The Relationship between the Electrochemical and Chemical Oxidation of Ferrocene‐Containing Carbonyl‐Phosphane‐β‐Diketonato‐Rhodium(I) Complexes – Cytotoxicity of [Rh(FcCOCHCOPh)(CO)(PPh3)]

Ferrocene‐containing rhodium(I) complexes of the type [Rh(FcCOCHCOR)(CO)(PPh3)] with R = Fc (ferrocenyl), 1, Ph (phenyl), 2, CH3, 3, and CF3, 4, have been studied by cyclic voltammetry (CV) and bulk electrolysis techniques in CH3CN. Two isomers for complexes 2–4 were detected. Results are consistent with RhI being oxidised first in an electrochemically irreversible two‐electron transfer process, followed by the electrochemical reversible oxidation of each ferrocenyl group in a one‐electron transfer process at slightly larger potentials. Only the Epa(Rh) CV peaks resolved into two separate waves, each one being associated with an isomer. Slow isomerisation kinetics allowed the detection of two isomers of 2–4. Epa(Rh) and other compound physical parameters relates to the second‐order rate constant for the oxidative addition of CH3I to complexes 1–4 in acetone. Rhodium(III) reduction of oxidised 1, 2, 3 and 4 was observed at large negative potentials, while for [Rh(FcCOCHCOCF3)(CH3)(I)(CO)(PPh3)] (9) it was observed at –1.492 V vs. Fc/Fc+. Complex 2 was slightly more cytotoxic than the free FcCOCH2COPh ligand but less cytotoxic than cisplatin.