Complexation and Oxygenation in Cobalt(II)–Diamine–Oxygen Systems

Abstract

The general pattern of equilibria involved in the complexation and oxygenation in cobalt(II)–diamine (phenanthroline or bipyridine)–oxygen systems was suggested. The set of equilibria included the following reactions: dissociation of protonated diamine cations; the formation of cobalt(II) mono-, bis-, and tris-diamine complexes, a hydroxo aqua complex, a hydroxo dimer, and a dihydroxo complex (monomer); various pathways to the dihydroxo dimer; and oxygenation of the hydroxo dimer. A mathematical model of the process was derived based on the material balances for cobalt and diamine and on the electroneutrality equation. The data of pH-metric studies of the systems in air and in an inert atmosphere and manometric data were used to calculate the individual equilibrium constants for each step of the process.