Synthesis, Characterization and Reactivity of Diamine-bis(triphenylphosphine)ruthenium(II) Complexes as Catalysts for Selective and Direct Hydrogenation of Cyanamid Aldehyde

Abstract

The diamine-bis(triphenylphosphine)ruthenium(II) complexes using 1,4-butanediamine and N1-(2-aminoethyl)-1,2-ethanediamine as co-ligands has been made available for the first time. These complexes were characterized by NMR, IR, and mass spectroscopy in addition to the elemental analysis. The chemical behavior of the phosphine and diamine ligands during the complexation reactions was manipulated by 31P{1H} NMR spectroscopy at room temperature. In case of using triamine as bidentate co-ligand one of the chloride ligand in dichloromethane solvent was self-abstracted from the coordination sphere of the ruthenium center atom to the outer sphere which permitted monocationic complex with one chloride and three nitrogen bonds formation. This hemilabile of N1-(2-aminoethyl)-1,2-ethanediamine has been confirmed step by step, by 31P{1H} NMR as well as FAB-MS, additionally only 1,4-butanediamine ligand in complex 3 was totally exchanged by CH3CN ligand when complex 3 and 4 were dissolved in CH3CN solvent which confirmed that: seven membered diamines-ruthenium(II) complexes are less stable than the others. Complexes 3 and 4 showed a high degree of catalytic activity and selectivity in the direct hydrogenation of the ?,?-unsaturated aldehyde substrate (cyanamid aldehyde) under mild hydrogenation condition, additionally the role of different co-catalysts are shortly investigated in this process