Ruthenium (II) complexes of NO ligands: Synthesis, characterization and application in transfer hydrogenation of carbonyl compounds

• Three new azo-containing Schiff Bases and their Ru (II) complexes were synthesized.
• The complexes were performed as catalysts for the transfer hydrogenation.
• It was observed that azo group has got remarkably increasing effect on the catalytic activity.
• Best active catalyst has found to be complex 5.

New Schiff base ligands including azo group such as (4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(phenylimino)methyl)phenol 2, 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(naphthalen-1-ylimino)methyl)phenol 3, 2-((E)-(benzylimino)methyl)-4-((E)-(4-ethylphenyl)diazenyl)phenol 4 and azo group-free ligand (E)-2-((benzylimino)methyl)phenol 8 and their ruthenium complexes 5–7 and 9 with [RuCl2(p-cymene)] were synthesized and characterized by spectroscopic techniques including 1H and 13C NMR, FT-IR and UV–Vis. According to the UV–visible, IR and NMR data, the Ru (II) complexes 5–7 and 9 are formed by the coordination of N, O atoms of the ligands. Molecular structures of the complex 7 and complex 9 were determined by single crystal X-ray diffraction studies. These Ruthenium (II) complexes 5–7 and 9 were used as catalysts for the transfer hydrogenation of a series of ketones and benzaldehyde in 2-propanol. Following the comparison of complex 9 with the other three azo containing complexes 5–7, it was observed that azo group has got remarkable increasing effect on the catalytic activity. The results showed that the complex 5 is efficient than the other Ru (II) complexes.

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