INEQUIVALENT COORDINATION OF THIOSEMICARBAZONE LIGANDS IN COBALT (III) AND CHROMIUM (III) COMPLEXES

Chromium (III) and cobalt (III) complexes derived from 2-ketobutyric acid thiosemicarbazone (H(2)Kbtsc) have been prepared and characterized. Crystal structure analyses have shown both products to be mixed ligand complexes of the type M(HKbtsc) (Kbtsc) in which the thiosemicarbazone ligand is present in singly deprotonated ''thione'' and doubly deprotonated ''thiol'' forms. In each complex, the metal ion is bound to two tridentate ligands in a distorted octahedral geometry with meridional stereochemistry. Small but consistent structural differences between the two types of ligands are observed. Spectroscopic and electrochemical data are consistent with the formulations of these compounds as derived from the crystallographic results.