Electrochemical oxidation of monosubstituted chromium carbonyl complexes. Ligand and solvent effects

Abstract

The influence of basic aprotic solvents on the electrochemical oxidation of chromium carbonyl complexes [Cr(CO)₅L]{L = CO, PPh₃, S(NC₄H₈O)₂, S[N(CH₂Ph)₂]₂, HNC₄H₈O, SC(NH₂)₂, SC-(NHEt)₂, or SC(NMe₂)₂} has been examined. The oxidation potentials (E_p^ox) depend on the solvent donor strength (DN), producing nearly linear relationships with intercepts and slopes determined fundamentally by the nature of L. The potentials estimated at DN= 0 for all studied complexes as well as the slopes ΔE_p^ox/ΔDN(sensitivity of the potentials to the solvent) for the complexes with sulphur ligands are smooth functions of the π-acceptor capacity of the ligands expressed as the Graham π parameter. The results are discussed considering outer-sphere complex interactions.