Effect of ammonia on the Zn(Hg)/Zn(II) electrode reactions in aqueous chloride solutions

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

“…The solutions we investigated contained, along with complexes Zn , also complexes Zn , Zn(en) 2 (OH) + , and Zn(en) 2 (OH) 2 [8]. Therefore, we can write (5) where (6) provided the conditions of mutual conversion of the said complexes are reversible. To calculate values of parameter ∆, we used the overall stability constants for complexes Zn , Zn , Zn(en) 2 (OH) + , and Zn(en) 2 (OH) 2 , which were determined in [8], specifically, β 3,0 = 10 12.97 å -3 , β 2,0 = 10 10.81 å -2 , β 2,1 = 10 14.45 å −3 , and β 2,2 = 10 15.67 å -4 (1 M NaClO 4 , 25°ë).…”

“…there takes place the preceding reversible chemical step (9) This step precedes the slow electrochemical step (10) The composition of the electrochemically active complex Znen 2+ we have established coincides with the composition of the electrochemically active complex that had been established by Morinaga [9] in the course of electroreduction of trisethylenediamine complexes of zinc(II) in the presence of gelatin additives. It would be of interest to mention that the ion of zinc(II) in the electrochemically active complex Znen 2+ is bounded to two nitrogen atoms, as is the case with the electrochemically active complex Zn [1][2][3][4][5][6][7].…”

“…In particular, it was established that, in solutions of a high ionic strength, the electroreduction of ammonia [1][2][3][4][5][6][7] and hydroxyammonia [1,7] complexes of zinc(II) on zinc amalgam and a mercury electrode involves preliminary abstraction of some ammonia molecules and/or hydroxyl ions and the formation of complexes Zn , which take part in the slow electrochemical step. In [7], a conclusion was drawn about an inner-sphere mechanism of a two-electron electrochemical step involving complexes Zn .…”

“…Processes of electroreduction of labile complexes of zinc(II) with various ligands include an electrochemical step and preceding reversible chemical steps, in which some ligands are abstracted with the formation of electrochemically active complexes that take part in a discharge step [1][2][3][4][5][6][7]. In particular, it was established that, in solutions of a high ionic strength, the electroreduction of ammonia [1][2][3][4][5][6][7] and hydroxyammonia [1,7] complexes of zinc(II) on zinc amalgam and a mercury electrode involves preliminary abstraction of some ammonia molecules and/or hydroxyl ions and the formation of complexes Zn , which take part in the slow electrochemical step.…”