Improved syntheses of versatile ruthenium hydridocarbonyl catalysts containing electron-rich ancillary ligands

Clean, high-yield routes are established to the important catalyst chlorobis(tricyclohexylphosphine)ruthenium hydridocarbonyl [RuHCl(CO)(PCy(3))(2)] 2 and its N-heterocyclic carbene (NHC) derivatives RuHCl(CO)(NHC)(PCy(3)) (3a: NHC=IMes; 3b, NHC=H(2)IMes; IMes=1,3-dimesitylimidazol-2-ylidene). These complexes are obtained by treating chlorotris(tricyclohexylphosphine)ruthenium hydridocarbonyl [RuHCl(CO)(PPh(3))(3)] 1 with tricyclohexylphosphine [PCy(3)], or with the appropriate NHC ligand, then PCy(3). Advantages over prior routes to these complexes lie in the high yields from a conveniently accessible precursor, the absence of by-products that otherwise prove difficult to remove, and the short reaction times under experimentally convenient conditions.