Photoredox Reactions of the Binuclear Complex Ions [(NC) 5 Co(III)NCM(II)(CN) 5 ] 6‐ (M = Fe and Ru)

The electronic spectra of the complex ions [(NC) 5 Co(III)NCM(II)(CN) 5 ] 6‐ (M = Fe and Ru) exhibit absorption bands which are assigned to [Co(III) to M(II)] intervalence charge transfer (IT) transitions. There is strong evidence that upon irradiation of these bands the aqueous complexes underwent a redox reaction under formation of Co(II)(CN) 5 3‐ and M(III)(CN) 6 3‐ . In the absence of oxygen these intermediates regenerated the starting complexes in a thermal redox reaction. This reaction was used to prepare the binuclear complexes. It is suggested that the photochemical redox reaction as well as its thermal reversal are closely related processes. This relationship is discussed on the basis of a theoretical model. The complex Co(CN) 5 3‐ which is assumed to be formed as one of the primary products of the photolysis can be intercepted with oxygen. The analysis of the reaction products indicated that the reaction with oxygen produced [(NC) 5 CoO 2 Co(CN) 5 ] 6‐ which underwent further reactions.