title: Mononuclear Nonheme High-Spin Iron(III)-Acylperoxo Complexes in Olefin Epoxidation and Alkane Hydroxylation Reactions.
abstract: Mononuclear nonheme high-spin iron(III)-acylperoxo complexes bearing an N-methylated cyclam ligand were synthesized, spectroscopically characterized, and investigated in olefin epoxidation and alkane hydroxylation reactions. In the epoxidation of olefins, epoxides were yielded as the major products with high stereo-, chemo-, and enantioselectivities; cis- and trans-stilbenes were oxidized to cis- and trans-stilbene oxides, respectively. In the epoxidation of cyclohexene, cyclohexene oxide was formed as the major product with a kinetic isotope effect (KIE) value of 1.0, indicating that nonheme iron(III)-acylperoxo complexes prefer C═C epoxidation to allylic C-H bond activation. Olefin epoxidation by chiral iron(III)-acylperoxo complexes afforded epoxides with high enantioselectivity, suggesting that iron(III)-acylperoxo species, not high-valent iron-oxo species, are the epoxidizing agent. In alkane hydroxylation reactions, iron(III)-acylperoxo complexes hydroxylated C-H bonds as strong as those in cyclohexane at -40 °C, wherein (a) alcohols were yielded as the major products with high regio- and stereoselectivities, (b) activation of C-H bonds by the iron(III)-acylperoxo species was the rate-determining step with a large KIE value and good correlation between reaction rates and bond dissociation energies of alkanes, and (c) the oxygen atom in the alcohol product was from the iron(III)-acylperoxo species, not from molecular oxygen. In isotopically labeled water (H2(18)O) experiments, incorporation of (18)O from H2(18)O into oxygenated products was not observed in the epoxidation and hydroxylation reactions. On the basis of mechanistic studies, we conclude that mononuclear nonheme high-spin iron(III)-acylperoxo complexes are strong oxidants capable of oxygenating hydrocarbons prior to their conversion into iron-oxo species via O-O bond cleavage.
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Lee
authors.affiliation: University of Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB , 38000 Grenoble, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Clémancey
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Mi Sook
authors.initials: MS
authors.lastname: Seo
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025-7015, United States.
authors.forename: Ritimukta
authors.initials: R
authors.lastname: Sarangi
authors.affiliation: University of Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB , 38000 Grenoble, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Latour
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Nam
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry
chemical_list: D000473:Alkanes; D000475:Alkenes; D004852:Epoxy Compounds; D005290:Ferric Compounds; D014867:Water