Synthesis, characterization, electrochemistry, DFT and kinetic study of the oligothiophene-containing complex [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)

Abstract

The synthesis, electrochemistry, oxidative addition kinetics and computational chemistry study are presented for the [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] complex. Through chemical and electrochemical oxidation, this rhodium triphenylphosphine complex was converted from rhodium(I) to a rhodium(III) complex. The chemical kinetics, studied by the NMR, UV/Vis and IR, of the oxidative addition of CH3I to [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] indicated the formation of rhodium(III) alkyl 1, rhodium(III) acyl 1 and rhodium(III) alkyl 2 isomers respectively. A theoretical density functional theory study shed light on the geometry of the different reactants, transition states and reaction products. The second order rate constant of the [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] + CH3I oxidative addition reaction is 0.0027 mol−1 dm3 s−1 in CHCl3 at 25 °C. A linear relationship was established between the irreversible electrochemical oxidation potential of rhodium(I), Epa(Rh) and the second order rate constant of the oxidative addition reaction for a series of 17 different [Rh(β-diketonato)(CO)(PPh3)] complexes.