Oxidation potential of [Rh(β-diketonato)(P(OPh)3)2] complexes-Relationships with experimental, electronic and calculated parameters

The electrochemical behaviour of the series of ten [Rh(RCOCHCOR′)(P(OPh)3)2] complexes with R, R′ = CF3, CF3 (1), CF3, Ph (C6H5) (2), CF3, CH3 (3), Ph, Ph (4), CF3, Fc (ferrocenyl = (η5-C5H5)Fe(η5-C5H4)) (5), CH3, Ph (6), CH3, CH3 (7), Fc, CH3 (8), Fc, Ph (9) and Fc, Fc (10) by means of cyclic voltammetry in CH3CN shows Rh(I) being oxidized in an electrochemically irreversible two-electron transfer process at a lower oxidation potential than Fe. Relationships between the electrochemical oxidation potential of rhodium (Epa) and experimental oxidation potential (as measured by the second order oxidative addition rate constant k2), density functional theory calculated charges and energies (ΣQMulliken, ΣQHirshfeld, ΣQMDC, ΣQBader, ΣQNPA, ionization potential and EHOMO) and electronic parameters of the β-diketonato ligand RCOCHCOR′ (electronegativities (χR + χR′), pKa, Hammett meta substituent constants (σR + σR′) and Lever electronic parameter EL) of [Rh(β-diketonato)(P(OPh)3)2] complexes 1-10, show that Epa can be predicted with a high degree of accuracy for related [Rh(β-diketonato)(P(OPh)3)2] complexes.