Transfer hydrogenation of ketones catalysed by new half-sandwich ruthenium(II) complexes bearing the sulfonated phosphane (meta-sulfonatophenyl)diphenylphosphane potassium salt (TPPMS)

New half-sandwich ruthenium(II) complexes [RuCl2(eta(6)-arene)(TPPMS)] [eta(6)-arene = p-cymene (1a), benzene (1b)] and (RuCl(eta(6)-arene)(TPPMS)(2)][Cl] [eta(6)-arene = p-cymene (2a), benzene (2b)] containing the water-soluble (meta-sulfonatophenyl)diphenylphosphane potassium salt (TPPMS) have been synthesised. The X-ray analysis for complex la revealed that, in the solid state, complex anions are held together in the crystal lattice by weak electrostatic interactions with potassium cations leading to a linear chain structure. The extent of the association in solution depends on the solvent and the determination of the size of the particles in THF can be accomplished using Multiangle Light Scattering (MALS). The new complexes proved to be excellent catalysts for transfer hydrogenation of ketones and the hydrophilic properties of the TPPMS ligand allow the catalyst recovery. The hydride derivative [RuClH(eta(6)-p-cymene)(TPPMS)] (4) has also been shown to be an efficient catalyst for these processes. Moreover, when la was used as catalyst, complex 4 was observed as the main product after the catalysis, supporting the implication of hydride species in transfer hydrogenation catalysis. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).