Kinetic Investigation of the Reaction of Dioxygen with the Copper(I) Complex [Cu(PimiPr2)(CH3CN)]CF3SO3 {PimiPr2 = Tris[2-(1,4-diisopropylimidazolyl)]phosphine}

Abstract

Model complexes for copper proteins such as hemocyanin or tyrosinase have been investigated in detail during the last four decades due to their potential to become valuable catalysts for selective oxidations of organic substrates. However, so far most of these compounds can only be investigated in aprotic solvents at lower temperatures. Therefore, industrial applications on a larger scale are still missing. In contrast the copper(I) complex with the ligand tris[2-(1,4-diisopropylimidazolyl)]phosphine can form a quite stable dinuclear copper peroxido complex in the protic solvent methanol at room temperature. The kinetic analysis of the reaction of [Cu(PimiPr2)(CH3CN)]CF3SO3 with dioxygen in methanol is reported. The results allowed to obtain rate constants and activation parameters (ΔH# = 25 ± 2 kJ mol–1 and ΔS# = –121 ± 8 J mol–1 K–1) for the formation of the reactive intermediate, a mononuclear copper superoxido complex, prior to the consecutive reaction to a dinuclear peroxido complex.