The stepwise complex formation in the cobalt(III)-azide system

Abstract

Measurements of conditional potential of the Co III/Co II system in several sodium azide solutions (0.30–1.78 M) of ionic strength 2.0 M, held with sodium perchlorate, in aqueous medium at 25°C, lead to the following overall formation constants: β 1 = 3 x 10 8 M- −1, β 2 = 1 x 10 15 M −2, β 3 = 7 x 10 19 M −3, β 4 = 1.5 x 10 23 M −4, β 5 = 1.3 x 10 23 M −5 and β 6 = 1.0 x 10 24 M −6. Calculations require introduction of the stepwise formation constants of the cobalt(II) complexes and E 0′ for Co III/Co II in non-complexing media, from literature data, in order to calculate the Leden's function, F 0(L), referred to Co III complexes. The first three formation constants were estimated from the linear plot of (logβ n )/ n vs n (number of ligands) with β 4, β 5 and β 6 data.