Synthesis, structure and properties of nickel and copper complexes containing N, O-hydrazone Schiff base ligand

The compound 2-(1-(2-methyl-2-phenylhydrazono) ethyl) phenol, HLNNMePh, was synthesized by solvent-free condensation of o-hydroxyacetophenone and N, N-methylphenylhydrazine and was analytically and spectroscopically characterized. The reaction of HLNNMePh with nickel acetate and copper acetate in the presence of NEt3 resulted the corresponding [M(L-NNMePh)(2)] complexes (M = Ni, 1; Cu, 2), which were structurally characterized by X-ray diffraction methods. A four-coordinate square planar environment around the metal centre was found for both compounds, in which the two LNNMePh ligands act as bidentate N, O-chelators and exhibit a pseudo-trans conformation. These compounds are the first structurally characterized transition metal complexes containing the kappa(2)-N, O-2-(1-(2-methyl-2-phenylhydrazono) ethyl) phenolate ligand, L-NNMePh. Copper complex [Cu(L-NNMePh)(2)], 2, was tested as catalyst, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical), for the aerobic oxidation of benzyl alcohol, as model reaction. Low yields of the corresponding aldehyde were observed by using air at atmospheric pressure as the oxidant in toluene as solvent. (C) 2017 Elsevier B.V. All rights reserved.