Ruthenium(II) hydrazone Schiff base complexes: Synthesis, spectral study and catalytic applications

Ruthenium(II) hydrazone Schiff base complexes of the type [RuCl(CO)(B)(L)] (were B = PPh3, AsPh3 or Py; L = hydrazone Schiff base ligands) were synthesized from the reactions of hydrazone Schiff base ligand (obtained from isonicotinoylhydrazide and different hydroxy aldehydes) with [RuHCl(CO)(EPh3)2(B)] (where E = P or As; B = PPh3, AsPh3 or Py) in 1:1 molar ratio. All the new complexes have been characterized by analytical and spectral (FT-IR, electronic, 1H, 13C and 31P NMR) data. They have been tentatively assigned an octahedral structure. The synthesized complexes have exhibited catalytic activity for oxidation of benzyl alcohol to benzaldehyde and cyclohexanol to cyclohexanone in the presence of N-methyl morpholine N-oxide (NMO) as co-oxidant. They were also found to catalyze the transfer hydrogenation of aliphatic and aromatic ketones to alcohols in KOH/Isopropanol.

Graphical abstractRuthenium(II) hydrazone Schiff base complexes were synthesized and characterized. They have been assigned an octahedral structure. The new complexes were found to be efficient oxidation and transfer hydrogenation catalysts.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new series of ruthenium(II) hydrazone Schiff base complexes were synthesized from ruthenium(II) precursor complexes and ligands. ► Elemental analysis data obtained has confirmed the proposed molecular formula of the complexes. ► Spectral studies of the ligands and the complexes have proved the binding modes of ligand with central metal ion. ► Synthesized complexes have showed very good catalytic activity in the oxidation of primary and secondary alcohols. ► Effective catalytic activities have also observed for the transfer hydrogenation reactions of ketones by the newly synthesized complexes.