MAGNETIC AND ELECTRONIC SPECTRAL STUDIES OF FOUR, FIVE AND SIX COORDINATED COMPLEXES OF SUBSTITUTED HYDRAZIDE AND HYDRAZONES WITH DIVALENT NICKEL AND COBALT METAL IONS

Metal complexes of divalent Nickel and Cobalt metal ions have been synthesized with picolinic acid hydrazide (PH) , ortho -hydroxy acetophenone picolinoyl hydrazone ( APH) and ortho-hydroxy acetophenone iso-nicotinoyl hydrazone (AIH) ligands and were isolated at both high pH and low pH. These complexes were characterized by elemental analyses and also by electronic spectral studies and magnetic measurements. Ligands PH and AIH act as tridentate, while APH is tetradentate. All form two types of complexes, depending upon pH of the reaction mixture. At high pH complexes formed are monomeric while at high pH complexes were found to be dimeric. Dimerisation is initiated by enolic oxygen which acts like a bridging ligand between two metal ions.