Radical mechanisms cobalt macrocycle

The availability of only one coordination site due to the large rigid equatorial ligand of the cobalt porphyrin macrocycle would appear to make such an intermediate unlikely. Viewed as a transition state with a large component of C—H bond formation, the Co—C bond formation would occur later in the process. In the extreme of complete C—H bond formation prior to Co—C formation, the intermediate is indistinguishable from a radical mechanism. 

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