Reversible cobalt-nitrogen alkyl and acyl group migration in cobalt porphyrins

Article abstract of DOI:10.1021/ic50226a061

The one-electron electrochemical oxidation of ethyl(5,10,15,20-tetraphenylporphinato)cobalt(III) (EtCo^IIITPP) causes intramolecular rearrangement of the ethyl group to give (N-ethyl-5,10,15,20-tetraphenylporphinato)cobalt(II) (N-EtCo^IITPP)⁺. Sodium borohydride reduction of N-EtCo^IITPP⁺ regenerates EtCo^IIITPP 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 EtCo^IIITPP) one-electron oxidative rearrangement to (N-(ethoxycarbonyl)-5,10,15,20-tetraphenylporphinato)cobalt(II), showed that the initial site of oxidation is at the porphyrin ring to give the corresponding π-cation radical. In this case the cobalt to nitrogen migration occurs upon warming a solution of the π-cation radical.