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Wang, Bin,Lee, Yong-Min,Clé,mancey, Martin,Seo, Mi Sook,Sarangi, Ritimukta,Latour, Jean-Marc,Nam, Wonwoo American Chemical Society 2016 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.138 No.7
<P>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 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 degrees 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 ((H2O)-O-13) experiments, incorporation of 180 from (H2O)-O-18 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.</P>
Lu, Xiaoyan,Li, Xiao-Xi,Seo, Mi Sook,Lee, Yong-Min,Clé,mancey, Martin,Maldivi, Pascale,Latour, Jean-Marc,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.1
<P>A mononuclear nonheme iron(IV)-amido complex bearing a tetraamido macrocyclic ligand, [(TAML)Fe<SUP>IV</SUP>(NHTs)]<SUP>−</SUP> (<B>1</B>), was synthesized via a hydrogen atom (H atom) abstraction reaction of an iron(V)-imido complex, [(TAML)Fe<SUP>V</SUP>(NTs)]<SUP>−</SUP> (<B>2</B>), and fully characterized using various spectroscopies. We then investigated (1) the p<I>K</I><SUB>a</SUB> of <B>1</B>, (2) the reaction of <B>1</B> with a carbon-centered radical, and (3) the H atom abstraction reaction of <B>1</B>. To the best of our knowledge, the present study reports for the first time the synthesis and chemical properties/reactions of a high-valent iron(IV)-amido complex.</P> [FIG OMISSION]</BR>
Cho, Kangwoo,Qu, Yan,Kwon, Daejung,Zhang, Hao,Cid, Clé,ment A.,Aryanfar, Asghar,Hoffmann, Michael R. American Chemical Society 2014 Environmental science & technology Vol.48 No.4
<P>We have investigated electrochemical treatment of real domestic wastewater coupled with simultaneous production of molecular H<SUB>2</SUB> as useful byproduct. The electrolysis cells employ multilayer semiconductor anodes with electroactive bismuth-doped TiO<SUB>2</SUB> functionalities and stainless steel cathodes. DC-powered laboratory-scale electrolysis experiments were performed under static anodic potentials (+2.2 or +3.0 V NHE) using domestic wastewater samples, with added chloride ion in variable concentrations. Greater than 95% reductions in chemical oxygen demand (COD) and ammonium ion were achieved within 6 h. In addition, we experimentally determined a decreasing overall reactivity of reactive chlorine species toward COD with an increasing chloride ion concentration under chlorine radicals (Cl·, Cl<SUB>2</SUB><SUP>–</SUP>·) generation at +3.0 V NHE. The current efficiency for COD removal was 12% with the lowest specific energy consumption of 96 kWh kgCOD<SUP>–1</SUP> at the cell voltage of near 4 V in 50 mM chloride. The current efficiency and energy efficiency for H<SUB>2</SUB> generation were calculated to range from 34 to 84% and 14 to 26%, respectively. The hydrogen comprised 35 to 60% by volume of evolved gases. The efficacy of our electrolysis cell was further demonstrated by a 20 L prototype reactor totally powered by a photovoltaic (PV) panel, which was shown to eliminate COD and total coliform bacteria in less than 4 h of treatment.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-4/es404137u/production/images/medium/es-2013-04137u_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es404137u'>ACS Electronic Supporting Info</A></P>
Achieving One-Electron Oxidation of a Mononuclear Nonheme Iron(V)-Imido Complex
Hong, Seungwoo,Lu, Xiaoyan,Lee, Yong-Min,Seo, Mi Sook,Ohta, Takehiro,Ogura, Takashi,Clé,mancey, Martin,Maldivi, Pascale,Latour, Jean-Marc,Sarangi, Ritimukta,Nam, Wonwoo American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.41
<P>A mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe<SUP>V</SUP>(NTs)(TAML)]<SUP>−</SUP> (<B>1</B>), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe<SUP>V</SUP>(NTs)(TAML<SUP>+•</SUP>)] (<B>2</B>); <B>2</B> is a diamagnetic (<I>S</I> = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (<I>S</I> = 1/2) with the one-electron oxidized ligand (TAML<SUP>+•</SUP>). <B>2</B> is a competent oxidant in C–H bond functionalization and nitrene transfer reaction, showing that the reactivity of <B>2</B> is greater than that of <B>1</B>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-41/jacs.7b08161/production/images/medium/ja-2017-081612_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b08161'>ACS Electronic Supporting Info</A></P>