[Ru((R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl)(H)-(MeCN) (THF)2](BF4), a catalyst system for hydrosilylation of ketones and for isomerization, intramolecular hydrosilylation, and hydrogenation of olefins

Article abstract of DOI:10.1021/om9603979

(R)-2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl ((R)-BINAP) reacted with cis-[Ru(MeCN)₂(COD)(η³-C₃H ₅)](BF₄) (COD = cycloocta-1,5-diene) to generate two isomers of [Ru(MeCN)((R)-BINAP)((1-3-η):(5,6-η)-C₈H ₁₁)]-(BF₄) (1) that reacted with an excess of dihydrogen gas (pressure H₂ ～1 atm, ambient temperature) in THF and methylene chloride (～5:1) to generate [Ru((R)-BINAP)-(H)(MeCN)(THF)₂](BF₄) (2). Reactions effected using 2 mol % 2 as catalyst include hydrogenation of (Z)-methyl α-acetamidocinnamate, hydrosilylation of ethyl acetoacetate by chlorodimethylsilane, tandem, stereoselective isomerization of (rac)-3-buten-2-ol via a partial kinetic resolution (ee of 3-buten-2-ol 42% S at 50% conversion) to initially generate (Z)-2-buten-2-ol, followed by isomerization of the enol to 2-butanone, and competing isomerization and intramolecular hydrosilylation of dimethyl(2-propen-1-oxy)silane.

Full text of DOI:10.1021/om9603979

3782
Organometallics 1996, 15, 3782-3784
[Ru ((R)-2,2′-bis(d ip h en ylp h osp h in o)-1,1′-bin a p h th yl)(H)-
(MeCN)(THF )2](BF 4), a Ca ta lyst System for
Hyd r osilyla tion of Keton es a n d for Isom er iza tion ,
In tr a m olecu la r Hyd r osilyla tion , a n d Hyd r ogen a tion of
Olefin s
J ason A. Wiles, Christopher E. Lee, Robert McDonald,† and Steven H. Bergens*
Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2
Received May 22, 1996X
Summary: (R)-2,2′-Bis(diphenylphosphino)-1,1′-binaph-
thyl ((R)-BINAP) reacted with cis-[Ru(MeCN)2(COD)(η3-
C3H5)](BF4) (COD ) cycloocta-1,5-diene) to generate two
isomers of [Ru(MeCN)((R)-BINAP)((1-3-η):(5,6-η)-C8H11)]-
(BF4) (1) that reacted with an excess of dihydrogen gas
(pressure H2 ∼1 atm, ambient temperature) in THF and
methylene chloride (∼5:1) to generate [Ru((R)-BINAP)-
(H)(MeCN)(THF)2](BF4) (2). Reactions effected using 2
mol % 2 as catalyst include hydrogenation of (Z)-methyl
R-acetamidocinnamate, hydrosilylation of ethyl acetoac-
etate by chlorodimethylsilane, tandem, stereoselective
isomerization of (rac)-3-buten-2-ol via a partial kinetic
resolution (ee of 3-buten-2-ol 42% S at 50% conversion)
to initially generate (Z)-2-buten-2-ol, followed by isomer-
ization of the enol to 2-butanone, and competing isomer-
ization and intramolecular hydrosilylation of dimethyl-
(2-propen-1-oxy)silane.
formations that usually involve oxidative additions,
insertions, and reductive eliminations) catalyzed by
ruthenium(II)-bis(phosphine) complexes are rare and
tend to require either reactive substrates or elevated
temperatures.3 Of the nearly 200 reports describing
ruthenium-BINAP or related catalysts, we are aware
of only two examples that catalyze such reactions:
hydrosilylation of reactive nitrones3e and one isomer-
ization of an olefin.4 Both the enormous success of
chiral ruthenium(II)-bis(phosphine) complexes as cata-
lysts for enantioselective hydrogenations and their near-
absence in other reductive-type additions to double
bonds encouraged us to extend ruthenium-BINAP
chemistry to the catalyst system described in this report.
We have developed a moderately air-stable, crystalline
complex of ruthenium(II) and (R)-BINAP that under-
goes facile hydrogenation to produce a catalyst system
Nearly all reported examples of enantioselective reac-
tions catalyzed by chiral ruthenium(II)-bis(phosphine)
complexes (the most common are of 2,2′-bis(diphen-
ylphosphino)-1,1′-binaphthyl (BINAP)) are hydrogena-
tions1 and transfer hydrogenations2 of olefins or ketones.
These reactions generally occur with high turnover
numbers and enantiomeric excesses (ee). Reports of
other reductive-type additions to double bonds (trans-
(2) (a) Brown, J . M.; Brunner, H.; Leitner, W.; Rose, M. Tetrahe-
dron: Asymmetry 1991, 2, 331. (b) Saburi, M.; Ohnuki, M.; Ogasawara,
M.; Takahashi, T.; Uchida, Y. Tetrahedron Lett. 1992, 33, 5783. (c)
Geneˆt, J .-P.; Ratovelomanana-Vidal, V.; Pinel, C. Synlett 1993, 478.
(d) Hashiguchi, S.; Fujii, A.; Takehara, J .; Ikariya, T.; Noyori, R. J .
Am. Chem. Soc. 1995, 117, 7562.
(3) We limit our discussion to bis(phosphine) ligands because of the
high success obtained with their use in homogeneous catalysis and
because, in general, multidentate, chiral ligands are required to obtain
high ee values. For examples of high enantioselectivity obtained using
monodentate, chiral phosphine ligands see: (a) Hayashi, T.; Niizuma,
S.; Kamikawa, T.; Suzuki, N.; Uozumi, Y. J . Am. Chem. Soc. 1995,
117, 9101. For examples of Ru(bis(phosphine))-catalyzed reactions
other than hydrogenations, see the following. For isomerization of
olefins: (b) Frauenrath, H.; Philipps, T. Angew. Chem., Int. Ed. Engl.
1986, 25, 274. (c) Frauenrath, H.; Kaulard, M. Synlett 1994, 517. For
intramolecular hydrosilylation of ketones, (d) Burk, M. J .; Feaster, J .
E. Tetrahedron Lett. 1992, 33, 2099. For hydrosilylation of nitrones:
(e) Murahashi, S.-I.; Watanabe, S.; Shiota, T. J . Chem. Soc., Chem.
Commun. 1994, 725.
* To whom correspondence should be addressed. E-mail: Steve.
Bergens@UAlberta.ca.
† Faculty Service Officer, Structure Determination Laboratory.
X Abstract published in Advance ACS Abstracts, August 1, 1996.
(1) For excellent reviews on the discovery literature in this area
see: (a) Takaya, H.; Ohta, T.; Noyori, R. In Catalytic Asymmetric
Synthesis; Ojima, I., Ed.; VCH: New York, 1993; p 1. (b) Noyori, R. In
Aymmetric Catalysis in Organic Synthesis; Wiley-Interscience: New
York, 1994; p 16. For recent examples see: (c) Kitamura, M.; Tokunaga,
M.; Noyori, R. J . Am. Chem. Soc. 1993, 115, 144. (d) Mezzetti, A.;
Costella, L.; Del Zotto, A.; Rigo, P. Gazz. Chim. Ital. 1993, 123, 155.
(e) Hoke, J . B.; Hollis, L. S.; Stern, E. W. J . Organomet. Chem. 1993,
455, 193. (f) Manimaran, T.; Wu, T.-C.; Kolbucar, W. D.; Kolich, C. H.;
Stahly, G. P.; Fronczek, F. R.; Watkins, S. E. Organometallics 1993,
12, 1467. (g) Chiba, T.; Miyashita, A.; Nohira, H. Tetrahedron Lett.
1993, 34, 2351. (h) Wan, K.; Davis, M. E. Tetrahedron: Asymmetry
1993, 4, 2461. (i) Chan, A. C. S.; Laneman, S. Inorg. Chim. Acta 1994,
223, 165. (j) Kitamura, M.; Hsiao, Y.; Ohta, M.; Tsukamoto, M.; Ohta,
T.; Takaya, H.; Noyori, R. J . Org. Chem. 1994, 59, 297. (k) Geneˆt, J .
P.; Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.; Can˜o
De Andrade, M. C.; Laffitte, J . A. Tetrahedron: Asymmetry 1994, 5,
665. (l) Geneˆt, J . P.; Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.;
Pfister, X.; Bischoff, L.; Can˜o De Andrade, M. C.; Darses, S.; Galopin,
C.; Laffitte, J . A. Tetrahedron: Asymmetry 1994, 5, 675. (m) Masima,
K.; Kusano, K.; Sato, N.; Matsumura, Y.; Nozaki, K.; Kumobayashi,
H.; Sayo, N.; Hori, Y.; Ishizaki, T.; Akutagawa, S.; Takaya, H. J . Org.
Chem. 1994, 59, 3064. (n) Chan, A. C. S.; Chen, C. C.; Yang, T. K.;
Huang, J . H.; Lin, Y. C. Inorg. Chim. Acta 1995, 234, 95. (o) Geneˆt, J .
P.; Ratovelomanana-Vidal, V.; Can˜o De Andrade Tetrahedron Lett.
1995, 36, 2063. (p) Ohkuma, T.; Ooka, H.; Hashiguchi, S.; Ikariya, T.;
Noyori, R. J . Am. Chem. Soc. 1995, 117, 2675. (q) Kitamura, M.;
Tokunaga, M.; Noyori, R. J . Am. Chem. Soc. 1995, 117, 2931. (r) Burke,
M. J .; Harper, G. P.; Kalberg, C. S. J . Am. Chem. Soc. 1995, 117, 4423.
(s) Geneˆt, J . P.; Ratovelomanana-Vidal, V.; Can˜o De Andrade, M. C.;
Pfister, X.; Guerreiro, P.; Lenoir, J . Y. Tetrahedron Lett. 1995, 36, 4801.
(4) Sun, Y.; LeBlond, C.; Wang, J .; Blackmond, D. G. J . Am. Chem.
Soc. 1995, 117, 12647.
(5) Schrock, R. R.; J ohnson, B. F. G.; Lewis, J . J . Chem. Soc., Dalton
Trans. 1974, 951.
(6) We identified, but did not quantify, propylene in solution by 1H
NMR spectroscopy.
(7) The two isomers of 1 were produced in a ratio of 0.9:1.0. We
believe they are diastereomers with opposite absolute configurations
about the sp2 carbons in (1-3-η):(5,6-η)-C8H11. We have been unable
to separate the two isomers of 1 and confirm that they are diastere-
omers.
(8) Small amounts (<2-3%) of each of two other species formed as
well as 1. We tentatively identify one as [Ru(MeCN)2((R)-BINAP)(η3-
C3H5)](BF4), on the basis of NMR data. We purified 1 by recrystalli-
zation from a solution of methylene chloride-acetonitrile (∼1:3) by slow
addition of diethyl ether (resulting in isolation of 1‚0.17MeCN‚
0.2Et2O‚0.56CH2Cl2). We could not detect [Ru(MeCN)2((R)-BINAP)-
(η3-C3H5)](BF4) in recrystallized 1. The amount of the other, unidenti-
fied impurity (∼2-3%) did not change, even after several recrystalli-
zations of 1. We believe this species to be in equilibrium with 1 in
solution. We note that fac-[Ru((R)-BINAP)(H)(MeCN)3](BF4) is the only
detectable species in solution upon hydrogenation of 1 followed by
addition of excess acetonitrile.
S0276-7333(96)00397-4 CCC: $12.00 © 1996 American Chemical Society

Communications
Organometallics, Vol. 15, No. 18, 1996 3783
for hydrosilylation of ketones and for isomerization,
intramolecular hydrosilylation, and hydrogenation of
olefins.
We found that reaction between cis-[Ru(MeCN)2-
(COD)(η3-C3H5)](BF4)5 (COD ) cycloocta-1,5-diene) and
(R)-BINAP in acetone resulted in activation of an allylic
C-H bond of COD and subsequent formation of propy-
lene6 and two isomers7 of [Ru(MeCN)((R)-BINAP)((1-
3-η):(5,6-η)-C8H11)](BF4) (1; eq 1).8,9 Complex 1 was
F igu r e 1. Crystal structure of (S′)-1‚0.5C2H4Cl2, as de-
termined by X-ray diffraction. The positions of the hydro-
gen atoms are based on geometries of the parent carbon
atoms. Non-hydrogen atoms are represented at the 20%
probability level. Hydrogen atoms are shown with artifi-
cially small thermal parameters for (1-3-η):(5,6-η)-C8H11
and are not shown for (R)-BINAP. Selected bond lengths
(Å): Ru-C(1), 2.260(11); Ru-C(2), 2.165(11); Ru-C(3),
2.289(10); Ru-C(5), 2.395(14); Ru-C(6), 2.402(12); Ru-
P(1), 2.332(2); Ru-P(2), 2.378(2); Ru-N, 2.075(9).
isolated as moderately air-stable, lemon-yellow needles
in 83% yield after recrystallization. Figure 1 shows the
crystal structure of (S′)-1 (S′ designates the absolute
configuration of the central allylic carbon (C(2)) in (1-
3-η):(5,6-η)-C8H11).10
Compound 1 reacted in an excess of dihydrogen gas
(pressure H2 ∼1 atm, room temperature) in mixtures
of THF and methylene chloride (∼5:1)11 to yield cyclooc-
tane12 and the air-sensitive hydride [Ru((R)-BINAP)-
(H)(MeCN)(THF)2] (BF4) (2; eq 2).13 Exchange of sol-
vento ligands on 2 was facile, and it was necessary to
cool solutions to -78 °C to obtain partially resolved
NMR spectra.14 The magnitude of the coupling between
the phosphorus atoms and the hydride (28 Hz) indicated
that the hydride occupied a coordination site cis to both
phosphines. We did not detect (by NMR spectroscopy)
further reaction between 2 and dihydrogen gas under
these conditions. Addition of excess acetonitrile (aceto-
nitrile-ruthenium ∼5:1) to 2 resulted in quantitative
formation of fac-[Ru((R)-BINAP)(H)(MeCN)3](BF4) (3).15
Table 1 summarizes the reactions we effected using
2 mol % 2 as catalyst. The rate, the yield, and the
magnitude of the ee for hydrogenation of methyl R-ac-
etamidocinnamate (Table 1, entry 1) are comparable to
those reported for other rhodium- and ruthenium-
BINAP complexes as catalysts.16 Reaction between 2
and rac-3-buten-2-ol (4; Table 1, entry 2) resulted in a
stereoselective isomerization to generate significant
quantities of the simple enol (Z)-2-buten-2-ol (maximum
concentration ∼0.055 M). We were unable to detect
(using NMR spectroscopy) the E isomer in solution.
Although this enol was previously generated via isomer-
ization of 4 using rhodium-bis(phosphine) catalysts,17
the rhodium catalysts were substantially less stereose-
(9) For other examples of ruthenium complexes containing (1-3-
η):(5,6-η)-C8H11, see: Ashworth, T. V.; Nolte, M. J .; Reimann, R. H.;
Singleton, E. J . Chem. Soc. Chem. Commun. 1977, 937. Bouachir, F.;
Chaudret, B.; Neibecker, D.; Tkatchenko, I. Angew. Chem. 1985, 347.
Ashworth, T. V.; Chalmers, A. A.; Liles, D. C.; Meintjies, E.; Singleton,
E. Organometallics 1987, 6, 1543.
(10) Crystals suitable for structure determination by X-ray diffrac-
tion were obtained by liquid-liquid diffusion of methanol into a 1,2-
dichloroethane solution of 1 at room temperature. Crystal data: Mr )
1008.21; monoclinic, space group P21 (No. 4); a ) 12.8559(8) Å, b )
13.0675(8) Å, c ) 14.9401(9) Å, â ) 91.678(6)°, V ) 2508.8(3) Å3, Z )
2, dcalcd ) 1.335 g cm-3; crystal size 0.56 × 0.08 × 0.06 mm; µ(Cu KR)
) 4.040 mm-1. Data were measured using a Siemens P4/RA diffrac-
tometer with Cu KR radiation (λ ) 1.541 78 Å; maximum 2q ) 110.0°);
3315 independent reflections (3179 with I > 2σ(I)) were measured. The
structure was solved via direct methods (SHELX-8619). Full-matrix,
least-squares refinement on F2 (SHELXL-93 yielded R1 ) 0.043 (I >
2σ(I)) and wR2 ) 0.1306 (all data).
(11) Methylene chloride was required to dissolve 1 at high enough
concentrations to obtain satisfactory NMR spectra of 2. Compound 2
rapidly decomposes in the presence of methylene chloride at room
temperature. It was therefore necessary to keep these solutions of 2
at -78 °C as much as possible. The catalytic reactions were carried
out at lower concentrations of 1 (see Table 1) and, except for one
reaction (Table 1, entry 2), in the absence of methylene chloride.
(12) Identified and quantified by 1H NMR spectroscopy and by gas
chromatography (retention time confirmed by comparison to an
authentic sample). 1H NMR spectra measured of solutions early in the
hydrogenation showed the presence of cyclooctene (∼30% versus
cyclooctane), indicating that cyclooctene is initially formed by hydro-
genation of (1-3-η):(5,6-η)-C8H11 in 1.
(13) The rapid exchange of solvento ligands did not allow us to
isolate 2. We characterized 2 by 1H and 31P NMR spectroscopy. The
solution also contained [Ru(R)-BINAP)(H)(MeCN)2(THF)](BF4) (∼15%)
that resulted from reaction between 2 and the excess acetonitrile
present in crystals of 1. Two other species with 31P NMR spectra
similar to that of 2 existed in solution in amounts too small to allow
integration by NMR spectroscopy. We identify one as [Ru((R)-BINAP)-
(H)(MeCN)3](BF4) (on the basis of its 31P NMR spectrum), and we
propose that the other is [Ru((R)-BINAP)(H)(THF)3](BF4).
(14) 1H NMR (400.1 MHz, -78 °C): δ -13.05 (app t, J ) 28.0 Hz,
1H), 2.74 (s, 3H, CH3CN), 6.00-8.72 (m, aromatic). 31P{1H} NMR
(161.9 MHz, -78 °C): δ 72.22 (d, J P-P ) 49.6 Hz, 1P), 81.34 (d, J P-P
) 49.8 Hz, 1P).
(15) 1H NMR (400.1 MHz, -78 °C): δ -13.48 (app t, J ) 24.1 Hz,
1H), 1.84 (s, 3H, CH3CN), 1.87 (s, 3H, CH3CN), 2.22 (s, 3H, CH3CN),
6.00-8.85 (m, aromatic). 31P{1H} NMR (161.9 MHz, -78 °C): δ 64.22
(d, J P-P ) 40.1 Hz, 1P), 69.89 (d, J P-P ) 40.5 Hz, 1P).
(16) Noyori, R.; Ikeda, T.; Ohkuma, T.; Widhalm, M.; Kitamura, M.;
Takaya, H.; Akutagawa, S.; Sayo, N.; Saito, T.; Taketomi, T.; Kumoba-
yashi, H. J . Am. Chem. Soc. 1989, 111, 9134. For the rhodium-BINAP-
catalyzed hydrogenation of the corresponding acid, see: Miyashita, A.;
Takaya, H.; Souchi, T.; Noyori, R. Tetrahedron 1984, 40, 1245.
(17) Bergens, S. H.; Bosnich, B. J . Am. Chem. Soc. 1991, 113, 958.

3784 Organometallics, Vol. 15, No. 18, 1996
Communications
Ta ble 1. Rea ction s Ca ta lyzed by 2a
propen-1-oxy)silane (5) with 2 (Table 1, entry 4) resulted
in competing intramolecular hydrosilylation and isomer-
ization to generate (Z)-dimethyl(1-propen-1-oxy)silane
(81%), (E)-dimethyl(1-propen-1-oxy)silane (13%), and
2,2-dimethyl-1-oxa-2-silacyclopentane (6%, resulting from
intramolecular hydrosilylation). Both silyl enol ethers
underwent intramolecular hydrosilylation to generate
2,2-dimethyl-1-oxa-2-silacyclopentane upon heating to
60 °C (Table 1, entry 5). We believe that hydrosilylation
of the silyl enol ethers proceeded via reverse isomer-
ization to regenerate 5. The hydrosilylation of ethyl
acetoacetate by chlorodimethylsilane (Table 1, entry 6)
proceeded at a reasonable rate, but with low ee. To the
best of our knowledge, 2 is the first reported ruthenium-
(II)-BINAP complex to catalyze hydrosilylations of
olefins and ketones.
We propose that 2 was the active catalyst generated
by reaction between 1 and dihydrogen gas. The facile
substitution of the solvento ligands in 2 (assuming that
acetonitrile is displaced during catalysis) and the ability
of the hydride ligand to undergo insertion and elimina-
tion reactions allow the ruthenium center to present the
equivalent of four vacant coordination sites during
catalysis. Further, 2 is not sterically hindered, the
ruthenium center is in a low oxidation state, and it
apparently undergoes oxidative additions, insertions,
and reductive eliminations. The combination of these
abilities distinguishes 2 from previously reported ru-
thenium-bis(phosphine) complexes, and we believe it
accounts for the activity of 2 toward the catalytic
reactions we present in this communication. Finally,
this catalyst system will, in principle, lend itself well
to mechanistic investigations because the proposed
active catalyst can easily be generated in high concen-
trations.
a
All reactions were carried out using 2 mol % 2 in THF unless
stated otherwise. Compound 2 was generated before addition of
substrate by hydrogenation of 1 ([2] ) 2.6 mM, pressure H2 ) 1
atm, ∼2 min), followed by purging of the solution with argon gas
b
(∼1 min). Value in parentheses is the time required for complete
reaction: number of turnovers/min ) (mol of substrate)/(mol of
catalyst)t. c Reaction carried out in methanol. See the Supporting
d
Information for determination of yields, ee’s, and absolute con-
figurations. e Initial rate of isomerization; reaction carried out in
a mixture of THF and CH2Cl2 (∼20:1). f 87% Z and 13% E isomers.
The remaining product (6%) was 2,2-dimethyl-1-oxa-2-silacyclo-
pentane. Generated as a mixture of monomer and polymer.18
g
h
Excess chlorodimethylsilane was used to minimize the effect of
its loss from evaporation on hydrosilylation.
Ack n ow led gm en t. This work was supported by the
Natural Sciences and Engineering Research Council of
Canada and by the University of Alberta.
lective than complex 2 and generated the enol as a
mixture of isomers. A partial kinetic resolution of the
R and S enantiomers of rac-4 occurred during the
isomerization. The ee of 4 was 42% S at 50% conversion
(time 60 min, reaction mixture composition 50% 4, 42%
enol, 8% 2-butanone). The rate of isomerization of the
enol to 2-butanone (Table 1, entry 3) varied little over
the course of the reaction. Reaction of dimethyl(2-
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental procedures and analytical data for all new compounds
and a full report on the X-ray structure of 1, including tables
of experimental details, atomic coordinates, interatomic dis-
tances and angles, torsional angles, and anisotropic thermal
parameters (36 pages). Ordering information is given on any
current masthead page.
(18) Massol, M.; Barrau, J .; Stage, J .; Bouyssiers, B. J . Organomet.
Chem. 1974, 80, 47.
(19) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
OM9603979