As part of a broader effort aimed at understanding the kinetics of multielectron-transfer processes, especially at electrochemical interfaces, we have been exploring the chemistry of dioxorhenium-(V) species.1-3 With pyridyl (py) or bipyridyl (bpy) moieties as ancillary ligands, these species are oxidizable by one electron, 1a, b, 2h and reducible by two or even three electrons with uptake of an equivalent number of protons, 1a, b, 2h e.g.:4 (formula omitted) In an earlier report on the synthesis, spectroscopy, and electrochemical thermodynamics of the first cis complexes, we noted qualitatively (single-sweep-rate cyclic voltammetry peak separation measurements) that the kinetic reversibility of reaction 1 b is much greater than that of reaction la.1a We further suggested that the reactivity difference could be due, in part, to differences in thermodynamic accessibility for the kinetic intermediate state, Re(IV).1a We now wish to report in preliminary detail (1) the mechanisms for electrochemical reduction of cis-and trans-di-oxorhenium(V) species in acidic and neutral solutions and (2) quantitative measures of the electrochemical exchange kinetics at near-neutral pH*.5 From (1) and (2) we indeed find that access to Re(IV) is an important factor in differentiating cis/ trans electrochemical kinetics and, further, that a semiquantitative reactivity analysis is possible based on comparisons to isoelectronic osmium species.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry