Surprising and often unprecedented chemistry is evident for organometallic complexes of metalloporphyrins.(1) This is clearly the case for alkyl/aryl complexes of paramagnetic iron(III) porphyrins that exhibit the following atypical reactivities : (i) reversible migration of the alkyl/aryl ligand from the metal center to a porphyrin pyrrole nitrogen;(2) (ii) hydrometalation of alkynes to give sigma-vinyliron(III) porphyrins;(3) (iii) "insertion" of dioxygen into the Fe-C bond of alkyl/aryl-iron(III) porphyrins to give a transient organic peroxide complex;(4) (iv) "insertion" of CO,(5,6) CO2,(5) and SO27 into the Fe-C bond of alkyliron(III) porphyrins; and (v) a novel alkyl group free radical "inter-change" with alkyl halides.(8) Mechanistic investigations of the CO "insertion" and alkyl group interchange reactions reveal a facile thermal homolysis of the Fe-C bond as an initial step.(5,6,8) The reverse reaction is nearly diffusion controlled on the basis of pulsed radiolysis measurements.(9)??