The electrochemical oxidation of a series of [Rh(RCOCHCOR')(CO)(PPh3)] complexes studied in acetonitrile, containing 0.100 mol dm(-3) tetra-n-butylammonium hexafluorophosphate as supporting electrolyte, shows that Rh(I) is being oxidized in an electrochemically irreversible two-electron transfer process, at peak anodic potentials ranging from E-pa(Rh) = 0.29-0.57 V vs. FC/FC+. R and R' groups on the beta-diketonato ligand (RCOCHCOR') which are more electron withdrawing, reduce electron density on the rhodium atom to a larger extent than electron donating groups do. This leads to a higher, more positive, electrochemical oxidation potential, E-pa(Rh). Relationships were established between the electrochemical quantity, Epa(Rh), and chemical oxidation, in terms of the second order kinetic oxidative addition rate constant, k(2), as well as other parameters related to the electronic effect of the R and R' groups through conjugation on rhodium in [Rh(RCOCHCOR')(CO)(PPh3)]; such as the sum of the group electronegativities (Gordy Scale) of the R and R' groups (chi(R) (+) chi(R')), the Hammett meta sigma values (sigma(R) (+) sigma(R')) and the pK(a) of the free beta-diketone R'COCH2COR. E-pa can also be predicted by the density functional theory calculated HOMO energy and the two-electron adiabatic ionization potential, IP2e-, of these [Rh(RCOCHCOR')(CO)(PPh3)] complexes. (C) 2013 Elsevier Ltd. All rights reserved.