title: High-valent iron in chemical and biological oxidations.
abstract: Various aspects of the reactivity of iron(IV) in chemical and biological systems are reviewed. Accumulated evidence shows that the ferryl species [Fe(IV)O](2+) can be formed under a variety of conditions including those related to the ferrous ion-hydrogen peroxide system known as Fenton's reagent. Early evidence that such a species could hydroxylate typical aliphatic C-H bonds included regioselectivities and stereospecificities for cyclohexanol hydroxylation that could not be accounted for by a freely diffusing hydroxyl radical. Iron(IV) porphyrin complexes are also found in the catalytic cycles of cytochrome P450 and chloroperoxidase. Model oxo-iron(IV) porphyrin complexes have shown reactivity similar to the proposed enzymatic intermediates. Mechanistic studies using mechanistically diagnostic substrates have implicated a radical rebound scenario for aliphatic hydroxylation by cytochrome P450. Likewise, several non-heme diiron hydroxylases, AlkB (Omega-hydroxylase), sMMO (soluble methane monooxygenase), XylM (xylene monooxygenase) and T4moH (toluene monooxygenase) all show clear indications of radical rearranged products indicating that the oxygen rebound pathway is a ubiquitous mechanism for hydrocarbon oxygenation by both heme and non-heme iron enzymes.
authors.affiliation: Department of Chemistry, Princeton University, Washington Road, Princeton, NJ 08544, USA. jtgroves@princeton.edu
authors.forename: John T
authors.initials: JT
authors.lastname: Groves
mesh_terms: D002384:Catalysis; D042926:Cytochrome P-450 CYP4A / Q000737:chemistry / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000737:chemistry; D006900:Hydroxylation; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008665:Metalloporphyrins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D019159:Nonheme Iron Proteins / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000737:chemistry / Q000378:metabolism
chemical_list: C045076:Fenton's reagent; D008024:Ligands; D008665:Metalloporphyrins; D019159:Nonheme Iron Proteins; C066317:ferryl iron; D030421:Peroxynitrous Acid; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; D007501:Iron; D010105:Oxygenases; D042926:Cytochrome P-450 CYP4A