CONTROLLING VALENCE TAUTOMERISM OF COBALT COMPLEXES CONTAINING THE BENZOSEMIQUINONE ANION AS LIGAND

The transformation from Co(II) to Co(III) (e.g., 1 --> 2) is displayed by the compounds of type 1 in solution when the temperature is lowered (L is a bidentate N-donor ligand with a diimine structure, 3,5-dtbsq- the 3,5-di-tert-butylbenzosemiquinone anion, and 3,5-dtbcat- the corresponding catecholate ion). In the process one electron is transferred from the Co center to one of the 3,5-dtbsq- ligands to form the catecholate ligand. Microcrystalline samples in which L is phenanthroline undergo the transformation abruptly at about 240 K.