SPECTROPHOTOMETRY AND VOLTAMMETRY OF COBALT TRIETHANOLAMINE COMPLEXESIN AQUEOUS-SOLUTIONS IN THE ABSENCE AND PRESENCE OF OXYGEN

The absorption spectra of solutions of Co-II and Co-III in the presenc e of triethanolamine (TEA) are reported. For the former complexes ther e is no evidence for chelation, but a bischelate is formed with the la tter. Saturation of Co-II-TEA solutions with oxygen yields more than o ne new, dioxygen-containing, species that age slowly. The oxygen may b e partly removed by bubbling nitrogen through the solutions. The elect roreduction of cobalt-triethanolamine complexes in aqueous solutions i n the presence of oxygen was followed voltammetrically on a stationary Pt disk electrode. Strong catalytic enhancement of the electroreducti on current of oxygen involved with the complex was achieved. A. mechan ism for the formation of the electrochemically active species, involvi ng OH- and O-2-bridged dimeric species of both Co-II and Co-III, was s uggested. A pseudo first order was established for the reversible reac tion of this complex formation. Relevant rate and equilibrium constant s were obtained. Copyright (C) 1997 Elsevier Science Ltd.