FORMATION OF THE TRIBUTYLTIN IRON(III) PORPHYRIN COMPLEX BY A FREE-RADICAL PROCESS

Surprising and often unprecedented chemistry is evident for organometa llic complexes of metalloporphyrins.(1) This is clearly the case for a lkyl/aryl complexes of paramagnetic iron(III) porphyrins that exhibit the following atypical reactivities: (i) reversible migration of the a lkyl/aryl ligand from the metal center to a porphyrin pyrrole nitrogen ;(2) (ii) hydrometalation of alkynes to give sigma-vinyliron(III) porp hyrins;(3) (iii) ''insertion'' of dioxygen into the Fe-C bond of alkyl /aryl-iron(III) porphyrins to give a transient organic peroxide comple x;(4) (iv) ''insertion'' of CO,(5,6) CO2,(5) and SO27 into the Fe-C bo nd of alkyliron(III) porphyrins; and (v) a novel alkyl group free radi cal ''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 p ulsed radiolysis measurements.(9)