Polarography of bis-(O,O′ diethyldithiophosphato) nickel (II)

Abstract

The polarographic behaviour of bis-(O,O′-diethyldithiophosphato) nickel (II), Ni(DTP) 2, at the dropping mercury electrode has been examined in ethanol and ethanol-water media. In ethanol, a single wave that is almost completely controlled by diffusion is obtained and has been attributed to the catalytic reduction of nickel (II) in the presence of the complexing agent, DTP. In ethanol-water mixtures, in which the water content is less than 40% v/v, two waves are obtained. The first wave is the catalytic wave that arises from the complexed nickel (II) and the second wave is the reduction wave of nickel (II) that is not complexed by DTP. In the presence of acid, in addition to the nickel wave, a catalytic hydrogen wave is also obtained. Mechanisms involving adsorption and complexation have been proposed for both catalytic waves. Nickel (II) forms with DTP, relatively weak complexes in which the nickel-sulphur bond is readily disrupted when the dielectric constant of the solvent medium is increased.