Oxidative addition of H-SiR3 to Di- and triruthenium carbonyl complexes bearing a bridging azulene ligand: Isolation of new silylruthenium complexes and catalytic hydrosilylation of ketones

Article abstract of DOI:10.1021/om0200050

Oxidative addition of PhMe₂SiH to di- and triruthenium carbonyl clusters bearing 4,6,8-trimethylazulene as the bridging ligand was studied in relation to mechanisms of hydrosilylation of ketones catalyzed by these complexes. Reaction of PhMe₂SiH with (μ₃,η⁵:η⁵-4,6,8-trimethylazulene)Ru ₃(CO)₇ (3) resulted in liberation of a CO ligand, oxidative addition of the Si-H bond, and hydrogenation of one carbon-carbon double bond in the azulene ligand to form a novel 46-electron cluster, (μ₂,η³:η⁵-4,5-dihydro-4,6,8-trimethy lazulene)Ru₃(H)(SiMe₂Ph)(CO)₆ (6). In contrast, (μ₂,η³:η⁵-4,6,8-trimethylazulene)Ru ₂(CO)₅ (4) reacted with HMe₂SiPh to give (μ₂,η³:η⁵-4,5-dihydro-4,6,8-trimethy lazulene)Ru₂(CO)₅(SiMe₂Ph)₂ (7), which has a unique Ru→Ru dative bond, by way of oxidative addition of two molecules of PhMe₂SiH to the starting diruthenium complex followed by hydrogenation of a carbon-carbon double bond in the azulene ligand. In contrast to the fact that the diruthenium complexes 4 and 7 are not catalytically active, the triruthenium clusters 3 and 6 are catalysts for the hydrosilylation of acetophenone with moderate catalytic activity. NMR observation of intermediates in the catalytic hydrosilylation of acetophenone using 6 as catalyst suggests the existence of a reaction pathway without a cluster fragmentation, in which the triruthenium cluster is involved in the catalytic cycle.

Full text of DOI:10.1021/om0200050

Organometallics 2002, 21, 3023-3032
3023
Oxid a tive Ad d ition of H-SiR3 to Di- a n d Tr ir u th en iu m
Ca r bon yl Com p lexes Bea r in g a Br id gin g Azu len e
Liga n d : Isola tion of New Silylr u th en iu m Com p lexes a n d
Ca ta lytic Hyd r osilyla tion of Keton es
Kouki Matsubara,†,§ Kazuhiro Ryu,‡ Tomoyuki Maki,‡ Takafumi Iura,‡ and
Hideo Nagashima*,†,‡,§
Institute of Advanced Material Study, Interdisciplinary Graduate School of Engineering
Sciences, and CREST, J apan Science and Technology Corporation (J ST), Kyushu University,
Kasuga, Fukuoka 816-8580, J apan
Received J anuary 2, 2002
Oxidative addition of PhMe2SiH to di- and triruthenium carbonyl clusters bearing 4,6,8-
trimethylazulene as the bridging ligand was studied in relation to mechanisms of hydrosi-
lylation of ketones catalyzed by these complexes. Reaction of PhMe2SiH with (µ3,η5:η5-4,6,8-
trimethylazulene)Ru3(CO)7 (3) resulted in liberation of a CO ligand, oxidative addition of
the Si-H bond, and hydrogenation of one carbon-carbon double bond in the azulene ligand
to form a novel 46-electron cluster, (µ2,η3:η5-4,5-dihydro-4,6,8-trimethylazulene)Ru3(H)(SiMe2-
Ph)(CO)6 (6). In contrast, (µ2,η3:η5-4,6,8-trimethylazulene)Ru2(CO)5 (4) reacted with HMe2-
SiPh to give (µ2,η3:η5-4,5-dihydro-4,6,8-trimethylazulene)Ru2(CO)5(SiMe2Ph)2 (7), which has
a unique RufRu dative bond, by way of oxidative addition of two molecules of PhMe2SiH to
the starting diruthenium complex followed by hydrogenation of a carbon-carbon double
bond in the azulene ligand. In contrast to the fact that the diruthenium complexes 4 and 7
are not catalytically active, the triruthenium clusters 3 and 6 are catalysts for the
hydrosilylation of acetophenone with moderate catalytic activity. NMR observation of
intermediates in the catalytic hydrosilylation of acetophenone using 6 as catalyst suggests
the existence of a reaction pathway without a cluster fragmentation, in which the
triruthenium cluster is involved in the catalytic cycle.
In tr od u ction
In contrast, reactions involving activation of hydrosi-
lanes by multinuclear metal carbonyls have not been
investigated fully. In the cluster-catalyzed hydrosilyla-
tion, multinuclear intermediates may be involved in the
catalytic cycle. This may lead to reactivities and selec-
tivities different from those accomplished by conven-
tional rhodium-phosphine- or platinum-based catalysts.3
In fact, Co2(CO)8 catalyzes both hydrosilylation and
silylformylation of unsaturated molecules,4 and catalytic
cycles that include silyl-cobalt intermediates have been
proposed.5 Studies by Matsuda and Ojima on tetra-
nuclear Rh or Co-Rh mixed carbonyls revealed their
high reactivity in the silylformylation of alkynes and
in other reactions.6,7 Mechanisms involving possible
intermediates with various nuclearity have been dis-
cussed on the basis of the analysis of metallic species
Transition metal catalyzed hydrosilylation of unsat-
urated molecules is one of the powerful tools in the
synthesis of organosilicon compounds, which themselves
are useful for the production of silicon-based organic
materials and polymers and for unique intermediates
in organic synthesis.1 A number of transition metal salts
or complexes are known to be active toward catalytic
hydrosilylation. In particular, numerous experimental
as well as theoretical studies have been undertaken
using mononuclear rhodium or platinum compounds.2
† Institute of Advanced Material Study.
‡ Interdisciplinary Graduate School of Engineering Sciences.
§ CREST.
(1) For reviews for catalytic hydrosilylation reactions: (a) Compre-
hensive Handbook on Hydrosilylation; Marciniec, B. Ed.; Pergamon
Press: Oxford, 1992. (b) Marciniec, B. In Applied Homogeneous
Catalysis with Organometallic Compounds; Cornils, B., Herrmann, W.
A., Eds.; VCH: Weinheim, 1996; Vol. 1, Chapter 2.6, p 487. (c) Ojima,
I. In The Chemistry of Organosilicon Compounds; Patai, S., Rappoport,
Z., Eds.; Wiley: New York, 1989; p 1479. (d) Brook, M. A. In Silicon
in Organic, Organometallic, and Polymer Chemistry; Wiley: New York,
2000; Chapter 12.8, p 401. (e) Spier, J . L. Adv. Organomet. Chem. 1978,
17, 407.
(2) (a) Chalk, A. J .; Harrod, J . F. J . Am. Chem. Soc. 1967, 89, 1640.
(b) A recent experimental work on the mechanisms of catalytic
hydrosilylation: Maruyama, Y.; Yamamura, K.; Nakayama, I.; Yoshi-
uchi, K.; Ozawa, F. J . Am. Chem. Soc. 1998, 120, 1421, and references
therein. (c) A recent representative report for theoretical studies on
the mechanisms of hydrosilylation: Sakaki, S.; Mizoe, N.; Sugimoto,
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therein.
(3) For recent general reviews on organometallic clusters: (a)
Catalysis by Di- and Polynuclear Metal Cluster Complexes; Adams, R.
D., Cotton, F. A., Eds.; Wiley-VCH: Canada, 1998. (b) Metal Clusters
in Chemistry; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-
VCH: Weinheim, 1999. (c) Gonza´rez-Moraga, G. Cluster Chemistry;
Springer-Verlag: Berlin, 1993. (d) The Chemistry of Metal Cluster
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35, 41.
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837.
(5) (a) Seitz, F.; Wrighton, M. S. Angew. Chem., Int. Ed. Engl. 1988,
27, 289. (b) Sakurai, H.; Miyoshi, K.; Nakadaira, Y. Tetrahedron Lett.
1977, 2671. (c) Chatani, N.; Komada, T.; Kajiwara, Y.; Murakami, H.;
Kakiuchi, F.; Ikeda, S.; Murai, S. Chem. Lett. 2000, 14.
10.1021/om0200050 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 06/11/2002

3024 Organometallics, Vol. 21, No. 14, 2002
Matsubara et al.
Sch em e 1
formed in the reactions of the clusters with either
unsaturated substrates or organosilanes.7 However, it
has been difficult to specify the net active species,
becausethereactionsoften involvecluster fragmentation.7c-e
Although not very many examples have been reported
on the ruthenium carbonyl catalyzed hydrosilylation,8
reactions of hydrosilanes with several ruthenium car-
bonyl clusters have been investigated.9-12 Products of
the reactions of Ru3(CO)12 with hydrosilanes were found
to be dependent on the structure of silanes used, and
in many cases, cluster fragmentation was involved.8,9
Certain ruthenium clusters, (µ3-6-methylaminopyridine)-
Ru3(µ-H)(CO)9,10a-d [(µ2-3,5-dimethylpyrazole)Ru3(µ-H)
(µ-CO)3(CO)7]-,10e and [Ru3(µ-H)(µ-NO)(CO)10]-,10f the
trimetallic framework of which is reinforced by the
introduction of bridging ligands, undergo oxidative
addition of hydrosilanes without cluster fragmentation
to form the corresponding triruthenium clusters with
Ru-Si bonds. Little is known about catalytic hydrosi-
lylations using these clusters. An important report from
the viewpoint of both reactions and mechanisms was
published by G. Su¨ss-Fink, in which [Ru3H(CO)11]- was
reversibly reacted with two molecules of HSiR3 to form
[Ru3H(SiR3)2(CO)10]- and where both of the clusters
exhibited catalytic activity toward silylformylation and
hydrosilylation of ethylene at 100 °C.11 However, the
characterization of the clusters and the characteristics
of the catalytic reactions have not been reported in
detail. Thus, all of these data in the literature suggest
that further investigation is warranted in order to figure
out whether cluster intermediates are involved in the
hydrosilylation reactions catalyzed by organometallic
clusters.
Sch em e 2
Previously we reported that a triruthenium carbonyl
cluster bearing a µ3-acenaphthylene ligand, (µ3,η2:η3:η5-
acenaphthylene)Ru3(CO)7 (1), is an active catalyst for
the hydrosilylation of ketones and aldehydes (Scheme
1, eq 1), the reduction of acetals and cyclic ethers, and
the ring-opening polymerization of cyclic ethers (Scheme
1, eq 2).12 The silyl-ruthenium cluster, (µ3,η2:η3:η5-
acenaphthylene)Ru3(H)(SiR3)(CO)6 (2), was isolated from
the reaction of 1 with R3SiH, which is a possible
intermediate in the catalytic cycle, contributing to
activating the Si-H bond in hydrosilanes for the reac-
tion with organic molecules (Scheme 2). However, it was
proven experimentally that 2 is not active toward
hydrosilylation of ketones. Although NMR studies to
detect the net catalytic species revealed that unstable
species with a structure similar to 2 exist in the reaction
solution of 1 and PhMe2SiH, further characterization
of this species was hampered because of its instability.12
Within this context, we were interested in the catalytic
and stoichiometric reactions of (µ3,η5:η5-4,6,8-trimeth-
ylazulene)Ru3(CO)7 (3) with R3SiH.13 Since 3 has a
structure closely related to 1, a similar reaction behavior
was anticipated in the reaction with R3SiH. A further
advantage in the investigation of 3 is that analogous
compounds with a different nuclearity, as shown in
Figure 1, (µ2,η3:η5-4,6,8-trimethylazulene)Ru2(CO)5 (4)
and (µ3,η5:η5-4,6,8-trimethylazulene)Ru4(CO)9 (5), could
also be subjected to stoichiometric and catalytic reac-
tions with hydrosilanes, which should provide further
elucidation of the effect of nuclearity on the reactivity
of ruthenium carbonyl clusters toward R3SiH.13
(6) (a) Matsuda, I.; Ogiso, A.; Sato, S.; Izumi, Y. J . Am. Chem. Soc.
1989, 111, 2332. (b) Ojima, I.; Donovan, R. J .; Clos, N. Organometallics
1991, 10, 2606.
(7) (a) Matsuda, I.; Fukuta, Y.; Tsuchihashi, T.; Nagashima, H.; Itoh,
K. Organometallics 1997, 16, 4327. (b) Ojima, I.; Clos, N.; Donovan,
R. J .; Ingallina, P. Organomettalics 1990, 9, 3127. (c) Ojima, I.;
Ingallina, P.; Donovan, R. J .; Clos, N. Organometallics 1991, 10, 38.
(d) Ojima, I.; Donovan, R. J .; Ingallina, P.; Clos, N.; Shay, W. R.;
Eguchi, M.; Zeng, Q.; Korda, A. J . Cluster Sci. 1992, 3, 423. (e) Ojima,
I.; Li, Z.; Donovan, R. J .; Ingallina, P. Inorg. Chim. Acta 1998, 270,
279.
(8) (a) Nesmeyanov, A. N.; Friedlina, R. K.; Chuskovskaya, E. C.;
Petrov, R. G.; Belyavsky, A. B. Tetrahedron 1962, 17, 61. (b) Ojima,
I.; Fuchikami, T.; Yatabe, M. J . Organomet. Chem. 1981, 221, C36. (c)
Seki, Y.; Takeshita, K.; Kawamoto, K.; Murai, S.; Sonoda, N. J . Org.
Chem. 1986, 51, 3890. (d) Seki, Y.; Takeshita, K.; Kawamoto, K.; Murai,
S.; Sonoda, N. Angew. Chem., Int. Ed. Engl. 1980, 19, 928. (e) Hilal,
H. S.; Khalaf, S.; J ondi, W. J . Organomet. Chem. 1993, 452, 167.
(9) (a) Buuren, G. N.; Willis, A. C.; Einstein, W. B.; Peterson, R. K.;
Pomeroy, R. K.; Sutton, D. Inorg. Chem. 1981, 20, 4361. (b) Brookes,
A.; Knox, S. A. R.; Stone, F. G. A. J . Chem. Soc. (A) 1971, 3469. (c)
Knox, S. A. R.; Stone, F. G. A. J . Chem. Soc. (A) 1969, 2559. (d) Vancea,
L.; Graham, W. A. G. Inorg. Chem. 1974, 13, 511. (e) Kotani, S.;
Tanizawa, T.; Adachi, T.; Yoshida, T.; Sonogashira, K. Chem. Lett.
1994, 1665. (f) Braunstein, P.; Galsworthy, J . R.; Massa, W. J . Chem.
Soc., Dalton Trans. 1997, 4677.
(10) (a) Cabeza, J . A.; Fernandez-Colinas, J . M.; Garcia-Granda, S.;
Llamazares, A.; Lopez-Ortiz, F.; Riera, V.; Van der Maelen, J . F.
Organometallics 1994, 13, 426. (b) Cabeza, J . A.; Garc´ıa-Granda, S.;
Llamazares, A.; Riera, V.; Van der Maelen, J . F. Organometallics 1993,
12, 2973. (c) Cabeza, J . A.; Llamazares, A.; Riera, V.; Triki, S.; Ouahab,
L. Organometallics 1992, 11, 3334. (d) Cabeza, J . A.; Franco, R. J .;
Llmazares, A.; Riera, V.; Bois, C.; J eannin, Y. Inorg. Chem. 1993, 32,
4640. (e) Cabeza, J . A.; Franco, R. J .; Riera, V.; Garc´ıa-Granda, S.;
Van der Maelen, J . F. Organometallics 1995, 14, 3342. (f) Cabeza, J .
A.; Franco, R. J .; Riera, V. Inorg. Chem. 1994, 33, 5952.
(11) (a) Su¨ss-Fink, G.; Ott, J .; Schmidkonz, B.; Guldner, K. Chem.
Ber. 1982, 115, 2487. (b) Su¨ss-Fink, G.; Reiner, J . J . Mol. Catal. 1982,
16, 231. (c) Su¨ss-Fink, G. Angew. Chem., Int. Ed. Engl. 1982, 21, 73.
(d) Su¨ss-Fink, G.; Reiner, J . J . Organomet. Chem. 1981, 221, C36.
(12) Nagashima, H.; Suzuki, A.; Iura, T.; Ryu, K.; Matsubara, K.
Organometallics 2000, 19, 3579.
In this paper, we wish to report the difference in
catalytic activity among 1, 3, 4, and 5 using the
(13) Nagashima, H.; Suzuki, A.; Nobata, M.; Aoki, K.; Itoh, K. Bull.
Chem. Soc. J pn. 1998, 71, 2441.

New Silylruthenium Complexes
Organometallics, Vol. 21, No. 14, 2002 3025
reactions sometimes provides important information on
the net catalytically active species.3 Within this context,
we examined the stoichiometric reaction of 3 with
PhMe2SiH. In a closely related reaction, we achieved
the isolation of a silyl-ruthenium cluster 2 from 1, as
described earlier.12
Rea ction of 3 w ith P h Me2SiH. Treatment of 3 with
PhMe2SiH (5 equiv to 1 equiv of 3) in benzene-d6 at 40
°C for 16 h results in the formation of a novel silyl-
ruthenium complex (µ2,η3:η5-4,6,8-trimethyl-4,5-dihydro-
azulene)Ru3(H)(CO)6(SiMe2Ph) (6) in 50% yield (Scheme
3, eq 1). As reported earlier, reaction of 1 with HSiMe2-
Ph proceeds at 80 °C to form 2.12 In sharp contrast, the
reaction of 3 to 6 proceeds even at room temperature,
at which the catalytic hydrosilylation of acetophenone
occurrs. In other words, the silyl ruthenium complexes
6 can be generated in the actual catalytic reaction.
F igu r e 1. Multinuclear ruthenium compounds with bridg-
ing conjugate π-electron ligands, 1, 3, 4, and 5.
1
hydrosilylation of acetophenone with PhMe2SiH as a
probe. The products obtained from the reaction of
PhMe2SiH with 3 or 4, which show a moderate or low
catalytic activity toward hydrosilylation, were charac-
terized as possible intermediates in the catalytic cycle.
It is important that the reaction of PhMe2SiH with both
3 and 4 proceed without fragmentation of the cluster
framework to give novel di- or trinuclear silyl-ruthenium
complexes with unique structures, 6 and 7, respectively
(Scheme 3). Of importance is that the triruthenium silyl
complex 6 has been shown to be a better catalyst than
3. Monitoring the catalytic hydrosilylation using 6
revealed that 6 is converted to other species during the
reaction, whereas it is regenerated completely after the
reaction is completed. This offers interesting evidence
for the involvement of cluster species in the catalytic
hydrosilylation.
Spectral data of 6 are listed in Table 2. The H NMR
spectrum of 6 shows a singlet at δ -13.6 assignable to
a bridging Ru-H. Existence of a Ru-SiMe2Ph moiety
is suggested by H resonances (δH 0.57 and 0.61 as two
1
singlets due to the diastereotopic SiMe groups and
peaks from δH 6.96-7.02 to 7.30-7.33 due to the SiPh
moiety) and a single 29Si resonance (δ 43.18).14 Six peaks
observed at δC 192-213 in the 13C NMR spectrum and
six νCO absorptions seen in the IR spectrum indicate the
presence of six CO ligands. An IR absorption with a
relatively low wavenumber (1885 cm-1) indicates that
one of the CO ligands should be bridging two ruthenium
centers.15 1H and 13C resonances due to the azulene
moiety have been assigned completely with the aid of
the H-H and H-C COSY techniques. Five 1H (H1-
H5) and eight 13C (C1-C6, C9, C10) resonances show a
typical upfield shift due to the fact that these carbons
are bonded to the metal centers. Multiplets consisting
of three protons, appearing at δH 0.74-0.93, and a
doublet at δH 0.57, due to a methyl group, suggest the
existence of a CH3-CH-CH2- moiety in the azulene
ligand. In other words, one carbon-carbon double bond
in the azulene ligand in the precursor 3 is hydrogenated
during the reaction.
Resu lts a n d Discu ssion
Com p a r ison of th e Ca ta lytic Activity of 1, 3, 4,
a n d 5 in th e Hyd r osilyla tion of Acetop h en on e. As
noted above, complexes bearing a bridging acenaphth-
ylene or 4,6,8-trimethylazulene ligand catalyze the
hydrosilylation of acetophenone at room temperature.
In the presence of a catalytic amount (1 mol %) of 1, 3,
4, or 5, hydrosilylation of acetophenone in benzene was
carried out. The results are shown in Table 1. When
HSiMe2(CH2)2Me2SiH is used as the silane, the yield of
the silyl ether reaches 91% after 1.5 h with 1 as a
catalyst. In contrast, the reaction with 3 is slower (31%
yield after 1.5 h and 89% after 20 h), whereas 5 is
inactive. Although the reaction is much slower, some
acetophenones are hydrosilylated by 4. The reactions
with PhMe2SiH in the presence of 1 or 3 are slower than
those with HSiMe2(CH2)2Me2SiH;12 the yield of the silyl
ether with 1 as a catalyst reaches over 91% after 9 h,
whereas only 52% yield is obtained after 12 h with 3.
These results suggest that the catalytic activity of
triruthenium clusters 1 and 3 toward hydrosilylation
of acetophenone is higher than that of the others. Since
an oxidative addition of R3SiH to metallic species is
believed to be involved in the initial step of the catalytic
hydrosilylation, the reaction of R3SiH with transition
metal complexes has been investigated by isolation of
the products, which possess silyl-metal bonds.1 The
analysis of metal species involved in slow catalytic
These spectral features of 6 are consistent with the
molecular structure derived from an X-ray single-crystal
structure determination as illustrated in Figure 2.15 The
crystallographic data are shown in Table 3, and the
representative bond distances and angles are listed in
Table 4. The compound 6 possesses a triruthenium
framework with Ru-Ru distances of 2.905(1), 2.891(1),
and 2.761(1) Å. A PhMe2Si moiety is bonded to the Ru-
(3) atom with a Ru-Si distance of 2.392(2) Å. Six CO
ligands are bound to the cluster, and each ruthenium
atom has two CO ligands. The relatively short Ru(3)-
C(15) distance (2.658(10) Å) and the Ru(1)-C(15)-O(1)
angle of 164.6(10)° provide evidence for a semibridging
interaction of this CO ligand between Ru(1) and Ru(3)
(14) Multiruthenium complexes having H-Ru-Si moieties report-
edly show peaks due to the bridging hydride at δ -9 to -17, whereas
these compounds provide the 29Si signals at δ 10-60: Corey, J . Y.;
Braddock-Wilking, D. Chem. Rev. 1999, 99, 175.
(15) A bridging hydride ligand across the Ru(2) and Ru(3) atoms
was visible in the difference Fourier map after refinement, but could
not be refined because the quality of the data was not very good.

3026 Organometallics, Vol. 21, No. 14, 2002
Matsubara et al.
Sch em e 3
Ta ble 1. Hyd r osilyla tion of Acetop h en on e w ith
[HSiMe2CH2]2 a n d P h Me2SiH Ca ta lyzed by 1, 3, 4,
a n d 5
conjugated π-ligand. Both 2 and 6 have the Ru(H)(SiR3)-
(CO)6 moiety, and the acenaphthylene ligand in 2 acts
as a triply bridging 10-electron donor to the cluster
moiety. In contrast, the dihydroazulene ligand in 6
behaves as a doubly bridging eight-electron donor
ligand. As a consequence, the total electron count of 6
is 46 (that of 2 is 48), and the Ru(H)(SiR3)(CO)6 moiety
in 6 is coordinatively unsaturated. The 46-electron
cluster is formally rationalized by the existence of a Ru-
Ru double bond.17 The Ru(2)-Ru(3) bond length of
2.761(1) Å, which is slightly shorter than the other two
Ru-Ru distances, may be responsible for the double
bonded nature of Ru(2)-Ru(3), though it is in the range
of the usual Ru-Ru single bond distance in other
clusters.18 The semibridging interaction of a carbonyl
ligand may mitigate the unsaturated nature of the
metal centers in 6.19 There have been some early
examples of unsaturated clusters or their equivalents
in osmium chemistry, and one of the more famous
examples is the 46-electron cluster [Os3H2(CO)10], which
is known to undergo a number of reactions.20 Coordi-
natively unsaturated triruthenium clusters are not as
common, compared to the triosmium analogues, and 6
entry
catalyst
hydrosilane
time (h)
yield (%)b
1
2
1
3
[HSiMe2CH2]2
[HSiMe2CH2]2
1.5
1.5
21
1.5
35
91
31
89
1
12
0
3
4
4
5
[HSiMe2CH2]2
[HSiMe2CH2]2
1.5
30
2
5
6
1
3
PhMe2SiH
PhMe2SiH
9
12
91
52
a
All reactions have been carried out using 1 mol % of the
catalysts, 1, 3, 4, or 5, in a 5 mm φ NMR tube in benzene-d6 at 20
b
°C. Yields of the products were determined by 1H NMR spec-
troscopy, based on the integral value of the internal standard (1,2-
dichloroethane).
atoms.16 Cp-like coordination of the carbons in the five-
membered ring to the Ru(1) atom and a η3-allyl interac-
tion of the three carbons in the seven-membered ring
with the Ru(2) atom bring about the µ2,η3:η5-coordina-
tion mode of the dihydroazulene ligand to the triruthen-
ium framework.
As described in our previous paper, reaction of 1 with
trialkylsilanes results in dissociation of a CO ligand
followed by oxidative addition of a Si-H bond to afford
the silyl cluster 2.12 A major difference of the structure
of 6 from that of 2 is the coordination mode of the
(17) (a) Metal-metal multiple bonds and coordinative unsaturation
of clusters, see: Compounds with Multiple Bonds Between Metal Atoms;
Cotton, F. A., Walton, R., Wiley: New York, 1980. (b) Recent reports
about coordinatively unsaturated clusters having metal-metal double
bonds: Su¨ss-fink, G.; Godefroy, I.; Ferrand, V.; Neels, A.; Stoeckli-
Evans, H. J . Chem. Soc., Dalton Trans. 1998, 515, Bruce, M. I.; Skelton,
B. W.; White, A. H.; Zaitseva, N. N. J . Chem. Soc., Dalton Trans. 1999,
1445.
(18) Usual Ru-Ru bond distances in triruthenium carbonyl clusters,
for example, [Ru3(CO)12],19a (µ2,η5:η5-guaiazulene)Ru3(CO)7,19b and 1,18b
are in the range 2.7-3.0 Å: (a) Churchill, M. R.; Hollander, F. J .;
Hutchinson, J . P. Inorg. Chem. 1977, 16, 2655. (b) J ohnson, B. F. G.;
Shephard, D. S.; Edwards, A. J .; Braga, D.; Parisini, E.; Raithby, P.
R. J . Chem. Soc., Dalton Trans. 1995, 3307.
(19) Examples of unsaturated complexes having semibridging CO
ligands, see: (a) Field, J . S.; Haines, R. J .; Mulla, F. J . Organomet.
Chem. 1990, 389, 227. (b) Field, J . S.; Haines, R. J .; Stewart, M. W.;
Sundermeyer, J .; Woollam, S. F. J . Chem. Soc., Dalton Trans. 1993,
947.
(20) For reviews: (a) Deeming, A. J . Adv. Organomet. Chem. 1986,
26, 1. (b) Deeming, A. J . In Comprehensive Organometallic Chemistry
II; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford;
Vol. 7, Chapter 12.
(16) Semibridging CO ligands can be identified by means of X-ray
crystallography or IR spectra. The absorption due to the semibridging
CO ligands is generally observed at 1850-1900 cm-1, which is lower
than those of usual terminal CO ligands, for example: (a) Curtis, M.
D.; Han, K. R.; Butler, W. M. Inorg. Chem. 1980, 19, 2096. (b)
Sterenberg, B. T.; J ennings, M. C.; Puddephatt, R. J . Organometallics
1999, 18, 2162. (c) Oke, O.; McDonald, R.; Cowie, M. Organometallics
1999, 18, 1629. (d) Baxter, R. J .; Knox, G. R.; Pauson, P. L.; Spicer,
M. D. Organometallics 1999, 18, 215. (e) Cotton, F. A. Prog. Inorg.
Chem. 1976, 21, 1, and reference therein.

New Silylruthenium Complexes
Ta ble 2. Sp ectr a l Da ta of 6 a n d 7a
Organometallics, Vol. 21, No. 14, 2002 3027
6
7
1H (δ)
RuH
H1
-13.6 (s)
4.35 (dd, J ) 1.8,
3.87 (dd, J ) 1.9, 2.9 Hz)
2.7 Hz)
H2
H3
4.37 (t, J ) 2.7 Hz) 3.95 (t, J ) 2.9 Hz)
2.29 (dd, J ) 1.8,
2.7 Hz)
3.50 (dd, J ) 1.9, 2.9 Hz)
H5
5.22 (s)
4.99 (s)
H7(eq)b
H7(ax)b
H8b
0.93 (m)
0.93 (m)
0.74 (m)
1.75 (s)
2.06 (dd, J ) 4.9, 16.6 Hz)
1.52 (dd, J ) 2.2, 16.6 Hz)
0.9 (m)
F igu r e 2. Perspective drawing of 6, (µ2,η3:η5-4,6,8-tri-
methyl-4,5-dihydroazulene)Ru3(H)(CO)6(SiMe2Ph) with 50%
probability thermal ellipsoids.
Me4
1.64 (s)
Me6
Me8
SiMe
1.20 (s)
1.31 (s)
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 6 a n d 7
0.57 (d, J ) 7.1 Hz) 0.59 (d, J ) 7.1 Hz)
0.57 (s), 0.61 (s)
0.84 (s), 0.88 (s),
0.95 (s), 0.97 (s)
6
7
SiPh
6.96-7.02 (3H)
7.30-7.33 (2H)
7.78 (dd, J ) 1.3, 7.9 Hz,
2H) 7.57 (dd, J ) 1.3,
7.9 Hz, 2H) 7.16-7.32 (6H)
empirical formula
fw
C
27H28O6Ru3Si
C33H38O4Ru2Si2
756.95
293(2)
0.71069
orthorhombic
P212121
16.701(4)
20.81(2)
9.530(2)
90
779.90
293(2)
0.71069
triclinic
P1h
temperature, K
wavelength, Å
cryst syst
space group
a, Å
13C{1H} (δ)
C1
C2
C3
C4
C5
C6
C7
C8
81.7
86.0
80.5
63.8
96.0
70.4
50.1
28.1
101.7
88.7
25.3
33.7
20.4
87.7
85.0
88.5
81.4
100.9
70.7
53.5
29.1
112.2
63.5
23.1
32.5
10.990(3)
14.709(5)
9.685(3)
93.816(12)
112.652(6)
77.36(2)
1409.6(8)
2
b, Å
c, Å
R, deg
â, deg
90
90
3312(3)
8
1.518
γ, deg
C9
V, Å3
C10
Me4
Me6
Me8
SiMe
SiPh
CO
Z
D(calcd), Mg/m3
abs coeff, mm-1
F(000)
1.835
1.668
766
1.018
1536
18.6
5.8, 7.6
133.6, 146.3
5.9, 6.1, 7.0, 8.0
132.3, 133.8, 146.9, 147.8
cryst size, mm
θ range, deg
no. of indep reflns
no. of reflns collected
0.50 × 0.40 × 0.20 0.38 × 0.18 × 0.15
2.84 to 27.47
4960
2.63 to 30.00
5391
192.5, 195.6, 199.8, 199.0, 200.0, 203.4, 209.4
204.7, 208.3, 213.2
4960 [Rint ) 0.00] 5360 [Rint ) 0.00]
29Si (δ)c
43.2
22.3, 27.4
2048, 2014, 1955, 1920
no. of reflns obsd (>2σ) 3609
3188
IR (cm-1)d νCO 2048, 2023, 1972,
no. of data/restraints/
params
4660/0/334
5360/0/370
1941, 1911, 1885
goodness-of-fita on F2
R indices [I>2σ(I)]b
0.973
1.028
a
Measured in benzene-d6 at room temperature. The numbering
of the protons and carbons in 4,6,8-trimethyl-4,5-dihydroazulene
ligand is shown above. Two hydrogen atoms bonded to C(7) were
located at equatorial (eq) and axial (ax) positions. They were
assigned on the basis of NOE, 1H-1H COSY, and HMQC NMR
measurements. c The 29Si NMR measurements were carried out
R1 ) 0.0682
wR2 ) 0.1613
R1 ) 0.0926
wR2 ) 0.1833
1.054 and -1.589
R ) 0.0588
wR2 ) 0.0966
R ) 0.1329
wR2 ) 0.1152
0.626 and -0.638
b
R indices (all data)c
larg diff peak & hole,
e Å-3
d
using INEPT technique. IR spectra were recorded using KBr
tablets.
GOF ) [Σw(Fo2 - Fc2)2/(N - P)]1/2
.
R(F) ) ∑||F0| - |Fc||/∑|F0|.
a
b
c wR(F2) ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2
.
2
is a rare example of a completely characterized unsatur-
ated triruthenium cluster.21
As pointed out earlier, the reaction of 3 with PhMe2-
SiH involves hydrogenation of a carbon-carbon double
bond in the azulene ligand of 3. The hydrogenation
produces a sp3 carbon (C8). The methyl group bound to
the C(8) atom is located at the face of the azulene plane
opposite the triruthenium moiety. This indicates that
the addition of hydrogen atoms occurs from the direction
of the triruthenium moiety. The reaction of PhSiMe2D
with 3 leads to the addition of two deuterium atoms to
the C(7) and C(8) carbons (6-d ), and their cis-configu-
ration was confirmed by the NOE enhancement between
Me(8) and H(7) (Scheme 4).22 Thus, at least two
molecules of PhMe2SiH react with 3 and take part in
(21) Examples of coordinatively unsaturated triruthenium carbonyl
clusters: (a) Hutchins, L. D.; Duesler, E. N.; Paine, R. T. Organome-
tallics 1984, 3, 399. (b) Nagashima, H.; Fukahori, T.; Aoki, K.; Itoh,
K. J . Am. Chem. Soc. 1993, 115, 10430. (c) Field, J . S.; Haines, R. J .;
Mulla, F. J . Organomet. Chem. 1992, 439, D56. (d) Knox, S. A. R.;
Koepke, J . W.; Andrews, M. A.; Kaesz, H. D. J . Am. Chem. Soc. 1975,
97, 3942.

3028 Organometallics, Vol. 21, No. 14, 2002
Matsubara et al.
Ta ble 4. Rep r esen ta tive Bon d Dista n ces a n d
An gles in 6
absorptions indicate the existence of four-coordinated
COs. The upfield shift of 1H and 13C resonances due to
H1-H5 and C1-C6, C9, and C10 suggests the coordi-
nation of these eight carbons to the diruthenium moiety.
Bond Distances (Å)
Ru(1)-Ru(2)
Ru(2)-Ru(3)
Ru(1)-C(1)
Ru(1)-C(3)
Ru(1)-C(10)
Ru(2)-C(7)
Ru(1)-C(14)
Ru(2)-C(17)
Ru(3)-C(19)
C(15)-O(1)
C(17)-O(3)
C(18)-O(5)
2.9048(14)
2.7605(13)
2.286(10)
2.289(11)
2.270(9)
2.206(10)
1.853(10)
1.869(12)
1.851(10)
1.153(12)
1.141(14)
1.165(14)
Ru(1)-Ru(3)
Ru(3)-Si(1)
Ru(1)-C(2)
Ru(1)-C(9)
Ru(2)-C(6)
Ru(2)-C(8)
Ru(1)-C(15)
Ru(2)-C(16)
Ru(3)-C(18)
C(14)-O(2)
C(16)-O(4)
C(19)-O(6)
2.8908(14)
2.392(2)
2.260(11)
2.312(10)
2.270(9)
1
Other H and 13C resonances similar to those observed
in 7 indicate the existence of a 4,5-dihydro-4,6,8-
trimethylazulene ligand similar to 6.
2.257(9)
The molecular structure of 7 as determined by X-ray
single-crystal structural analysis supports all of these
spectral features, as shown in Figure 3. Crystallographic
data are shown in the right-hand column of Table 3,
and representative bond distances and angles are listed
in Table 5. The molecule contains two ruthenium atoms,
and each ruthenium atom has two CO ligands and one
PhMe2Si group. The Ru-Si bond lengths are 2.442(3)
and 2.404(3) Å. The dihydroazulene ligand is bound to
the diruthenium moiety in the µ2,η3:η5-coordination
mode. An important feature of this diruthenium com-
pound is the electron configuration of both ruthenium
atoms; the Ru(1) species has an 18-electron configura-
tion, whereas the Ru(2) moiety has a 16-electron con-
figuration. The Ru-Ru distance of 3.141(2) Å is longer
than the usual Ru-Ru bond length in diruthenium
carbonyl complexes,24 but it is still within bonding
distance.25 This suggests the existence of a Ru(1)fRu(2)
dative bond. RufRu dative bonds are not common in
diruthenium carbonyl complexes, but are seen in two
diruthenium complexes, (Cl3Si)2(CO)4(PMe3)RufRu(CO)3-
(SiCl3)2 [Ru-Ru ) 2.995(1) and 2.975(1) Å] and (Cl3-
Si)2(CO)3(tBuNC)2RufRu(CO)3(SiCl3)2 [Ru-Ru ) 2.9488
(2) Å], reported by Pomeroy and co-workers.26
1.879(10)
1.925(11)
1.852(12)
1.164(12)
1.146(13)
1.186(13)
Bond Angles (deg)
Ru(1)-Ru(2)-Ru(3) 61.30(3) Ru(1)-Ru(3)-Ru(2) 61.81(3)
Ru(2)-Ru(1)-Ru(3) 56.89(3) Ru(1)-Ru(3)-Si(1) 113.86(8)
Ru(2)-Ru(3)-Si(1) 123.60(7) Ru(1)-C(14)-O(2)
174.4(10)
168.4(9)
174.8(11)
115.3(8)
125.3(10)
121.7(8)
Ru(1)-C(15)-O(1)
Ru(2)-C(17)-O(3)
Ru(3)-C(19)-O(6)
C(4)-C(5)-C(6)
C(6)-C(7)-C(8)
164.6(10) Ru(2)-C(16)-O(4)
176.3(10) Ru(3)-C(18)-O(5)
174.1(10) C(10)-C(4)-C(5)
118.7(8) C(5)-C(6)-C(7)
127.2(8) C(7)-C(8)-C(9)
Sch em e 4
Similar to the formation of 6 from 3, the reaction of 4
with PhMe2SiH is accompanied by hydrogenation of a
carbon-carbon double bond in the azulene ligand in 4.
Experiments using PhMe2SiD revealed the introduction
of two deuterium atoms in the dihydroazulene ligand
in 7 (Scheme 6). The stereochemical analysis of the C(8)
carbon in the X-ray crystal structure shows that the
Me(8) group is located at the side opposite the diruthe-
nium moiety. The cis-configuration of the two deuterium
atoms was determined by 1H NOE experiments of Me(8)
and C(7)-H in 7. This suggests that hydrogen or
deuterium atoms, activated by diruthenium species,
contribute to the formation of the dihydro- or dideute-
rioazulene ligand. Although further studies are required
to clarify the reduction mechanism, one of the plausible
schemes is shown in Scheme 7. An alternation of the
coordination mode from µ2,η3:η5- to µ2,η1:η5- is seen in
the hydrogenation of the azulene ligand, presumably via
formation of two ruthenium hydrides by activation of
these silanes with ruthenium clusters, followed by
transfer of these hydrides from the metal centers to the
azulene ligand. Similar reaction pathways, i.e., the
oxidative addition of two molecules of PhMe2SiH to the
diruthenium species and subsequent transfer of the
resulting ruthenium-hydrides to the azulene ligand, are
seen in the reaction of 4 to 7 (vide infra). Analysis of
the organic products in the reaction mixture reveals the
formation of PhMe2SiOH; this suggests that one of the
PhMe2Si groups in the disilyl intermediate has been
removed by reaction with trace amounts of water
contained in the reaction medium to form 6. A possible
23
mechanism is shown in Scheme 5.
Rea ction of 4 w ith P h Me2SiH. Since the diruthen-
ium compound 4 shows some catalytic activity in the
hydrosilylation of acetophenone, we considered it worth-
while to examine the reaction of 4 with HMe2SiPh to
compare it to that of 3. Reaction of 4 with HMe2SiPh (5
equiv to 4) for 18 h in benzene at 60 °C gives a
disilylated ruthenium complex 7 in 60% yield (Scheme
3, eq 2). The spectral data of 7 are listed in Table 2.
(23) The deuterium content in the hydride ligand of 6-d formed by
the reaction of 3 with PhMe2SiD was 50%. This suggests existence of
H/D exchange processes with Ru-H and PhMe2Si-D, though the
mechanism is not clear at present.
(24) Usual Ru-Ru bond distances in diruthenium carbonyl com-
plexes, for example, (µ2,η3:η5-guaiazulene)Ru2(CO)5: 2.8795(5) and
2.894(2) Å,24a (µ2,η3:η5-4,6,8-trimethyl azulene)Ru2(CO)5: 2.8603(8) Å,24b
(µ,η1:η2:η2:η3-Me2SiCH2CH2SiMe2C8H8)Ru2(CO)5: 2.9340(5) Å.24c (a)
Matsubara, K.; Oda, T.; Nagashima, H. Organometallics 2001, 20, 881.
(b) Matsubara, K.; Tsuchiya, K. Mima, S.; Nagashima, H. Unpublished
data. (c) Goddard, R.; Woodward, P. J . Chem. Soc., Dalton Trans. 1980,
559.
(25) Certain ruthenium clusters have Ru-Ru bonds of which
distances are as long as 3.2 Å: (a) Hogarth, G.; Phillips, J . A.; Van
Gastel, F.; Taylor, N. J .; Marder, T. B.; Carty, A. J . J . Chem. Soc.,
Chem. Commun. 1988, 1570. (b) J ohnson, B. F. G.; Lewis, J .; Mace, J .
M.; Raithby, P. R.; Vargas, M. D. J . Organomet. Chem. 1987, 321, 409.
(26) Diruthenium carbonyl complexes having M-M dative bonds:
J iang, F.; Male, J . L.; Biradha, K.; Leong, W. K.; Pomeroy, R. K.;
Zaworotko, M. J . Organometallics 1998, 17, 5810.
1
This new complex has no Ru-H signal in H NMR and
two resonances in 29Si NMR (δ 22.3 and 27.4). Four 13C
resonances at δC 199-209 and the same number of νCO
(22) Using DSiMe2Ph (99%-d1), deuterium contents in H(7)(eq) and
H(8) of the dihydroazulene ligand were >95%, which were determined
by 1H and 2H NMR measurements. Details are shown in the Support-
ing Information.

New Silylruthenium Complexes
Organometallics, Vol. 21, No. 14, 2002 3029
Sch em e 5
Ta ble 5. Rep r esen ta tive Bon d Dista n ces a n d
An gles in 7
Bond Distances (Å)
Ru(1)-Ru(2)
Ru(2)-Si(2)
Ru(1)-C(2)
Ru(1)-C(9)
Ru(2)-C(5)
Ru(2)-C(6)
Ru(1)-C(15)
Ru(2)-C(16)
C(15)-O(2)
C(17)-O(4)
3.141(2)
2.404(3)
2.245(9)
2.290(9)
2.189(9)
2.314(9)
1.87(1)
1.869(9)
1.14(1)
1.15(1)
Ru(1)-Si(1)
Ru(1)-C(1)
Ru(1)-C(3)
Ru(1)-C(10)
Ru(2)-C(4)
Ru(1)-C(14)
Ru(2)-C(17)
C(14)-O(1)
C(16)-O(3)
2.442(3)
2.24(1)
2.250(9)
2.40(1)
2.201(9)
1.86(1)
1.868(9)
1.15(1)
1.15(1)
Bond Angles (deg)
Ru(2)-Ru(1)-Si(1) 156.70(8) Ru(2)-Ru(1)-C(14)
81.3(3)
Ru(2)-Ru(1)-C(15)
Ru(1)-Ru(2)-C(16)
C(14)-Ru(1)-C(15)
Si(2)-Ru(2)-C(16)
Ru(1)-C(15)-O(2)
Ru(2)-C(17)-O(4)
C(4)-C(5)-C(6)
82.7(3)
85.4(3)
Ru(1)-Ru(2)-Si(2) 162.63(8)
Ru(1)-Ru(2)-C(17)
Si(2)-Ru(2)-C(17)
Ru(1)-C(14)-O(1)
Ru(2)-C(16)-O(3)
C(5)-C(4)-C(10)
C(5)-C(6)-C(7)
90.3(3)
81.9(3)
177(1)
89.2(4)
81.6(3)
176.3(9)
178.6(9)
126.5(9)
119.4(9)
175(1)
F igu r e 3. Perspective drawing of 7, (µ2,η3:η5-4,6,8-tri-
methyl-4,5-dihydroazulene)Ru2(CO)4(SiMe2Ph)2 with 50%
probability thermal ellipsoids.
121.1(9)
124.4(9)
113.0(8)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
Sch em e 6
the reaction of (µ2,η3:η5-guaiazulene)Ru2(CO)5 with
phosphorus24a or isonitrile ligands.27
Catalytic Hydr osilylation of Keton es with P h Me2-
SiH Usin g th e Silyl Com p lexes 6 a n d 7. Possible
catalytic cycles for hydrosilylation of unsaturated mol-
ecules have been well investigated both experimentally
and theoretically, and one of the plausible catalytic
cycles is illustrated in Scheme 8a.1 The oxidative
addition of H-Si to metallic species to form H-M-Si
species is believed to initiate the catalytic cycle. In the
Co2(CO)8-catalyzed hydrosilylation of olefins, the Si-
Co species formed by the reaction of Co2(CO)8 with
trialkylsilanes is involved in the catalytic cycle as shown
in Scheme 8b.5 The silyl-hydride cluster 6 may be
considered as a related species to the catalytically active
H-M-Si species shown in Scheme 8a, whereas the
disilyldiruthenium complex 7 may be an analogue of the
Si-Co species, shown in Scheme 8b. Starting from these
analogies, we were interested in whether 6 and 7 may
be intermediates in the catalytic hydrosilylation. It has
been noted above that the silyl-hydride cluster 6 is a
46-electron compound and coordinatively unsaturated.
The disilyldiruthenium complex 7 possibly forms an
unsaturated species with the cleavage of the dative Ru-
Ru bond. These unsaturated species may provide higher
activity to 6 and 7 in the catalytic hydrosilylation of
acetophenone than in the cases of 3 and 4.
(27) Matsubara, K.; Mima, S.; Oda, T.; Nagashima. H. J . Organomet.
Chem. 2002, 650, 96.

3030 Organometallics, Vol. 21, No. 14, 2002
Matsubara et al.
Sch em e 7
Sch em e 8
silyl ether of 4-tert-butylcyclohexanol (Scheme 9, eq 1)
and in the ratios of 1,4- to 1,2-addition product from
mesityl oxide (Scheme 9, eq 2).12
Further investigation to see intermediary species in
the catalytic hydrosilylation of acetophenone by 1H
NMR provided interesting time-dependent NMR spectra
as shown in Figure 4. To a solution of 6 (0.1 equiv to
1.0 equiv of acetophenone) in C6D6 were added ac-
etophenone and HSiMe2Ph (0.9 equiv to 1.0 equiv of
acetophenone), and the 1H NMR spectrum of this
solution was monitored periodically. At the initial stage
(after 0.1 h of the addition (Figure 4a), where no reaction
of acetophenone has taken place, the 1H NMR spectrum
of the metal hydride region shows a Ru-H signal of 6 at
δH -13.6 as a single peak. After 0.5 h, 52% of acetophen-
one and 51% of PhMe2SiH have been consumed. At this
stage, the peak intensity at δH -13.6 (Ru-H of 6) has
decreased significantly, and several other hydride sig-
nals appear, including a Ru-H at δH -10.0 as a major
peak (Figure 4b). After 12 h, 92% of acetophenone and
all of the PhMe2SiH have been converted to the corre-
sponding silyl ether. At this stage (Figure 4c), the peak
at δH -13.6 is regenerated and can be observed as
almost one peak. Analysis of the other 1H resonances
reveals that at the initial stage only the peaks due to
acetophenone, PhMe2SiH, and 6 can be observed,
whereas at the final stage, only the signals attributed
to unreacted acetophenone (∼8%), PhMe2SiO(CH3)-
CHPh (92%), and 6 are visible. The peak intensity of
the signal at δH -13.6, when compared with that of the
solvent signal, is almost identical before and after the
reaction. The results unequivocally show that the
cluster 6 reacts with acetophenone and HSiMe2Ph to
form some kind of catalytic intermediates as transient
species during the reaction and is regenerated after all
of the hydrosilane has been converted (Figure 4c). As
has been described in the Introduction, cluster com-
pounds often undergo fragmentation of the cluster
framework in the reaction with HSiR3, leading to
alternation of the nuclearity. Once the cluster frame-
work is fragmented, its complete re-formation from the
fragmentation products to the original cluster is dif-
ficult. Therefore, the present observation suggests that
the intermediates of the catalytic hydrosilylation should
contain the triruthenium framework derived from 6; thus
the cluster species should be involved in the catalytic
cycle.28
Ta ble 6. Hyd r osilyla tion of Acetop h en on e w ith
HSiMe2P h Ca ta lyzed by 3, 6, a n d 7
entry
catalyst
time (h)
yield (%)b
1
2
4
3
6
7
12
12
12
52
100
0
a
All reactions were carried out using 1 mol % of catalysts 3, 6,
b
or 7 in a 5 mm φ NMR tube in benzene-d6 at 20 °C. Yields of the
products were determined by 1H NMR spectroscopy, based on the
integral value of the internal standard (1,2-dichloroethane).
A mixture of acetophenone, HSiMe2Ph (1 equiv of
HSiMe2Ph to 1 equiv of acetophenone), and a catalytic
amount of 6 or 7 (1 mol % to acetophenone) was
dissolved in C6D6, and the reaction was monitored
1
periodically using H NMR. Although 7 was inactive, 6
revealed higher activity in the catalytic hydrosilylation
of acetophenone than the precursor 3, as shown in Table
6. After 12 h, all of the charged acetophenone was
consumed in the reaction using 6, whereas the conver-
sion was 52% in the reaction catalyzed by 3 under the
same conditions. Hydrosilylations of 4-tert-butylcyclo-
hexanone and mesityl oxide were also catalyzed by 6.
Comparable experiments with 1 and 3 as the catalysts
revealed that yields of the products after 8 h (4-tert-
butylcyclohexanone) and 12 h (mesityl oxide) at room
temperature are in the order 6 > 1, 3. Only small
differences were observed in the cis/trans ratios of the

New Silylruthenium Complexes
Organometallics, Vol. 21, No. 14, 2002 3031
Sch em e 9
be involved in the catalytic hydrosilylation reactions
1
catalyzed by 3. Furthermore, H NMR measurements
in the hydrosilylation of acetophenone with PhMe2SiH
in the presence of a catalytic amount of 6 revealed that
6, the concentration of which decreased during the
course of the reaction, is regenerated after the reactants
have been consumed. This suggests that cluster frag-
mentation is not involved in the reaction. The interme-
diates in the catalytic cycle could be triruthenium
structures closely related to 6. We consider that these
results provide new and interesting aspects in consider-
ing molecular cluster species as important intermediates
in homogeneous catalysis. Further investigation is in
progress on the reactions of multiruthenium carbonyl
clusters bearing acenaphthylene or azulene ligands,
including more detailed experiments on the transient
species derived from the reaction of 6 and organosilanes
and on the application of 6 and 7 to other catalytic
reactions with hydrosilanes.
F igu r e 4. 1H NMR spectra (the hydride region) in the
hydrosilylation of acetophenone catalyzed by 6. (a) After
0.1 h, no reaction has taken place. (b) After 0.5 h, 52% of
acetophenone and 51% of HSiMe2Ph have been converted
to the silyl ether. (c) After 12 h, 92% of acetophenone and
all of HSiMe2Ph have been consumed.
Exp er im en ta l Section
Con clu sion
Gen er a l P r oced u r es. All manipulations were carried out
under an argon atmosphere using standard Schlenk tech-
niques. Ether, THF, benzene, toluene, heptane, hexane, and
benzene-d6 were distilled from benzophenone ketyl and stored
under an argon atmosphere. All of the other reagents were
distilled just before use. NMR spectra were taken with a J EOL
Lambda 400 or 600 spectrometer. Chemical shifts were
recorded in ppm from the internal standard (1H, 13C: solvent)
or the external standard (29Si: tetramethylsilane). Assign-
ments of the NMR signals were performed with the aid of
DEPT and 2D techniques. IR spectra were recorded in cm-1
on a J ASCO FT/IR-550 spectrometer. The ruthenium com-
plexes 1, 3, 4, and 5 were prepared according to the published
methods.12,20b,29
As described above, we confirmed experimentally the
difference in reactivity of di-, tri-, and tetraruthenium
complexes bound to 4,6,8-trimethylazulene toward cata-
lytic hydrosilylation. The triruthenium cluster showed
a higher catalytic activity than the other two. Di- and
triruthenium clusters, 4 and 3, were subjected to
stoichiometric reactions with PhMe2SiH, and a disi-
lyldiruthenium complex 7 having a Ru-Ru dative bond
and a 46-electron silylhydridoruthenium cluster 6 have
been isolated and characterized. The diruthenium com-
plex 4 shows low activity in the catalytic hydrosilylation
of acetophenone, whereas the disilyldiruthenium com-
plex 7 is inactive. This indicates that the formation of
7 from 4 in a potential catalytic cycle hinders the
reaction. In contrast, the catalytic activity of the silyl-
ruthenium cluster 6 is higher than that of 3. This
provides a possibility that generation of 6 from 3 may
Oxid a tive Ad d ition of HSiMe2P h to (µ3,η5:η5-4,6,8-
Tr im eth yla zu len e)Ru 3(CO)7 (3). To a solution of 3 (100 mg,
0.15 mmol) dissolved in C6H6 (30 mL) was added PhMe2SiH
(102 mg, 0.75 mmol). The mixture was heated at 40 °C for 16
h. After removal of the solvent in vacuo, column chromatog-
raphy (silica gel, φ 1.5 × 5 cm at -78 °C) of the residue, by
eluting with a 5:1 mixture of hexane and CH2Cl2, gave 6 as a
red solid (59 mg, 0.076 mmol; 50% yield), mp 134°C (dec). FAB-
MS: 781 (M + 1). Anal. Calcd for Ru3SiO6C27H28: C, 41.58;
H, 3.62. Found: C, 41.17; H, 3.68. Spectroscopic data are listed
in Table 2.
(28) Detailed investigation on the NMR spectrum during the hy-
drosilylation should give further information on the catalytic inter-
mediates. Unfortunately, attempted assignment of the spectrum shown
in Figure 4b was hampered because the existence of dual metallic
species, the starting materials, and the products made the NMR
spectrum complicated.
(29) Churchill, M. R.; Wormald, J . Inorg. Chem. 1973, 12, 191.

3032 Organometallics, Vol. 21, No. 14, 2002
Matsubara et al.
Oxid a tive Ad d ition of HSiMe2P h to (µ2,η3:η5-4,6,8-
Tr im eth yla zu len e)Ru 2(CO)5 (4). To a solution of 4 (100 mg,
0.20 mmol) dissolved in C6H6 (20 mL) was added PhMe2SiH
(136 mg, 1.00 mmol), and the mixture was heated at 60 °C for
18 h. After removal of the solvent in vacuo, column chroma-
tography (silica gel, φ 1.5 × 5 cm at -78 °C) of the residue, by
eluting with a 4:1 mixture of hexane and CH2Cl2, gave 7 as a
yellow solid (90 mg, 0.12 mmol; 60% yield), mp 196 °C (dec).
Anal. Calcd for Ru2Si2O4C33H38: C, 52.29; H, 5.06. Found: C,
51.57; H, 4.97. Spectroscopic data are listed in Table 2.
Ca ta lytic Hyd r osilyla tion of Acetop h en on e. In a 5 mm
φ NMR tube, acetophenone (0.77 mmol), a trialkylsilane
[HSiMe2Ph or {HSiMe2(CH2)}2] (0.77 mmol), and a catalytic
amount of 1, 3, 4, 5, 6, or 7 (1 mol %, 7.7 µmol) were dissolved
in C6D6 (0.6 mL) containing 1,2-dichloroethane (0.077 mmol).
The NMR sample was carefully degassed several times and
tometer Control on a Pentium computer. The absorption
collection was carried out empirically. The structures were
solved by the Patterson method (DIRDIF94 PATTY)30a and
were refined using full-matrix least squares (SHELXL97)30b
based on F2 of all independent reflections measured. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. All H atoms were located at ideal positions and
were included in the refinement, but were restricted to ride
on the atom to which they were bonded. Isotopic thermal
factors of H atoms were held to 1.2-1.5 times (for methyl
groups) Ueq of the parent atoms.
Ack n ow led gm en t. A part of this study was finan-
cially supported by the J apan Society for the Promotion
of Science (Grants-In-Aid for Scientific Research,
12750768 and 13450374).
1
sealed in vacuo, and H NMR spectra were taken periodically.
1
1
Su p p or tin g In for m a tion Ava ila ble: The H NOE, H-
Identification of the products was performed according to the
1H COSY, H-13C HMQC, and 1H-13C HMBC NMR spectra
1
1
literature.11 The yield of the products was determined by H
of 6 and 7, 2D NMR spectra of 6-d 2.5 and 7-d 2, and detailed
crystallographic data (excluding structure factors) of 6 and 7
are available free of charge via the Internet at http://pubs.
acs.org.
NMR, based on the integral value of the internal standard (1,2-
dichloroethane).
X-r a y Da ta Collection a n d Red u ction . Crystal data and
measurement data of both 6 and 7 are summarized in Table
3. Single crystals of 6 and 7 were grown from a dichlo-
romethane/hexane solution at -30 °C. Data were collected
using a Rigaku RAXIS RAPID imaging plate diffractometer
with graphite-monochromated Mo KR radiation (λ ) 0.71069
Å). All data of 6 and 7 were taken at 296(2) K. Data collection
was carried out using the program system MSC/AFC Diffrac-
OM0200050
(30) (a) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W.
P.; de Gelder, R.; Israel, R.; Smits, J . M. M. The DIRDIF-94 program
system, Technical Report of the Crystallography Laboratory; Univer-
sity of Nijmegen: The Netherlands, 1994. (b) Sheldrick, G. M.
SHELXL-97; 1997.