Electrochemical properties of metal complexes of dithio-acid derivatives and their application in extraction polarography

Metal complexes with dithiocarbamic (dtc), xanthic (xan) and dithiophosphoric (dtp) acids give rise to one or more polarographic waves in dimethylformamide and in mixtures of extracting solvents and ethanol. The electrons are found to be transferred stepwise in the case of unfilled d-shell metal complexes. The shift of half-wave potential depends on the ligand, increasing in the order dtp < xan < dtc. In solvents with low solvation power the electrode processes are more reversible. The linear dependence of the limiting current on the chelate concentration has been used for determining the metal in the organic phase without re-extraction. Pb(II), Bi(III) and As(III) have been separated with dtp as extractant, and the concentrations of Co(II), Ni(II) and Zn(II) complexes (simultaneously extracted) have been determined polarographically.