Reactions of diruthenium tetrahydride complex (η5-C5Me5)Ru(μ-H)4 Ru(η5-C5Me5) with vinylsilanes: Formation of a μ-silylene complex via successive Si-H and Si-C bond cleavage of dimethylvinylsilane

3406

Organometallics 2001, 20, 3406-3422

Rea ction s of Dir u th en iu m Tetr a h yd r id e Com p lex

(η⁵-C₅Me₅)Ru (µ-H)₄Ru (η⁵-C₅Me₅) w ith Vin ylsila n es:

F or m a tion of a µ-Silylen e Com p lex via Su ccessive Si-H

a n d Si-C Bon d Clea va ge of Dim eth ylvin ylsila n e

Toshiro Takao, Masa-aki Amako, and Hiroharu Suzuki*

Department of Applied Chemistry, Graduate School of Science and Engineering,

Tokyo Institute of Technology, and CREST, J apan Science and Technology Corporation (J ST),

2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, J apan

Received February 23, 2001

The diruthenium complex {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiMe₂(CHdCH₂)} (5a ; Cp* ) η⁵-C₅-

Me₅) containing a µ-vinylsilane ligand was prepared by the reaction of Cp*Ru(µ-H)₄RuCp*

(1) with dimethylvinylsilane. The µ-η²:η²-coordination mode of dimethylvinylsilane was

1

confirmed by means of H, ¹³C, and ²⁹Si NMR and IR spectroscopy. The Si-C(sp²) bond of

5a was readily cleaved upon thermolysis with liberating hydrogen and resulted in formation

of the µ-silylene, µ-ethylidyne complex (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-H) (8) via the µ-silyl,

µ-vinyl complex (Cp*Ru)₂(µ-η²-HSiMe₂)(µ-η²-CHdCH₂) (9a ) as an intermediate. The reaction

of 1 with trimethylvinylsilane rendered cleavage of both Si-C(sp²) and Si-C(sp³) bonds,

which resulted in formation of 8. Treatment of 8 with carbon monoxide led to formation of

the µ-ethylidene complex by migration of the hydride to the bridging carbon; thus {Cp*Ru-

(CO)}₂(µ-CHMe)(µ-SiMe₂) (10) was obtained. The reaction of 8 with ethylene afforded the

µ-vinyl, µ-silylene complex (Cp*Ru)₂(µ-η²-CHdCH₂)(µ-SiMe₂)(µ-H)(CH₂dCH₂) (11). The

reaction of 8 with molecular hydrogen resulted in a re-formation of 1 with liberating

dimethylethylsilane, which showed formation of the Si-C bond on the dinuclear system.

The molecular structures of 5a , 8, and 10 were determined by single-crystal X-ray diffraction

studies.

In tr od u ction

the role of individual metal centers of a cluster complex.

We will use the term multimetallic activation to refer

to a distinctive manner of activation achieved by the

concerted interaction among substrates and many metal

centers.²

We have demonstrated several examples of multi-

metallic activation by using ruthenium polyhydride

cluster complexes {Cp*Ru(µ-H)}₃(µ₃-H)₂²and Cp*Ru(µ-

H)₄RuCp*⁴as precursors of active species. These com-

plexes can generate multimetallic active species by

transferring hydride ligands to a hydride acceptor or

by elimination of hydride ligands as dihydrogen. Previ-

ously we reported that the reaction of a dinuclear

ruthenium tetrahydride complex Cp*Ru(µ-H)₄RuCp* (1)

with secondary silanes R₂SiH₂afforded bis(µ-silyl)

Activation of an inert bond, such as C-H and C-C

bonds, has been an attractive and challenging target of

organometallic chemistry.¹We have demonstrated cleav-

age of C-H and C-C bonds in the reaction of a

trinuclear ruthenium pentahydride complex {Cp*Ru-

(µ-H)}₃(µ₃-H)₂(Cp* ) η⁵-C₅Me₅) with cyclopentadiene.^2a

Once a substrate is incorporated into a reaction site in

the cluster, even an inert bond could be activated under

mild conditions. Both multielectron transfer among the

substrate and metal centers and entropy gain by

multiple coordination could facilitate the activation of

an inert bond in di- and polymetal cluster complexes.

Although many stoichiometric and catalytic reactions

using cluster complexes have so far been developed,³it

is still uncertain the effect of multiple coordination and

(3) See for example: (a) Adams, R. D.; Cotton, F. A. Catalysis by

Di- and Polynuclear Metal Cluster Complexes; Wiley-VCH: New York,

1998. (b) Dyson, P. J .; Mclndoe, J . S. Transition Metal Carbonyl Cluster

Chemistry; Gordon and Breach Science Publishers: Newark, NJ , 2000.

(4) (a) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Moro-oka, Y.

Organometallics 1988, 7, 2243. (b) Suzuki, H.; Omori, H.; Take, Y.;

Moro-oka, Y. Organometallics 1988, 7, 2579. (c) Omori, H.; Suzuki,

H.; Moro-oka, Y. Organometallics 1989, 8, 1576. (d) Omori, H.; Suzuki,

H.; Moro-oka, Y. Organometallics 1989, 8, 2270. (e) Suzuki, H.;

Kakigano, T.; Igarashi, M.; Tanaka, M.; Moro-oka, Y. J . Chem. Soc.,

Chem. Commun. 1991, 283. (f) Omori, H.; Suzuki, H.; Kakigano, T.;

Moro-oka, Y. Organometallics 1992, 11, 989. (g) Suzuki, H.; Takao,

T.; Tanaka, M.; Moro-oka, Y. J . Chem. Soc., Chem. Commun. 1992,

476. (h) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima,

M.; Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 1129. (i)

Takao, T.; Suzuki, H.; Tanaka, M. Organometallics 1994, 13, 2554. (j)

Takao, T.; Yoshida, S.; Suzki, H.; Tanaka, M. Organometallics 1995,

14, 3855. (k) Tada, K.; Oishi, M.; Suzuki, H.; Tanaka, M. Organo-

metallics 1996, 15, 2422.

(1) (a) J anowicsz, A. H.; Bergman, R. G. J . Am. Chem. Soc. 1982,

104, 352. (b) Hoyano, J . K.; Graham, W. A. G. J . Am. Chem. Soc. 1982,

104, 3723. (c) J anowicsz, A. H.; Bergman, R. G. J . Am. Chem. Soc.

1983, 105, 3929. (d) Watson, P. L. J . Am. Chem. Soc. 1983, 105, 6491.

(e) J ones, W. D.; Feher, F. J . Organometallics 1983, 2, 562. (f) Fendrick,

C. M.; Marks, T. J . J . Am. Chem. Soc. 1984, 106, 2214. (g) Bergman,

R. G. Science 1984, 223, 902. (h) Crabtree, R. H. Chem. Rev. 1985, 85,

245. (i) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970.

(2) (a) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J . Am.

Chem. Soc. 1994, 116, 10779. (b) Takemori, T.; Suzuki, H.; Tanaka,

M. Organometallics 1996, 15, 4364. (c) Inagaki, A.; Takaya, Y.;

Takemori, T.; Suzuki, H.; Tanaka, M.; Haga, M. J . Am. Chem. Soc.

1997, 119, 625. (d) Matsubara, K.; Okamura, R.; Tanaka, M.; Suzuki,

H. J . Am. Chem. Soc. 1998, 120, 1108. (e) Matsubara, K.; Inagaki, A.;

Tanaka, M.; Suzuki, H. J . Am. Chem. Soc. 1999, 121, 7421. (f) Inagaki,

A.; Takemori, T.; Tanaka, M.; Suzuki, H. Angew. Chem., Int. Ed. 2000,

39, 404.

Publication on Web 07/11/2001

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3407

of two Si-H bonds of a secondary silane affords the

µ-silyl complex from a µ-silane complex, and a µ-silylene

complex from a µ-silyl complex as shown below. In a

series of reactions of 1 with dihydrosilanes, there

occurred such stepwise transformation of dihydrosilanes

on the dinuclear system, in which it was clearly seen

that each ruthenium center acts as a binding site and

an activation site. This is a typical example of bimetallic

activation.

As mentioned above, the multiple coordination and

multielectron transfer would cause the activation of

inert bonds. To define the effectiveness of multiple

coordination, we use vinylsilanes, which have two types

of functional group (Fg), i.e., an Si-H bond and a CdC

double bond. Vinylsilanes can coordinate on ruthenium

through both the Si-H and CdC bonds, so they appar-

ently are suitable for multiple coordination. As a result

of coordination through both the Si-H and CdC bonds,

a µ-vinylsilane complex {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiMe₂-

(CHdCH₂)} (5a ) was obtained by the reaction of 1 with

dimethylvinylsilane. Subsequent thermolysis of 5a re-

sulted in cleavage of the Si-C(sp²) bond and led to

formation of a µ-silylene-µ-ethylidyne complex, (Cp*Ru)₂-

(µ-SiMe₂)(µ-CCH₃)(µ-H) (8). The µ-vinylsilane complex

5a plays an important role in stepwise Si-H/Si-C bond

scission, and these results establish that the bimetallic

activation can be achieved by this multiple coordination.

complexes {Cp*Ru(µ-η²-HSiR₂)}₂(µ-H)(H) (2a , R ) Ph;

2b, R ) Et)^4gand a µ-silane complex {Cp*Ru(µ-H)}₂(µ-

η²:η²-H₂SiR₂) (3, R ) ^tBu).^4jIt was characteristic of these

complexes that two-electron-three-center (2e-3c) in-

teractions were involved in bonding the ruthenium,

silicon, and hydride ligand. Such agostic 2e-3c interac-

tions are often considered to be a “frozen” intermediate

for oxidative addition reaction of an Si-H bond,⁵and

actually these 2e-3c bonds are thermally cleaved to

form Ru-Si σ-bonds. Treatment of 3 with an additional

equivalent of a less bulky silane, such as phenylsilane,

resulted in formation of a mixed-bridged bis(µ-silyl)

complex (Cp*Ru)₂(µ-η²-HSi^tBu₂)(µ-η²-HSiPhH)(µ-H)(H)

(2c) via oxidative addition of the η²-coordinated Si-H

bond.^4jThe two η²-coordinated Si-H bonds of bis(µ-silyl)

complex 2a were subsequently cleaved upon thermolysis

to generate a bis(µ-silylene) complex {Cp*Ru(µ-SiPh₂)-

(µ-H)}₂(4), but 2b did not afford the corresponding bis-

(µ-diethylsilylene) complex.⁴ⁱThe difference in thermal

reactivity between 2a and 2b probably was due to the

substituent effect on the bridging silicon; the electron-

withdrawing phenyl group would intensify back-dona-

tion from the Ru d-orbital into a σ*(Si-H)-orbital, re-

sulting in the formation of the Ru-Si σ-bond, while the

electron-releasing ethyl group has the opposite effect.⁶

In the reactions of 1 with secondary silanes, σ-coor-

dination of the Si-H bond preceded the oxidative

addition; that is, formation of the σ-complex is followed

by the cleavage of the Si-H bond. Successive cleavage

Resu lts a n d Discu ssion

Rea ction of Cp *Ru (µ-H)₄Ru Cp * (1) w ith Vin yl-

sila n e Ha vin g On e Si-H Bon d . Reaction of tetrahy-

(6) (a) Lightenberger, D. L.; Rai-Chaudhuri, A. J . Am. Chem. Soc.

1989, 111, 3583. (b) Lightenberger, D. L.; Rai-Chaudhuri, A. Organo-

metallics 1990, 9, 1686. (c) Lightenberger, D. L.; Rai-Chaudhuri, A.

Inorg. Chem. 1990, 29, 975. (d) Lightenberger, D. L.; Rai-Chaudhuri,

A. J . Am. Chem. Soc. 1990, 112, 2492.

(5) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151.

3408 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

dride complex Cp*Ru(µ-H)₄RuCp* (1) with dimethylvi-

nylsilane HSiMe₂(CHdCH₂) in toluene at 0 °C resulted

in quantitative formation of a µ-dimethylvinylsilane

complex, {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiMe₂(CHdCH₂)} (5a).

Complex 5a was fully characterized on the basis of its

complex {Cp*Ru(µ-H)}₂(µ-η²:η²-^tBu₂SiH₂) (3; δ 75.5)

appeared in the high-field region compared to that of

the µ-di-tert-butylsilyl ligand of the mixed-bridged bis-

(µ-di-tert-butylsilyl; µ-diphenylsilyl) complex (Cp*Ru)₂-

(µ-η²-HSi^tBu₂)(µ-η²-HSiPh₂)(µ-H)(H) (2c; δ 115.4 for

Si^tBu₂).^4jThe J _Si-Hmeasured at -70 °C was 54.1 Hz,

while that value was reduced to 31.0 Hz at 23 °C, which

also implies the existence of a site-exchange process of

the hydrides, and the J _Si-Hof 31.0 Hz measured at 23

°C means the average value among J _Si-Ha, J _Si-Hb, and

J _Si-Hc

.

The signals for Cp* ligands in 5a were observed at δ

¹H, ¹³C, and ²⁹Si NMR and IR spectra and FD-MS. An

X-ray diffraction study of 5a established the coordina-

tion of dimethylvinylsilane in a µ-η²:η²-mode.

1.87 (s, 15H) and 1.51 (s, 15H) in the ¹H NMR spectrum.

1

In the H NMR spectrum of 5a measured at 23 °C in

toluene-d₈, signals for the vinyl group appeared at δ 4.50

(dd, 1H, -CHdCH₂), δ 3.87 (d, 1H, -CHdCH₂), and δ

3.72 (d, 1H, -CHdCH₂). These shifts were significantly

lower than those of the µ-vinylsilyl ligand of 6 (δ 1.44,

1.83, and 1.99)⁴ⁱand those of the coordinated ethylene

in {Cp*Ru(µ-η²-CHdCH₂)}₂(η²-CH₂dCH₂) (7; δ 1.86).^4h

This suggests that back-donation from the ruthenium

center is relatively reduced in 5a and the CdC bond is

coordinated to the ruthenium center somewhat weakly.

This is consistent with the downfield shifts of the ¹³C

resonances for vinylic carbons in 5a and the short Ru-C

bond length revealed by the X-ray diffraction studies

on 5a .

1

In the H NMR spectrum of 5a measured at -70 °C,

three sharp signals assignable to hydride ligands were

observed at δ -9.28 (H^a), δ -14.54 (H^b), and δ -20.22

(H^c), each with an intensity of 1H. These signals

broaden and flatten at higher temperature. This strongly

indicates a site-exchange process of the hydride ligands,

which is discussed later.

The resonances for hydride ligands, H^a, H^b, and H^c,

coupled with each other. The values of J _H-Hestimated

from curve-fitting simulation using the gNMR program

are as follows: J _Ha-Hb) 1.8 Hz, J _Hb-Hc) 3.9 Hz, J _Hc-Ha

) 2.9 Hz. A set of satellite signals due to coupling with

the ²⁹Si nucleus was observed around the signal of H^a

(δ -9.28) at -70 °C. Thus, the resonance observed at δ

-9.28 was assigned to the hydride of a Ru-H-Si 2e-

3c interaction. The J _Si-Hvalue was determined on the

basis of the ²⁹Si NMR spectrum measured at -70 °C.

The observed J _Si-Hvalue of 54.1 Hz lies in the range of

those reported for the 2e-3c interaction among Si, H,

and M (20-140 Hz).^5,7The 2e-3c Ru-H-Si interaction

was also supported by the red-shift of the ν_Ru-H-Si

compared to the ν_Si-Hof the uncoordinated Si-H bond

in the IR spectrum. The ν_Ru-H-Siof 5a appeared at 1943

cm^-1, which was lower than the ν_Si-Hof uncoordinated

Si-H bonds (ca. 2100 cm^-1), but larger than that for

the ν_Ru-H-Siof the µ-silane complex 3 (1790 cm^-1), in

which µ-η²:η²-coordination of tert-butylsilane has been

well defined.^4jThis is probably due to weak back-

donation from the ruthenium centers to σ*(Si-H) in 5a

as compared with that of µ-silane complex 3.

The ¹³C NMR signals for the coordinated vinyl group

of the µ-vinylsilane ligand were also observed at lower

field, δ 62.7 (t, J _C-H) 154.1 Hz, -CHdCH₂) and δ 68.0

(d, J _C-H) 136.1 Hz, -CHdCH₂), respectively, than

those of the µ-vinylsilyl ligand of 6, δ 55.7 (-CHdCH₂)

and δ 48.3 (-CHdCH₂),⁴ⁱand the coordinated ethylene

ligand of 7, δ 48.9.^4h

Two diastereomers, 5b and 5b′, were obtained by the

reaction of 1 with a slight excess of (()-HSiPhMe(CHd

CH₂) in toluene at 0 °C (eq 2). The product ratio 5b/5b′

The ²⁹Si signal of 5a appeared at δ -8.6, which was

at substantially higher field than for bridging silicon

ligands. The ²⁹Si signal of the σ-bonded µ-vinylsilyl

ligand of (Cp*Ru)₂(µ-η²-HSiPh₂){µ-η²-SiPh₂(CHdCH₂)}-

(µ-H)(H) (6)⁴ⁱwas observed at lower field (δ 18.5) in

comparison with that of 5a . Such a high-field shift most

likely is due to η²-coordination of the Si-H bond. The

same trend also was observed between µ-silane and

µ-silyl complexes; the ²⁹Si signal of µ-di-tert-butylsilane

was estimated as 56:44 on the basis of the ¹H NMR

spectrum measured at 23 °C. The ratio of these dia-

stereomers was not changed on heating the mixture.

(7) Corey, J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3409

Sch em e 1

molecular H/D exchange reaction occurred between 5a

and the remaining excess HSiMe₂(CHdCH₂). This hy-

dride exchange reaction was carried out only between

Si-H and Ru-H, and elimination of coordinated vinyl-

silane was not observed. This was confirmed by the

reaction of 5a with a large excess of HSiPhMe(CHd

CH₂). This reaction did not afford µ-phenylmethylvinyl-

silane complexes 5b and 5b′ at ambient temperature,

and the reaction of the mixture of 5b and 5b′ with

HSiMe₂(CHdCH₂) also did not afford 5a .

F lu xion a l Beh a vior of th e µ-η²:η²-Dim eth ylvi-

n ylsila n e Com p lex. While hydride signals of 5a , H^a,

H^b, and H^c, were observed as three sharp signals at -70

°C, they broadened and flattened at higher temperature

and coalesced into one signal at 30 °C, which implies

the site-exchange of the hydride ligands in complex 5a

(Figure 1). From the line-shape analysis of the variable-

temperature ¹H NMR spectra, the ∆G^qvalue of this

fluxional process was estimated at 12.6 ( 0.1 kcal mol^-1

at 0 °C (∆S^q) -0.9 ( 1.5 cal mol^-1K^-1, ∆H^q) 12.4 (

0.4 kcal mol^-1). Since all three signals broadened

simultaneously, their site-exchange occurred randomly,

and the rates of the individual site-exchange process,

i.e., H^a/H^b, H^b/H^c, H^c/H^a, were probably equal. Actually,

simulated signals obtained by using the same k values

fit well to the recorded spectra. This site-exchange of

hydride ligands most likely proceeds via the µ-silyl

intermediate A shown in Scheme 2, which was formed

by oxidative addition of the σ-coordinated Si-H bond.

Similar ∆S^qand ∆H^qvalues were obtained from a VT-

NMR study of a mixture of diastereomers {Cp*Ru(µ-

H)}₂{µ-η²:η²-HSiPhMe(CHdCH₂)} (5b and 5b′; for 5b,

∆S^q) -2.3 ( 0.8 cal mol^-1K^-1, ∆H^q) 12.1 ( 0.2 kcal

mol^-1, for 5b′, ∆S^q) -0.6 ( 0.7 cal mol^-1K^-1, ∆H^q)

12.3 ( 0.2 kcal mol^-1).

This fact strongly indicates this reaction is kinetically

controlled and 5b is a sterically favored isomer. Al-

though isolation of these two diastereomers has not yet

1

been done, well-separated H NMR signals distinguish

these diastereomers from each other. While signals for

Cp*, hydride, and vinyl protons of each isomers were

very closely observed, signals for the substituent groups

on the bridging silicon appeared separately. This peak

separation can be attributed to the ring current shield-

ing effect of the Cp* ligand; that is, the methyl reso-

nance of the axial position on the silicon was observed

at higher region than that of the equatorial methyl

group. Thus, we assigned the methyl signals observed

at δ 0.30 to 5b (axial) and δ 0.68 to 5b′ (equatorial),

respectively.

The ²⁹Si signal of 5b and 5b′ appeared in high field

as that of 5a , at δ -11.7 and -2.9, respectively. The

J _Si-Hvalues measured at 23 °C, 38.9 Hz for 5b and 39.0

Hz for 5b′, strongly indicate 2e-3c interactions among

Ru, Si, and H.

The signals of Me groups on the bridging silicon in

5a broadened above 30 °C, which means that there is

another fluxional process including inversion of the

H-Si-CdC moiety at higher temperature (Scheme 3).

Two sharp signals assignable to methyl groups on the

bridging silicon were observed at δ 0.45 and 0.05 at -30

°C.

Rea ction Mech a n ism of 1 w ith Dim eth ylvin yl-

sila n e. The reaction of Cp*Ru(µ-H)₄RuCp* (1) with

dimethylvinylsilane was monitored by means of ¹H

NMR at -15 °C. Complex 1 slowly reacted with vinyl-

silane to give 5a exclusively, and liberation of hydrogen.

This was confirmed on the basis of the signal at δ 4.51.

During the reaction no intermediate or dimethylethyl-

silane could be detected. When the reaction was carried

out using 1-d₄and DSiMe₂(CHdCH₂), incorporation of

deuterium into the vinyl group was not observed. This

result shows that insertion of the vinyl group into the

Ru-H bond was negligible and suggests that coordina-

tion of the Si-H bond of dimethylvinylsilane preceded

coordination of the vinyl group. Thus, the reaction most

likely proceeded as shown in Scheme 1. Two hydride

ligands eliminate as dihydrogen followed by coordina-

tion of the Si-H bond of dimethylvinylsilane. This

hydrogen elimination seems to proceed associatively. In

this reaction, it can be seen that dimethylvinylsilane

plays the role of a trapping reagent for the dinuclear

coordinatively unsaturated species as di-tert-butylsilane

did.

While the line-widths at half-height of those signals

W_1/2were 1.4 Hz at -30 °C, they increased to 6.4 Hz at

50 °C. Though we could not simulate this behavior

accurately due to a concomitant gradual thermolysis of

5a that occurred above room temperature (vide infra),

the ∆G^qvalue was roughly estimated at ca. 15.8 ( 0.4

kcal mol^-1at 0 °C (∆S^q) -24.5 ( 3.9 cal mol^-1K^-1

,

∆H^q) 9.2 ( 1.2 kcal mol^-1). The large negative ∆S^q

value compared to that for the hydride site-exchange

process implies that this process requires a more steri-

cally restricted transition state. In the case of the µ-η²:

η²-phenylmethylvinylsilane complexes 5b and 5b′, the

5b/5b′ ratio did not change on heating at 70 °C. While

two methyl groups on the silicon of 5a , axial and

equatorial, exchanged their positions by inversion of the

H-Si-CdC moiety, isomerization between 5b and 5b′

was not observed at any temperature. Isomerization

between the two diastereomers, 5b and 5b′, likely occurs

as a result of inversion of the H-Si-CdC moiety. Lack

of isomerization seems to be due to the influence of one

phenyl group on the silicon; that is, the electron-

withdrawing character of the phenyl group increases the

Treatment of 1-d₄with 5.0 equiv of HSiMe₂(CHdCH₂)

yielded a partially deuterated µ-vinylsilane complex in

which the H/D ratio of the hydride ligand was estimated

at 86:14. The H/D ratio was much larger than the

anticipated value (H/D ) 1:2) from the reaction path

shown in Scheme 1. This result shows that an inter-

3410 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

F igu r e 1. Variable-temperature ¹H NMR spectra of {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiMe₂(CHdCH₂)} (5a ) showing hydride signals

(left) and results of simulation (right). In the recorded spectrum at 70 °C, newly produced signals were found. 1 and 8

mean hydride signals of Cp*Ru(µ-H)₄RuCp* and (Cp*Ru)₂(µ-SiMe₂)(µ-CMe)(µ-H), respectively. They are produced by the

thermolysis of 5a . Asterisked signal represents thermally produced unidentified compounds.

back-donation from the ruthenium center and strength-

ens the Ru-Si bond.

One of the three hydride ligands of 5a , H(3), is bridged

between Ru(1) and Si, forming the 2e-3c interaction.

The Si-H(3) distance, 1.68(6) Å, is reasonably longer

than those reported for organosilicon compounds (1.48

Å).⁸This supports the decrease in the bonding interac-

tion between Si and H by σ-coordination to Ru(1).

X-r a y Cr ysta l Str u ctu r e of th e µ-Vin ylsila n e

Com p lex 5a . The structure of 5a was determined by

X-ray crystallography using a single crystal obtained

from heptane at -20 °C. The structure of 5a , shown in

Figure 2, establishes the unique µ-η²:η²geometry of the

HSiMe₂(CHdCH₂). The crystal data for 5a are given in

the Experimental Section (Table 4), and the selected

bond lengths and bond angles are listed in Table 1.

(8) (a) Wells, A. F. In Structural Inorganic Chemistry, 3rd ed.; Oxford

University Press: London, England, 1962; p 696. (b) Baxter, S. G.;

Mislow, K.; Blount, J . F. Tetrahedron 1980, 36, 605. (c) Allemand, J .;

Gerdil, R. Cryst. Struct. Commun. 1979, 8, 927.

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3411

Sch em e 2

Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for 5a

Sch em e 3

Ru(1)-Ru(2)

Ru(1)-Si

2.7300(7)

2.386(2)

1.67(5)

1.61(6)

1.56(4)

Ru(2)-C(1)

Ru(2)-C(2)

Ru(2)-H(1)

Ru(2)-H(2)

C(1)-C(2)

Si-C(3)

2.224(7)

2.212(6)

1.85(5)

1.96(6)

1.39(1)

1.870(7)

1.66(4)

Ru(1)-H(1)

Ru(1)-H(2)

Ru(1)-H(3)

Si-C(2)

1.890(7)

1.916(8)

Si-C(4)

Si-H(3)

Ru(2)-Ru(1)-Si

Ru(1)-Ru(2)-C(2)

Ru(1)-Si-C(2)

Ru(1)-Si-C(4)

C(2)-Si-C(4)

Ru(2)-C(1)-C(2)

Si-C(2)-C(1)

71.97(5) Ru(1)-Ru(2)-C(1)

92.1(2)

36.5(3)

112.7(2)

94(1)

102.5(3)

72.2(4)

84.1(2)

101.8(2)

120.5(3)

111.4(4)

71.3(4)

C(1)-Ru(2)-C(2)

Ru(1)-Si-C(3)

C(2)-Si-C(3)

C(3)-Si-C(4)

Ru(2)-C(2)-C(1)

122.4(6)

interaction between Si and Ru(2). Other hydrides, H(1)

and H(2), are found between two rutheniums.

The bond lengths and angles of the coordinated vinyl

group are almost the same as those of coordinated

alkenes that have previously been reported; the C(1)-

C(2) distance (1.39(1) Å) is in the range of normal CdC

double bonds, but it is shorter than the C-C distance

of the coordinated ethylene in {Cp*Ru(µ-η²-CHdCH₂)}₂-

(η²-CH₂dCH₂) (7) by ca.0.08 Å.^4hThe Ru(2)-C(1) and

Ru(2)-C(2) distances (2.228(7) and 2.218(6) Å, respec-

tively) are longer than the Ru-C distances of the

coordinated ethylene in 7 by ca. 0.06 Å. These results

and NMR data for the coordinated vinyl group strongly

suggest that the π-coordination of the vinyl group in

dimethylvinylsilane to Ru(2) was considerably weak-

ened.

Although X-ray crystallography is not the best method

to determine the location of the H atom attached to a

heavy atom, the observed Si-H bond lengthening is

consistent with the reduced J _Si-Hcoupling obtained by

¹H and ²⁹Si NMR spectroscopy and red-shift of the ν_Si-H

(vide supra). The Ru(1)-Si(1) distance (2.384(2) Å) is

slightly shorter than those in the µ-silyl and µ-silane

complexes (2.680(3)-2.414(3) Å).^4g,i,jThe Ru(2)-Si(1)

distance of 3.019(2) Å shows that there is no bonding

Th er m olysis of µ-Vin ylsila n e Com p lex 5a ; Si-C

Bon d Clea va ge Lea d in g to a µ-Silylen e-µ-Eth yli-

d yn e Com p lex. There have been few examples of

oxidative addition of a Si-C bond to a metal center.⁹

Sakaki et al. theoretically investigated the oxidative

(9) (a) Thomson, S. K.; Young, G. B. Organometallics 1989, 8, 2068.

(b) Burger, P.; Bergman, R. G. J . Am. Chem. Soc. 1993, 115, 10462.

(c) Lin, W.; Wilson, S. R.; Girolami, G. S. J . Am. Chem. Soc. 1993,

115, 3022. (d) Lin, W.; Wilson, S. R.; Girolami, G. S. Organometallics

1994, 13, 2309. (e) Shelby, Q. D.; Lin, W.; Girolami, G. S. Organome-

tallics 1999, 18, 1904. (f) Hofmann, P.; Heiss, H.; Neiteler, P.; Mu¨ller,

G.; Lachmann, J . Angew. Chem., Int. Ed. Engl. 1990, 29, 880. (g)

Kakiuchi, F.; Furuta, K.; Murai, S. Organometallics 1993, 12, 15. (h)

Schubert, U. Angew. Chem., Int. Ed. Engl. 1994, 33, 419. (i) Akita,

M.; Hua, R.; Nakanishi, S.; Tanaka, M.; Moro-oka, Y. Organometallics

1997, 16, 5572. (j) Hua, R.; Akita, M.; Moro-oka, Y. Chem. Commun.

1996, 541.

F igu r e 2. Molecular structure of {Cp*Ru(µ-H)}₂{µ-η²:η²-

HSiMe₂(CHdCH₂)} (5a ), with thermal ellipsoids at 30%

probability level.

3412 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

Sch em e 4

addition of Si-X (X ) H, F, C, and Si) to the Pt(PH₃)₂

fragment by the ab initio MO/MP4 method and dem-

onstrated that the activation energy of the Si-Si and

the Si-C oxidative addition is greater than that of the

Si-H oxidative addition.¹⁰The high activation energy

is ascribed to the requirement for turning the direction

of the sp³orbital of the carbon atom to a metal center.

Unlike most mononuclear complexes, a cluster complex

most probably activates even an Si-C bond due to the

cooperative action of adjacent metal centers if the silane

molecule has functionality capable of coordination to the

metal centers. Multiple coordination of a substrate to

the multimetallic centers brings about an entropic

advantage in the bond-breaking reaction.

¹H, ¹³C, and ²⁹Si NMR and IR spectral data and FD-

MS, as well as analytical data. The structure of 8 was

unambiguously determined by means of X-ray diffrac-

tion study (vide infra). The X-ray study established a

dinuclear structure bridged by a silylene and an eth-

ylidyne ligand as a result of Si-C bond cleavage

followed by insertion of the CdC double bond into one

of the Ru-H bonds. In the ¹³C NMR spectrum of 8, the

ethylidyne carbon atom signal was observed at very low

field (δ 387.7), and the methyl group resonance of the

ethylidyne ligand was found at δ 3.95 as a singlet in

the ¹H NMR spectrum. Both NMR data distinctively

show the bridged ethylidyne structure of 8. The ²⁹Si

signal of the µ-silylene ligand of 8 was observed at low

field (δ 197.8), the typical value for a µ-silylene ligand.

The signals of the hydride ligand and Cp* were observed

at δ -17.94 and 1.76 as sharp peaks in the ¹H NMR

spectrum at any temperature, respectively.

Thermolysis of complex 5a at 80 °C afforded a

µ-silylene, µ-ethylidyne complex (Cp*Ru)₂(µ-SiMe₂)(µ-

CCH₃)(µ-H) (8) in 70% yield via Si-C(sp²) bond cleavage

(eq 3). Complex 8 was fully characterized by means of

The signals of the methyl groups of 8 were observed

at δ 0.66 and 1.70 as broad peaks in the ¹H NMR

spectrum measured at 10 °C. They became a set of two

sharp signals at lower temperature and coalesced into

one signal at 60 °C. The activation energy ∆G^qof this

fluxional process calculated at the coalescence temper-

ature was estimated at ca. 15.0 kcal mol^-1(∆S^q) -7.7

( 0.4 cal mol^-1K^-1, ∆H^q) 12.5 ( 0.1 kcal mol^-1). The

exchange of two methyl signals on bridging silicon can

be accounted for by the processes A-D shown in Scheme

4; paths A-D are the mechanisms that involve µ-silyl,

terminally bonded ethylidene, terminally bonded si-

lylene, and µ-vinylidene intermediates, respectively.

Formation of the µ-ethylidene ligand was confirmed

by the reaction of 8 with carbon monoxide (vide infra).

(10) Sakaki, S.; Ieki, M. J . Am. Chem. Soc. 1993, 115, 2373.

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3413

F igu r e 3. (a) Molecular structure of (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-H) (8), with thermal ellipsoids at 30% probability level.

The crystal submitted to the diffraction studies included the form of 8 that is 44.3% disordered about the hydride position,

which is drawn by a white line. (b) View of the Ru₂SiC core of 8 along the Ru-Ru axis.

Reversible transformation between a bridging and

terminally bonded alkylidene has often been proposed

yl group of the ethylidyne ligand during the H/D

exchange reaction (vide infra) indicates that site-

exchange between the hydride and methyl proton of the

ethylidyne ligand takes place. Irradiation of the methyl

protons of the µ-ethylidyne ligand at 50 °C resulted in

a 10% decrease of the intensity of the hydride resonance,

but the rate of hydride migration was considerably

slower than the estimated value by the line-shape

analysis (k ) 77.2 s^-1). Thus, the fluxionality of two

methyl groups on the silicon atom could not be explained

by the µ-vinylidene mechanism D.

Path A involves reductive elimination between µ-si-

lylene and hydride followed by a swing around the Ru-

Si bond. Eisenberg et al. proposed a rapid reductive

elimination/oxidative addition mechanism for the flux-

ional process of the dirhodium µ-silylene complex Rh₂H₂-

(µ-SiPhH) (CO)₂(dppm)₂.¹⁶The ∆G^qvalue was calculated

to be 12 ( 1 kcal mol^-1both at -30 °C and at 25 °C,

which indicated a very small ∆S^qfor the process.

Similarly, rotation around the Ru-Si bond of the µ-silyl

group formed by the reductive elimination of µ-silylene

with the hydride of complex 8 followed by the oxidative

addition should move the hydride ligand from the

bottom to the upper side of the Ru₂SiC moiety. This

rearrangement could explain the temperature depen-

dence of NMR signals for the methyl groups on the

bridging silicon atom and is consistent with the very

small ∆S^qvalue. So, it was assumed that the fluxionality

of 8 was most probably due to path A.

The X-ray diffraction study was carried out using a

red-brown single crystal of 8 obtained from cold toluene/

pentane mixed solution. The structure of 8 is shown in

Figure 3, and selected bond lengths and angles are listed

in Table 2. Disordered atoms, Si(1), C(1), C(2), C(3), and

C(4), were refined isotropically. Location of the hydride

ligands was determined in the differential Fourier map

and refined isotropically.

The Ru(1)-Ru(2) distance of 2.5888(15) Å corresponds

to a Ru-Ru double bond and is consistent with the bond

order between Ru atoms anticipated from the EAN rule

applied to 8. The small Ru(1)-Si(1)-Ru(2) angle

for isomerization reactions of dinuclear complexes.¹¹

A

few examples of transformation of bridging to the

terminal alkylidene have been reported.¹²Rotation of

the terminal alkylidene ligand around the MdC bond

has been well investigated, and the activation energy

∆G^qof the rotation is 10.4 kcal mol^-1for (C₅H₅)Fe-

(dppm)(dCH₂).¹³

As for the µ-silylene ligand, while there was no

isolated example of the transformation of bridging to

the terminal silylene ligand, such a rearrangement was

proposed in some isomerization reactions.¹⁴Tilley et al.

proposed reversible transformation of a bridging silylene

to terminal silylene followed by rotation around the Rud

Si bond in the silylene isomerization of (Cp*Ru)₂{µ-

SiPh(OMe)}(µ-OMe)(µ-H).^14aBut, the rate of this re-

arrangement was relatively slow and this isomeriza-

tion was irreversible; it took more than 24 h at

room temperature. Rotation of the terminal silylene

around the MdSi bond was observed in (C₅H₅)W(CO)₂-

{(SiMe₂)‚‚‚NEt₂‚‚‚(SiMe₂)}, and the activation param-

eters were estimated at ∆H^q) 17.4 kcal mol^-1and ∆S^q

) 11.7 cal mol^-1K^{-1 15}

.

Both path B and path C are possible, but when

compared to a mononuclear system, they seem to

require a more crowded transition state for dinuclear

complexes due to the neighboring metal center in their

rotation around the MdC or MdSi bond. So, larger

negative ∆S^qvalues would be observed.

Hydride migration via a µ-vinylidene intermediate is

also possible (path D). A 1,3-shift of the methyl proton

of the ethylidyne ligand possibly affords a µ-vinylidene

intermediate. Incorporation of deuterium into the meth-

(11) Colborn, R. E.; Dyke, A. F.; Knox, S. A. R.; Mead, K. A.;

Woodward, P. J . Chem. Soc., Dalton Trans. 1983, 2099.

(12) (a) Messerle, L.; Curtis, M. D. J . Am. Chem. Soc. 1982, 104,

889. (b) Herrmann, W. A.; Bauer, C. Organometallics 1982, 1, 1101.

(13) (a) Brookhart, M.; Tucker, J . R.; Flood, T. C.; J ensen, J . J . Am.

Chem. Soc. 1980, 102, 1203. (b) Schilling, B. E. R.; Hoffmann, R.;

Lightenberger, D. L. J . Am. Chem. Soc. 1979, 101, 585.

(14) (a) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics

1992, 11, 3918. (b) Tobita, H.; Kawano, Y.; Ogino, H. Chem. Lett. 1989,

2155.

(15) Ueno, K.; Masuko, A.; Ogino, H. Organometallics 1997, 16,

5023.

(16) (a) Wang. W. D.; Eisenberg, R. J . Am. Chem. Soc. 1990, 112,

1833. (b) Wang. W. D.; Eisenberg, R. Organometallics 1992, 11, 908.

3414 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for 8

lower temperature (30 °C). Complex 5a was completely

consumed after 80 h. Generation of an intermediary

µ-silyl, µ-vinyl complex (Cp*Ru)₂(µ-η²-HSiMe₂)(µ-CHd

CH₂)(µ-H)(H) (9a ) was observed at the beginning (eq 4),

Ru(1)-Ru(2)

Ru(2)-Si(1)

Ru(2)-C(1)

Ru(2)-H(1)

Si(1)-C(4)

2.5888(15)

2.335(3)

1.918(13)

1.77(4)

Ru(1)-Si(1)

Ru(1)-C(1)

Ru(1)-H(1)

Si(1)-C(3)

C(1)-C(2)

2.337(3)

1.913(13)

1.78(4)

1.961(12)

1.489(16)

1.893(12)

Ru(2)-Ru(1)-Si(1)

Si(1)-Ru(1)-C(1)

Ru(1)-Ru(2)-C(1)

Ru(1)-Si(1)-Ru(2)

Ru(1)-Si(1)-C(4)

Ru(2)-Si(1)-C(4)

Ru(1)-C(1)-Ru(2)

Ru(2)-C(1)-C(2)

56.31(8) Ru(2)-Ru(1)-C(1)

47.6(4)

56.38(8)

102.7(4)

117.6(4)

119.0(4)

105.9(5)

136.7(9)

102.8(4)

47.4(4)

67.31(9) Ru(1)-Si(1)-C(3)

Ru(1)-Ru(2)-Si(1)

Si(1)-Ru(2)-C(1)

122.3(4)

121.6(4)

85.0(5)

Ru(2)-Si(1)-C(3)

C(3)-Si(1)-C(4)

Ru(1)-C(1)-C(2)

138.2(9)

(67.31(9)°) also suggests a strong bonding interaction

between rutheniums.¹⁷Two Cp* ligands are nearly

parallel to each other, and centroids of the two Cp*

ligands and the ruthenium atoms are located on an

almost straight line. The Ru-Si(1) distance of 2.336 Å

(av) is in the normal range of the Ru-Si σ-bond, and

the relatively short Ru-C(1) distance of 1.916 Å (av)

indicates an ethylidyne ligand. The Ru₂SiC moiety is

slightly folded; the dihedral angle between Ru(1)-Ru-

(2)-Si(1) and Ru(1)-Ru(2)-C(1) is 165.7(6)°. Small

steric repulsion among C(1), Si(1), and H(1) would cause

the divergence from the planarity of the Ru₂SiC moiety.

The view along the Ru(1)-Ru(2) axis clearly shows that

the ruthenium centers are sterically less crowded.

The Si(1)‚‚‚H(1) distance of 2.02(9) Å is considerably

short. It is only 10% longer than the η²-Si-H distance

of 1.802(5) Å of (η⁵-C₅MeH₄)Mn(CO)PMe₃(η²-HSiPh₂F)

determined by neutron diffraction.¹⁸H(1), moreover,

seemed to lean toward Si(1); the dihedral angle between

Ru(1)-Ru(2)-Si(1) and Ru(1)-Ru(2)-H(1) is 76(4)° is

considerably smaller than that between Ru(1)-Ru(2)-

C(1) and Ru(1)-Ru(2)-H(1) (119(4)°). It is difficult to

determine the accurate position of the hydrogen atom

attached to transition metals by means of X-ray diffrac-

tion studies, but the facts of the relatively short

Si(1)‚‚‚H(1) distance and inclination of the Ru-H bond

to the Si atom may imply a very weak interaction

between Si and H. The J _Si-Hvalue of 22.7 Hz was in

and the concentration of 9a was maximized after 12 h

(ca. 20%). Complex 9a was characterized on the basis

1

of the H and ²⁹Si NMR spectra. The spectra were very

similar to those of the analogous µ-η²-silyl, µ-η¹:η²-vinyl

complex, (Cp*Ru)₂(µ-η²-HSi^tBu₂)(µ-CHdCH₂)(µ-H)(H)

(9b), which was independently prepared by the reaction

of µ-silane complex 3 with acetylene (eq 5; see Experi-

1

mental Section). In the H NMR spectra of the reaction

1

the gray zone between J _Si-Hof the 2e-3c Si-H

2

interaction and J _Si-Hof the silyl hydride complexes,

but it seems to imply a weak interaction, too. It cannot

be concluded from both this X-ray study and NMR data,

but if there were some kind of interaction between H

and Si, the fluxional behavior of 8 could be well

documented by path A in Scheme 4.¹⁹

mixture after 12 h, two singlets assignable to Cp* of 9a

were observed at δ 1.69 and 2.00. The signals of vinyl

groups appeared at δ 6.71 (dd, J ) 10.8, 7.6 Hz), δ 3.17

(dd, J ) 7.6, 2.4 Hz), and δ 3.08 (dd, J ) 10.8, 2.4 Hz).

The signals for the hydride ligands were found as 2:1

of two peaks at δ -14.10 and -13.19, in which the signal

found at δ -13.19 was broadened at lower temperature.

The ²⁹Si signal of the bridging silicon ligand was found

at δ 71.5 with a 59.6 Hz coupling constant between the

hydride at -70 °C, which strongly indicated a 2e-3c

interaction between Ru, Si, and hydride.

Cleavage of the Si-C(vinyl) bond of 5a was monitored

1

in a sealed tube by means of H NMR spectroscopy at

(17) (a) Coleman, J . M.; Dahl, L. F. J . Am. Chem. Soc. 1967, 89,

542. (b) Stevenson, D. L.; Dahl, L. F. J . Am. Chem. Soc. 1967, 89, 3721.

(c) Dahl, L. F.; De Gil, E. R.; Feltham, R. D. J . Am. Chem. Soc. 1969,

91, 1653. (d) Connelly, N. G.; Dahl, L. F. J . Am. Chem. Soc. 1970, 92,

7470. (e) Connelly, N. G.; Dahl, L. F. J . Am. Chem. Soc. 1970, 92, 7472.

(18) (a) Shubert, U.; Scholz, G.; Mu¨ller, J .; Ackermann, K.; Wo¨rle

B.; Stansfield, R. F. D. J . Organomet. Chem. 1986, 306, 303. (b)

Shubert, U.; Ackermann, K.; Wo¨rle B. J . Am. Chem. Soc. 1982, 104,

7378.

(19) The bond distance for Si(1A)‚‚‚H(1A) (2.27(7) Å) is slightly

longer than Si(1)‚‚‚H(1). The dihedral angles C(1A)-Ru(1)-Ru(2)-Si-

(1A), C(1A)-Ru(1)-Ru(2)-H(1A), and Si(1A)-Ru(1)-Ru(2)-H(1A) are

169.6(9)°, 102(3)°, and 88(3)°, respectively. These values are slightly

different from the structure with high occupancy, but still imply weak

interaction between the hydride and the bridging silicon atom. We are

now investigating the presence of this agostic interaction between Si

and H by MO calculation and will report in due course.

As the concentration of complex 9a decreased, gen-

eration of both µ-silylene, µ-ethylidyne complex 8 and

tetrahydride complex 1 began to be observed. After 80

h, the ratio between 8 and 1 reached 80:20. The yield

1

of 8(+1) was estimated at 70% on the basis of the H

NMR spectra. The formation of 1 can be explained by

the reaction of 8 with the liberated dihydrogen (vide

infra).

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3415

Two mechanisms can be possible for the Si-C(sp²)

bond cleavage; one is direct oxidative addition, and the

other is a â-Si elimination mechanism. Wakatsuki et

al. showed a Si-C scission via â-Si elimination in the

reaction of a vinylsilane with a ruthenium hydride

complex,²⁰and several groups reported synthesis of

silylated alkenes by â-Si elimination.²¹The formation

of 9a could be rationalized considering an oxidative

addition of a C-H bond of the coordinated ethylene that

was generated by insertion of a vinyl group into a Ru-H

bond followed by â-Si elimination. We consider, how-

ever, it is a case of an oxidative addition of a Si-C bond

because the Si-C bond of triphenylsilane was also

cleaved upon the reaction of 1, yielding bis-µ-diphenyl-

silylene complex 4 and benzene.²²

F igu r e 4. ¹H NMR spectra of the methyl group of the

µ-ethylidyne ligand in the H/D exchange reaction of 8 with

benzene-d₆at 100 °C after 48 h.

In t er m olecu la r H /D E xch a n ge R ea ct ion b e-

tw een 8 a n d Ben zen e-d ₆. µ-Silylene, µ-ethylidyne

complex 8 was stable in even refluxing toluene for

several days. Although 8 did not show any decomposi-

tion in C₆D₆at 100 °C in a sealed NMR tube, H/D

exchange reaction between 8 and C₆D₆took place. It

causes a slight change in the ¹H NMR signal for the

methyl group of the ethylidyne ligand as well as

disappearance of the hydride signal. Incorporation of

deuterium into the methyl group of the ethylidyne

ligand was shown by the observation of a 1:1:1 triplet

signal assignable to µ-CCH₂D, which newly appeared

beside the signal of the methyl proton of the µ-ethyli-

dyne ligand in 10 h. Prolonged heating resulted in

appearance of another 1:2:3:2:1 quintet signal assign-

able to µ-CCHD₂, as shown in Figure 3. ²H NMR

measurements on this sample clearly showed incorpora-

tion of deuterium into both the methyl group and

hydride site. This result indicates occurrence of aromatic

C-H bond activation as well as a hydride site-exchange

process via path D in Scheme 4, i.e. hydride migration

via a µ-vinylidene intermediate.

µ-Eth ylid yn e Com p lex via Si-C/Si-C Bon d Clea v-

a ge. The reaction of Cp*Ru(µ-H)₄RuCp* (1) with a

vinylsilane having no Si-H bond was also carried out.

We used a Si-H bond as an anchor to the metal center

because it is well known that oxidative addition of a

Si-H bond to a coordinatively unsaturated metal center

proceeds readily and forms a thermally stable M-Si

bond. As mentioned above, several types of µ-silicon

ligands were obtained in the reactions of 1 with second-

ary silanes. In the reaction of 1 with dimethylvinylsi-

lane, which has one Si-H bond and a vinyl group,

coordination of both Si-H and CdC bonds to the

ruthenium centers were observed as stated above, and

it was shown that µ-η²:η²-coordination of vinylsilane

would facilitate Si-C bond scission. When trimethylvi-

nylsilane, which has no Si-H bond, was employed as a

reactant, successive Si-C(sp²) and Si-C(sp³) bond

cleavage occurred.

The reaction of 1 with 2.5 molar equiv of trimethylvi-

nylsilane at 45 °C afforded µ-dimethylsilylene, µ-eth-

ylidyne complex (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-H) (8) in

70% yield (eq 6). Small amounts of unidentified byprod-

ucts could be removed by rinsing with pentane to give

analytically pure 8.

Incorporation of deuterium into the methyl group of

the η⁵-pentamethylcyclopentadienyl ligand also was

observed by means of ²H NMR, which indicates revers-

ible C-H bond scission/formation of the methyl group

via a fulvene intermediate. While deuterium was in-

corporated into µ-ethylidyne, Cp*, and hydride sites,

incorporation into methyl groups on the bridging silicon

was not observed.

This H/D exchange reaction seemed to be derived from

the coordinatively unsaturated character of 8. Electron

deficiency of the ruthenium center would require an

intra- and/or intermolecular σ-coordination of the C-H

bond.

Th e Rea ction of Cp *Ru (µ-H)₄Ru Cp * (1) w ith

Tr im et h ylvin ylsila n e; F or m a t ion of µ-Silylen e,

(20) (a) Wakatsuki, Y.; Yamazaki, H.; Nakano, M.; Yamamoto, Y.

J . Chem. Soc., Chem. Commun. 1991, 703. (b) Wakatsuki, Y.; Yamaza-

ki, H. J . Organomet. Chem. 1995, 500, 349. (c) Mise, T.; Takaguchi,

Y.; Umemiya, T.; Shimizu, S.; Wakatsuki, Y. Chem. Commun. 1998,

699.

(21) See for example: (a) Yi, C. S.; He, Z.; Lee, D. W.; Rheingold, A.

L.; Lam, K.-C. Organometallics 2000, 19, 2036. (b) Kakiuchi, F.;

Yamada, A.; Chatani, N.; Murai, S.; Furukawa, N.; Seki, Y. Organo-

metallics 1999, 18, 2033. (c) Marciniec, B.; Pietraszuk, C. Organome-

tallics 1997, 16, 4320. (d) Seitz, F.; Wrighton, M. S. Angew. Chem.,

Int. Ed. Engl. 1988, 27, 289.

When the reaction was carried out in a sealed tube

at 0 °C, formation of trimethylethylsilane and methane

was confirmed by means of ¹H NMR spectroscopy. While

hydrogen was eliminated to form µ-vinylsilane complex

5a in the reaction of dimethylvinylsilane, two hydrides

were removed as trimethylethylsilane via hydrogenation

of the vinyl group in this case. Though mechanistic

details are not yet available at the present time, it can

(22) Bis-µ-diphenylsilylene complex {Cp*Ru(µ-SiPh₂)(µ-H)} (4) was

obtained by the reaction of Cp*Ru(µ-H)₄RuCp* with triphenylsilane

with liberating benzene. Takao, T.; Amako, M.; Tanaka, M.; Suzuki,

H. Manuscript in preparation.

3416 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

be said that two Si-C bonds were cleaved by the

cooperative action of two rutheniums. This activation

was assumed to be achieved via formation of a µ-trim-

ethylvinylsilane intermediate as shown below. Agostic

Si-C interaction was observed in a d₀titanium complex

[Cp₂Ti{C(η²-H₃C-SiMe₂)dCPhMe}]⁺, and this SiC‚‚‚Ti

interaction was investigated theoretically by an ab initio

MO method.^23,24

µ-η²:η²-Coordination of trimethylvinylsilane would

result in the ready cleavage of the Si-C(sp³) bond under

such mild conditions. Si-C(sp³) scission on the dinuclear

system was also reported by Girolami et al.^9c-eThe

reaction of {Cp*Ru(µ-Cl)}₄with Mg(CH₂SiMe₃)₂resulted

in formation of µ-methylidene complex (Cp*Ru)₂(µ-CH₂)-

(µ-Cl)(SiMe₃) via formation of an intermediate trimeth-

ylsilylmethyl complex. This terminally bonded trime-

thylsilyl group, however, would not afford the µ-silylene

ligand by further oxidative addition of the Si-C(sp³)

bond. It was assumed that a bridging chloride ligand

decreases the electron density on the ruthenium centers

so that oxidative addition of Si-C(sp³) was suppressed.

F igu r e 5. Molecular structure of {Cp*Ru(CO)}₂(µ-SiMe₂)-

(µ-CHMe) (10), with thermal ellipsoids at 30% probability

level.

Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for 10

Ru(1)-Ru(2)

Ru(2)-Si

2.8268(5)

2.369(1)

2.076(5)

1.874(8)

1.889(5)

1.149(4)

Ru(1)-Si

Ru(1)-C(1)

Ru(2)-C(2)

Si-C(5)

C(1)-O(1)

C(3)-C(4)

2.359(1)

1.814(4)

1.883(8)

1.497(8)

1.161(5)

1.438(7)

Ru(1)-C(3)

Ru(2)-C(3)

Si-C(6)

C(2)-O(2)

Ru(2)-Ru(1)-Si

Si-Ru(1)-C(3)

53.45(4) Ru(2)-Ru(1)-C(1)

46.9(2)

56.28(5)

102.5(2)

121.4(3)

122.1(3)

103.5(4)

177.0(4)

137.5(4)

103.0(2)

46.3(2)

Ru(1)-Ru(2)-Si

Si-Ru(2)-C(3)

Ru(1)-Ru(2)-C(3)

Ru(1)-Si-Ru(2)

Ru(1)-Si-C(6)

Conversely, formation of

a µ-trimethylsilylmethyl

67.53(6) Ru(1)-Si-C(5)

group by reductive elimination between silyl and µ-me-

thylidene occurred in the fluxional process of the

complex.

Rea ction of µ-Silylen e, µ-Eth ylid yn e Com p lex 8

w ith Ca r bon Mon oxid e a n d Eth ylen e. Due to the

coordinatively unsaturated metal centers of 8 (32e) and

its sterically less crowded ruthenium centers as revealed

by X-ray studies, complex 8 readily reacts with some

small molecules.

120.1(3)

120.3(3)

176.0(4)

86.8(2)

Ru(2)-Si-C(5)

C(5)-Si-C(6)

Ru(2)-C(2)-O(2)

Ru(1)-C(3)-C(4)

Ru(2)-Si-C(6)

Ru(1)-C(1)-O(1)

Ru(1)-C(3)-Ru(2)

Ru(2)-C(3)-C(4)

135.7(5)

that the hydride migration to the bridging carbon

resulted in formation of the µ-ethylidene ligand.

The µ-ethylidene carbon signal was observed at δ

142.7 (d, J _C-H) 137.4 Hz) in the ¹³C NMR spectrum,

which is characteristic for the alkylidene carbon. The

²⁹Si signal of the µ-silylene ligand was observed in the

low-field region (δ 213.2). The ν_COwas observed at 1912

The reaction of complex 8 with 9 atm of CO at 120 °C

yielded µ-silylene, µ-ethylidene complex {Cp*Ru(CO)}₂-

(µ-SiMe₂)(µ-CHMe) (10) (eq 7). Complex 10 was purified

and 1899 cm^-1, which were assignable to ν_symand ν_asym

,

respectively. The trans structure was confirmed by the

fact that the intensity of ν_asymwas stronger than that

of ν_sym. The structure of complex 10 was determined by

means of X-ray diffraction studies; the ORTEP diagram

is shown in Figure 5, and selected bond lengths and

angles are listed in Table 3.

While complex 8 did not react with propylene, it did

react with 1 atm of ethylene at room temperature to

yield µ-silylene, µ-vinyl complex (Cp*Ru)₂(µ-SiMe₂)(µ-

η²-CHdCH)(µ-H)(CH₂dCH₂) (11) as the sole product (eq

8). Complex 11 was characterized by means of ¹H, ¹³C,

1

and ²⁹Si NMR and H-¹H and ¹³C-¹H COSY.

1

In the H NMR spectrum of 11, the proton signals of

the µ-η²-coordinated vinyl group were found at δ 1.69

(d, J ) 9.2 Hz), δ 2.38 (d, J ) 6.4 Hz), and δ 8.96 (dd,

J ) 9.2, 6.4 Hz). Such a low-field shift of the R-proton

of the vinyl group is characteristic for the proton on the

by column chromatography on alumina and could be

isolated in 47% yield. All of the spectral data are

consistent with the µ-ethylidene structure. It was shown

(23) Eisch, J . J .; Piotrowski, A. M.; Brownstein, S. J .; Gabe, E. J .;

Lee, F. L. J . Am. Chem. Soc. 1985, 107, 7219.

(24) Koga, N.; Morokuma, K. J . Am. Chem. Soc. 1988, 110, 108.

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3417

betw een Tw o Br id gin g Elem en ts. When complex 8

was treated with 1 atm of hydrogen at room tempera-

ture, dinuclear tetrahydride complex 1 was generated.

Complex 8 was completely consumed within 48 h. The

dimethylsilylene and ethylidyne bridges were mainly

eliminated as dimethylethylsilane, and the yield of

dimethylethylsilane was estimated roughly at 30% by

1

means of H NMR spectroscopy. While a few unidenti-

fied organosilicon compounds were produced, there was

no sign of formation of dimethylvinylsilane or dimeth-

1

ylsilane in the H NMR spectrum.

It was assumed that the reaction proceeded as shown

in Scheme 4. Hydrogen coordinates on one ruthenium

as a 2e donor; then hydride ligands migrate on the

bridging ethylidyne ligand to form an intermediate

similar to A of the reaction of carbon monoxide and

ethylene. Coordination of the second hydrogen molecule

and reduction of both bridging ligands would occur

(intermediate B). Reductive elimination of dimethyl-

ethylsilane from the intermediacy silyl-alkyl complex

C forms tetrahydride complex 1. Re-formation of the

µ-vinylsilane intermediate from A would be also possible

by â-hydrogen elimination of the µ-ethylidene ligand.

Sometimes vinylsilanes were detected as side-products

of hydrosilylation, which implied the formation of vi-

nylsilyl intermediates of the silyl-metalation path (i.e.,

olefin insertion into an M-Si bond).¹⁹In this reaction,

however, formation of neither vinylsilanes nor vinylsi-

lane complexes was detected, and thus it supports the

mechanism shown in Scheme 4.

carbene carbon and strongly suggests µ-σ:π-coordination

of the vinyl group. The ¹³C signals of the vinyl group

were found at δ 39.6 (t, J _C-H) 157.7 Hz) and δ 174.2

(d, J _C-H) 154.8 Hz), which also implied µ-σ:π-coordina-

tion. Signals of the π-coordinated ethylene were found

1

at δ 1.00, 1.10, 1.50, and 1.60 in the H NMR spectrum

and δ 36.8 (t, J _C-H) 155.5 Hz) and δ 41.9 (t, J _C-H

)

156.2 Hz) in the ¹³C NMR spectrum. The µ-silylene

coordination was confirmed by the ²⁹Si signal found at

δ 205.7 (s).

Complex 11 slowly decomposed at 40 °C under an

argon atmosphere and mainly regenerated complex 8

with a small amount of unidentified byproducts. Inser-

tion of the coordinated ethylene into the Ru-Si bond

was not observed.

When a π-acceptor coordinates to one ruthenium, the

reductive elimination of hydride and µ-ethylidyne would

be promoted and result in formation of the µ-ethylidene

ligand. Carbon monoxide seems to be small enough to

coordinate on the intermediate A in Scheme 3, so

dicarbonyl complex 10 would be produced. On the other

hand, ethylene is so large that coordination of the second

ethylene is suppressed and â-H elimination to form the

µ-σ:π-vinyl group takes place instead.

While we previously showed a reaction of bis-µ-

silylene complex 4 with acetylene to form 2,5-disilaru-

thenacyclopentene complex {Cp*Ru(µ-H)}₂{µ-η²-SiPh₂C-

(H)dC(H)SiPh₂}, in which Si-C coupling also occurred,⁴ⁱ

this was a case of reductive Si-C bond formation on

the dinuclear system. Girolami et al. showed reversible

Si-C bond formation on the dinuclear complex (Cp*Ru)₂-

(µ-Cl)(µ-CH₂)(SiR₃) by means of a dynamic NMR

study.^9c-eAkita et al. also showed Si-C coupling

between a µ-methylene and a terminally bonded silyl

group and reductive elimination of tetramethylsilane by

thermolysis of {CpRu(CO)}₂(µ-CH₂)(µ-CO) in the pres-

ence of trimethylsilane.^9i,j,25These reactions support the

Rea ction of µ-Silylen e, µ-Eth ylid yn e Com p lex 8

w ith Molecu la r Hyd r ogen ; Red u ctive Elim in a tion

Sch em e 5

3418 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

Sch em e 6

reductive Si-C bond formation step from the intermedi-

ate C in Scheme 4. Although a number of complexes

containing two bridging group 14 elements have been

prepared, a coupling reaction between two bridging

elements is still rare.²⁶Especially, the coupling reaction

including the µ-silylene ligand is quite limited.²⁷Fryzuk

et al. proposed a Si-C coupling reaction between µ-silyl

and µ-alkyl ligands only in catalytic hydrosilylation

using a dirhodium complex.²⁸To the best of our knowl-

edge, this is the first example of the reductive elimina-

tion between µ-silylene and another bridging element

by using an isolated dinuclear complex.

was also shown in this reaction. Oxidative addition of

even an inert Si-C(sp³) bond was achieved on the

dinuclear system, which is a typical example of bimetal-

lic activation.

Complex 8 obtained by the reaction of Cp*Ru(µ-

H)₄RuCp* (1) with vinylsilanes is a novel type of

complex that has both a silylene and an ethylidyne

bridge in its structure. Coordinatively unsaturated

metal centers of 8 led to easy reaction with 2e donors.

Treatment of µ-silylene, µ-ethylidyne complex 8 with

small 2e donors, CO and CH₂dCH₂, resulted in the

transformation of the µ-ethylidyne ligand to the µ-eth-

ylidene and µ-vinyl ligand, respectively. In the reaction

of H₂, elimination of both the µ-ethylidyne and µ-silylene

bridge of 8 as dimethylethylsilane was observed, and

complex 1 was regenerated. Reductive elimination of

bridging ligands is a new type of reaction of dinuclear

systems, and we are eager to investigate the further

reactivity of 8 to build up dinuclear catalytic reaction

systems using bimetallic activation.

Con clu sion

The µ-vinylsilane complex {Cp*Ru(µ-H)}₂{µ-η²:η²-

HSiMe₂(CHdCH₂)} (5a ) was obtained by the reaction

of Cp*Ru(µ-H)₄RuCp* (1) with dimethylvinylsilane. A

unique µ-η²:η²-coordination of HSiMe₂(CHdCH₂) was

confirmed on the basis of ¹H, ¹³C, and ²⁹Si NMR and IR

spectral and X-ray diffraction studies. Both Si-H and

CdC bond coordination renders the Si-C(sp²) bond

subject to scission under mild conditions. This demon-

strates that the Si-C(sp²) bond was activated by

multiple coordination. Thermolysis of 5a yielded µ-si-

lylene, µ-ethylidyne complex (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)-

(µ-H) (8) via formation of µ-silyl, µ-vinyl complex

(Cp*Ru)₂(µ-η²-HSiMe₂)(µ-CHdCH₂)(µ-H)(H) (9a ) as an

intermediate.

Exp er im en ta l Section

Gen er a l P r oced u r es. All experiments were carried out

under an argon atmosphere. All compounds were treated with

Schlenk techniques. Reagent grade toluene was dried over

sodium-benzophenone ketyl and stored under an argon atmo-

sphere. Pentane was dried over phosphorus pentoxide and

stored under an argon atmosphere. Benzene-d₆, toluene-d₈,

and THF-d₈were dried over sodium-benzophenone ketyl and

stored under an argon atmosphere. Dimethylvinylsilane and

Dimethylvinylsilane-d were synthesized by the reduction of

chlorodimethylvinylsilane by LiAlH₄or LiAlD₄in diglyme,

respectively. (()-Phenylmethylvinylsilane and (()-phenyl-

methylvinylsilane-d were synthesized by the reduction of (()-

chlorophenylmethylvinylsilane by LiAlH₄or LiAlD₄in diethyl

ether, respectively. Trimethylvinylsilane and other substrates

were used as received. IR spectra were recorded on a J ASCO

FT/IR-5000 spectrophotometer. ¹H and ¹³C NMR spectra were

recorded on J EOL GX-500, Varian Gemini-3000, and Varian

INOVA-400 Fourier transform spectrometers with tetrameth-

ylsilane as an internal standard. Variable-temperature ¹H

NMR spectra were recorded on a Varian INOVA-400. ²⁹Si

The reaction of 1 with trimethylvinylsilane also

yielded 8, in which both Si-C(sp²) and Si-C(sp³) bonds

were cleaved. The effect of two neighboring rutheniums

(25) Akita, M.; Oku, T.; Hua, R.; Moro-oka, Y. J . Chem. Soc., Chem.

Commun. 1993, 1670.

(26) (a) Saez, I. M.; Andrews, D. G.; Maitlis, P. M. Polyhedron 1988,

7, 827. (b) Maitlis, P. M. J . Organomet. Chem. 1995, 500, 239. (c)

Maitlis, P. M.; Long, H. C.; Quyoum, R.; Turner, M. L.; Wang, Z.-Q. J .

Chem. Soc., Chem. Commun. 1996, 1.

(27) Ogino, H.; Tobita, H. Adv. Organomet. Chem. 1998, 42, 223.

(28) (a) Fryzuk, M. D.; Piers, W. E.; Einstein, F. W. B.; J ones, T.

Can. J . Chem. 1989, 67, 883. (b) Fryzuk, M. D.; Rosenberg, L.; Rettig,

S. J . Organometallics 1996, 15, 2871. (c) Fryzuk, M. D.; Rosenberg,

L.; Rettig, S. J . Organometallics 1991, 10, 2537.

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3419

Ta ble 4. Cr ystr a llogr a p h ic Da ta for 5a a n d 10

NMR spectra were recorded on a J EOL EX-270 and a Varian

INOVA-400 with tetramethylsilane as an external standard.

²H NMR spectra were recorded on a J EOL EX-270 and a

Varian INOVA-400 with benzene-d₆as an internal standard.

Field-desorption mass spectra were recorded on a Hitachi GC-

MS M80 high-resolution mass spectrometer. Coldspray ioniza-

tion mass (CSI-MS)²⁹spectra of a mixture of 5b/5b′ were

recorded on a J EOL J MS-700T equipped with the CSI source

at the Chemical Analysis Center at Chiba University. Elemen-

tal analyses were performed by the Analytical Facility at the

Research Laboratory of Resources Utilization, Tokyo Institute

of Technology. The dinuclear ruthenium tetrahydride complex

(η⁵-C₅Me₅) Ru(µ-H)₄Ru(η⁵-C₅Me₅) (1) and (η⁵-C₅Me₅)Ru(µ-D)₄-

Ru(η⁵-C₅Me₅) (1-d₄) were prepared according to a previously

published method.⁴

5a

10

(a) Crystal Parameters

formula

cryst syst

space group

a, Å

b, Å

c, Å

R, deg

â, deg

γ, deg

V, Å³

C

₂₄H₄₂Ru₂Si

C₂₆H₄₀O₂Ru₂Si

triclinic

P1h

monoclinic

C_c

10.458(1)

19.093(1)

13.474(1)

9.826(3)

15.554(4)

9.698(3)

96.08(2)

113.94(2)

91.97(2)

1342.2(6)

2

105.387(8)

1236.7(6)

4

1.436

23

Z

D

_calcd, g cm^-1

1.521

23

11.89

temp, °C

µ(Mo KR), cm^-1

cryst dimens, mm

11.94

X-r a y Da ta Collection a n d Red u ction . X-ray-quality

crystal of 5a , 8, and 10 were obtained directly from the

preparations described below and mounted on glass fibers.

Diffraction experiments were performed on a Rigaku AFC-5R

four-circle diffractometer with graphite-monochromated Mo

KR radiation (λ ) 0.71069 Å) at 23 °C. Intensity data were

collected using a ω/2θ scan technique; three standard reflec-

tions were recorded every 150 reflections. The data for 5a and

10 were processed using the TEXSAN crystal solution pack-

age³⁰operating on an IRIS Indigo computer, and the data for

8 were processed using the SHELX-97 programs.³¹Neutral

atom scattering factors were obtained from the standard

sources.³²In the reduction of the data, Lorentz/polarization

corrections and empirical adsorption corrections based on

azimuthal scans were applied to the data for each structure.

0.10 × 0.15 × 0.30 0.10 × 0.20 × 0.20

(b) Data Collection

diffractometer

radiation

Rigaku AFC-5R

Mo KR

Rigaku AFC-5R

Mo KR

(λ ) 0.71069 Å)

graphite

ω/2θ

(λ ) 0.71069 Å)

graphite

ω/2θ

monochromator

scan type

2θ_max, deg

50.0

scan speed, deg min^-116.0

16.0

no. of refins collected

no. of ind data

no. of ind data obsd

2493

2354

2173

5038

4735

4069

(c) Refinement

0.022

0.020

0.00

254

R

R_w

0.029

0.01

280

b

Str u ctu r e Solu tion a n d Refin em en t for 5a a n d 10. The

Ru atom positions were determined using direct methods

employing the MITHRIL-90³³and SAPI-91³⁴direct-methods

routines for 5a and 10, respectively. In each case the remaining

non-hydrogen atoms were located from successive difference

Fourier map calculations using the DIRDIF-92 programs.³⁵In

both cases the non-hydrogen atoms were refined anisotropi-

cally by using full-matrix least-squares techniques on F. In

the case of 5a , the positions of hydrogen atoms bonded to the

Ru were located by sequential difference Fourier synthesis and

were refined isotropically. Crystal data and results of the

analyses are listed in Table 4.

p factor

no. of variables

GOF

1.96

2.78

Va r ia ble-Tem p er a tu r e NMR Sp ectr a a n d Dyn a m ic

NMR Sim u la tion s. Variable-temperature NMR studies were

performed in flame-sealed NMR tubes in THF-d₈/toluene-d₈

) 5:1 for 5a and toluene-d₈for 8 using a Varian INOVA-400

Fourier transform spectrometer with tetramethylsilane as an

internal standard. NMR simulations for hydride ligands H^a

(δ -9.28), H^b(δ -14.54), and H^c(δ -20.22) of 5 were performed

using gNMR v4.1.0. (Ivory Soft, 1995-1999). The ¹H-¹H

coupling constants between them were estimated at 1.8

(J _Ha-Hb), 2.9 (J _Ha-Hc), and 3.9 (J _Hb-Hc) Hz from line shapes of

signals. The J _Si-Hwas estimated at 36.3 Hz from the line shape

of satellite signals around H^a. Initial line widths (W) of these

signals related to T₂were estimated at 3.20 Hz (H^a), 2.55 Hz

(H^b), and 2.82 Hz (H^c) from line widths of these signals at the

lowest temperature. Final simulated line shapes were obtained

via an iterative parameter search upon the exchange constant

k. Full details of the fitting procedure may be found in the

Supporting Information. The rate constants that accurately

modeled the experimental spectra at each temperature are

given in Figure 1. The activation parameters ∆H^qand ∆S^q

were determined from the plot of ln(k/T) versus 1/T. Estimated

standard deviations (σ) in the slope and y-intercept of the

Eyring plot determined the error in ∆H^qand ∆S^q, respectively.

The standard deviation in ∆G^qwas determined from the

formula σ(∆G^q)²) σ(∆H^q)²+ [Tσ(∆S^q)]²- 2Tσ(∆H^q)σ(∆S^q).

P r ep a r a t ion of {Cp *R u (µ-H )}₂{µ-η²:η²-H SiMe₂(CH d

CH₂)} (5a ). Toluene (15 mL) and Cp*Ru(µ-H)₄RuCp* (0.229

g, 0.480 mmol) were charged in a reaction flask and cooled at

-78 °C in a dry ice/methanol bath. After 2.5 equiv of dimeth-

ylvinylsilane (0.15 mL, 1.20 mmol) was added, the solution

was gradually warmed to 5 °C with vigorous stirring. The

reaction mixture was stirred for 7 h. The color of the solution

changed from red to reddish-purple; 0.269 g of 5a was obtained

as a dark red solid on removal of the solvent and remaining

silanes under reduced pressure (100% yield). A single crystal

of 5a was obtained from heptane solution at -20 °C. ¹H NMR

(500 MHz, 23.0 °C, toluene-d₈): δ 4.50 (dd, J _H-H) 11.0, 2.0

Str u ctu r e Solu tion a n d Refin em en t for 8. The structure

was solved by direct methods using SHELXS-97^31aand refined

by full-matrix least-squares technique on F²with SHELXL-

97.^31bThe bridging silicon ligand, the methyl group of the

µ-ethylidyne ligand, and the hydride ligand of 8 were disor-

dered over two sites related by a C_ssymmetry with 55.7 and

44.3% occupancy for each site, and the disordered atoms (C(1),

C(2), C(3), C(4), Si(1), and H(1)) were refined isotropically. All

hydrogen atoms were located by difference Fourier maps and

refined isotropically, while all non-hydrogen atoms except for

disordered atoms were refined anisotropically. Crystal data

and results of the analyses are listed in Table 5.

(29) Sakamoto, S.; Fujita, M.; Kim, K.; Yamaguchi, K. Tetrahedron

2000, 56, 955.

(30) TEXAN, Crystal Structure Analysis Package; Molecular Struc-

ture Corporation: 1985 and 1992.

(31) (a) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure

Solution; University of Gottingen: Germany, 1997. (b) Sheldrick, G.

M. SHELXL-97, Program for Crystal Structure Solution; University

of Gottingen: Germany, 1997.

(32) International Tables for X-ray Crystallography; Kynoch Press:

Birmingham, U.K., 1975; Vol. 4.

(33) Gilmore, C. J . MITHRIL 90, MITHRIL, an integrated direct

methods computer program; University of Glasgow: Scotland, 1990.

(34) Fan, H.-F. SAPI91, Structure Analysis Programs with Intel-

ligent Control; Rigaku Corporation: J apan, 1991.

(35) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;

Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C.

DIRDIF92, The DIRDIF program system; Technical Report of the

Crystallography Laboratory: University of Nijmegen, The Nether-

lands, 1992.

3420 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

Ta ble 5. Cr ysta llogr a p h ic Da ta for 8

(b) Data Collection

(a) Crystal Parameters

formula

cryst syst

space group

a, Å

b, Å

c, Å

R, deg

â, deg

γ, deg

V, Å³

C

₂₄H₄₀Ru₂Si

diffractometer

radiation

monochromator

scan type

Rigaku AFC-5R

Mo KR (λ ) 0.71069 Å)

graphite

ω/2θ

50.0

triclinic

P1h

10.411(6)

14.072(5)

10.015(5)

100.77(4)

117.82(4)

71.52(4)

1229.5(11)

2

2θ_max, deg

scan speed, deg min^-1

no. of reflns measd

no. of ind reflns

16.0

4579

4321

3337

no. of reflns obsd [I > 2σ]

Z

(c) Refinement

D

_calcd, g cm^-1

1.509

20

12.84

0.10 × 0.20 × 0.15

R1 [I > 2σ]

0.0354

0.0871

259

temp, °C

wR2 [I > 2σ]

no. of params

GOF on F²

µ(Mo KR), cm^-1

cryst dimens, mm

1.037

Hz, 1H, -CHdCH₂), 3.87 (dd, J _H-H) 15.0, 2.0 Hz, 1H, -CHd

CH₂), 3.72 (dd, J _H-H) 15.0, 11.0 Hz, 1H, -CHdCH₂), 1.84 (s,

15H, Cp*), 1.48 (s, 15H, Cp*), 0.78 (s, 3H, Si-CH₃), 0.28 (s,

H). ¹³C{¹H} NMR (100 MHz, 23.0 °C, benzene-d₆): (5b) δ 147.7

(ipso-C Ph), 135.0 (Ph), 127.4 (Ph), 127.2 (Ph), 92.7 (C₅Me₅),

85.3₇(s, C₅Me₅), 70.4 (-CHdCH₂), 65.0 (-CHdCH₂), 12.1

(C₅Me₅), 10.7 (C₅Me₅), 7.2 (Si-CH₃). (5b′) δ 147.0 (ipso-C Ph),

134.9 (Ph), 126.7 (Ph), 126.6 (Ph), 92.8 (C₅Me₅), 85.3₆(s, C₅-

Me₅), 66.2 (-CHdCH₂), 64.0 (-CHdCH₂), 12.0 (C₅Me₅), 10.8

(C₅Me₅), 6.4 (Si-CH₃). ²⁹Si NMR (79.5 MHz, 23.0 °C, benzene-

1

3H, Si-CH₃), -14.50 (br, W_1/2) 1275 Hz, 3H, Ru-H). H NMR

(400 MHz, -70.0 °C, toluene-d₈/THF-d₈) 1:5): δ 4.38 (dd,

J _H-H) 8.2, 3.4 Hz, 1H, -CHdCH₂), 3.49 (m, 1H, -CHdCH₂),

3.27 (m, 1H, -CHdCH₂), 1.86 (s, 15H, Cp*), 1.43 (s, 15H, Cp*),

0.45 (s, 3H, Si-CH₃), 0.04 (s, 3H, Si-CH₃), -9.28 (br, J _Si-H

)

d₆): (5b) δ -11.7 (d, J _Si-H) 38.9 Hz); (5b′) δ -2.9 (d, J _Si-H)

36.3 Hz, 1H, Ru-H-Si), -14.54 (br, 1H, Ru-H), -20.22 (br, 1H,

Ru-H). ¹³C NMR (125 MHz, 23.0 °C, toluene-d₈): δ 92.1 (s,

C₅Me₅), 85.2 (s, C₅Me₅), 68.0 (d, J _C-H) 136.1 Hz, -CHdCH₂),

62.7 (t, J _C-H) 154.1 Hz, -CHdCH₂), 12.5 (q, J _C-H) 126.6

39.0 Hz). CSI-MS: m/z 622. The Coldspray ionization mass

spectrum was measured, and the intensities of the obtained

isotopic peaks for [C₂₉H₄₄Ru₂Si - 2H]⁺agreed with the

calculated value within experimental error.

Hz, C₅Me₅), 10.6 (q, J _C-H) 126.4 Hz, C₅Me₅), 10.5 (q, J _C-H

)

Rea ction of Cp *Ru (µ-D)₄Ru Cp * (1-d ₄) w ith HSiMe₂-

(CHdCH₂). Toluene (5 mL) and Cp*Ru(µ-D)₄RuCp* (10 mg,

0.021 mmol) were charged in a reaction flask and cooled at

-78 °C in a dry ice/methanol bath. After 5 equiv of dimeth-

ylvinylsilane (13 µL, 0.10 mmol) was added, the solution was

gradually warmed to 5 °C with vigorous stirring. The reaction

mixture was stirred for 18 h. After the solvent and excess

silane were removed under reduced pressure, the residual solid

118.9 Hz, Si-CH₃), 9.1 (q, J _C-H) 114.6 Hz, Si-CH₃). ²⁹Si NMR

(79.5 MHz, 23.0 °C, THF-d₈): δ -8.0 (d, J _Si-H) 31.0 Hz). ²⁹Si

NMR (79.5 MHz, -70.0 °C, THF-d₈): δ -8.6 (d, J _Si-H) 54.1

Hz). IR (KBr, cm^-1): 2961, 2902, 1943 (ν(Ru-H-Si)), 1541,

1526, 1477, 1452, 1377, 1313, 1222, 116, 1025, 832, 748. FD-

MS: m/z 562. The field desorption mass spectrum was

measured, and the intensities of the obtained isotopic peaks

for C₂₄H₄₂Ru₂Si agreed with the calculated value within

experimental error. Anal. Calcd for C₂₄H₄₂Ru₂Si: C, 51.40; H,

7.55. Found: C, 50.30; H, 6.98.

1

was dissolved in toluene-d₈. H NMR studies upon this solid

reveal that the H/D ratio of the hydride region was 86:14. The

reaction of 1 with 3.0 equiv of DSiMe₂(CHdCH₂) also afforded

partially deuterated 5a . The H/D ratio was estimated at 47:

P r ep a r a tion of {Cp *Ru (µ-H)}₂{µ-η²:η²-HSiP h Me(CHd

CH₂)} (5b a n d 5b′). The same procedure as for 5a was used

for preparing a mixture of 5b and 5b′ with 0.106 g of 1 (0.222

mmol) and 74 µL of (()-phenylmethylvinylsilane (0.445 mmol)

in 10 mL of toluene; 0.123 g of a red solid was obtained

including two diastereomers, 5b and 5b′, on removal of the

solvent under reduced pressure (90% yield). The ratio between

5b and 5b′ was estimated as 56:44 by means of ¹H NMR

spectroscopy. ¹H NMR (400 MHz, 30.0 °C, THF-d₈): (5b) δ 7.55

(m, 2H, Ph), 7.18 (m, 2H, Ph), 7.10 (m, 1H, Ph), 4.54 (dd, J _H-H

) 10.0, 2.4 Hz, 1H, -CHdCH₂), 3.71 (dd, J _H-H) 15.0, 2.0 Hz,

1H, -CHdCH₂), 3.64 (dd, J _H-H) 15.0, 10.0 Hz, 1H, -CHd

CH₂), 1.72 (s, 15H, Cp*), 1.59 (s, 15H, Cp*), 0.30 (s, 3H, Si-

CH₃), -14.50 (br, W_1/2) 1400 Hz, 3H, Ru-H); (5b′) δ 7.33 (m,

1

53 by means of H NMR.

Rea ction of DSiMe₂(CHdCH₂) w ith {Cp *Ru (µ-H)}₂{µ-

η²:η²-HSiP h Me(CHdCH₂)} (5b a n d 5b′). A 20.3 mg sample

of a mixture of {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiPhMe(CHdCH₂)}

(5b and 5b′; 0.033 mmol) was placed in a reaction flask and

dissolved in 10 mL of toluene. The reaction flask was cooled

at -78 °C in a dry ice/methanol bath; then 80 µL of DSiMe₂-

(CHdCH₂) (1.36 mmol) was added. The reaction mixture was

vigorously stirred for 5 h at 5 °C. After the solvent and excess

silane were removed under reduced pressure, the residual solid

was dissolved in toluene-d₈. ¹H NMR studies of this solid reveal

that 70% of the hydride ligands of 5b and 5b′ were replaced

by deuterium and no 5a was produced.

2H, Ph), 7.06 (m, 2H, Ph), 6.99 (m, 1H, Ph), 4.47 (dd, J _H-H

)

P r ep a r a t ion of (Cp *R u )₂(µ-SiMe₂)(µ-CCH₃)(µ-H ) (8).

Toluene (20 mL) and Cp*Ru(µ-H)₄RuCp* (0.546 g, 1.15 mmol)

were charged in a reaction flask at 23 °C. After 2.5 equiv of

trimethylvinylsilane (0.44 mL, 2.86 mmol) was added, the

solution was gently heated at 45 °C with vigorous stirring for

24 h. The solvent and remaining silanes were removed under

reduced pressure, and the residual solid was rinsed with 2 mL

of pentane three times. Removal of pentane under reduced

pressure afforded 0.478 g of 8 as a dark brown crystalline solid

9.2, 2.8 Hz, 1H, -CHdCH₂), 3.46 (dd, J _H-H) 15.0, 2.8 Hz,

1H, -CHdCH₂), 3.39 (dd, J _H-H) 15.0, 9.2 Hz, 1H, -CHd

CH₂), 1.70 (s, 15H, Cp*), 1.59 (s, 15H, Cp*), 0.68 (s, 3H, Si-

CH₃), -14.50 (br, W_1/2) 1400 Hz, 3H, Ru-H). ¹H NMR (400

MHz, -70.0 °C, THF-d₈): (5b) δ 7.52 (m, 2H, Ph), 7.22 (m,

2H, Ph), 7.14 (m, 1H, Ph), 4.54 (dd, J _H-H) 9.6, 2.4 Hz, 1H,

-CHdCH₂), 3.64 (m, 2H, -CHdCH₂and -CHdCH₂), 1.69 (s,

15H, Cp*), 1.58 (s, 15H, Cp*), 0.28 (s, 3H, Si-CH₃), -9.15 (s,

J _Si-H) 38.0 Hz, 1H, Ru-H-Si), -14.25 (m, 1H, Ru-H), -19.79

(m, 1H, Ru-H); (5b′) δ 7.31 (m, 2H, Ph), 7.10 (m, 2H, Ph), 7.03

(m, 1H, Ph), 4.43 (dd, J _H-H) 8.8, 2.8 Hz, 1H, -CHdCH₂),

3.32 (m, 2H, -CHdCH₂and -CHdCH₂), 1.66 (s, 15H, Cp*),

1.61 (s, 15H, Cp*), 0.66 (s, 3H, Si-CH₃), -9.45 (s, J _Si-H) 35.2

Hz, 1H, Ru-H-Si), -14.21 (m, 1H, Ru-H), -20.20 (m, 1H, Ru-

1

(71% yield). H NMR (500 MHz, 10.0 °C, toluene-d₈): δ 3.95

(s, 3H, CCH₃), 1.76 (s, 30H, Cp*), 1.70 (br, 3H, Si-CH₃), 0.66

(br, 3H, Si-CH₃), -17.94 (s, 1H, Ru-H). ¹H NMR (500 MHz,

-60.0 °C, toluene-d₈): δ 4.01 (s, 3H, CCH₃), 1.75 (s, 3H, Si-

CH₃), 1.71 (s, 30H, Cp*), 0.75 (s, 3H, Si-CH₃), -17.78 (s, J _Si-H

) 22 Hz, 1H, Ru-H). ¹³C NMR (125 MHz, -60.0 °C, toluene-

Reactions of Diruthenium Tetrahydride Complex

Organometallics, Vol. 20, No. 16, 2001 3421

d₈): δ 387.7 (s, CCH₃), 91.8 (s, C₅Me₅), 40.0 (q, J _C-H) 124.9

813. Anal. Calcd for C₂₀H₅₄Ru₂Si: C, 55.87; H, 8.44. Found:

C, 55.83; H, 8.38.

Hz, CCH₃), 14.3 (q, J _C-H) 119.1 Hz, Si-CH₃), 13.1 (q, J _C-H

)

119.1 Hz, Si-CH₃), 11.1 (q, J _C-H) 126.6 Hz C₅Me₅). ²⁹Si NMR

(80 MHz, 23.0 °C, benzene-d₆): δ 197.8 (d, J _Si-H) 22.7 Hz).

IR (KBr, cm^-1): 2908, 1930, 1736, 1667, 1551, 1450, 1379,

1261, 1027, 919. Anal. Calcd for C₂₄H₄₀Ru₂Si: C, 51.59; H, 7.22.

Found: C, 51.18; H, 7.21. FD-MS: m/z 560. The field desorp-

tion mass spectrum was measured, and the intensities of the

P r ep a r a tion of {Cp *Ru (CO)}₂(µ-SiMe₂)(µ-CHMe) (10).

Toluene (10 mL) and (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-H) (8)

(0.132 g, 0.23 mmol) were charged in a glass autoclave with 7

atm of carbon monoxide. The reaction vessel was heated at

90 °C with vigorous stirring for 19 h. The color of the solution

changed to bright yellow. After the solvent was evaporated

under reduced pressure, the yellow residual solid was dissolved

in 4 mL of toluene and purified by column chromatography

on neutral alumina (Merck Art. 1097) with pentane/toluene

(10:1). A bright yellow fraction was collected, and from this

the solvent was removed under reduced pressure; 0.065 g of

obtained isotopic peaks for

C₂₄H₄₀Ru₂Si agreed with the

calculated value within experimental error.

Th er m olysis of {Cp *R u (µ-H )}₂{µ-η²:η²-H SiMe₂(CH d

CH₂)} (5a ). An NMR tube was charged with benzene-d₆(0.3

mL) and {Cp*Ru(µ-H)}₂{µ-η²:η²-HSiMe₂(CHdCH₂)} (5a ) (0.005

g, 0.009 mmol). The tube was sealed and then heated at 30

°C. The resonances assignable to (Cp*Ru)₂(µ-η²-HSiMe₂)(µ-

CHdCH₂)(µ-H)(H) (9a ) and (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-H)

(8) gradually appeared. The conversion of 5a was 50% in 10

h, and the yields of 9a and 8 were estimated at 20 and 8% by

1

10 was obtained as a yellow solid (31% yield). H NMR (300

MHz, 23.0 °C, benzene-d₆): δ 7.74 (q, J _H-H) 7.4 Hz, 1H,

-CHCH₃), 2.86 (d, J _H-H) 7.4 Hz, 1H, -CHCH₃), 1.78 (s, 15H,

Cp*), 1.71 (s, 15H, Cp*), 1.12 (s, 3H, Si-CH₃), 1.01 (s, 3H,

Si-CH₃). ¹³C NMR (68 MHz, 23.0 °C, benzene-d₆): δ 205.5 (s,

CO), 203.8 (s, CO), 142.7 (d, J _C-H) 137.4 Hz, -CHCH₃), 98.6

(s, C₅Me₅), 97.7 (s, C₅Me₅), 37.9 (q, J _C-H) 124.1, -CHCH₃),

12.2 (q, J _C-H) 120.1 Hz, Si-CH₃), 11.9 (q, J _C-H) 116.9 Hz,

Si-CH₃), 10.9 (q, J _C-H) 127.0 Hz, C₅Me₅), 10.2 (q, J _C-H) 126.6

Hz, C₅Me₅). ²⁹Si NMR (54 MHz, 23.0 °C, benzene-d₆): δ 213.2

1

means of H NMR at that point, respectively. The content of

9a was then decreased by prolonged heating at 30 °C. After

50 h, 5a and 9a disappeared, and 8 and other unidentified

complexes were finally found. The yield of 8 was estimated at

1

50% by means of H NMR. When the tube was heated at 80

°C, 5a was completely consumed in 1 h. During this reaction

generation of intermediate 9a could not be monitored. The

yield of 8 was 90% at that condition. ¹H NMR of 9a (300 MHz,

23.0 °C, benzene-d₆): δ 6.71 (dd, J _H-H) 10.8, 7.6 Hz, 1H,

-CHdCH₂), 3.17 (dd, J _H-H) 7.6, 2.4 Hz, 1H, -CHdCH₂), 3.08

(dd, J _H-H) 10.8, 2.4 Hz, 1H, -CHdCH₂), 2.00 (s, 15H, Cp*),

1.69 (s, 15H, Cp*), 0.62 (s, 3H, Si-CH₃), 0.54 (s, 3H, Si-CH₃),

-13.19 (s, 2H, Ru-H), -14.10 (s, 1H, Ru-H). ²⁹Si NMR of 9a

(80 MHz, -70.0 °C, THF-d₈): δ 71.5 (d, J _Si-H) 59.6 Hz).

H/D Exch a n ge Rea ction of (Cp *Ru )₂(µ-SiMe₂)(µ-CCH₃)-

(µ-H) (8) with Ben zen e-d₆. Benzene-d₆(0.3 mL) and (Cp*Ru)₂-

(µ-SiMe₂)(µ-CCH₃)(µ-H) (8; 0.010 g, 0.018 mmol) were charged

in an NMR tube. The tube was sealed and heated in an oil

bath at 100 °C for 2 days. New signals of the methyl group of

the µ-ethylidyne ligand assignable to isotopomers of 9a were

observed at δ 4.00 (s, µ-CCH₃), δ 3.97 (t, J _H-D) 2.0 Hz,

µ-CCH₂D), and δ 3.94 (br, µ-CCHD₂), respectively. The inten-

(s). IR (KBr, cm^-1): 2896, 2436, 1912 (ν_sym(CO)), 1899 (ν_asym

(CO)), 1481, 1379, 1288, 1234, 1015, 843, 764. Anal. Calcd for

₂₆H₄₀O₂Ru₂Si: C, 50.79; H, 6.56. Found: C, 50.61; H, 6.70.

-

C

FD-MS: m/z 616. The field desorption mass spectrum was

measured, and the intensities of the obtained isotopic peaks

for C₂₆H₄₀O₂Ru₂Si agreed with the calculated value within

experimental error.

P r ep a r a tion of (Cp *Ru )₂(µ-SiMe₂)(µ-η²-CHdCH₂)(µ-H)-

(CH₂dCH₂) (11). Toluene (10 mL) and (Cp*Ru)₂(µ-SiMe₂)(µ-

CCH₃)(µ-H) (8) (0.390 g, 0.70 mmol) were charged in a reaction

flask. The solution was stirred under 1 atm of ethylene for 5

h at ambient temperature. The color of the solution changed

from dark brown to orange. After the solvent was evaporated

under reduced pressure, 0.046 g of brown residual solid was

obtained. The content of 11 was estimated at 90% by ¹H NMR

1

analysis. Correlation between H-¹H and ¹H-¹³C of coordinate

1

sity ratio of those signals was estimated at 4.6:3.6:1.0 by H

ethylene and the vinyl group of 11 was confirmed by means

1

of ¹H-¹H COSY and H-¹³C COSY. H NMR (300 MHz, 23.0

NMR spectra measured after 48 h, which means µ-CCH₃:µ-

CCH₂D:µ-CCHD₂) 1.5:1.8:1.0. At the same time, it was

observed that the intensity of the residual proton signal of

benzene-d₆was increased. ²H NMR spectra showed that

deuterium was incorporated into methyl groups of η⁵-C₅Me₅

(δ 1.70), a methyl group of µ-ethylidyne (δ 3.96), and a hydride

site (δ -17.87).

°C, benzene-d₆): δ 8.96 (dd, J _H-H) 9.2, 6.4 Hz, 1H, -CHd

CH₂), 2.38 (d, J _H-H) 6.4 Hz, 1H, -CHdCH₂), 1.69 (d, J _H-H

)

9.2 Hz, 1H, -CHdCH₂), 1.65 (s, 15H, Cp*), 1.60 (m, 1H, C₂H₄),

1.50 (m, 1H, C₂H₄), 1.48 (s, 15H, Cp*), 1.18 (s, 3H, Si-CH₃),

1.15 (s, 3H, Si-CH₃), 1.10 (m, 1H, C₂H₄), 1.00 (m, 1H, C₂H₄),

-11.85 (s, 1H, Ru-Η). ¹³C NMR (68 MHz, 23.0 °C, benzene-

d₆): δ 174.2 (d, J _C-H) 154.8 Hz, -CHdCH₂), 93.2 (s, C₅Me₅),

P r ep a r a tion of (Cp *Ru )₂(µ-η²-HSi^tBu ₂)(µ-CHdCH₂)(µ-

H)(H) (9b). Toluene (10 mL) and {Cp*Ru(µ-H)}₂(µ-η²:η²-HSi^t-

Bu₂) (3) (0.154 g, 0.25 mmol) were charged in a reaction flask

at 23 °C. The solution was stirred under 1 atm of acetylene at

ambient temperature for 4 days. The color of solution changed

from purple to red. The solvent was removed under reduced

pressure. After the products were dissolved in 15 mL of

pentane, a small amount of black precipitate was removed by

filtration. Removal of the solvent afforded 0.141 g of 9b as an

orange solid (88% yield). ¹H NMR (300 MHz, 23.0 °C, benzene-

d₆): δ 6.77 (dd, J _H-H) 11.2, 8.0 Hz, 1H, -CHdCH₂), 3.89 (dd,

J _H-H) 11.2, 2.1 Hz, 1H, -CHdCH₂), 3.03 (dd, J _H-H) 8.0,

2.1 Hz, 1H, -CHdCH₂), 1.98 (s, 15H, Cp*), 1.60 (s, 15H, Cp*),

1.34 (s, 9H, Si-^tBu), 1.27 (s, 9H, Si-^tBu), -13.17 (br, 1H, Ru-

H), -14.56 (br, 1H, Ru-H), -14.83 (s, 1H, J _Si-H) 59 Hz, Ru-

H). ¹³C NMR (76 MHz, 23.0 °C, benzene-d₆): δ 153.8 (d, J _C-H

) 142.3 Hz, -CHdCH₂), 95.3 (s, C₅Me₅), 89.6 (s, C₅Me₅), 58.4

(dd, J _C-H) 161.5, 145.5 Hz, -CHdCH₂), 32.8₃(q, J _C-H) 124.9

Hz, CMe₃), 32.7₉(q, J _C-H) 124.9 Hz, CMe₃), 27.5 (s, CMe₃),

26.8 (s, CMe₃), 12.1 (q, J _C-H) 126.4 Hz, C₅Me₅), 11.2 (q, J _C-H

) 126.9 Hz, C₅Me₅). ²⁹Si NMR (54 MHz, 23.0 °C, benzene-d₆):

δ 98.8 (d, J _Si-H) 57.2 Hz). IR (KBr, cm^-1): 2980, 2902, 2852,

2062 (ν(Ru-H)), 1581 (ν(Ru-H-Si)), 1477, 1454, 1377, 1026,

92.9 (s, C₅Me₅), 41.9 (t, J _C-H) 156.2, C₂H₄), 39.6 (t, J _C-H

)

157.7, -CHdCH₂), 36.8 (t, J _C-H) 155.5, C₂H₄), 18.5 (q, J _C-H

) 123.5 Hz, Si-CH₃), 11.9 (q, J _C-H) 120.9 Hz, Si-CH₃), 10.9

(q, J _C-H) 126.4 Hz, C₅Me₅), 9.9 (q, J _C-H) 126.7 Hz, C₅Me₅).

²⁹Si NMR (54 MHz, 23.0 °C, benzene-d₆): δ 205.7 (s).

Rea ction of (Cp *Ru )₂(µ-SiMe₂)(µ-CCH₃)(µ-H) (8) w ith

H₂. An NMR tube equipped with a Roto Tite valve was charged

with benzene-d₆(0.3 mL) and (Cp*Ru)₂(µ-SiMe₂)(µ-CCH₃)(µ-

H) (8) (0.005 g, 0.009 mmol). The tube was degassed and then

charged with 1 atm of hydrogen and kept at 25 °C. The

progress of the reaction was monitored by means of ¹H NMR.

The resonance assignable to Cp*Ru(µ-H)₄RuCp* (1) and dim-

ethylethylsilane gradually appeared. The conversion of 8 to 1

was 20% in 3 h, and it took 48 h to consume all of 8. Owing to

its low boiling temperature, the yield of dimethylethylsilane

1

as estimated by means of H NMR spectra seemed not to be

accurate, but the yield was roughly estimated at 30%. Genera-

tion of dimethylethylsilane was confirmed by the observation

1

of H NMR signals as follows, and correlation between each

signal was confirmed by the decoupling experiments (400 MHz,

23.0 °C, benzene-d₆): δ 4.07 (triplet of septet, J _H-H) 3.0, 2.8

3422 Organometallics, Vol. 20, No. 16, 2001

Takao et al.

Hz, 1H, SiH), 0.93 (t, J _H-H) 8.1 Hz, 3H, CH₂CH₃), 0.48 (dq,

J _H-H) 8.1, 2.8 Hz, 2H, CH₂CH₃), 0.01 (d, J _H-H) 3.0 Hz, 6H,

SiCH₃).

Co., Inc., for generous gifts of pentamethylcyclopenta-

diene and several kinds of silanes.

Su p p or tin g In for m a tion Ava ila ble: Tables of atomic

coordinates and thermal parameters, bond lengths and angles,

torsion angles, and structure refinement details and ORTEP

drawing of 5a , 8, and 10 with full numbering schemes.

Parameters for the dynamic NMR simulations of 5a , 5b, and

8. This material is available free of charge via the Internet at

http://pubs.acs.org.

Ack n ow led gm en t. This research was supported by

fellowships of the J apan Society for the Promotion of

Science for J apanese J unior Scientists. We thank Dr.

Masako Tanaka for assistance with the X-ray structure

determination. We also thank to Prof. Kentaro Yamagu-

chi and Mr. Shigeru Sakamoto for measurement of the

CSI-MS spectroscopy. We acknowledge Kanto Chemical

OM010147E

Article Doi

Reactions of diruthenium tetrahydride complex (η5-C5Me5)Ru(μ-H)4 Ru(η5-C5Me5) with vinylsilanes: Formation of a μ-silylene complex via successive Si-H and Si-C bond cleavage of dimethylvinylsilane

DOI: 10.1021/om010147e

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Article abstract of DOI:10.1021/om010147e

Full text of DOI:10.1021/om010147e

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