Ruthenium catalysts and their use in the asymmetric hydrogenation of weakly coordinating substrates

A catalyst of Ru comprising bidentate phosphine ligands is described which is obtained by a process that comprises treating equimolar amounts of an appropriate Ru complex and a bidentate diphosphine ligand with an acid of the formula H-Anion, wherein the anion is a non-coordinating anion, said acid being used in a ratio of 1 molar equivalent per mole of Ru complex and the treatment being carried out in a non-coordinating or weakly coordinating medium, under an oxygen-free atmosphere.Said catalyst is useful for the preparation of the preferred isomer of the Hedione(R), having the configuration (+)-(1R)-cis, and of many other substrates comprising highly hindered carbon-carbon double bonds.