The kinetics of reduction of palladium (II) complexes with β-alanine at dropping mercury electrode and the complexes’ stability constants

Abstract

By using dc and ac polarography, the kinetics of electroreduction of the palladium (II) complexes with β-alanine at a dropping mercury electrode was studied in solutions with the palladium (II) concentration from 2 × 10−5 to 2 × 10−4 M and variable β-alanine and sodium perchlorate concentrations (pH 6–12). One polarographic wave was observed in solutions with pH 9 and 10 at the β-alanine overall concentration of cβala = 1 × 10−3 to 5 × 10−2 M; two waves, at lower pH or higher cβala. It was concluded on the formation of different forms of palladium (II) complexes in the studied solutions; the complexes contained two to four β-alanine coordinated anions. Using the limiting diffusion currents for the two waves at pH 9–11 and cβala = 0.1 and 0.5 M, the stepwise stability constant for the Pd(βala)42− complex was calculated. Using two ac peaks observed at pH 7–8 and cβala = 1 × 10−2 to 0.1 M, the stepwise stability constant for the Pd(βala)3−. was calculated. The perchlorate ions adsorbed at the dropping mercury electrode, as well as βala− anions at their higher concentrations, hamper the electroreduction of the palladium (II) complexes with β-alanine.