5994 Organometallics 2010, 29, 5994–6001
DOI: 10.1021/om100852x
Preparation of Thiolate-Bridged Dinuclear Ruthenium Complexes
Bearing a Phosphine Ligand and Application to Propargylic
Reduction of Propargylic Alcohols with 2-Propanol
Masahiro Yuki, Yoshihiro Miyake, and Yoshiaki Nishibayashi*
Institute of Engineering Innovation, School of Engineering, The University of Tokyo,
Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
Received September 2, 2010
Novel thiolate-bridged dinuclear ruthenium complexes bearing a phosphine ligand, [Cp*Ru{PhP-
(C6H4-o-S)2}RuCp*](OTf)2, [CpRu{PhP(C6H4-o-S)2}RuCp*(OH2)](OTf)2, and [Cp*Fe{PhP(C6H4-
o-S)2}RuCp*](OTf)2, are prepared and characterized by X-ray analysis. These dinuclear complexes
work as effective catalysts toward propargylic reduction of propargylic alcohols with 2-propanol via
allenylidene complexes as key intermediates to give the corresponding alkynes in good to high yields.
Chart 1
Introduction
Since the first report on the ruthenium-catalyzed propargylic
substitution reactions of propargylic alcohols with nucleo-
philes to give the corresponding propargylic-substituted
products in good to high yields with a complete selectivity,1
we have found novel transformations of propargylic alcohols
catalyzed only by thiolate-bridged diruthenium complexes
[Cp*RuCl(μ-SR)]2 (1; R=Me, Et, nPr, iPr).2,3 More recently,
we have developed enantioselective versions of these catalytic
reactions by using optically active thiolate-bridged diruthenium
complexes [Cp*RuCl( μ-SR*)]2 (SR*=(R)-SCH(Et)C6H2Ph3
and (R)-SCH(Et)C6H3Ph2) as catalysts.4 The result of the
density functional theory calculation on the model reaction
also supports the proposed reaction pathway of the ruthenium-
catalyzed propargylic substitution reactions of propargylic
alcohols with nucleophiles, where ruthenium-allenylidene
complexes work as key intermediates and where the possible
charge transfer between two ruthenium atoms (synergistic effect)
is one of the key factors to promote the catalytic reactions.5
As an extension of our study, we have envisaged the change
from chloride ligand in 1 to a phosphine ligand because the
catalytic activity of diruthenium complexes was affected to
a considerable degree by halide ligands coordinated to the
ruthenium atoms in 1.6 Toward this end, we have designed a
stepwise incorporation of two different transition metals to
prepare the corresponding thiolate-bridged dinuclear com-
plexes bearing a phosphine ligand (Chart 1). Herein, we de-
scribe the results of the preparation of thiolate-bridged dinuclear
ruthenium complexes bearing a phosphine ligand and their
*To whom correspondence should be addressed. E-mail: ynishiba@
sogo.t.u-tokyo.ac.jp.
(1) For recent selected examples, see: (a) Nishibayashi, Y.; Milton,
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;
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2009, 48, 2534. (i) Miyake, Y.; Uemura, S.; Nishibayashi, Y. ChemCatChem
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Yamazaki, H.; Hidai, M. Organometallics 1989, 8, 1232. (b) Q€u, J.-P.;
Masui, D.; Ishii, Y.; Hidai, M. Chem. Lett. 1998, 1003. (c) Hidai, M.;
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(5) The result of the density functional theory calculation on the model
reaction also supports the proposed reaction pathway of the ruthenium-
catalyzed propargylic substitution reactions of propargylic alcohols with
nucleophiles, where ruthenium-allenylidene complexes work as key inter-
mediates; see: (a) Ammal, C. S.; Yoshikai, N.; Inada, Y.; Nishibayashi, Y.;
Nakamura, E. J. Am. Chem. Soc. 2005, 127, 9428. (b) Sakata, K.; Miyake, Y.;
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metallics 2009, 28, 1138.
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