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

“…It must be mentioned that the values of the diffusion coefficient for complexes of zinc(II) containing ethylenediamine presented by us are considerably smaller than the value of the diffusion coefficient for complexes of zinc(II) containing ammonia, specifically, D = (1.0 ± 0.1) × 10 -5 cm 2 s -1 , which was determined at 25°C in [7]. This is probably due to larger dimensions of ethylenediamine complexes of zinc(II), which, as follows from [8], form associates with perchlorate ions at high concentrations of perchlorate ions. From a linear dependence of lnD on 1/T we calculated the activation energy for the process of diffusion of complexes of zinc(II) containing ethylenediamine.…”

“…Table 2 As seen from Table 2, upon going from small values of time t 1 ≈ 0.3-0.7 s to larger values of t 1 , the magnitude of coefficient b k noticeably diminishes. The decrease in the values of coefficient b k had also been observed for the reduction of ammonia and hydroxyammonia complexes of zinc(II) [7] and bisethylenediamine complexes of palladium(II) [13].…”

“…As was established in [8], the formation of simple ethylenediamine complexes of zinc(II) in 1 M NaClO 4 solutions of pH 9.5-11.5 is accompanied by the formation of its mixed hydroxyethylenediamine complexes.…”

“…In Table 1 and further on, we give values of [en] that were calculated for 25°C, for the protonation constants for ethylenediamine at other temperatures are unknown. The average value of the diffusion coefficient for different forms of complexes of zinc(II) that were present in the investigated solutions [8], which was calculated from the values presented in Table 1, amounts to (5.9 ± 1.1) × 10 -6 cm 2 s -1 at 25°ë and coincides, to within errors, with the value 6.45 × 10 -6 cm 2 s -1 , which we calculated for complexes Zn (0.1 M KNO 3 , 25°C) from the data reported in [9]. It must be mentioned that the values of the diffusion coefficient for complexes of zinc(II) containing ethylenediamine presented by us are considerably smaller than the value of the diffusion coefficient for complexes of zinc(II) containing ammonia, specifically, D = (1.0 ± 0.1) × 10 -5 cm 2 s -1 , which was determined at 25°C in [7].…”

“…In connection with this it seemed of interest to investigate the mechanism of electroreduction of the ethylenediamine and hydroxyethylenediamine complexes of zinc(II) [8] and compare it with the mecha-…”