Kinetics of reduction of palladium(II) complexes with ethylamine on a dropping-mercury electrode

The reduction kinetics of palladium(II) complexes containing ethylamine is studied on a dropping-mercury electrode in solutions of pH 8-13.5 with different ethylamine concentrations in the presence of sodium perchlorate. An irreversible character of the reduction and a diffusion nature of limiting currents are established. Parameters of electrochemical kinetics and diffusion coefficient for the complexes are determined. At pH 11 and 12, the half-wave potential is independent of the ethylamine concentration in the concentration range 0.01 to 0.1 M. Tetraethylamine complexes of palladium(II) predominate in solution and presumably take part in the slow electrochemical step. Raising ethylamine concentration to 2 M makes E-1/2 more negative, due to specific ethylamine adsorption. Limiting currents of two waves, which occur at pH 8 and overall ethylamine concentration 0.01-0.02 M, are used to calculate two constants. One is the step stability constant for complex Pd (eta)(4)(2+) The other is the equilibrium constant for deprotonation of a ligand in Pd (eta)(4)(2+), which occurs at pH 13.1-13.5 and ethylamine concentrations 1 and 2 M.