The electrochemical oxidation of tris (2,4,6-tri-methyl-phenyl) phosph
ine (TMP) in acetonitrile was investigated on a platinum electrode. A
fast mono-electronic transfer (E-p = 0.71 V vs sce) gives rise to the
corresponding long-lived phosphoniumyl cation radical. This electroche
mically generated radical undergoes a slow reaction with residual wate
r, generating the corresponding phosphine oxide (TMPO) and hydro phosp
honium (TMPH+). The kinetics of the decay of the cation radical has be
en studied, and a reaction mechanism is proposed. When TMP is oxidized
on a platinum electrode at potentials higher than 1.5 V vs see, a fas
t surface reaction involving residual water takes place. This process
was studied by voltammetry at a rotating ring-disk electrode; the same
products, TMPO and TMPH+ were formed. (C) 1997 Elsevier Science Ltd.