Ruthenium(II) unsymmetrical N₂O₂ tetradentate Schiff-base complexes: synthesis, characterization, and catalytic studies

A series of six-coordinate ruthenium(II) complexes [Ru(CO)(L x )(B)] (B = PPh3, AsPh3 or Py; L x = unsymmetrical tetradentate Schiff base, x = 5–8; L5= salen-2-hyna, L6= Cl-salen-2-hyna, L7= valen-2-hyna, L8= o-hyac-2-hyna) have been prepared by reacting [RuHCl(CO)(EPh3)2(B)] (E = P or As) with unsymmetrical Schiff bases in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (infrared, electronic, 1H, 31P, and 13C NMR) data. An octahedral structure has been assigned for all the complexes. The new complexes are efficient catalysts for the transfer hydrogenation of ketones and also exhibit catalytic activity for the carbon–carbon coupling reactions.