Redox properties of cobalt chelates with delocalised electronic structure
Abstract
Polarographic techniques are employed to investigate the effect of ligand on the formal redox couples cobalt(III)–cobalt(II) and cobalt(II)–cobalt(I) in cobalt complexes having tetradentate Schiff's bases or dimethylglyoximato-di-anions as equatorial chelating ligands and Lewis bases as axial ligands. Fast electrode reactions show that the electron is accepted into a delocalised molecular orbital in both reduction processes. Increasing delocalisation on to the equatorial ligand shifts the redox potential towards less cathodic values. The effect of charge donated by axial ligands is apparent since a linear relationship between pKa values and the polarographic half-wave potential of the cobalt(III)–cobalt(II) couples is obtained.
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