Photolysis of copper(II) oxalato complexes in aqueous solution. Identification and reactions of an intermediate

Abstract

The intermediate responsible for the transient absorption band (λ_max= 385 nm), produced by flash photolysis of copper(II) oxalato complexes in deaerated aqueous solution, is identified as CuCO₂ by comparison with an apparently identical species formed by reaction of Cu^I ions with ·CO^–₂ radicals in the pulse radiolysis of the Cu^II/oxalate/formate system. CuCO₂ decays by first-order kinetics with the rate constant dependent on pH, Cu^II and oxalate ion concentrations. The decay kinetics are explained by two competing reactions of CuCO₂: (a) protonolysis to Cu^II and HCO₂H, (b) reaction with Cu^II to give Cu^I and CO₂.