The one-electron electrochemical oxidation of ethyl (5,10,15,20-tetraphenylporphinato)cobalt(III) (EtComTPP) causes intramolecular rearrangement of the ethyl group to give (,-V-ethyl-5,10,15,20-tetraphenylporphinato)cobalt(II) (Ar-EtCoI1TPP)+. Sodium borohydride reduction of vV-EtConTPP+ regenerates EtComTPP but by an intermolecular rearrangement. Low-temperature studies on (ethoxycarbonyl) (5,10,15,20-tetraphenylporphinato)cobalt(III), which also exhibits (but at a slower rate than that of EtComTPP) one-electron oxidative rearrangement to (yV-(ethoxycarbonyl)-5,10,15,20-tetraphenylporphinato)cobalt(II), showed that the initial site of oxidation is at the porphyrin ring to give the corresponding ir-cation radical. In this case the cobalt to nitrogen migration occurs upon warming a solution of the -cation radical.The redox chemistry of organocobalt compounds is an area of current interest, especially in the context of the chemistry of vitamin B12. Electrochemical parameters have been reported for organo derivatives of cobalamins,1"4 cobinamides,1"3 cobaloximes,5 and cobalt Schiffs bases.6•7Chemical and electrochemical reduction of organocobalt complexes usually results in cleavage of the cobalt-carbon bond.8•9 Oxidation may also cleave this bond, yielding a variety of products; however, in the case of the cobaloximes,5•10 the initial oneelectron oxidation product of the organocobaloximes has been stabilized at low temperatures and EPR measurements indicate that this species is best described as an organocobalt(IV) complex.5•11"13We wish to report that one-electron electrochemical oxidation of organocobalt(III) porphyrins results inter alia in the migration of the organo group from cobalt to a nitrogen of the porphyrin macrocycle. A migration of this type has not, to our knowledge, been previously observed for organocobalt complexes. Moreover, subsequent reduction of the N-substituted cobalt porphyrin results in the re-formation of the cobalt-carbon bond.Cyclic voltammetry on ethyl(5,10,15,20-tetraphenylporphinato)cobalt(III) (EtComTPP, 1) at a platinum electrode