Redox properties of cobalt chelates with delocalized electronic structure: organometallic derivatives

Abstract

Polarographic techniques are employed to investigate the electrode processes and to point out the influence of equatorial and axial ligands on the half-wave potentials of reversible electron transfers corresponding to formal redox couples Co^III→ Co^II, Co^II→ Co^I, and to one-electron oxidation, in some series of organometallic cobalt chelates. Free-energy relationships are found between the E_½ and the pK_a values of the hydrocarbon acid corresponding to the organic group in the axial position, showing that the effect is due to charge donation from the organic group, decreasing the electron affinity of the particle. The change of equatorial ligand has a parallel effect of E_½ of both reduction and oxidation waves.