Synthesis and characterization of copper(II) complexes of the methylpyruvate Schiff base of S-methyldithiocarbazate (Hmpsme) and the X-crystal structures of Hmpsme and [Cu(mpsme)Cl]

New copper(II) complexes of general formula, [Cu(mpsme)X] (mpsme = anionic form of the methylpyruvate Schiff base of S-methyldithiocarbazate; X = Cl-, Br-) have been prepared and characterized by a variety of physico-chemical techniques. Based on magnetic and spectral evidence, a square-planar struc ture is assigned to these complexes. Reaction of the Schiff base with coppe r(II) nitrate does not yield a nitrato-copper(II) complex of the ligand. In stead, hydrolysis of the Schiff base occurs with the concomitant formation of the copper(II) complex of the pyruvic acid Schiff base of S-methyldithio carbazate. Based on magnetic and spectral evidence. an oxygen-bridged squar e-planar structure is assigned to this complex. The crystal and molecular s tructures of the Schiff base, Hmpsme and its chlorocopper(II) complex, [Cu( mpsme)Cl] have been determined by X-ray diffraction. The [Cu(mpsme)Cl] comp lex has a distorted square-planar structure with the ligand coordinated to the copper(II) ion as a uninegatively charged tridentate chelating agent vi a the carbonylic oxygen atom, the azomethine nitrogen atom and the thiolato sulfur atom. The fourth coordination position around the copper(II) ion is occupied by the chloride ligand. The distortion from regular square-planar geometry is attributed to the restricted bite size of the ligand. (C) 2001 Published by Elsevier Science Ltd.