X‐ray Absorption Spectroscopic and Electrochemical Studies of Tris(catecholato(2−))chromate( V / IV / III ) Complexes

Contrary to popular belief, the redox chemistry of Cr–catecholato complexes [CrIII(cat)3]3− has been shown by X-ray absorption spectroscopic data to be predominantly metal-based and not ligand-based. The observed increase in the energies of the edge and pre-edge features of the spectra (see picture) and the decrease in the CrO bond lengths on oxidation are consistent with the formation of [CrIV(cat)3]2− and [CrV(cat)3]−, both with a strong electron delocalization between the metal ion and the ligands.