Neue Kobalt(II)-Chelate als O2-Träger

Abstract

The uptake of molecular oxygen by cobalt(II) chelates of a series of new and known four- and fivedentate ligands has been studied in aqueous solution by spectrophotometric and potentiometric methods and by an O₂-sensitive electrode. The stability of the binuclear O₂-adduct of general composition (Z)CoO₂Co(Z) as measured by the rate of decomposition into Co^III and peroxide strongly depends (1) on the donor groups in the coordination sphere Z and (2) on the geometry of the CoO₂Co group. Whenever Z contains coordinated H₂O, a double bridged species (Z)Co • μ(O₂, OH) • Co(Z) is formed. The additional OH-bridge greatly stabilises the O₂-adduct. The rate of decomposition of the O₂-adduct varies over at least 6 orders of magnitude.