Synthesis and unexpected electrochemical reaction of p-substituted phenyl diphenylphosphinites

A series of para-substituted phenyl diphenylphosphinites [Ph2POPh-p-R, where RH (1), CH3 (2), tBu (3) and Cl (4)] were prepared in near quantitative yields, by the reaction between the desired para-substituted phenol and chlorodiphenylphosphine, in the presence of triethylamine. The electrochemical data obtained for the phosphinite series, showed a one-electron oxidation of the free electron-pair of the phosphorous atom, as well as either the oxidation or the electrochemical decomposition of this phosphinite radical cation. The oxidation peak potential was found to be dependent on the group-electronegativity of the respective para-R-substituent. An unexpected reaction occurred between the electrochemical internal standard, free ferrocene, in its ferricinium ion form and the radical cation of the oxidized diphenyl phosphinite, leading to uncharacteristic electrochemical behaviour.