The electrooxidation of the tetraphenylborate ion revisited

The electrochemistry of the tetraphenylborate ion, BPh4−, has been studied by cyclic voltammetry and coulometry in water, methanol, ethanol, acetonitrile, acetone, dimethylformamide and dichloromethane under an N2 atmosphere. While a one-electron and somewhat irreversible oxidation (with an E1/2 of 0.87 V vs. SCE at a glassy carbon electrode) is observed in dichloromethane, eqn. (i), the oxidation is somewhat complicated in all other solvents by the occurrence of several consecutive reactions. Epa, the anodic peak potential in cyclic voltammetry, changes from 0.41 V vs. SCE in water to 0.94 V vs. SCE in dimethylformamide at a glassy carbon electrode. The variation in Epa with solvent (S) is explained by invoking reaction (ii). The coulometric results in solvents other than dichloromethane indicate a disproportionation of S–BPh3, eqn. (iii).