Synthesis and electrochemistry of p-substituted phenyl diphenylphosphinite rhodium(I) complexes

A series of para-substituted phenyl diphenylphosphinite-containing rhodium(I) complexes of the form [Rh(CH3COCHCOCH3)CO(Ph2POPh-p-R)], where R = H (1), CH3 (2), tBu(3) and Cl(4)] were prepared. The electrochemical data obtained for this series, showed the oxidation of both the two electron oxidation of the Rh(I) to Rh(III) and the one electron oxidation of the phosphorus moiety are dependent on the group-electronegativity of the respective para-R-substituent. An unexpected reaction of the phosphinite occurred with the electrochemical internal standard ferrocene, in its ferricinium-ion form. XPS characterisation of the rhodium(I) complexes revealed a linear correlation between the binding energies of both the rhodium 3d5/2 and phosphorus 2p electron levels and the Gordy group electronegativity of the R-group.51