Convenient and improved protocols for the hydrogenation of esters using Ru catalysts derived from (P,P), (P,N,N) and (P,N,O) ligandsDedicated to Professor David Cole-Hamilton on the occasion of his retirement and for his outstanding contribution to transition metal catalysis.Electronic supplementary information (ESI) available: Full experimental procedures and data for reaction products. See DOI: 10.1039/c2dt30973d

An improved protocol where a pre-cursor, [Ru(Cl) 2 (NBD)(Py) 2 ], is treated with ligands to form [RuCl 2 (bidentate ligand)(diamine)] pre-catalysts for ester hydrogenation is reported. This family of catalysts, as well as a range of ruthenium complexes of tridentate P^N^X (X = NR 2 , OH) ligands have been investigated in the hydrogenation of aromatic esters. A range of aromatic esters can be hydrogenated in high yields at temperatures between 30 °C and 100 °C. Several active catalysts have been identified and applied in the hydrogenation of aromatic esters at temperatures as low as 30 °C.