Synthesis and characterization of some four- and five-coordinate copper(II) complexes of 6-methyl-2-formylpyridinethiosemicarbazone (HNNS) and the X-ray crystal structures of the [Cu(NNS)(CH 3COO)(H 2O)] and [Cu (HNNS) (H20) (S04)) - H2O complexes

Abstract

Copper(II) complexes of general formula, [Cu(NNS)(H 2O) x X] · nH 2O (NNS − = uninegatively charged tridentate thiosemicarbazone ligand formed from 6-methyl-2-formylpyridine; X = NCS −, CH 3COO −, N 3 −; x = 0,1; n = 0.5, 1) and [Cu(HNNS)(H 2O)(SO 4)] · H 20 have been synthesized and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for the [Cu(NNS)X] (X = NCS −, N 3 −) complexes and a five-coordinate structure for the [Cu(HNNS)(H 2O)(SO 4)] · H 2O complex. The crystal structures of the [Cu(NNS)(CH 3COO)(H 2O)] and [Cu(HNNS)(H 2O)(SO 4)] · H 2O complexes have been determined by X-ray diffraction. The acetato complex has a distorted square-pyramidal geometry with the thiosemicarbazone ligand acting as a uninegatively charged tridentate NNS chelating agent and the fourth and fifth coordination positions of the copper(II) ion are occupied by a unidentate acetate and water ligand, respectively. The sulphato-complex is also five-coordinate with the thiosemicarbazone coordinated as a neutral NNS ligand and the fourth and fifth coordination sites are occupied by a water molecule and a unidentate sulphate ligand, respectively.