Kinetics and mechanism of electroreduction of ethylenediamine and hydroxyethylenediamine complexes of zinc(II) on a dropping-mercury electrode

The kinetics of electroreduction of ethylenediamine and hydroxyethylenediamine complexes of zinc(II) on a dropping-mercury electrode (DME) in 1 M NaClO₄ solutions of pH 9–11.5 is studied at different ethylenediamine concentrations at 25, 35, and 50°C. One wave with a diffusion limiting current is observed at an overall concentration of zinc(II) complexes of 2 × 10^–5 M and current recording times t ₁ = 0.3–4 s. The polarographic peak that distorts the wave at t ₁ 0.5 s, pH 11.5, and 25°C is due to the accumulation of insoluble reduction products on the electrode surface. The slow electrochemical step on DME involves complexes Znen²⁺, which form in preceding reversible chemical steps from complexes present in solution.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 397–405.Original Russian Text Copyright © 2005 by Kurtova, Kravtsov, Tsventarnyi.