Atom transfer and electron exchange processes with cobalt complexes

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The results of some investigations of several redox processes involving cobalt complexes are presented. For the first group of reactions below, oxidation appears to be accomplished in a single act by the direct addition of the oxidizing atom or group to the cobaltous complex: On the other hand, cases studied which appear to involve an electron transfer type of process include: (1) Co(CN)5−3+Fe(CN)6−3+H2O= [Co(CN)5(H2O)]−2+Fe(CN)6−4 (2) Co(C2O4)3−4+Ce(IV)=Co(C2O4)5−3+Ce(III) (3) CoV−2+Fe(CN)5−3=CoV−1+Fe(CN)6−4 (V=ethylene diaminetetracetate) (4) Co*(C2O4)3−4+Co(C2O4)3−3 = exchange (5) Co V−2+Co*V−1 = exchange Reactions of the first type are generally faster than those of the second, and possible explanations are discussed, along with some details of the kinetics of the reactions and a description of the several new complexes involved. In particular, an examination of the energy level diagrams predicted by Crystal Field Theory provides some explanation of the slowness of the electron transfer processes.