Unprecedented formation of a μ-oxobridged polymeric copper(II) complex : evaluation of catalytic activity in synthesis of 5-substituted 1H-tetrazoles

Abstract

The reaction of CuCl2·2H2O with Schiff base ligand, 4-[(2-hydroxy-3-methoxybenzylidene)amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3-one] (hmdpH), in 1:1 molar ratio led to a novel and unprecedented oxo-bridged polymeric copper (II) complex, [Cu(μ-O) (hmdp)]n. The complex was isolated as crystalline solid and characterized by FTIR, UV–visible and EPR spectroscopic techniques. The molecular structure of the complex was also determined by single crystal X-ray diffraction studies. The formation of the complex is unique and unprecedented in the sense that one of the CH3 group of the 4-aminoantipyrene unit of the Schiff base ligand is oxidized in situ to CH2OH, during the complex formation. The catalytic potential of the complex has been demonstrated in the synthesis of a series of 5-substituted 1H-tetrazoles via [3 + 2]-cycloaddition reactions of substituted benzonitriles and sodium azide in ethylene glycol.