Synthesis, characterization and thermal behaviour of mixed-ligand complexes of cobalt(III) with dimethylglyoxime and some amino acids

Non-electrolyte complexes of the general formula [Co(Hdmg)(2)(HA)X] where H dmg = dimethylglyoximato monoanion, HA = alanine, threonine or histidine an d X = Cl, Br, I, SCN were synthesized and characterized by elemental analys es, IR, UV-Visible and H-1 NMR spectra. The complexes are pseudo-octahedral with two dimethylglyoximato ligands N-bonded to the metal in the equatoria l plane, the two axial sites being occupied by one amino acid molecule and one halogen or pseudo halogen anion. The thermal behaviour of these cobalt( III) complexes, determined by thermogravimetry (TG) and differential therma l analysis (DTA), shows that the dimethylglyoximato ligand is thermally mor e stable than the two other ligands.