Derivative Cyclic Voltammetry: Applications in the Investigation of the Energetics of Organometallic Electrode Reactions

Abstract

Derivative cyclic voltammetry (DCV) can offer significant advantages in the investigation of electrode reactions when compared with conventional cyclic voltammetry (CV). Redox potentials can be accurately determined for incorporation in thermochemical cycles that allow for the determination of thermodynamic quantities that are of interest to organometallic chemists. Applications towards the determination of solution bond dissociation energies and Bronsted acidities for metal hydrides and metal hydride cation radicals are presented. However, perhaps the greatest advantages of DCV arise from the absence of double-layer charging currents in the derivative voltammograms. This effect makes the technique especially suitable for kinetic and mechanistic studies of the reactions of electrode-generated reactive intermediates. The use of DCV for this purpose is highlighted with case studies from our laboratories. This includes the substitution of one- and two-electron donors in 17-electron cation radicals by two-electron donor nucleophiles. Kinetic parameters show that both types of processes appear to involve 19-electron intermediates or transition states. Also included are some rather unusual reactions that proceed via initial reversible cation radical dimerization.