized by broad signals in the
hydride region. Unfortunately, due to multiple exchange and
redistribution processes, we were not able to isolate or charac-
terize any species.
We have treated the silyl σ-dihydrogen complexes with
ethylene in toluene-d8. Remarkably, 3MeCl2 and 3Cl3 do not
react at all and are stable under an atmospheric pressure of
ethylene. In contrast, 3Me2Cl gives the new hydrido η2-ethylene
complex RuClH(η2-C2H4)(PCy3)2 (4) in addition to traces of
ethane, chlorodimethylvinylsilane, and chloroethyldimethylsilane
(see Scheme 3). Complex 4 can be directly formed by reaction
of 2 with ethylene. The 1H NMR spectrum of 4 shows a broad
peak for the ethylene protons at δ 2.83 and a very shielded
triplet at δ -21.48 (JPH ) 17.6 Hz), in agreement with a hydride
trans to a vacant site. The 4:1 ratio for these two signals is
consistent with the proposed 16-electron formulation. An
analogous PiPr3 complex has already been experimentally and
theoretically characterized.24,25 The reaction is reversible, as
addition of HSiMe2Cl (2 equiv) on 4 leads to the formation of
3Me2Cl and traces of the same organic products. When C2H4
was bubbled into a toluene-d8 solution of 2 with an excess of
HSiMe2Cl (10 equiv), 3Me2Cl was the only detected complex,
which means that, under these conditions, it is more stable than
4.
Replacing ethylene by styrene yields the new silyl η6-arene
complex RuCl(SiMe2Cl)(η6-C8H10)(PCy3) (5) (see Scheme 3).
Compound 5 was fully characterized by NMR spectroscopy.
Hydrogenation of styrene into ethylbenzene and coordination
to the Ru center was confirmed by 1H and 13C NMR data. The
arene resonances are shifted to higher field as a result of
coordination to the metal center.26,27 Five signals of equal
intensity are observed between δ 4.35 and 6.19 in the 1H NMR
spectrum, and hydrogenation of the vinyl group is evidenced
by the corresponding signals of the ethyl group at δ 1.06 and
2.29. The silyl ligand is characterized by two singlets at δ 1.06
and 1.22, which correlate to one singlet at δ 51.0 in the
29Si{1H,31P} NMR spectrum. Arene coordination to the metal
(24) Coalter, J. N., III; Bollinger, J. C.; Huffman, J. C.; Werner-
Zwanziger, U.; Caulton, K. G.; Davidson, E. R.; Gerard, H.; Clot, E.;
Eisenstein, O. New J. Chem. 2000, 24, 9-26.
(25) Gerard, H.; Clot, E.; Giessner-Prettre, C.; Caulton, K. G.; Davidson,
E. R.; Eisenstein, O. Organometallics 2000, 19, 2291-2298.
(26) Burgio, J.; Yardy, N. M.; Petersen, J. L.; Lemke, F. R. Organo-
metallics 2003, 22, 4928-4932.
(23) Gelabert, R.; Moreno, M.; Lluch, J. M.; Lledos, A.; Pons, V.;
Heinekey, D. M. J. Am. Chem. Soc. 2004, 126, 8813-8822.
(27) Borowski, A. F.; Sabo-Etienne, S.; Chaudret, B. J. Mol. Catal. A
2001, 174, 69-79.

ActiVation of Chlorosilanes at Ruthenium
Organometallics, Vol. 26, No. 15, 2007 3717
Table 3. Thermodynamic Data (kJ mol-1) Calculated for
the Reaction of RuClH(η2-H2)(PMe3)2 (S2) with HSiMe3-nCln
To Form S3Me3-nCln and H2 (n ) 1-3)
center is the driving force of the reaction of styrene with
3Me2Cl, leading to the formation of 5. In situ monitoring of
1
the addition of 1 equiv of styrene to 3Me2Cl by H and 31P
S3Me2Cl
S3MeCl2
NMR showed the quantitative formation of 5 and free PCy3.
R1 ) Me
R1 ) Cl
R1 ) Me
R1 ) Cl
S3Cl3
Discussion
∆E
-36.9
-38.5
-14.0
-30.2
-31.0
-8.7
-63.7
-66.5
-42.1
-55.3
-56.1
-34.6
-78.3
-81.3
-62.3
∆Ha
∆Ga
The reaction of the 16-electron hydrido σ-dihydrogen complex
2 with a series of chlorosilanes gives access to the corresponding
16-electron silyl σ-dihydrogen complexes 3 with concomitant
dihydrogen evolution. The bonding mode of the various ligands
in the coordination sphere of the metal in 3 has been evaluated
by combining NMR, X-ray, and DFT studies. The bonding
distance of the σ-dihydrogen ligand can be estimated by NMR
either by T1 measurements or by deuteration experiments from
the JHD values. T1(min) values lead to rather large H-H distance
ranges, since the physical model which is used to determine
the distance is strongly dependent on the rotation speed of the
σ-dihydrogen ligand.20,28 The following ranges have been
obtained: 0.99-1.24 Å for 3Me2Cl, 0.93-1.17 Å for 3MeCl2,
and 0.95-1.19 Å for 3Cl3. It is thus difficult to establish a trend,
as the values largely overlap for the three complexes. It was
possible to prepare the partially deuterated σ-dihydrogen
complexes RuCl(SiMe3-nCln)(η2-HD)(PCy3)2 (3Me3-nCln-d, n
) 1-3). Measurements of the JHD coupling constants give
access to the corresponding H-D distances by using the model
developed by Gru¨ndemann et al.29 The following values were
obtained: 1.05 ( 0.01 Å for 3Cl3, 1.08 ( 0.01 Å for 3MeCl2,
and 1.21 ( 0.01 Å for 3Me2Cl. They fall within the range
derived from T1 data. Introduction of only one chlorine
substituent leads to the stretched dihydrogen complex 3Me2Cl,
whereas by replacing Me by one or two Cl, the complexes
display a dihydrogen ligand at the unstretched/stretched
borderline.19-21 In the case of 3MeCl2-d the dHD value of 1.08
( 0.01 Å compares well with the H-H distance of 1.05(3) Å,
as determined by X-ray diffraction for 3MeCl2. Importantly,
DFT studies indicate a similar trend, with 3Me2Cl displaying a
much more stretched H-H ligand (1.387 Å) than 3MeCl2 (1.073
Å) and 3Cl3 (1.063 Å).
Various isomers were optimized at the DFT/B3PW91 level.
The σ-dihydrogen isomer was always the lowest in energy but
was almost degenerate with the σ-silane isomer. It should be
noted that a similar situation was previously reported by Maseras
and Lledos for the osmium model OsCl(CO)(PH3)2“H2SiR3”.30
In our system, the strongest σ-donor ligand was always located
trans to the empty coordination site. Thus, for the silyl
σ-dihydrogen isomers, the silyl is trans to the vacant site,
whereas for the hydrido σ-silane isomers, the hydride is trans
to the vacant site. Moreover, in the case of S3MeCl2 and
S3Me2Cl, the only isomers that could be optimized with a
σ-dihydrogen ligand had a Me in the equatorial plane. Dihy-
drogen isomers with a Cl in the equatorial plane never
converged. No isomer with a σ-dihydrogen ligand orthogonal
to the equatorial plane could be optimized. Notably, for both
the σ-silane and silyl formulations, the Ru-Si distance is little
affected (maximum variation of 0.006 Å). All three σ-dihydro-
gen isomers of the S3 series present a SISHA interaction (2.009,
2.204, and 2.172 Å) between the silicon and one hydrogen of
the σ-dihydrogen ligand. This is of course in favor of an easy
process leading to a hydrido σ-silane isomer from the corre-
a At 298.15 K.
sponding silyl σ-dihydrogen species. This corresponds to a
prototype of the σ-CAM mechanism and is the microreverse
pathway of the reaction illustrated in eq 1 in the Introduction.5
Indeed, the two isomers of S3MeCl2 and S3Me2Cl are almost
degenerate: +6.6 and +8.4 kJ mol-1 for the σ-silane, respec-
tively. Our data complement those recently reported by Vy-
boishchikov and Nikonov on an iron system31 and highlight
again the preference of silicon to be hypervalent.
The addition of the silane compound HSiMe3-nCln (n ) 1-3)
to the 16-electron hydrido σ-dihydrogen species 2, leading to
the formation of the corresponding silyl σ-dihydrogen complexes
3 with concomitant dihydrogen evolution, can be analyzed by
DFT by using the models S2 and S3. The thermodynamic
quantities are gathered in Table 3. The energy values are all
negative, regardless of the number of chloro substituents on Si.
We note, again, a more important difference between S3Me2Cl
on one side and S3MeCl2 and S3Cl3 on the other side. We have
already mentioned that when 3 was exposed to a dihydrogen
atmosphere, the reactions were complex, far from just a
reversible process which would give back 2 and free silane. In
such a case, we would expect ∆G values closer to 0, as was
observed for example in the case of dihydrogen/dinitrogen
substitution in 1.32
Reactivity studies toward ethylene also highlight the specific
properties of 3Me2Cl versus the two other complexes. In the
absence of excess silane, no reaction with ethylene was observed
for 3MeCl2 and 3Cl3, whereas addition of ethylene to 3Me2Cl
leads to the formation of the hydrido η2-ethylene complex
RuClH(C2H4)(PCy3)2 (4). The reaction of 4 with 2 equiv of
HSiMe2Cl leads back to 3Me2Cl, in addition to products
resulting from hydrosilylation and dehydrogenative silylation.
This is in agreement with the fact that when 2 is placed under
catalytic conditions, i.e., excess HSiMe2Cl and excess C2H4,
we only detected 3Me2Cl and the catalysis proceeded.
As mentioned in the Introduction, during our NMR study on
dehydrogenative silylation of ethylene with chlorosilanes
HSiMe3-nCln (n ) 1, 2) and RuH2(η2-H2)2(PCy3)2 (1) as a
catalyst precursor, we detected the formation of new silane
compounds as well as chloro ruthenium complexes and in
particular traces of 2.11,14 The same observation was made when
performing the reactions in the presence of an amine (NEt3).
This excluded HCl formation in solution and confirmed that
Si-Cl bond activation really occurred at the ruthenium center,
leading to redistribution products.26,33,34 When a large excess
of HSiMe2Cl (about 20 equiv) was added to 2, new organosi-
lanes were detected, in agreement with redistribution reactions
(31) Vyboishchikov, S. F.; Nikonov, G. I. Chem. Eur. J. 2006, 12, 8518-
8533.
(32) Ben Said, R.; Hussein, K.; Tangour, B.; Sabo-Etienne, S.; Barthelat,
J. C. J. Organomet. Chem. 2003, 673, 56-66.
(28) Morris, R. H.; Wittebort, R. J. Magn. Reson. Chem. 1997, 35, 243-
250.
(29) Grundemann, S.; Limbach, H. H.; Buntkowsky, G.; Sabo-Etienne,
S.; Chaudret, B. J. Phys. Chem. A 1999, 103, 4752-4754.
(30) Maseras, F.; Lledos, A. Organometallics 1996, 15, 1218-1222.
(33) Ben Said, R.; Hussein, K.; Barthelat, J.-C.; Atheaux, I.; Sabo-
Etienne, S.; Grellier, M.; Donnadieu, B.; Chaudret, B. Dalton Trans. 2003,
4139-4146.
(34) Osipov, A. L.; Gerdov, S. M.; Kuzmina, L. G.; Howard, J. A. K.;
Nikonov, G. I. Organometallics 2005, 24, 587-602.

3718 Organometallics, Vol. 26, No. 15, 2007
Lachaize et al.
Figure 3. Energy profile as a function of the H1-H2 distance in S3Me2Cl. Comparison of the two isomers with R1 ) Cl, Me.
Figure 4. Energy profile as a function of the H1-H2 distance in S3MeCl2. Comparison of the two isomers with R1 ) Cl, Me.
at the ruthenium center. H2SiMe2, HSiMe3, and HSiMeCl2 were
in particular characterized in non-negligible quantities. Two
organometallic species were identified: as expected, 3Me2Cl
was the major species, since HSiMe2Cl was used in a very large
excess, but 3MeCl2 was also detected, whereas we did not see
any trace of 3Cl3.
The difference of activity between 3Me2Cl and the two other
complexes 3MeCl2 and 3Cl3 toward ethylene can be explained
by a stronger Ru-Si bond when more Cl substituents are
introduced. However, it is rather surprising that, under an
ethylene atmosphere, the H2 ligand remains coordinated to the
Ru center. The main difference highlighted by the theoretical
study is that in the case of S3Me2Cl (R1 ) Me) the σ-dihy-
drogen ligand is extremely stretched (H-H distance of 1.387
Å) and the σ-silane isomer (R1 ) Cl) is very close in energy
(+6.6 kJ mol-1). We can assume that in 3Me2Cl we have a
delocalized system favoring ethylene coordination. In contrast,
in 3MeCl2 and 3Cl3, it is more difficult to coordinate the olefin
trans to the σ-donor silyl ligand.
optimization was conducted on all the other parameters. In the
case of S3Me2Cl (R1 ) Me) the minimum corresponds to a
very stretched dihydrogen structure (H-H distance of 1.387
Å) and a very flat potential energy curve is observed from 1.0
to 1.7 Å, which means that dihydrogen activation can occur
with essentially no activation barrier (Figure 3). On the other
hand, for S3Me2Cl (R1 ) Cl) the minimum corresponds to a
σ-silane structure (Si-H1 1.878 Å) with the hydrogen H2
displaying a cis interaction with H1 (1.659 Å).15 As reported
by Nikonov et al., the complex Cp*RuCl(η2-HSiMe2Cl)(PiPr3)
is characterized by a σ-silane coordination with a stretched Ru-
Si distance of 2.3982(7) Å and an additional RuCl‚‚‚SiCl
interligand interaction.35 In the case of S3MeCl2 the minimum
for (R1 ) Me) now has a H-H distance of 1.073 Å and the
curve is flatter for the σ-silane isomer (R1 ) Cl) than for the
σ-dihydrogen isomer (R1 ) Me) (Figure 4). Only one isomer
was optimized in the case of S3Cl3. It has a silyl σ-dihydrogen
structure with a dH-H distance of 1.063 Å (Si-H1 distance of
2.172 Å) (Figure 5). It is interesting here to mention that the
“SiCl3” complex [Cp(PMe3)2Ru(η2-HSiCl3)]+ reported by Lemke
et al. displays a σ-silane structure, as evidenced by X-ray (Si-H
Figures 3-5 show the energy profile as a function of the
H-H distance in S3. In the case of S3Me2Cl and S3MeCl2 the
two isomers resulting from the position of the substituents on
Si are shown in Figures 3 and 4, respectively. The H-H distance
was constrained to values varying from 0.8 to 1.9 Å, and the
(35) Osipov, A. L.; Vyboishchikov, S. F.; Dorogov, K. Y.; Kuzmina, L.
G.; Howard, J. A. K.; Lemenovskii, D. A.; Nikonov, G. I. Chem. Commun.
2005, 3349-3351.

ActiVation of Chlorosilanes at Ruthenium
Organometallics, Vol. 26, No. 15, 2007 3719
Figure 5. Energy profile and variation of the Si-H1 distance as a function of the H1-H2 distance in S3Cl3.
Table 4. Selected Bond Distances of the Optimized Geometries of RuCl(SiMe3-nCln)(η2-H2)(PMe3)2 (S3Me3-nCln, n ) 1-3) with
the H1-H2 Distance Constraint at 1.1 Åa
S3Me2Cl
S3MeCl2
S3Cl3
for SISHA
consideration
R1 ) Me
R1 ) Cl
R1 ) Me
R1 ) Cl
R1 ) Cl
Si··‚H1
2.183
2.128
2.185
R2 ) Cl,
R3 ) Cl
2.286
2.135
2.142
for Ru back-bonding
consideration
Ru-Si
R2 ) Me,
R3 ) Cl
2.317
R2 ) Me,
R2 ) Me,
R3 ) Cl
2.293
R2 ) Cl,
R3 ) Me
R3 ) Cl
2.327
+15.6
2.269
∆E (between
rotamers)
0.0
0.0
+12.9
a R1 is the silicon substituent which is in the equatorial plane. Distances are given in Å, angles in deg, and relative energies in kJ mol-1
.
Table 5. Selected Bond Distances of the Optimized
Geometries of RuCl(SiMe3-nCln)(η2-H2)(PMe3)2 (S3Me3-nCln,
n ) 1-3) with the H1-H2 Distance Constraint at 1.8 Å for
bond is thus favored. Even if the variations are rather small,
this phenomenon is indicated by the shortening of the Ru-Si
distances. An important study on a series of silyl complexes
containing the CpRu(PR3)2 moiety has been reported by Lemke
et al. He analyzed in great detail by NMR and X-ray parameters
the effect of Si substituents on the d(Ru)-σ*(Si-R) π-back-
bonding interaction.37-39 A similar study was performed by
Nikonov et al. on the addition of HSiMe3-nCln (n ) 1-3) to
Cp*RuH3(PR3). In that case, extensive redistribution at Si was
observed, leading to a mixture of various silyl dihydride or silyl
hydrido chloro complexes.34 It is interesting to compare the three
curves shown in Figures 3-5 and set up the dH-H distance at
1.1 Å. One can see that the energy differences between the two
isomers R1 ) Me, Cl for S3Me2Cl and S3MeCl2 are similar:
+15.6 and +12.9 kJ mol-1, respectively. The dH-H distance of
1.1 Å is very close to the value found for the 3Cl3 minimum
with a corresponding Si‚‚‚H distance of 2.142 Å, indicative of
a SISHA interaction. When the Si‚‚‚H distances in S3Me2Cl
and S3MeCl2 are compared, it seems that SISHA are favored
when R1 is a chloride. If we now consider the intercepts of the
two curves shown in Figures 3 and 4, H-H distances of 1.8
and 1.7 Å are found for S3Me2Cl and S3MeCl2, respectively,
with an energy difference with the points at 1.1 Å, of ca. 6 and
9.5 kJ mol-1, respectively. Again, the energy differences are
small, but an increase is observed when adding more chloride,
a
S3Me2Cl and 1.7 Å for S3MeCl2
S3Me2Cl
S3MeCl2
(H1‚‚‚H2 ) 1.8 Å)
(H1‚‚‚H2 ) 1.7 Å)
for SISHA
consideration
Si··‚H1
for Ru back-bonding R2 ) Me, R2 ) Me,
consideration R3 ) Cl R3 ) Me
Ru-Si 2.322 2.319
∆Eb
+5.6 +6.1
R1 ) Me
R1 ) Cl
R1 ) Me
R1 ) Cl
1.825
1.831
1.846
1.849
R2 ) Cl,
R2 ) Me,
R3 ) Cl
2.289
R3 ) Cl
2.293
+9.5
+9.4
a R1 is the silicon substituent which is in the equatorial plane. Distances
are given in Å, angles in deg, and relative energies in kJ mol-1 b Relative
.
to the isomer with H1‚‚‚H2 ) 1.1 Å.
distance of 1.77(5) Å) and NMR data.36 The Ru-Si distance
of 2.329(1) Å is longer than that in the corresponding silyl
complex Cp(PMe3)2Ru(SiCl3) (2.265(2) Å). In our system, the
Ru-Si distance of 2.270 Å calculated for S3Cl3 by DFT/
B3PW91 is in agreement with a silyl formulation.
In order to better analyze the influence of the chloro
substituents, we have reported in Tables 4 and 5 some key
parameters derived from the DFT calculations. If we consider
the three dihydrogen isomers S3Me2Cl, S3MeCl2, and 3Cl3,
one key point on going from “SiMe2Cl” to “SiMeCl2” and
finally to “SiCl3” is that back-donation from Ru to the σ* orbital
of the R2 and R3 substituents are maximized in the case of
chloride versus methyl substituents. Formation of the Ru-Si
(37) Lemke, F. R.; Galat, K. J.; Youngs, W. J. Organometallics 1999,
18, 1419-1429.
(38) Freeman, S. T. N.; Lofton, L. L.; Lemke, F. R. Organometallics
2002, 21, 4776-4784.
(36) Freeman, S. T. N.; Lemke, F. R.; Brammer, L. Organometallics
2002, 21, 2030-2032.
(39) Freeman, S. T. N.; Petersen, J. L.; Lemke, F. R. Organometallics
2004, 23, 1153-1156.

3720 Organometallics, Vol. 26, No. 15, 2007
Lachaize et al.
Xcalibur Oxford Diffraction diffractometer, equipped with an
Oxford Cryosystems cryostream cooler device and using graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å). The complex
RuH2(η2-H2)2(PCy3)2 (1) was prepared according to published
procedures.40
which is consistent with a more advanced Si-H activation. For
the values at 1.7-1.8 Å (σ-silane formulation), the position of
the Si substituents is not as important as it was for a value of
1.1 Å (σ-dihydrogen formulation).
RuClH(η2-H2)(PCy3)2 (2). Method a. Addition of HSiMe2Cl
(33.2 µL, 0.30 mmol) at 0 °C to a stirred suspension of 1 (100.0
mg, 0.15 mmol) in 4 mL of pentane resulted in gas evolution and
in immediate dissolution. An orange solid precipitated after 10 min.
About 30 min later, the solution was filtered off and the solid was
washed with pentane (2 × 1.5 mL) at 0 °C, before being dried
under an argon flow and vacuum (40% yield).
Method b. Addition of a hexane solution of ClBCy2 (0.85 mL,
0.85 mmol) to a stirred suspension of 1 (407 mg, 0.61 mmol) in
pentane (4 mL) resulted in slow dissolution and progressive orange
coloration. A solid was formed after 45 min at room temperature.
The solution was filtered off at -60 °C, and the solid was washed
with pentane (2 × 1.5 mL). The orange solid was dried under an
argon flow and vacuum (95% yield).
1H NMR (C6D6, 293 K, 300.13 MHz): δ -16.07 (br s, 3H,
RuH3), 0.9-2.4 (66H, PCy3). 31P{1H} NMR (C6D6, 293 K, 121.49
MHz): δ 53.6 (s). Anal. Calcd for C36H69ClP2Ru: C, 61.72; H,
9.94. Found: C, 61.37; H, 9.88.
Conclusion
Addition of chlorosilanes to the 16-electron complex RuClH-
(η2-H2)(PCy3)2 leads to dihydrogen evolution and formation of
the corresponding silyl σ-dihydrogen complexes RuCl-
(SiMe3-nCln)(η2-H2)(PCy3)2. Several pathways can be proposed
to achieve the final products. Coordination of the silane to the
unsaturated species could lead to the 18-electron σ-dihydrogen
σ-silane species RuClH(η2-HSiMe3-nCln)(η2-H2)(PCy3)2. Evolu-
tion of dihydrogen, followed by oxidative addition of the silane,
would result in the formation of the ruthenium(IV) dihydride
complex RuClH2(SiMe3-nCln)(PCy3)2. Then, isomerization of
the dihydride into a σ-dihydrogen ligand would result in the
final product with a ruthenium in the reduced oxidation state
II. Alternatively, the first step could simply be the substitution
of the σ-dihydrogen ligand by the silane.
In view of all the data concerning the σ-silane complexes,
especially in ruthenium chemistry, a mechanism implying a
σ-CAM sequence can be proposed.5 Substitution of the σ-di-
hydrogen ligand by the silane results in the formation of the
σ-silane species RuClH(η2-HSiMe3-nCln)(PCy3)2. Then, a σ-CAM
process leads to the formation of the σ-dihydrogen complex
RuCl(SiMe3-nCln)(η2-H2)(PCy3)2. The most significant trend to
note is the importance of the location of the Cl substituents
which favor either a σ-silane or a σ-dihydrogen coordination.
The establishment of secondary interactions (SISHA) between
the silicon and the hydrogen atoms allows such a process to
occur with no activation barrier. Our system illustrates perfectly
a σ-CAM sequence as in eq 1. Moreover, as already pointed
out by Lemke, the influence of the Si substituents has to be
taken into account, since the effect on the electron density
transferred from Ru to Si-R is greatly influenced by the nature
of the R substituents.
RuCl(SiMe2Cl)(η2-H2)(PCy3)2 (3Me2Cl). Addition of 25 µL of
HSiMe2Cl (0.23 mmol) to a solution of 2 (20 mg, 0.028 mmol) in
0.5 mL of THF resulted in gas evolution, and the solution darkened.
An orange solid precipitated after 12 h at -30 °C. It was filtered
and dried in vacuo (79% yield).
2
1H NMR (C7D8, 288 K, 400.13 MHz): δ -13.75 (br t, JPH
)
9.7 Hz, 2H, Ru(σ-H2)), 1.41 (s, SiMe2). T1(min) (C7D8, 253 K,
300.13 MHz): 29 ms for the high-field signal. 31P{1H} NMR (C7D8,
288 K, 161.97 MHz): δ 46.7 (s). 29Si{1H,31P} NMR (C7D8, 288
K, 79.49 MHz): δ 85.7 (s). Anal. Calcd for C38H74Cl2P2RuSi: C,
57.55; H, 9.41. Found: C, 57.58; H, 8.89.
For comparison, NMR data for the free silane HSiMe2Cl are as
1
follows. H NMR (C7D8, 293 K, 400.13 MHz): δ 4.92 (septet,
1JSiH ) 223.3 Hz, SiH). 29Si{1H} NMR (C7D8, 293 K, 79.49
MHz): δ -11.1 (s). The 29Si chemical shift was taken from ref
41.
RuCl(SiMeCl2)(η2-H2)(PCy3)2 (3MeCl2). Addition of 4.6 µL
of HSiMeCl2 (0.044 mmol) to a suspension of 2 (31.0 mg, 0.044
mmol) in 3 mL of pentane resulted in total dissolution of the solid.
The resulting orange solution, kept at room temperature for 24 h,
gave small dark orange crystals suitable for X-ray measurements.
This compound was isolated using the same procedure as for
3Me2Cl: addition of 25 µL of HSiMe2Cl (0.24 mmol) to a solution
of 2 (20 mg, 0.028 mmol) in 0.5 mL of THF resulted in gas
evolution, and the solution darkened. An orange solid precipitated
after 12 h at -30 °C. It was filtered and dried in vacuo.
1H NMR (C7D8, 293 K, 400.13 MHz): δ -12.14 (br, 2H, Ru-
(σ-H2)), 1.78 (s, SiMe). T1(min) (C7D8, 253 K, 400.13 MHz): 27
ms for the high-field signal. 31P{1H} NMR (C7D8, 293 K, 161.97
MHz): δ 45.5 (s). 29Si{1H,31P} NMR (C7D8, 293 K, 79.49 MHz):
δ 72.6 (s). Anal. Calcd for C37H71Cl3P2RuSi: C, 54.63; H, 8.80.
Found: C, 54.82; H, 8.88.
Another alternative implying dihydrogen formation by direct
reaction of the hydride with the free silane cannot be excluded,
and further investigations will be performed to get more
information on the mechanism of the overall process.
It is remarkable that no reaction was observed with ethylene
in the case of 3MeCl2 and 3Cl3, whereas the ethylene complex
4 was obtained in the case of 3Me2Cl. The trans silyl effect
more prominent in 3MeCl2 and 3Cl3 might prevent any
coordination in the vacant site, whereas for 3Me2Cl, the SISHA
interaction between the silicon and one hydrogen of the stretched
dihydrogen ligand allows the formation of 4.
Experimental Section
General Methods. All reactions were performed using standard
Schlenk or drybox techniques under argon. Solvents were dried
and distilled prior to use. All reagents were purchased from Aldrich,
except RuCl3·3H2O, which came from Johnson Matthey Ltd., and
were used without further purification. NMR solvents were dried
using appropriate methods and degassed prior to use. NMR samples
of sensitive compounds were all prepared under an argon atmo-
sphere, using NMR tubes fitted with Teflon septa. NMR spectra
were recorded on Bruker DPX 300 (with 1H at 300.13 MHz, 31P at
121.49 MHz, and 13C at 75.46 MHz), AMX 400 (with 1H at 400.13
MHz, 31P at 161.98 MHz, 13C at 100.62 MHz, 29Si at 79.50 MHz,
For comparison, NMR data for the free silane HSiMeCl2 are as
follows. 1H NMR (C7D8, 293 K, 400.13 MHz): δ 5.32 (quar, 1JSiH
) 282.4 Hz, SiH). 29Si{1H} NMR (C7D8, 293 K, 79.49 MHz): δ
-14.7 (s).
RuCl(SiCl3)(η2-H2)(PCy3)2 (3Cl3). Addition of 4 µL of HSiCl3
(0.042 mmol) to a solution of 2 (20 mg, 0.028 mmol) in 0.5 mL of
THF resulted in darkening of the pale orange solution. An orange
solid precipitated after 12 h at -30 °C. It was filtered and dried in
vacuo.
(40) Borowski, A. F.; Sabo-Etienne, S.; Christ, M. L.; Donnadieu, B.;
Chaudret, B. Organometallics 1996, 15, 1427-1434.
(41) Dubois Murphy, P.; Taki, T.; Sogabe, T.; Metzler, R.; Squires, T.
G.; Gerstein, B. C. J. Am. Chem. Soc. 1979, 101, 4055-4058.
2
1
and H at 61.42 MHz), and AV 500 spectrometers (with H at
500.33 MHz, 31P at 202.55 MHz, 13C at 125.82 MHz, and 29Si at
99.40 MHz). Crystal data were collected at low temperature on an

ActiVation of Chlorosilanes at Ruthenium
1H NMR (C7D8, 293 K, 300.13 MHz): δ -12.02 (br t, JPH
9.0 Hz, 2H, Ru(σ-H2)). T1(min) (C7D8, 253 K, 300.13 MHz): 23
ms for the high-field signal. 31P{1H} NMR (C7D8, 293 K, 161.97
MHz): δ 46.0 (s). 29Si{1H,31P} NMR (C7D8, 293K, 99.40 MHz):
δ 14.8 (s). Anal. Calcd for C36H68Cl4P2RuSi: C, 51.85; H, 8.22.
Found: C, 52.63; H, 8.01.
Organometallics, Vol. 26, No. 15, 2007 3721
2
)
tential using the Durand-Barthelat method.45 The 16 electrons
corresponding to the 4s, 4p, 4d, and 5s atomic orbitals were
described by a (7s, 6p, 6d) primitive set of Gaussian functions
contracted to (5s, 5p, 3d). Standard pseudopotentials developed in
Toulouse were used to describe the atomic cores of all other non-
hydrogen atoms (C, Si, P, and Cl).46 A double-ú plus polarization
valence basis set was employed for each atom (d-type function
exponents were 0.80, 0.45, 0.45, and 0.65, respectively). For
hydrogen, a standard primitive (4s) basis contracted to (2s) was
used. A p-type polarization function (exponent 0.9) was added for
the hydrogen atoms directly bound to ruthenium. The geometries
of the various critical points on the potential energy surface were
fully optimized with the gradient method available in Gaussian 98.
Calculations of harmonic vibrational frequencies were performed
to determine the nature of each critical point. Constraints were used
only to calculate the potential energy curve along the H1‚‚‚H2
distance axis in the S3 series of complexes. The same calculations
using the B3LYP functional43,47 gave similar results, but the relevant
theoretical data were not as good as with B3PW91 in comparison
to the experimental data (see the Supporting Information).
For comparison, NMR data for the free silane HSiCl3 are as
follows. 1H NMR (C7D8, 293 K, 400.13 MHz): δ 5.73 (s, 1JSiH
)
370.6 Hz, SiH). 29Si{1H} NMR (C7D8, 293 K, 79.49 MHz): δ -9.6
(s).
RuClH(η2-C2H4)(PCy3)2 (4). Complex 4 resulted from C2H4
bubbling into a C7D8 solution of 2 (13.0 mg, 0.019 mmol). NMR
measurements of the sample showed the formation of 4 as the only
1
organometallic species. H NMR (C7D8, 273 K, 400.13 MHz): δ
-21.48 (t, 2JPH ) 17.6 Hz, 1H, RuH), 2.83 (br, 4H, RuC2H4). 31P-
{1H} NMR (C7D8, 273 K, 161.97 MHz): δ 36.5 (s). 13C{1H} NMR
(C7D8, 273 K, 100.62 MHz): δ 38.7 (br, C2H4). Any attempt to
isolate 4 failed.
RuCl(SiMe2Cl)(η6-C8H10)(PCy3) (5). Addition of 2.3 µL of
styrene (0.02 mmol) to a solution of 3Me2Cl (15 mg, 0.02 mmol)
in 1 mL of toluene resulted in an orange solution. The solution
was stirred overnight, and then the volatiles were removed under
reduced pressure, affording an orange oil. Stirring in pentane (2-3
mL) resulted in the formation of an orange solid at room
Acknowledgment. We thank the CNRS for support and the
CINES (Montpellier, France) for a generous allocation of
computer time. We gratefully acknowledge Prof. J.-C. Barthelat
and Dr. E. Clot for fruitful discussions on the theoretical study.
S.L. thanks the French Ministery “Education Nationale, Enseigne-
ment Supe´rieur, Recherche” for his AMN grant. A.C. thanks
the Spanish “Ministerio de Educacion y Ciencia” for a post-
doctoral fellowship.
1
temperature (95% yield). H NMR (C7D8, 293 K, 300.13 MHz):
δ 1.06 (s, 3H, SiMe), 1.06 (t, 3JHH ) 8 Hz, 3H, CH3 (Et)), 1.22 (s,
3
3H, SiMe), 1.60-1.90 (m, 33H, Cy), 2.29 (q, JHH ) 8 Hz, 2H,
3
3
CH2 (Et)), 4.35 (t, JHH ) 5.2 Hz, 1H, aromatic), 4.49 (d, JHH
)
5.8 Hz, 1H, aromatic), 4.86 (q, 3JHH ) 5.3 Hz, 1H, aromatic), 5.39
3
3
(d, JHH ) 5.7 Hz, 1H, aromatic), 6.19 (t, JHH ) 5.3 Hz, 1H,
aromatic). 13C{1H} NMR (C7D8, 293 K, 75.46 MHz): δ 11.7, 12.2,
14.5, 25.1, 26.8, 27.8, 27.9, 30.9, 71.7, 84.0, 84.6, 93.3, 97.3, 120.2.
31P{1H} NMR (C7D8, 293 K, 121.49 MHz): δ 36.7 (s). 29Si{1H,31P}
NMR (C7D8, 293 K, 99.40 MHz): δ 51.0 (s). Anal. Calcd for
C28H49Cl2PRuSi: C, 54.53; H, 8.01. Found: C, 54.01; H, 7.38.
Computational Details. DFT calculations were performed with
the Gaussian 98 series of programs42 using the nonlocal hybrid
functional denoted as B3PW91.43,44 For ruthenium, the core
electrons were represented by a relativistic small-core pseudopo-
Supporting Information Available: Text and tables giving
computational details and CIF files giving crystallographic data.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM700295G
(43) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
(44) Perdew, J. P.; Wang, Y. Phys. ReV. B 1992, 45, 13244-13249.
(45) Durand, P.; Barthelat, J. C. Theor. Chim. Acta 1975, 38, 283-302.
(46) Bouteiller, Y.; Mijoule, C.; Nizam, M.; Barthelat, J. C.; Daudey, J.
P.; Pelissier, M.; Silvi, B. Mol. Phys. 1988, 65, 295-312.
(42) Frisch, M. J., et al. Gaussian 98, revision A.11; Gaussian, Inc.,
Pittsburgh, PA, 2001.
(47) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785-789.