The dinuclear
cation [(C(6)Me(6))(2)Ru(2)(PPh(2))H(2)](+) (1) has been studied as the catalyst for the hydrogenation of
carbon-
carbon double and triple bonds. In particular, [1][BF(4)] turned out to be a highly selective hydrogenation catalyst for
olefin functions in molecules also containing reducible carbonyl functions, such as
acrolein,
carvone, and methyljasmonate. The hypothesis of molecular catalysis by dinuclear
ruthenium complexes is supported by catalyst-
poisoning experiments, the absence of an induction period in the kinetics of
cyclohexene hydrogenation, and the isolation and single-crystal X-ray structure analysis of the tetrafluoroborate
salt of the
cation [(C(6)Me(6))(2)Ru(2)(PPh(2))(CHCHPh)H](+) (2), which can be considered as an intermediate in the case of
phenylacetylene hydrogenation. On the basis of these findings, a catalytic cycle is proposed which implies that substrate hydrogenation takes place at the intact diruthenium backbone, with the two
ruthenium atoms acting cooperatively in the
hydrogen-transfer process.