Electrochemical reactions of pincer rhodium(I) complexes

• One electron oxidation of the Rh–H2 complex is observed in non-coordinating solvents.
• Reactivity is dominated by solvent upon oxidation in coordinating solvents.
• A mechanism to explain this reactivity is proposed and supported computationally.

The electrochemical properties of the (PCP)RhI(H2) (1-H2, PCP = κ3-C6H3–2,6-(CH2P(tBu2)) complex was examined by cyclic voltammetry in acetonitrile (MeCN), dimethylsulfoxide (DMSO) and 1,2-difluorobenzene (1,2-DFB). Upon oxidation in weakly or non-coordinating media such as 0.05 M NaBArF24 in 1,2-difluorobenzene, simple one electron oxidation to [(PCP)RhII(H2)]+ is observed. Conversely, in coordinating solvents (e.g. acetonitrile and dimethylsulfoxide) the reactivity is dominated by solvent coordinated species with a slight variation in the RhIII/II oxidation potentials as a function of the supporting electrolyte conductivity. A computational analysis of these reactions in support of the proposed mechanism is presented.

Oxidation of (PCP)RhI(H2) (1-H2, PCP = κ3-C6H3–2,6-(CH2P(tBu2)) in non-coordinating media such as 1,2-difluorobenzene results in simple one electron oxidation to [(PCP)RhII(H2)]+. In coordinating solvents (e.g. acetonitrile and dimethylsulfoxide) reactivity is dominated by solvent coordinated species. A computational analysis of these reactions in support of the proposed mechanism is presented.Figure optionsDownload as PowerPoint slide