Comparative transfer hydrogenation performance of homogeneous and heterogeneous ruthenium (II) catalysts derived from a Schiff base ligand

A new Schiff base ligand (E)-4-(((pyridin-2-ylmethylene)amino)methyl)phenol (L1H) 1 was synthesized and grafted to solid support successfully. Mononuclear Ru(II) complex 2, its solid supported analogue 4 and heterogeneous complex 5 were synthesized with [RuCl2(p-cymene)](2) and RuCl2(PPh3)dppb. According to the UV-visible, IR and NMR data, the Ru (II) complexes are formed by the coordination of both nitrogen atoms of the ligand. Molecular structures of the L1H 1 was determined by single crystal Xray diffraction study. The Ruthenium (II) complexes 2, 4 and 5 were used as catalysts for the transfer hydrogenation of various ketones in 2-propanol. Following the comparison of complexes 2, 4 and 5 between each other, it was observed that immobilized complexes have higher catalytic activity against the homogeneous structure. The results showed that the diphosphine incorporated complex 5 is more efficient than the other Ru (II) complexes. (C) 2016 Elsevier B.V. All rights reserved.