Electron transfer kinetics for weakly bonded, labile metal–ligand complexes

Abstract

The electron transfer kinetics for the weakly-bonded, labile Cu^I–L (L = CO and ethene) complexes have been investigated with square-wave voltammetry (SWV) in the ionic liquid solvent AlCl₃–EMIC (EMIC = 1-ethyl-3-methyl-1H-imidazolium chloride). The oxidation of Cu^I–L to Cu^II and free ligand proceeds through an asymmetric quasi-reversible electron transfer mechanism in which the heterogeneous rate constant (k⁰_a) is decreased relative to the rate constant for uncomplexed Cu^I, and the anodic transfer coefficient (β) is much less than 0.5. The Cu^I–L bond energies were determined using potentiomtric methods and found to be 9.4 (± 0.8) and 11.1 (± 0.1) kcal mol^–1 for the CO and ethene complexes, respectively.