Mechanistic study of ruthenium-catalyzed hydrosilation of 1- (Trimethylsilyl)-1-buten-3-yne

Article abstract of DOI:10.1021/ja973718w

Catalytic hydrosilation of 1-(trimethylsilyl)-1-buten-3-yne (1) with three kinds of hydrosilanes (HSiMePh₂, HSiMe₂Ph, and HSiEt₃) in CDCl₃ at 30 °C in the presence of a catalytic amount of RuHCl(CO)(PPh₃)₃ (2) gave five types of reaction products: (1E,3E)-CH(SiR₃)=CHCH=CHSiMe₃ (3), R₃SiCH₂-CH=CHCH₂SiMe₃ (4), R₃SiCH=C=CHCH₂SiMe₃ (5), (1Z,3E)- CH(SiR₃)=CHCH=CHSiMe₃ (6), and R₃SiC≡CCH=CHSiMe₃ (7). Detailed investigations on the stoichiometric reactions of intermediate ruthenium species provided definitive evidence for the catalytic mechanism comprised of two catalytic cycles, the Chalk-Harrod cycle A and the modified Chalk-Harrod cycle C, and their interconnecting processes B and D. Product 3 is formed by the insertion of 1 into the Ru-H bond of 2 followed by the reaction of the resulting terminal dienyl complex Ru(CH=CHCH=CHSiMe₃)Cl(CO)(PPh₃)₂ (8) with hydrosilane. The latter process regenerates 2 and the sequence of reactions proceeds catalytically (cycle A). The reaction of 8 with hydrosilane is accompanied by a side reaction giving Ru(SiR₃)Cl(CO)(PPh₃)₂ (9) and CH₂=CHCH=CHSiMe₃ (10), and the latter is further converted to 4 by hydrosilation (process B). Silyl complex 9 thus generated in the system is the key intermediate for catalytic cycle C. Thus the insertion of 1 into the Ru-SiR₃ bond of 9 via a formal trans-addition process forms an internal dienylruthenium complex Ru[C(CHSiR₃)CH=CHSiMe₃]Cl(CO)-(PPh₃)₂ (11), which reacts with hydrosilane to give 5 and 6 and to regenerate 9. A part of 11 also undergoes β-hydrogen elimination to give a dehydrogenative silation product 8 and hydride complex 2. Complex 2 thus formed resumes catalytic cycle A (process D). The catalytic intermediates 8, 9, and 11 were identified by NMR spectroscopy and/or elemental analysis. Factors controlling the catalytic cycles are discussed on the basis of the experimental observations.

Full text of DOI:10.1021/ja973718w

J. Am. Chem. Soc. 1998, 120, 1421-1429
1421
Mechanistic Study of Ruthenium-Catalyzed Hydrosilation of
1-(Trimethylsilyl)-1-buten-3-yne
Yooichiroh Maruyama, Kunihiro Yamamura, Isao Nakayama, Keigo Yoshiuchi, and
Fumiyuki Ozawa*
Contribution from the Department of Applied Chemistry, Faculty of Engineering, Osaka City UniVersity,
Sumiyoshi-ku, Osaka 558, Japan
ReceiVed October 27, 1997
Abstract: Catalytic hydrosilation of 1-(trimethylsilyl)-1-buten-3-yne (1) with three kinds of hydrosilanes
(HSiMePh2, HSiMe2Ph, and HSiEt3) in CDCl3 at 30 °C in the presence of a catalytic amount of RuHCl(CO)-
(PPh3)3 (2) gave five types of reaction products: (1E,3E)-CH(SiR3)dCHCHdCHSiMe3 (3), R3SiCH2-
CHdCHCH2SiMe3 (4), R3SiCHdCdCHCH2SiMe3 (5), (1Z,3E)-CH(SiR3)dCHCHdCHSiMe3 (6), and
R3SiCtCCHdCHSiMe3 (7). Detailed investigations on the stoichiometric reactions of intermediate ruthenium
species provided definitive evidence for the catalytic mechanism comprised of two catalytic cycles, the Chalk-
Harrod cycle A and the modified Chalk-Harrod cycle C, and their interconnecting processes B and D. Product
3 is formed by the insertion of 1 into the Ru-H bond of 2 followed by the reaction of the resulting terminal
dienyl complex Ru(CHdCHCHdCHSiMe3)Cl(CO)(PPh3)2 (8) with hydrosilane. The latter process regenerates
2 and the sequence of reactions proceeds catalytically (cycle A). The reaction of 8 with hydrosilane is
accompanied by a side reaction giving Ru(SiR3)Cl(CO)(PPh3)2 (9) and CH2dCHCHdCHSiMe3 (10), and the
latter is further converted to 4 by hydrosilation (process B). Silyl complex 9 thus generated in the system is
the key intermediate for catalytic cycle C. Thus the insertion of 1 into the Ru-SiR3 bond of 9 via a formal
trans-addition process forms an internal dienylruthenium complex Ru[C(dCHSiR3)CHdCHSiMe3]Cl(CO)-
(PPh3)2 (11), which reacts with hydrosilane to give 5 and 6 and to regenerate 9. A part of 11 also undergoes
â-hydrogen elimination to give a dehydrogenative silation product 8 and hydride complex 2. Complex 2 thus
formed resumes catalytic cycle A (process D). The catalytic intermediates 8, 9, and 11 were identified by
NMR spectroscopy and/or elemental analysis. Factors controlling the catalytic cycles are discussed on the
basis of the experimental observations.
Introduction
a hydrido ligand leads to the hydrosilation product. A basis of
the modified Chalk-Harrod mechanism is the formation of
alkenylsilanes in addition to alkylsilanes in the catalytic
hydrosilation of alkenes. That is, the formation of alkenylsilane
is best accounted for by â-hydrogen elimination of a â-silyl-
alkyl metal species formed by the insertion of alkene into a
metal-silicon bond. Recently, the modified Chalk-Harrod
mechanism was confirmed for several reaction systems with
ruthenium, rhodium, iridium, and palladium catalysts by the
studies of intermediate silylmetal complexes.4,5
An interesting question related to the mechanisms of catalytic
hydrosilation is how to select one of the two possible mecha-
nisms described above. There are evidences for the insertion
into a metal-hydrogen bond to be faster than the insertion into
a metal-silicon bond. However, even in such situations,
Transition metal-catalyzed hydrosilation of unsaturated hy-
drocarbons such as alkenes and alkynes is a versatile synthetic
means of organosilicon compounds.1 One of the most widely
accepted mechanisms for this catalysis was first proposed by
Chalk and Harrod in 1965 for the platinum-catalyzed hydrosi-
lation of alkenes.2 The key feature of the Chalk-Harrod
mechanism is the insertion of a coordinated alkene (or alkyne)
into a metal-hydrogen bond followed by reductive elimination
of alkyl (or alkenyl) and silyl ligands. Subsequently, the other
type of catalytic process, the so-called modified Chalk-Harrod
mechanism, was proposed.3 In this mechanism, a coordinated
alkene (or alkyne) inserts into a metal-silicon bond instead of
a metal-hydrogen bond, and the successive reductive elimina-
tion of the resulting â-silylalkyl (or â-silylalkenyl) ligand and
(1) (a) Hiyama, T.; Kusumoto, T. In ComprehensiVe Organic Synthesis;
Trost, B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 8, p
763. (b) Ojima, I. In The Chemistry of Organic Silicon Compounds; Patai,
S., Rappoport, Z., Eds.; John Wiley: Chichester, 1989; p 1479.
(2) (a) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87, 16. (b)
Harrod, J. F.; Chalk, A. J. J. Am. Chem. Soc. 1965, 87, 1133.
(3) (a) Seitz, F.; Wrighton, M. S. Angew. Chem., Int. Ed. Engl. 1988,
27, 289. (b) Randolph, C. L.; Wrighton, M. S. J. Am. Chem. Soc. 1986,
108, 3366. (c) Ferna´ndez, M. J.; Esteruelas, M. A.; Jime´nez, M. S.; Oro, L.
A. Organometallics 1986, 5, 1519. (d) Ojima, I.; Fuchikami, T.; Yatabe,
M. J. Organomet. Chem. 1984, 260, 335. (e) Onopchenko, A.; Sabourin,
E. T.; Beach, D. L. J. Org. Chem. 1983, 48, 5101. (f) Schroeder, M. A.;
Wrighton, M. S. J. Organomet. Chem. 1977, 128, 345. (g) Nesmeyanov,
A. N.; Freidlina, R. K.; Chukovskaya, E. C.; Petrova, R. G.; Belyavsky, A.
B. Tetrahedron 1962, 17, 61.
(4) (a) LaPointe, A. M.; Rix, F. C.; Brookhart, M. J. Am. Chem. Soc.
1997, 119, 906. (b) Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.;
Wright, L. J. Organometallics 1996, 15, 1793. (c) Hofmann, P.; Meier, C.;
Hiller, W.; Heckel, M.; Riede, J.; Schmidt, M. U. J. Organomet. Chem.
1995, 490, 51. (d) Bergens, S. H.; Noheda, P.; Whelan, J.; Bosnich, B. J.
Am. Chem. Soc. 1992, 114, 2128. (e) Duckett, S. B.; Pertsz, R. N.
Organometallics 1992, 11, 90. (f) Tanke, R. S.; Crabtree, R. H. Organo-
metallics 1991, 10, 415.
(5) For other studies on the mechanism of catalytic hydrosilation, see:
(a) Brunstein, P.; Knorr, M. J. Organomet. Chem. 1995, 500, 21. (b) Recatto,
C. A. Aldrichim. Acta 1995, 28, 85. (c) Esteruelas, M. A.; Herrero, J.; Oro,
L. A. Organometallics 1993, 12, 2377. (d) Lewis, L. N. J. Am. Chem. Soc.
1990, 112, 5998. (e) Tilley, T. D. In The Chemistry of Organic Silicon
Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley: Chichester, 1989;
p 1415.
S0002-7863(97)03718-9 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/06/1998

1422 J. Am. Chem. Soc., Vol. 120, No. 7, 1998
Maruyama et al.
Scheme 1
catalytic reactions frequently proceed via the modified Chalk-
Harrod mechanism.4d The other possibility to control the
catalytic mechanism may be found in the product forming steps.
Thus the C-H reductive elimination that is assumed at the final
stage of the modified Chalk-Harrod mechanism is nowadays
a very common and facile process,6 while definitive examples
of the C-Si reductive elimination as the product forming step
of the Chalk-Harrod mechanism are still limited.7 Although
it has been recently shown that the C-Si reductive elimination
can compete with the C-H reductive elimination in Ir(CH3)-
(H)(SiR3)(PMe3)3 type complexes, its relevance to actual
catalytic reactions has not been investigated.7e
hydrosilation: the Chalk-Harrod and modified Chalk-Harrod
cycles (A and C, respectively) and the processes connecting
these two cycles (B and D). We describe below the evidence
for the mechanisms in Scheme 1 and discuss the factors
controlling the hydrosilation processes.
Results and Discussion
1. Hydrosilation of 1 Catalyzed by 2. Reactions of 1-(tri-
methylsilyl)-1-buten-3-yne (1) with three kinds of hydrosilanes
(HSiR3 ) HSiMePh2, HSiMe2Ph, HSiEt3) were examined in
CDCl3 in the presence of a catalytic amount of RuHCl(CO)-
(PPh3)3 (2; 5 mol %) at 30 °C (eq 1). The reactions gave five
This paper reports our mechanistic study of hydrosilation of
1-(trimethylsilyl)-1-buten-3-yne (1) catalyzed by RuHCl(CO)-
(PPh3)3 (2).8 We found that this catalytic reaction is a rare
example where the ruthenium species responsible for most of
the catalysis can be identified. Furthermore, as can be seen
from Scheme 1, which is the summary of the present study,
the catalytic reaction was found to include an almost complete
array of the catalytic processes that are expected in the catalytic
(6) (a) Yamamoto, A. Organotransition Metal Chemistry, Fundamental
Concepts and Applications; Wiley-Interscience: New York, 1986. (b)
Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and
Applications of Organotransition Metal Chemistry; University Science
Books: Mill Valley, CA, 1987.
(7) (a) Tanaka, Y.; Yamashita, H.; Shimada, S.; Tanaka, M. Organo-
metallics 1997, 16, 3246. (b) Akita, M.; Hua, R.; Oku, T.; Tanaka, M.;
Moro-oka, Y. Organometallics 1996, 15, 4162. (c) Okazaki, M.; Tobita,
H.; Ogino, H. Organometallics 1996, 15, 2790. (d) Mitchell, G. P.; Tilley,
T. D. Organometallics 1996, 15, 3477. (e) Aizenberg, M.; Milstein, D. J.
Am. Chem. Soc. 1995, 117, 6456. (f) Ozawa, F.; Hikida, T.; Hayashi, T. J.
Am. Chem. Soc. 1994, 116, 2844. (g) Schubert, U. Angew. Chem., Int. Ed.
Engl. 1994, 33, 419. (h) Lin, W.; Wilson, S. R.; Girolami, G. S.
Organometallics 1994, 13, 2309. (i) Schubert, U.; Mu¨ller, C. J. Organomet.
Chem. 1989, 373, 165. (j) Brinkman, K. C.; Blakeney, A. J.; Krone-Schmidt,
W.; Gladysz, J. A. Organometallics 1984, 3, 1325.
(8) For examples of hydrosilation of conjugated enynes, see: (a)
Maruyama, Y.; Yoshiuchi, K.; Ozawa, F.; Wakatsuki, Y. Chem. Lett. 1997,
623. (b) Kusumoto, T.; Ando, K.; Hiyama, T. Bull. Chem. Soc. Jpn. 1992,
65, 1280. (c) Ishikawa, M.; Naka, A.; Ohshita, J. Organometallics 1992,
11, 3004. (d) Ohshita, J.; Furumori, K.; Matsuguchi, A.; Ishikawa, M. J.
Org. Chem. 1990, 55, 3277. (e) Kusumoto, T.; Hiyama, T. Chem. Lett.
1985, 1405. (f) Licchelli, M.; Greco, A. Tetrahedron Lett. 1987, 28, 3719.
(g) Bock, H.; Seidl, H. J. Am. Chem. Soc. 1968, 90, 5694.
kinds of products 3-7. Dienylsilanes 3 and 6 are the cis- and
trans-addition products of hydrosilane across the triple bond
of 1, respectively. Allylsilane 4 is the product formed by
hydrogenation followed by hydrosilation of 1. Allenylsilane 5
is the 1,4-adduct of hydrosilane across the enyne skeleton of 1.
Bis(silyl)butenyne 7 is the dehydrogenative silation product of
1. All compounds thus obtained were not isolated, but their
structures were successfully confirmed by NMR spectroscopy
and GC-mass spectrometry except for 4, for which the geometry

Ru-Catalyzed Hydrosilation of 1-(Trimethylsilyl)-1-buten-3-yne
J. Am. Chem. Soc., Vol. 120, No. 7, 1998 1423
Table 1. Catalytic Hydrosilation of
Table 2. Characteristic NMR Data for 8, 11a, 11b, and 11c
1-(Trimethylsilyl)-1-buten-3-yne (1) with HSiR3 in the Presence of
5 mol % of RuHCl(CO)(PPh3)3 (2)a
product ratioc
reaction
entry
HSiR3
timeb (h)
3
4
5
6
7
(5 + 6)
1
2
3
HSiMePh2
HSiMe2Ph
HSiEt3
64
22
73
6
14
4
8
81
72
6
4
3
3
2
25
87
76
32
28 15 29
a All reactions were run at 30 °C in CDCl3 with 1 and HSiR3 in a
1:1 ratio. b The time required for 100% conversion of 1. c Determined
1
by H NMR spectroscopy and GLC.
around the CdC bond could not be determined (see Experi-
mental Section).
Table 1 summarizes the results. The reaction rate and the
product distribution varied with the sort of hydrosilane em-
ployed. HSiMe2Ph exhibited the highest reactivity. HSiMePh2
and HSiMe2Ph provided allenylsilanes 5a and 5b in good
selectivities (entries 1 and 2). On the other hand, the reaction
with HSiEt3 showed almost no selectivity (entry 3). In the
following sections, we examine the formation processes of 3-7
in stoichiometric systems.
2. Formation of 3 and 4. Hydride complex 2 was inactive
toward hydrosilanes but readily reacted with 1 (1 equiv) in
CDCl3 at room temperature (eq 2). When the reaction was
a L ) PPh3. The data of 11d were taken from ref 16. b The Hc proton
was observed as a doublet (δ 4.97, J ) 17.7 Hz) at -20 °C in CDCl3.
examined by 31P{1H} NMR spectroscopy, the signals of 2 [δ
39.6 (br, 2P), 13.5 (br, 1P)] instantly disappeared and two new
singlets appeared at δ 31.2 and -4.7 in a 2:1 ratio. The latter
singlet was assigned to free PPh3 on the basis of its chemical
shift. On the other hand, the former singlet was assigned to
dienyl complex 8 based on the following NMR evidence.
Table 2 lists the characteristic NMR data of 8, together with
the data of the other dienylruthenium complexes prepared in
1
Complete H NMR data for 11c in CDCl3 at -20 °C are reported in
Experimental Section. c Not reported.
but readily decomposed during isolation. Therefore, further
experiments on the reactions of 8 were carried out without its
isolation.
Addition of an excess amount of hydrosilane (20 equiv) to
the solution of 8 led to two types of hydrosilation products 3
and 4 (eq 3). The reaction also gave ruthenium hydride 2 and
1
this study. The H NMR signal of H1 bound to the C1-carbon
of the dienyl ligand was observed at δ 7.99 as a doublet of
triplets due to the relatively large coupling to H2 on the C2-
carbon (3JH-H ) 12.4 Hz) and to the small couplings to two
phosphorus nuclei on ruthenium (3JH-P ) 2.1 Hz). The
appearance of only one singlet in the 31P{1H} NMR spectrum
3
as well as the small JH-P value on H1 suggested the trigonal
bipyramidal structure of 8 having two PPh3 ligands at the apical
positions and the dienyl ligand on the trigonal plane.9 The
geometry around the C1dC2 bond was assigned as trans on the
basis of the H1-H2 coupling constant (12.4 Hz).10 The other
1
features in the H NMR spectrum were fully consistent with
the structure depicted in Table 2. Complex 8 was stable in the
reaction solution of eq 2, which contains 1 equiv of free PPh3,
(9) Trigonal bipyramidal structures of closely related complexes have
been confirmed by X-ray diffraction studies: Torres, M. R.; Vegas, A.;
Santos, A.; Ros, J. J. Organomet. Chem. 1986, 309, 169. Rickard, C. E. F.;
Roper, W. R.; Taylor, G. E.; Waters, J. M.; Wright, L. J. J. Organomet.
Chem. 1990, 389, 375.
(10) The JH-H constant of 8 is in a typical range of the values for
ruthenium complexes having trans-dienyl ligands: Esteruelas, M. A.; Liu,
F.; On˜ate, E.; Sola, E.; Zeier, B. Organometallics 1997, 16, 2919.
silylruthenium 9. As shown in Table 3, the reaction with
HSiMe2Ph took place instantly at 30 °C (entry 2). In contrast,
the reactions with HSiMePh2 and HSiEt3 were rather slow and
3

1424 J. Am. Chem. Soc., Vol. 120, No. 7, 1998
Maruyama et al.
Table 3. Reactions of Dienyl Complex 8 with HSiR3 (20 equiv)a
product ratioc
reaction
entry
HSiR3
timeb (h)
2:9
3:4
1
2
3
HSiMePh2
HSiMe2Ph
HSiEt3
3
52:48
69:31
65:35
55:45
68:32
66:34
instant
3
a All reactions were run at 30 °C with a CDCl3 solution of 8 prepared
according to eq 2. The reaction solution contains 1 equiv of free PPh3.
b The time required for 100% conversion of 8, confirmed by 31P{1H}
NMR spectroscopy. c The ratio of 2/9 was determined by 31P{1H} NMR
spectroscopy. The ratio of 3/4 was determined by 1H NMR spectroscopy
with anisole as an internal standard.
they took 3 h for their completion under the same reaction
conditions (entries 1 and 3).
It can be seen from the table that for each run the amounts
of 2 and 9 are in good agreement with the amounts of 3 and 4,
respectively. This fact strongly indicates the presence of two
reaction pathways which correspond to process ii in cycle A
and process B, respectively (Scheme 1). In the former process
the reaction of 8 with hydrosilane affords 2 and 3 via C-Si
and Ru-H bond formation. On the other hand, the latter process
leads to C-H and Ru-Si bond formation and provides
1-(trimethylsilyl)-1,3-butadiene (10) and silyl complex 9.11 The
subsequent hydrosilation of 10 affords 4.13
3. Formation of 5, 6, and 7. We next examined the
reactions of silylruthenium complexes 9a-c formed in the
reactions of eq 3. The pure complexes were independently
prepared according to the Wakatsuki’s method reported for the
syntheses of SiMe3 and Si(OEt)3 analogues (eq 4).14,15 Treat-
Figure 1. Time-course of ruthenium complexes in the reaction of 9c
and 1 (5 equiv) in CDCl3 at 30 °C.
(kobsd ) 6.3 × 10-4 s-1) and was retarded by addition of free
PPh3 (0.33 equiv) to the benzene solution (kobsd ) 4.2 × 10-4
s-1). Similarly, 9a reacted with 1 to afford the insertion product
11a in quantitative yield. Complexes 11a and 11b thus prepared
were isolated as yellow crystalline solids and characterized by
NMR and IR spectroscopy and elemental analysis. An interest-
ing feature of 11 is the trans arrangement of the ruthenium
moiety and the SiR3 group around the double bond of the dienyl
ligand, indicating the occurrence of formal trans-addition of a
Ru-SiR3 bond to 1. Details of the structural assignments will
be described in Section 4.
Unlike the reactions of 9a and 9b, reaction of the SiEt3
analogue 9c with 1 (5 equiv) provided dienyl complex 8 in
addition to insertion product 11c. Also observed in the reaction
system by GLC analysis was the formation of 1-(trimethylsilyl)-
4-(triethylsilyl)-1-buten-3-yne (7c). As seen from the time-
course of ruthenium complexes in Figure 1, the formation of 8
proceeded following the conversion of 9c to 11c. After 70%
of 9c was consumed, complex 8 was further converted to some
unidentified ruthenium species: δ 31.6 (br), 31.3 (s), and 30.8
(s) in 31P{1H} NMR.
These experimental data indicate the sequence of reactions
shown in Scheme 2. Initially, the insertion of 1 into the Ru-
SiEt3 bond of 9c takes place. The subsequent â-hydrogen
elimination of 11c gives 7c and a coordinatively unsaturated
ruthenium hydride, the latter undergoes the insertion of 1 to
give 8 as already confirmed in eq 2. However, different from
eq 2, the reaction system of Figure 1 does not contain free PPh3,
which is essential to stabilize 8 in solution, and thereby complex
8 thus formed further undergoes decomposition to give unidenti-
fied ruthenium species (vide supra).
ment of hydride complex 2 with excess amounts of vinylsilanes
(10 equiv) in THF under reflux gave 9a-c, which were isolated
as orange crystalline solids and characterized by NMR spec-
troscopy and elemental analysis.
Complex 9b was treated with 20 equiv of 1 in CDCl3 at 30
°C (eq 5). The reaction proceeded obeying the first-order
kinetics with respect to the concentration of 9b up to 90%
conversion (kobsd ) 8.1 × 10-4 s-1), giving the insertion product
11b in quantitative yield. The reaction progress became slower
when benzene-d6 was used as the solvent in place of CDCl3
(11) The reactions of dienylruthenium complexes (8 and 11) with
hydrosilanes may proceed via a conventional mechanism comprised of
oxidative addition and reductive elimination processes or σ-bond metathesis.
The latter process has been documented for early transition metal
complexes,12 while definitive examples of σ-bond metathesis are still lacking
for late transition metals.
(12) (a) Voskoboynikov, A. Z.; Parshina, I. N.; Shestakova, A. K.; Butin,
K. P.; Beletskaya, I. P.; Kuz’mina, L. G.; Howard, J. A. K. Organometallics
1997, 16, 4041. (b) Radu, N. S.; Tilley, T. D. J. Am. Chem. Soc. 1995,
117, 5863. (c) Fu, P.-F.; Brard, L.; Li, Y.; Marks, T. J. J. Am. Chem. Soc.
1995, 117, 7157. (d) Woo, H.-G.; Walzer, J. F.; Tilley, T. D. J. Am. Chem.
Soc. 1992, 114, 7047.
(13) There is another possibility that 4 and 9 are formed by hydrogenation
of 3 by the aid of 2 and hydrosilane. However, this possibility can be
excluded because the reaction of 3 with HSiMe2Ph in the presence of 2
does not proceed at 30 °C.8a
(14) Wakatsuki, Y.; Yamazaki, H.; Nakano, M.; Yamamoto, Y. J. Chem.
Soc., Chem. Commun. 1991, 703.
(15) (a) Complex 9c is a known complex.4b (b) The synthesis of 9b was
reported just prior to submission of this paper: Marciniec, B.; Pietraszuk,
C. Organometallics 1997, 16, 4320.

Ru-Catalyzed Hydrosilation of 1-(Trimethylsilyl)-1-buten-3-yne
J. Am. Chem. Soc., Vol. 120, No. 7, 1998 1425
Scheme 2
Scheme 3
Table 4. Reactions of Dienyl Complexes 11a and 11b with HSiR3
in the Presence (entries 1, 3) or Absence (entries 2, 4) of Added
a
PPh3
product ratioc
reaction
entry
complex
HSiR3
timeb (h)
9:2
5:6:7
1
2
11a
11a
HSiMePh2
HSiMePh2
instant
5
>99:<1
87:13
96:4:0
83:5:12
3
4
11b
11b
HSiMe2Ph
HSiMe2Ph
instant
3
>99:<1
90:10:0
87:9:4
formed. However, in the presence of free PPh3, the â-hydrogen
elimination competes with the reaction of 11 with hydrosilane.
This is probably because the reaction with hydrosilane requires
prior dissociation of PPh3 ligand from 11, as supported by the
following kinetic data. Thus the reaction of 11b with HSiMe2-
Ph (20 equiv) at 30 °C in benzene-d6 proceeded at a convenient
96:4
a All reactions were run in CDCl3 at 30 °C with 11 and 20 equiv of
HSiR3. Entries 2 and 3 were conducted in the presence of free PPh3 (1
equiv). b The time required for 100% conversion of 11, confirmed by
NMR spectroscopy. c The ratio of 9/2 was determined by 31P{1H} NMR
spectroscopy. The ratio of 5/6/7 was determined by 1H NMR
spectroscopy with anisole as an internal standard.
rate for kinetic experiments. The first-order rate constant (kobsd
)
observed was 5.4 × 10-3 s-1. In contrast, in the presence of a
small amount of free PPh3 (0.33 equiv), the rate constant was
reduced to 1/16 (kobsd ) 3.4 × 10-4 s-1).
We next examined the reactions of isolated 11a and 11b with
hydrosilanes, HSiMePh2 and HSiMe2Ph, respectively (Table 4).
These reactions instantly took place in CDCl3 at 30 °C to give
two kinds of hydrosilation products 5 and 6, together with the
corresponding silyl complex 9a or 9b, respectively (entries 1
and 3). In the presence of free PPh3 (1 equiv), on the other
hand, the reaction progress became significantly slow and a
considerable amount of dehydrogenative silation product 7 was
formed in addition to 5 and 6 (entries 2 and 4). Also formed
in the reaction systems was hydridoruthenium complex 2, the
amount of which was in fair agreement with the amount of 7
produced.
The formation of 5, 6, 7, 9, and 2 is reasonably accounted
for by the processes in Scheme 3. Reaction of 11 with
hydrosilane with retention of the 2-rutheno-1,3-butadiene struc-
ture gives 6 and 9. On the other hand, 1,3-shift of the RuCl-
(CO)L2 moiety in 11 provides an allenylmethylruthenium
species 12, which reacts with hydrosilane to give 5 and 9.
Furthermore, â-hydrogen elimination of 11 gives 1,4-bis(silyl)-
butenyne 7 and a 16-electron hydridoruthenium complex, which
combines with PPh3 added to the system to give 2.
4. Characterization of 11. The NMR data of 11a-c are
listed in Table 2, together with the data of SiMe3 analogue 11d,
which was previously prepared by Wakatsuki and co-workers
by the insertion of Me3SiCtCCHdCHSiMe3 to hydride com-
1
plex 2.16 As a representative example, the H NMR spectrum
of 11b bearing a SiMe2Ph group exhibited the three signals
arising from olefinic protons H1, H3, and H4 at δ 5.04, 6.24,
and 5.34, respectively. Among them, H3 and H4 were coupled
to each other and the coupling constant (17.6 Hz) was typical
of trans-alkenes. On the other hand, the signal of H1 at δ 5.04
was observed as a singlet. These NMR data are very similar
to those of 11d, suggesting the closely related structures of 11b
and 11d. However, there is an important point that should be
clarified. Thus 11d has a trans arrangement of the Ru atom
and the SiMe3 group around the C1dC2 bond: the structure is
consistent with the cis-addition process common to alkyne
insertion. On the other hand, in the case of 11b, cis-addition
of the Ru-SiMe2Ph bond to 1 should provide a cis geometry
around the C1dC2 double bond. Therefore, we compared the
NMR data of 11b with the data of the complex independently
prepared by the insertion of PhMe2SiCtCCHdCHSiMe3 to 2
according to Wakatsuki’s method.16 Both data were in fair
agreement with each other. Consequently, the insertion of 1 to
9b was concluded to proceed via a formal trans-addition process.
The trans arrangement in 11b was also supported by the
formation of trans-addition product 6 in the reaction of 11b
with HSiMe2Ph (Table 4). The formal trans-addition of a
In Schemes 2 and 3, we assumed the â-hydrogen elimination
of 11. This reaction has already been reported for the
bis(trimethylsilyl) analogue of 11 (SiR3dSiMe3, 11d).16 As
seen from the data in Table 4, in the absence of free PPh3, this
reaction is much slower than the reaction with hydrosilane and
thereby no â-hydrogen elimination products (2 and 7) are
(16) Wakatsuki, Y.; Yamazaki, H.; Maruyama Y.; Shimizu, I. J.
Organomet. Chem. 1992, 430, C60.

1426 J. Am. Chem. Soc., Vol. 120, No. 7, 1998
Maruyama et al.
Table 5. Catalytic Hydrosilation of
1-(Trimethylsilyl)-1-buten-3-yne (1) with HSiR3 in the Presence of
5 mol % of Ru(SiR3)Cl(CO)(PPh3)2 (9a-c)a
product ratioc
reaction
entry catalyst
HSiR3
timeb (h)
3
4
5
6
7
(5 + 6)
1
2
3
9a
9b
9c
HSiMePh2
HSiMe2Ph
HSiEt3
3
3
7
1
4
2
2
3
2
92
86
86
4
5
9
1
2
1
96
91
95
4d
9c
HSiEt3
61
21 12 35
4
28
39
a All reactions were run at 30 °C in CDCl3 with 1 and HSiR3 in a
1:1 ratio. b The time required for 100% conversion of 1. c Determined
1
by H NMR spectroscopy and GLC. d The reaction was examined in
the presence of added PPh3 (1 equiv/Ru).
broadened further and then sharpened. On the other hand, the
H1 signal broadened and significantly shifted toward the higher
magnetic field along with a lowering of temperature.
It has been previously confirmed by X-ray diffraction study16
that complex 11d has a 2-butadienyl ligand bound to ruthenium
by a σ-bonding of the C2 carbon and by a weak π-coordination
of the C3dC4 bond (structure a in eq 7). Therefore, the
spectroscopic changes observed for H3 and H4 can be attributed
to the occurrence of reversible coordination of the C3dC4 bond
to ruthenium at the NMR time scale. On the other hand, the
spectroscopic change observed for H1 indicates the presence of
agostic interaction between H1 and ruthenium (structure b in
eq 7). The C3dC4 coordination is essential for the intercon-
version of the dienyl structure 11 to the allenylmethyl structure
12 in Scheme 3, while the agostic interaction of H1 is required
for the â-hydrogen elimination of 11 to give 7 and 2.
5. Hydrosilation of 1 Catalyzed by 9. In Section 3, we
showed that silyl complexes 9a and 9b undergo the insertion
of 1 to give the corresponding dienyl complexes 11a and 11b,
respectively. Furthermore, 11a and 11b thus formed reacted
with hydrosilane to give hydrosilation products 5 and 6 along
with the regeneration of silyl complexes 9a and 9b, respectively.
In the absence of free PPh3, these reactions selectively proceeded
without formation of any other hydrosilation products and
ruthenium complexes. Therefore, by using 9 as the catalyst,
we may expect a highly selective catalytic cycle that involves
9 and 11 as the ruthenium intermediates and provides 5 and 6
as the hydrosilation products.
Figure 2. Temperature dependence of the 1H NMR singals of olefinic
protons of 11b in toluene-d8.
metal-silicon bond to a CtC bond has some precedents in
catalytic17 as well as stoichiometric18 systems. The most
probable mechanism is the one, originally proposed by Ojima
et al.17 Thus the insertion does proceed via the common cis-
addition process, but the subsequent cis to trans isomerization
via a zwitterionic carbene-like intermediate leads to the formal
trans-addition product, which is sterically less demanding and
more stable than the cis-adduct (eq 6). Great stabilization of
R-carbanion by a silyl group facilitates the isomerization.
Table 5 summarizes the results of catalytic hydrosilation of
1 with 9a-c as the catalysts. The reactions in this table were
examined under the same reaction conditions as Table 1 except
for catalysts. It is seen that 9 is much more reactive than 2 as
the catalyst. Furthermore, 9 leads to higher selectivity than 2
for the formation of 5 and 6. This tendency is most obvious
for the reactions with HSiEt3. Thus the reaction with 2 forms
5c and 6c in totally 32% selectivity (Table 1, entry 3), while
the reaction with 9c provides 5c and 6c in totally 95% selectivity
(Table 5, entry 3). On the other hand, by addition of free PPh3,
the catalytic reaction with 9c is markedly suppressed and the
selectivity is significantly lowered (Table 5, entry 4). The
reaction time and the product ratio observed are comparable to
those in the reaction with 2 as the catalyst (Table 1, entry 3).
1
The H NMR signals of olefinic protons of 11b showed
significant temperature dependence (Figure 2). At 20 °C, H3
and H4 were observed as broad doublets and H1 as a sharp
singlet. With a drop in temperature, the H3 and H4 signals
(17) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P. Organometallics
1990, 9, 3127 and references therein.
(18) (a) Murakami, M.; Yoshida, T.; Kawanami, S.; Ito, Y. J. Am. Chem.
Soc. 1995, 117, 6408. (b) Yamashita, H.; Tanaka, M.; Goto, M. Organo-
metallics 1993, 12, 988.

Ru-Catalyzed Hydrosilation of 1-(Trimethylsilyl)-1-buten-3-yne
J. Am. Chem. Soc., Vol. 120, No. 7, 1998 1427
6. Catalytic Mechanisms. We could clearly observe most
of the elementary processes responsible for the hydrosilation
of 1 catalyzed by RuHCl(CO)(PPh3)3 (2). The experimental
data are consistent with the catalytic processes depicted in
Scheme 1, which is comprised of two catalytic cycles, the
Chalk-Harrod cycle A and the modified Chalk-Harrod cycle
C, and their interconnecting processes B and D.
The first stage is the insertion of 1 into the Ru-H bond of 2,
giving dienyl complex 8 (process i in cycle A). This reaction
takes place instantly under the catalytic conditions with libera-
tion of PPh3 (eq 2). Complex 8 then reacts with hydrosilane in
two reaction processes, process ii in cycle A and process B,
which compete with each other under the catalytic conditions
(eq 3 and Table 3). Process ii provides 1,4-bis(silyl)-1,3-
butadiene 3 with regeneration of 2, while process B forms
allylsilane 4 and silyl complex 9.
Silyl complex 9 thus generated in the system is the key
intermediate for catalytic cycle C. Insertion of 1 to 9 (process
iii) proceeds via formal trans-addition (eqs 5 and 6). The
resulting dienyl complex 11 then reacts with hydrosilane to give
hydrosilation products 5 and 6 (process iv). This reaction
proceeds rapidly in the absence of free PPh3 and regenerates
silyl complex 9, selectively (Table 4, entries 1 and 3).
Therefore, cycle C is operative in high selectivity by using 9
as the catalyst, which is coordinated with two PPh3 ligands and
realizes the catalytic system without free PPh3 (Table 5, entries
1-3). On the other hand, when the catalytic reaction is
conducted with catalyst 9 in the presence of added PPh3, the
reaction of 11 with hydrosilane is effectively retarded by free
PPh3 and thereby complex 11 also undergoes â-hydrogen
elimination (process D) to give 1,4-bis(silyl)-1,3-butenyne 7 and
hydride complex 2 (Table 4, entries 2 and 4). The resulting 2
starts cycle A again. Consequently, the catalytic hydrosilation
provides significant amounts of 3, 4, and 7 in addition to 5 and
6, especially in the reaction with HSiEt3 (Table 5, entry 4).
ease of the C-Si and C-H bond formation is not so clearly
correlated with the nature of silyl groups (see Tables 3 and 4),
but the structures of dienylruthenium complexes serve as the
more important factors to control the selectivity. Thus terminal
dienyl complex 8 reacts with hydrosilane to provide comparable
amounts of hydride and silyl complexes 2 and 9 via the C-Si
and C-H coupling reactions, respectively, while internal dienyl
complex 11 exclusively forms silyl complex 9 along with the
formation of the C-H coupling products 5 and 6. The exact
reason for the difference in the selectivities is presently uncertain
and is the subject to be clarified in due course.
Experimental Section
General. All manipulations were carried out under a nitrogen
atmosphere with standard Schlenk techniques. Nitrogen gas was dried
by passage through P2O5 (Merck, SICAPENT). NMR spectra were
recorded on JEOL JNM-A400 (1H NMR, 399.65 MHz) and Varian
Mercury 300 (1H NMR, 300.11 MHz; 13C NMR, 75.46 MHz; 31P NMR,
121.49 MHz) spectrometers. Chemical shifts are reported in δ ppm
1
referred to an internal SiMe4 standard for H and 13C NMR and to an
external 85% H3PO4 standard for 31P NMR. Mass spectra were
measured with a Shimadzu QP-5000 GC-mass spectrometer (EI, 70
eV, capillary column). GLC analysis was performed with a GL
Sciences GC-353 instrument equipped with a FID detector and a
capillary column (TC-1, 30 m). THF, Et2O, benzene, and hexane were
dried over sodium benzophenone ketyl and distilled just before use.
CH2Cl2 was dried over CaH2 and distilled just before use. CDCl3 was
purified by passage though an Al2O3 column and dried over Molecular
Sieves 4A. Benzene-d6 and toluene-d8 were dried over LiAlH4, vacuum
transferred, and stored under a nitrogen atmosphere. 1-(Trimethylsilyl)-
1-buten-3-yne (1)8d and RuHCl(CO)(PPh3)3 (2)19 were synthesized
according to the literature. 1-(Trimethylsilyl)-4-(triethylsilyl)-1-buten-
3-yne and 1-(trimethylsilyl)-4-(dimethylphenylsilyl)-1-buten-3-yne were
prepared by lithiation of 1 with BuLi, followed by treatment with
ClSiEt3 and ClSiMe2Ph, respectively. All other compounds were
obtained from commercial sources and used without purification.
Catalytic Hydrosilation of 1 (Tables 1 and 5). A typical procedure
(entry 1 in Table 1) is as follows. The complex RuHCl(CO)(PPh3)3
(2; 5.7 mg, 6.0 µmol) was placed in an NMR sample tube equipped
with a rubber septum cap, and the system was replaced with nitrogen
gas at room temperature. 1-(Trimethylsilyl)-1-buten-3-yne (1; 14.9 mg,
0.120 mmol) and anisole (4.0 µL, 0.037 mmol) as an internal standard
Conclusion
The present catalytic reaction involves both hydridoruthenium
(2) and silylruthenium (9) as the reaction intermediates. The
stoichiometric reactions in eqs 2 and 5 have suggested that 2 is
much more reactive than 9 toward the insertion of 1. The
difference in the reactivities was further supported by the
following experiment. Thus the treatment of a 1:1 mixture of
2 and 9b with 1 (1 equiv) in CDCl3 at room temperature led to
the selective conversion of 2 to 8 while 9b remained unreacted
(see Experimental Section). Despite the much higher reactivity
of 2 than 9, however, the modified Chalk-Harrod cycle C
predominates over the Chalk-Harrod cycle A when HSiMePh2
and HSiMe2Ph are employed. This is mainly due to the
selectivities in the reactions of dienyl complexes 8 and 11 with
hydrosilanes. Thus the reaction of 8 with HSiMePh2 or HSiMe2-
Ph in cycle A provides a considerable amount of 9, while the
reactions of 11 with these hydrosilanes in cycle C form 9 in
high selectivity. In these situations the catalytic cycle is
effectively shifted from A to C and cycle C is operative in high
selectivity. Therefore, we may consider that the selection of
the catalytic cycles (i.e., the Chalk-Harrod cycle A or the
modified Chalk-Harrod cycle C) takes place at the product-
forming steps.
1
for H NMR analysis were added. All components were dissolved in
CDCl3 (0.6 mL), and HSiMePh2 (23.8 mg, 0.120 mmol) was added.
The sample tube was placed in an oil bath controlled to 30 °C, and the
reaction progress was monitored by 1H NMR spectroscopy at intervals.
The amounts of 1 and reaction products were determined by measuring
the relative peak integration of the methyl protons of anisole (δ 3.81),
acetylenic proton of 1 (δ 2.94), and olefinic protons of the products.
After 64 h substrate 1 was consumed and products 3a, 4a, 5a, 6a, and
7a were formed in a 6:4:81:6:3 ratio in totally 100% yield. The product
ratio was also confirmed by GLC. All the catalytic reactions reported
in this paper were similarly conducted. In every run the silation
products were obtained in totally (100 ( 3)% yield.
Identification of the catalytic reaction products was performed by
NMR spectroscopy and GC-mass spectrometry without their isolation.
The geometries around the CdC bonds were determined on the basis
3
of JH-H coupling constants appearing on the olefinic proton signals
except for 4a-c, whose geometries could not be determined due to
the almost identical chemical shifts of two olefinic protons. The allenyl
structures of 5a-c were supported by the observations of characteristic
signals at around δ 212 in the 13C{1H} NMR spectra, assignable to the
center carbon of the allenyl group.
(1E,3E)-1-(Methyldiphenylsilyl)-4-(trimethylsilyl)-1,3-butadi-
ene (3a). 1H NMR (CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42
(m, 6H, Ph), 6.57-6.69 (m, 2H, dCH), 6.20 (d, J ) 17.0 Hz, 1H,
dCH), 5.94 (d, J ) 17.4 Hz, 1H, dCH), 0.68 (s, 3H, Si(CH3)Ph2),
Recently, Aizenberg and Milstein examined the reductive
elimination of Ir(CH3)(H)(SiR3)(PMe3)3 (SiR3 ) Si(OEt)3,
SiPh3, and SiEt3) and found that more alkyl substituents at
silicon facilitate more the C-Si reductive elimination than the
C-H reductive elimination.7e In our case, however, the relative
(19) Ahmad, N.; Levison, J. J.; Robinson, S. D.; Uttley, M. F. Inorg.
Synth. 1974, 15, 45.

1428 J. Am. Chem. Soc., Vol. 120, No. 7, 1998
Maruyama et al.
0.11 (s, 9H, Si(CH3)3). MS, m/z (rel intensity, %): 322 (M+, 5), 307
(9), 229 (8), 197 (100), 172 (11), 135 (17), 105 (11), 73 (20), 45 (13).
1-(Methyldiphenylsilyl)-4-(trimethylsilyl)-2-butene (4a). 1H NMR
(CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42 (m, 6H, Ph), 5.26-
5.30 (m, 2H, dCH), 2.02 (d, J ) 6.8 Hz, 2H, CH2), 1.38 (d, J ) 6.8
Hz, 2H, CH2), 0.73 (s, 3H, Si(CH3)Ph2), -0.09 (s, 9H, Si(CH3)3). MS,
m/z (rel intensity, %): 324 (M+, 3), 197 (100), 181 (5), 135 (8), 105
(7), 73 (13), 45 (9).
1-(Methyldiphenylsilyl)-4-(trimethylsilyl)-1,2-butadiene (5a). 1H
NMR (CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42 (m, 6H, Ph),
5.27 (dt, J ) 6.9 and 3.4 Hz, 1H, dCH), 4.85 (dt, J ) 6.9 and 8.5 Hz,
1H, dCH), 1.29 (m, 2H, CH2), 0.64 (s, 3H, Si(CH3)Ph2), -0.01 (s,
9H, Si(CH3)3). 13C{1H} NMR (CDCl3): δ 213.2 (dC)), 136.7 (Ph),
134.6 (Ph), 129.3 (Ph), 127.7 (Ph), 80.6 (dCH), 78.8 (dCH), 16.2
(CH2), -1.9 (Si(CH3)Ph2), -3.5 (Si(CH3)3). MS, m/z (rel intensity,
%): 322 (M+, 6), 307 (6), 229 (12), 197 (100), 172 (50), 135 (67),
105 (22), 73 (62), 45 (28).
(1Z,3E)-1-(Methyldiphenylsilyl)-4-(trimethylsilyl)-1,3-butadi-
ene (6a). 1H NMR (CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42
(m, 6H, Ph), 6.90 (dd, J ) 14.3 and 11.5 Hz, 1H, dCH), 6.53 (dd, J
) 18.1 and 11.5 Hz, 1H, dCH), 5.98 (d, J ) 14.3 Hz, 1H, dCH),
5.92 (d, J ) 18.1 Hz, 1H, dCH), 0.57 (s, 3H, Si(CH3)Ph2), -0.19 (s,
9H, Si(CH3)3). MS, m/z (rel intensity, %): 322 (M+, 1), 305 (1), 244
(16), 197 (9), 172 (21), 135 (100), 121 (8), 105 (11), 73 (30), 59 (13),
45 (12).
(1E)-1-(Trimethylsilyl)-4-(methyldiphenylsilyl)-1-buten-3-yne (7a).
1H NMR (CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42 (m, 6H, Ph),
6.65 (d, J ) 19.2 Hz, 1H, dCH), 6.08 (d, J ) 19.2 Hz, 1H, dCH),
0.71 (s, 3H, Si(CH3)Ph2), -0.10 (s, 9H, Si(CH3)3). MS, m/z (rel
intensity, %): 320 (M+, 3), 305 (12), 244 (16), 197 (16), 172 (21),
135 (100), 121 (11), 105 (15), 73 (31), 59 (16), 43 (14).
(1E,3E)-1-(Dimethylphenylsilyl)-4-(trimethylsilyl)-1,3-butadi-
ene (3b). 1H NMR (CDCl3): δ 7.50-7.57 (m, 2H, Ph), 7.34-7.42
(m, 3H, Ph), 6.52-6.65 (m, 2H, dCH), 6.03 (d, J ) 17.5 Hz, 1H,
dCH), 5.94 (d, J ) 17.0 Hz, 1H, dCH), 0.37 (s, 6H, Si(CH3)2Ph),
0.10 (s, 9H, Si(CH3)3). MS, m/z (rel intensity, %): 260 (M+, 1), 245
(4), 186 (21), 172 (30), 135 (37), 73 (100), 59 (29), 43 (26).
1-(Dimethylphenylsilyl)-4-(trimethylsilyl)-2-butene (4b). 1H NMR
(CDCl3): δ 7.50-7.57 (m, 2H, Ph), 7.34-7.42 (m, 3H, Ph), 5.22-
5.28 (m, 2H, dCH), 1.68 (d, J ) 6.4 Hz, 2H, CH2), 1.40 (d, J ) 6.6
Hz, 2H, CH2), 0.27 (s, 6H, Si(CH3)2Ph), -0.04 (s, 9H, Si(CH3)3). MS,
m/z (rel intensity, %): 262 (M+, 3), 135 (100), 112 (13), 97 (8), 73
(21), 43 (17).
1-(Dimethylphenylsilyl)-4-(trimethylsilyl)-1,2-butadiene (5b). 1H
NMR (CDCl3): δ 7.50-7.57 (m, 2H, Ph), 7.34-7.42 (m, 3H, Ph),
5.05 (ddd, J ) 6.9, 3.8 and 3.0 Hz, 1H, dCH), 4.81 (ddd, J ) 8.5, 8.5
and 6.9 Hz, 1H, dCH), 1.22-1.38 (m, 2H, CH2), 0.36 (s, 6H, Si(CH3)2-
Ph), 0.03 (S, 9H, Si(CH3)3). 13C{1H} NMR (CDCl3): δ 212.1 (dC)),
138.9 (Ph), 133.7 (Ph), 129.0 (Ph), 127.7 (Ph), 80.4 (dCH), 80.0
(dCH), 16.4 (CH2), -1.8 (Si(CH3)2Ph), -2.1 (Si(CH3)3). MS, m/z
(rel intensity, %): 260 (M+, 4), 245 (4), 186 (11), 172 (33), 135 (100),
73 (85), 43 (33).
(1Z,3E)-1-(Dimethylphenylsilyl)-4-(trimethylsilyl)-1,3-butadi-
ene (6b). 1H NMR (CDCl3): δ 7.50-7.57 (m, 2H, Ph), 7.34-7.42
(m, 3H, Ph), 6.89 (dd, J ) 13.5 and 10.7 Hz, 1H, dCH), 6.64 (dd, J
) 17.9 and 10.4 Hz, 1H, dCH), 5.91 (d, J ) 17.9 Hz, 1H, dCH),
5.82 (d, J ) 13.7 Hz, 1H, dCH), 0.44 (s, 3H, Si(CH3)2Ph), -0.01 (s,
9H, Si(CH3)3). MS, m/z (rel intensity, %): 260 (M+, 1), 245 (1), 186
(20), 172 (29), 135 (43), 73 (100), 59 (26), 43 (25).
(1E)-1-(Trimethylsilyl)-4-(dimethylphenylsilyl)-1-buten-3-yne (7b).
1H NMR (CDCl3): δ 7.52-7.66 (m, 4H, Ph), 7.36-7.42 (m, 6H, Ph),
6.58 (d, J ) 19.2 Hz, 1H, dCH), 6.02 (d, J ) 19.2 Hz, 1H, dCH),
0.44 (s, 3H, Si(CH3)2Ph), -0.08 (s, 9H, Si(CH3)3). MS, m/z (rel
intensity, %): 258 (M+, 15), 243 (100), 227 (11), 185 (13), 159 (29),
145 (13), 135 (48), 73 (28), 59 (19), 43 (36).
1-(Triethylsilyl)-4-(trimethylsilyl)-2-butene (4c). 1H NMR (CDCl3):
δ 5.21-5.25 (m, 2H, dCH), 1.63 (d, J ) 6.2 Hz, 2H, CH2), 1.40 (d,
J ) 6.6 Hz, 2H, CH2), 0.95 (t, J ) 7.7 Hz, 9H, SiCH2CH3), 0.59 (q,
J ) 7.7 Hz, 6H, SiCH2), -0.01 (s, 9H, Si(CH3)3). MS, m/z (rel
intensity, %): 242 (M+, 8), 213 (1), 115 (85), 87 (100), 73 (58), 59
(59), 45 (30).
1-(Triethylsilyl)-4-(trimethylsilyl)-1,2-butadiene (5c). 1H NMR
(CDCl3): δ 4.81 (ddd, J ) 6.9, 3.8, and 3.3 Hz, 1H, dCH), 4.70 (td
J ) 8.2 and 6.9 Hz, 1H, dCH), 1.26 (m, 2H, CH2), 0.95 (t, J ) 7.7
Hz, 9H, SiCH2CH3), 0.59 (q, J ) 7.7 Hz, 6H, SiCH2), 0.03 (s, 9H,
Si(CH3)3). 13C{1H} NMR (CDCl3): δ 211.8 (dCd), 78.8 (dCH), 77.7
(dCH), 16.5 (CH2), 7.3 (SiCH2CH3), 3.9 (SiCH2), -1.9 (Si(CH3)3).
MS, m/z (rel intensity, %): 240 (M+, 3), 223 (1), 211 (27), 183 (77),
155 (31), 115 (36), 109 (29), 87 (99), 73 (100), 59 (81), 45 (67).
(1Z,3E)-1-(Triethylsilyl)-4-(trimethylsilyl)-1,3-butadiene (6c). 1H
NMR (CDCl3): δ 6.88 (dd, J ) 14.0 and 10.7 Hz, 1H, dCH), 6.71
(dd, J ) 17.9 and 10.7 Hz, 1H, dCH), 5.91 (d, J ) 17.9 Hz, 1H,
dCH), 5.62 (d, J ) 14.0 Hz, 1H, dCH), 0.95 (t, J ) 7.7 Hz, 9H,
SiCH2CH3), 0.59 (q, J ) 7.7 Hz, 6H, SiCH2), 0.10 (s, 9H, Si(CH3)3).
MS, m/z (rel intensity, %): 240 (M+, 2), 211 (21), 183 (17), 155 (7),
138 (8), 124 (27), 101 (45), 87 (43), 73 (100), 59 (58), 45 (47).
(1E)-1-(Trimethylsilyl)-4-(triethylsilyl)-1-buten-3-yne (7c). 1H
NMR (CDCl3): δ 6.51 (d, J ) 19.2 Hz, 1H, dCH), 5.99 (d, J ) 19.2
Hz, 1H, dCH), 0.95 (t, J ) 7.7 Hz, 9H, SiCH2CH3), 0.59 (q, J ) 7.7
Hz, 6H, SiCH2), 0.09 (s, 9H, Si(CH3)3). MS, m/z (rel intensity, %):
238 (M+, 1), 210 (26), 195 (11), 181 (68), 167 (13), 153 (100), 139
(14), 127 (10), 113 (8), 97 (10), 83 (32), 73 (31), 59 (39), 45 (26).
Preparation of Ru(CHdCHCHdCHSiMe3)Cl(CO)(PPh3)2 (8)
(Eq 2). The complex RuHCl(CO)(PPh3)3 (2; 5.7 mg, 6.0 µmol) was
charged into an NMR sample tube equipped with a rubber septum cap,
and the system was replaced with nitrogen gas. CDCl3 and 1-(trim-
ethylsilyl)-1-buten-3-yne (1; 14.9 mg, 6.0 µmol) were added by means
of a syringe at room temperature. The color of the solution instantly
changed from pale yellow to red. The 31P{1H} NMR spectrum of the
solution exhibited two singlets at δ 31.2 and -4.7 in a 2:1 ratio,
assignable to 8 and free PPh3, respectively. No trace of the signals of
2 [δ 39.6 (br, 2P) and 13.5 (br, 1P)] was observed. The NMR data of
8 are listed in Table 2.
The same reaction was examined in a 100-mg sample of 2 in a
Schlenk tube. The reaction solution was concentrated to dryness at
room temperature to give a red oily material, which was dissolved in
CH2Cl2 (ca. 0.5 mL), and then Et2O (ca. 1 mL) was carefully layered.
The solvent layer was allowed to stand at -20 °C overnight, giving a
reddish brown solid (87 mg). The 31P{1H} NMR spectrum revealed
the formation of a complicated mixture, and thereby complex 8 could
not be isolated.
Reactions of 8 with Hydrosilanes (Table 3). A typical procedure
(entry 2) is as follows. A CDCl3 solution (0.6 mL) of 8 (6 µmol) was
prepared by the procedure describe above. Anisole (1.0 µL, 9.2 µmol)
as an internal standard for 1H NMR analysis and HSiMe2Ph (16.4 mg,
0.120 mmol) were added at room temperature. The color of the solution
instantly changed from red to orange. 31P{1H} NMR analysis of the
solution revealed the formation of RuHCl(CO)(PPh3)3 (2; δ 39.6 (br)
and 13.5 (br)) and Ru(SiMe2Ph)Cl(CO)(PPh3)2 (9b; δ 33.4 (s)) in a
69:31 ratio with consumption of 8. Complex 9b was identified by
using an authentic sample, independently prepared from RuHCl(CO)-
(PPh3)3 (2) and CH2dCHSiMe2Ph (vide infra). 1H NMR analysis of
the reaction solution revealed the formation of 3b and 4b in 68 and
32% yields, respectively. The reactions of 8 with HSiMePh2 and HSiEt3
were similarly conducted. For both cases, the reaction progress was
slow and it took 3 h for completion as confirmed by 1H NMR
spectroscopy.
Preparation of Ru(SiMe2Ph)Cl(CO)(PPh3)2 (9b) (Eq 4). The
complex RuHCl(CO)(PPh3)3 (2; 150 mg, 0.157 mmol) was suspended
in THF (20 mL), and CH2dCH(SiMe2Ph) (128 mg, 0.787 mmol) was
added at room temperature. The mixture was refluxed with stirring
for 12 h to give an orange solution. Volatile materials were removed
by pumping at room temperature, and the residue was purified by silica
gel column chromatography with a 1:1 mixture of CH2Cl2 and benzene
as eluent. The orange elution band was collected and concentrated to
dryness. The resulting oily product was treated with Et2O (4 mL) at 0
(1E,3E)-1-(Triethylsilyl)-4-(trimethylsilyl)-1,3-butadiene (3c). 1H
NMR (CDCl3): δ 6.49-6.60 (m, 2H, dCH), 5.89 (d, J ) 17.4 Hz,
1H, dCH), 5.86 (d, J ) 17.0 Hz, 1H, dCH), 0.95 (t, J ) 7.7 Hz, 9H,
SiCH2CH3), 0.59 (q, J ) 7.7 Hz, 6H, SiCH2), 0.10 (s, 9H, Si(CH3)3).
MS, m/z (rel intensity, %): 240 (M+, 3), 225 (5), 211 (35), 183 (48),
155 (21), 124 (34), 101 (40), 73 (100), 59 (69), 45 (42).

Ru-Catalyzed Hydrosilation of 1-(Trimethylsilyl)-1-buten-3-yne
J. Am. Chem. Soc., Vol. 120, No. 7, 1998 1429
°C to form orange crystals of 9b, which was collected by filtration
and dried under vacuum (48 mg, 37% yield). 1H NMR (CDCl3): δ
7.17-7.43 (m, 33H, Ph), 7.06 (m, 2H, SiPh), 0.50 (s, 6H, SiCH3). 31P-
{1H} NMR (CDCl3): δ 33.4 (s). IR (KBr): νCO 1913 cm-1. Anal.
Calcd for C45H41ClOP2RuSi: C, 65.56; H, 5.01. Found: C, 65.32; H,
4.95.
Similarly prepared were Ru(SiMePh2)Cl(CO)(PPh3)2 (9a, 58% yield)
and Ru(SiEt3)Cl(CO)(PPh3)2 (9c, 28% yield). Complex 9c was
identified by comparison of the NMR data with those reported.4b The
identification data for 9a are as follows. 1H NMR (CDCl3): δ 7.18-
7.40 (m, 34H, Ph), 7.07 (t, J ) 7.5 Hz, 2H, SiPh), 6.91 (t, J ) 7.5 Hz,
4H, SiPh), 0.71 (s, SiCH3). 31P{1H} NMR (CDCl3): δ 32.3 (s). IR
(KBr): νCO 1913 cm-1. Anal. Calcd for C50H43ClOP2RuSi: C, 67.75;
H, 4.89. Found: C, 67.49; H, 4.87.
Since complex 11c could not be isolated from the above reaction
system, its authentic sample was independently prepared by the reaction
of RuHCl(CO)(PPh3)3 (2) with Et3SiCtCCHdCHSiMe3. To a THF
suspension (10 mL) of 2 (100 mg, 0.105 mmol) was added 1-(trim-
ethylsilyl)-4-(triethylsilyl)-1-buten-3-yne (150 mg, 0.630 mmol). The
heterogeneous mixture was stirred at room temperature, giving a
homogeneous orange solution. The stirring was continued for 12 h,
and then the reaction solution was concentrated to dryness by pumping.
The resulting orange solid was subjected to silica gel column chroma-
tography with use of a 1:1 mixture of CH2Cl2 and benzene as eluent.
The orange elution band was collected and evaporated under reduced
pressure to give an orange solid of 11c (27 mg, 28% isolated yield).
The complex thus obtained was stable in solution at low temperature
(<0 °C) but readily decomposed at room temperature. Therefore, its
elemental analysis could not be carried out. 1H NMR (CDCl3, -20
°C): δ 7.74-6.93 (m, 30H, Ph), 5.79 (d, J ) 17.7, 1H, dCH), 4.97
(d, J ) 17.7, 1H, dCH), 4.41 (s, 1H, dCH), 0.63 (br, 9H, Si-
(CH2CH3)3), 0.18 (br, 6H, Si(CH2CH3)3), -0.04 (s, 9H, Si(CH3)3. 31P-
{1H} NMR (CDCl3, room temperature): 32.2 (br).
Reactions of 11a and 11b with Hydrosilanes (Table 4). To an
NMR sample tube containing Ru[C(dCHSiMe2Ph)CHdCHSiMe3]Cl-
(CO)(PPh3)2 (11b; 5.7 mg, 6.0 µmol) were added CDCl3 (0.6 mL) and
anisole (1.0 µL, 9.2 µmol) as an internal standard for NMR analysis.
After 11b was dissolved, HSiMe2Ph (16.4 mg, 0.120 mmol) was added.
The color of the solution instantly changed from yellow to orange
yellow. 1H NMR analysis of the solution revealed the formation of
5b and 6b in 90 and 10% yield, respectively, as confirmed by measuring
the relative peak integration of the methyl protons of anisole (δ 3.81)
and the olefinic protons of 5b (δ 4.81) and 6b (δ 5.91). Furthermore,
the 31P{1H} NMR analysis indicated the selective formation of 9b (δ
33.4).
Reaction of 9b with 1 (Eq 5). The complex Ru(SiMe2Ph)Cl(CO)-
(PPh3)2 (9b; 4.9 mg, 6.0 µmol) was placed in an NMR sample tube
equipped with a rubber septum cap. The system was replaced with
nitrogen gas, and toluene (1.0 µL, 9.4 µmol) and CDCl3 (0.6 mL) were
added. After 9b was dissolved, 1-(trimethylsilyl)-1-buten-3-yne (1; 14.9
mg, 0.120 mmol) was added, and then the tube was placed in an NMR
sample probe controlled to 30.0 ( 0.1 °C. The reaction progress with
time was followed by measuring relative peak integration of methyl
1
protons of toluene (δ 2.36) and 9b (δ 0.50) in H NMR spectra. The
reactions in C6D6 and in the presence of added PPh3 (0.33 equiv) were
similarly investigated.
Preparation of Ru[C(dCHSiMe2Ph)CHdCHSiMe3]Cl(CO)-
(PPh3)2 (11b). To a Schlenk tube containing Ru(SiMe2Ph)Cl(CO)-
(PPh3)2 (9b; 200 mg, 0.243 mmol) was added THF (10 mL) under a
nitrogen atmosphere. 1-(Trimethylsilyl)-1-buten-3-yne (1; 90.6 mg,
0.729 mmol) was added. The homogeneous solution was stirred at
room temperature for 3 h and then evaporated to dryness by pumping.
The resulting orange solid was dissolved in Et2O (ca.6 mL), the volume
of mixture was reduced to ca. 2 mL, and the solution was allowed to
stand at -70 °C overnight to give yellow crystals of 11b. The product
was collected by filtration, washed with Et2O (0.5 mL) at -78 °C, and
dried under vacuum (180 mg, 78% yield). The 1H and 31P NMR data
are listed in Table 2. IR (KBr): νCO 1926 cm-1. Anal. Calcd for
C52H53ClOP2RuSi2: C, 65.84; H, 5.63. Found: C, 65.45; H, 5.68.
Ru[C(dCHSiMePh2)CHdCHSiMe3]Cl(CO)(PPh3)2 (11a; 56% iso-
The reaction of 11b with HSiMe2Ph in the presence of 1 equiv of
added PPh3 was similarly examined. In this case, the formation of 7b
(δ 6.02) in addition to 5b and 6b and the formation of 2 (δ 39.6) in
addition to 9b were confirmed by 1H and 31P{1H} NMR spectroscopy,
respectively. The reactions of 11a with HSiMePh2 in the presence and
absence of free PPh3 were similarly investigated.
Kinetic Study of the Reaction of 11b with HSiMe2Ph in Benzene-
d6. Complex 11b (4.9 mg, 6.0 µmol) was loaded to an NMR sample
tube at room temperature, and the tube was capped with a rubber
septum. The system was replaced with nitrogen gas, and anisole (1.0
mL, 9.2 mmol) and C6D6 (0.6 mL) were added by means of a syringe.
After 11b was dissolved, HSiMe2Ph (16.4 mg, 0.120 mmol) was added,
and then the sample tube was placed in an NMR sample probe
controlled to 30.0 ( 0.1 °C. The amounts of 11b (δ 6.24) at intervals
were determined by measuring the relative peak integration of the
olefinic proton signal of 11b at δ 6.24 and the methyl proton signal of
1
lated yield) was similarly prepared. The H and 31P{1H} NMR data
are reported in Table 2. Additional data are as follows. IR (KBr):
νCO 1926 cm-1. Anal. Calcd for C57H55ClOP2RuSi2: C, 67.74; H,
5.49. Found: C, 67.47; H, 5.22.
Complex 11b was independently prepared starting from 2. To an
NMR sample tube containing RuHCl(CO)(PPh3)3 (2; 5.0 mg, 5.2 µmol)
were added C6D6 (0.6 mL) and 1-(trimethylsilyl)-4-(dimethylphenyl-
silyl)-1-buten-3-yne (8.1 mg, 31 µmol) at room temperature. The
initially heterogeneous mixture gradually turned to a homogeneous
orange solution over 30 min. The 31P{1H} NMR spectrum of the
reaction solution indicated the selective formation of 11b with liberation
of 1 equiv of PPh3. The 1H and 31P{1H} NMR data observed were in
fair agreement with the data of 11b listed in Table 2.
Reaction of 9c with 1 (Figure 1). The complex Ru(SiEt3)Cl(CO)-
(PPh3)2 (9c; 7.1 mg, 8.8 µmol) was placed in an NMR sample tube
equipped with a rubber septum cap, and the system was replaced with
nitrogen gas at room temperature. CDCl3 (0.8 mL) and anisole (1.0
µL, 9.2 µmol) as an internal standard for 1H NMR analysis were added.
After 9c was dissolved, 1-(trimethylsilyl)-1-buten-3-yne (1; 5.1 mg,
0.041 mmol) was added. The sample tube was placed in an NMR
sample probe controlled to 30.0 ( 0.1 °C. The amounts of ruthenium
complexes at intervals were determined by 31P{1H} NMR spectros-
copy: 9c (δ 35.1 (s)), 11c (δ 32.2 (br)), 8 (δ 31.2 (s)). At a later stage
of the reaction (>70% conversion of 9c), three singlets arising from
unidentified ruthenium species were observed at δ 31.6 (br), 31.3 (s),
and 30.8 (s).
1
anisole at δ 3.28 in H NMR spectra.
Competition Reaction of 2 and 9b with 1. To an NMR sample
tube containing RuHCl(CO)(PPh3)3 (2; 5.7 mg, 6.0 µmol) and
Ru(SiMe2Ph)Cl(CO)(PPh3)2 (9b; 4.9 mg, 6.0 µmol) were added CDCl3
(0.6 mL) and anisole (1.0 µL, 9.2 µmol) under a nitrogen atmosphere
at room temperature. After the complexes were dissolved, 1-(trimeth-
ylsilyl)-1-buten-3-yne (14.9 mg, 6.0 µmol) was added. The color of
the solution instantly changed from yellow to red. 1H and 31P{1H}
NMR analysis of the solution revealed the selective formation of 8
with consumption of 2. Complex 9b remained unreacted.
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Research on Priority Area “The Chemistry
of Inter-element Linkage” (No. 09239105) and a Grant-in Aid
for Encouragement of Young Scientists (No. 09750957) from
the Ministry of Education, Science, Sports and Culture, Japan.
JA973718W