KINETIC-STUDIES OF COMPLEXATION REACTIONS OF WATER-SOLUBLE HYDRAZONESWITH NICKEL(II) AND PALLADIUM(II) IONS

The kinetics of complexation reactions of five water-soluble heterocyc lic hydrazones with nickel(II) and palladium(II) ions have been invest igated by stopped-flow spectrophotometry. Rates of complexations with nickel(II) and palladium(II) in the absence of chloride ion were found to be proportional to the first order of the ligand and metal ion con centrations and to the inverse first order of the hydrogen ion concent ration except for the complexation of pha-(5-nitro-2-pyridyl)hydrazono -3-toluenesulfonic acid with palladium(II). Rates of complexation with palladium(II) in the presence of chloride ion were best described by a two-term expression, both terms being first order in the palladium i on and ligand concentrations and inverse first order in the hydrogen i on concentration. The first term has zero dependence of the chloride i on concentration, whereas the second is first order with respect to th e chloride ion concentration. The rate constant for each complexation reaction was determined. The complexation of the hydrazones with nicke l(II) was estimated to go according to an Eigen mechanism and that wit h palladium (II) according to the associative mechanism.