The Diverse Reactivity of Peroxy Ferric Porphyrin Complexes of Electron-Rich and Electron-Poor Porphyrins

Abstract

A systematic study of the properties and reactivities of iron(III) porphyrin peroxo complexes containing ligands with different electronic properties has been undertaken. While the spectral properties of the peroxo complexes do not show much variation, the stability of the complexes is dramatically increased by employing very electron-poor ligands such as 5,10,15,20-(pentafluorophenyl)porphyrin. The nucleophilicity of the peroxo moiety is decreased considerably by such electron-poor ligands: unlike all other iron(III) porphyrin peroxo complexes examined here, the perfluorinated peroxo complex does not epoxidize electron-poor olefins. However, this complex appears to have an unusually strong desire for a second axial ligand: it binds reversibly to triphenylphosphine. This interesting binding pattern is also observed for the perfluorinated iron−chloro complex. None of the complexes are capable of reacting with electron-rich olefins such as tetramethylethylene or with triphenylphosphine. Possible transition states for nucleophilic epoxidation are discussed.

cis-Dihydroxylation of Olefins by a Non-Heme Iron Catalyst: A Functional Model for Rieske Dioxygenases

“…An attractive hypothesis is the involvement of an h 2 -peroxo intermediate, which can only be derived from an iron complex with two labile sites cis to one another (Scheme 1). The few known Fe III (h 2 -O 2 2À ) species are unreactive as electrophiles [21,22] and are said to be activated by protonation. [21,23] À , and RuO 4 that effect the cis-dihydroxylation of alkenes.…”

Naphthalene Oxidation by Peracetic Acid Catalysed by Mn(III) Porphine-like Complexes: Nature of Intermediates and Pathways of their Formation

“…4) As mentioned already, Mn oxene complex formation is well known for Mn porphyrin complexes in their interaction with oxidants [13,25]. Recently [12] we obtained evidence of such complex formation in PMnCl (PONPc, TDCPP, TAP) interaction with [27,28] and characterized as a product of PorMn(III) interaction with KO 2 .À [29,30]; they have also been detected in PorFe reactions both with O 2 [31] and with tertbutylhydroperoxide in the presence of 2-methyimidazole [32]. Recently [30], peroxoiron(III)-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin was isolated in the solid state.…”

“…5). The inertness of peroxo complexes in typical olefin epoxidation has been noticed for Fe porphyrin derivatives [29,30,40].…”

“…Recently [12] we obtained evidence of such complex formation in PMnCl (PONPc, TDCPP, TAP) interaction with [27,28] and characterized as a product of PorMn(III) interaction with KO 2 .À [29,30]; they have also been detected in PorFe reactions both with O 2 [31] and with tertbutylhydroperoxide in the presence of 2-methyimidazole [32]. Recently [30], peroxoiron(III)-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin was isolated in the solid state. We suppose that the peroxo complex ONPcMn(O 2 )(X) formed in the catalytic system ONPcMnCl AcOOH Nf may produce the wellknown 1,4-peroxy-1,4-dihydronaphthalene (intermediate 4, reaction 3, Scheme 2), interaction of which with the Mn oxene complex leads to 3 (reaction 4, Scheme 2).…”

Transition Metal Peroxides. Synthesis and Role in Oxidation Reactions*Dedicated, on the occasion of his 80th birthday, to our ‘vitae ac studiorum magister in secunda et in adversa fortuna’ Emeritus Professor Giorgio Modena, Padova University, who showed us the way toward Chemistry.

“…Epoxidation of 2-cyclohexen-1-one and 2-methyl-1,4-naphthoquinone was observed, in 25 and 75% yield respectively, with the extremely nucleophilic Fe(III) complex 258,259 . These results opened new perspectives in the oxidation mechanisms of some enzymatic reactions.…”