Dioxygen Insertion into Iron(III)-Carbon Bonds. NMR Studies of the Formation and Reactivity of Alkylperoxo Complexes of Iron(III) Porphyrins

Article abstract of DOI:10.1021/ja00194a031

The behavior of PFe^IIICHR2 (P is a porphyrin dianion) in solution especially in the presence of dioxygen has been examined by (1)H and (2)H NMR measurements.Evidence for the photolytic Fe-C bond homolysis with the formation of PFe^II is presented.Addition of dioxygen to PFeCH2R produces two unstable intermediates, PFe^IIIO2CH2R and PFe^IIIOH, which may be directly observed at low temperatures.These form and decompose through the following reactions: PFe^IIICH2R + O2 -> PFe^IIIO2CHR2; PFe^IIIO2CHR2 -> PFe^IIIOH + O=CR2; 2PFe^IIIOH -> PFe^IIIOFe^IIIP + H2O.The formation of the product aldehyde or ketone has been established for methyl, ethyl, isopropyl, n-propyl, and benzyl ligands axially coordinating iron.The dioxygen insertion is retarded by the coordination of N-methylimidazole to the sixth iron coordination site or by employing a sterically encumbered porphyrin.PFe^IIIOH catalyzes the decomposition of ethyl hydroperoxide to give acetaldehyde as the major organic product.