A study of the anodic voltammetric properties of triphenylphosphine

Abstract

Although several bulk electrolysis studies of the electro-oxidation of triphenylphosphine (Ph 3P) have been published, and its products, triphenilphosphonium salts and triphenylphosphine oxide are well characterized, only scant and qualitative information on its anodic voltammetric properties is available. The voltammetric behavior of Ph 3P in acetonitrile solutions, using vitreous carbon anodes, is studied in detail. Results using dimethylformamide solvent with vitreous carbon and platinum anodes are also reported and compared. In ACN solution, with vitreous carbon anodes, the radical cation formed in the first electron transfer step reacts with residual water. A one-electron, diffusional, EC errev voltammetric peak is observed for the anodic electro-oxidation of Ph 3P at sweep rates higher than 0.020 Vs −1. The effect of a second charge transfer is experimentally observed at lower sweep rates. Implicit finite difference-simulated voltammograms are calculated to reproduce the results. The protonation reaction of Ph 3P is demonstrated to be slow in the time scale of cyclic voltammetry, but it is catalyzed by the Pt anode, where Ph 3P adsorption is also observed. Ph 3P is voltammetrically electro-oxidated in DMF in a two-electron E 1C 1E 2 process with E 2 ⩽ E 1. Diffusion coefficents for Ph 3P, based on these anodic voltammetric measurements, which agree with the known polarographic values, are given for the first time.