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A Two-State Reactivity Model Explains Unusual Kinetic Isotope Effect Patterns in C[BOND]H Bond Cleavage by Nonheme Oxoiron(IV) Complexes

Authors

  • Eric J. Klinker Dr.,

    1. Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455 (USA), Fax: (+1) 612-624-7029
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  • Sason Shaik Prof. Dr.,

    1. Department of Organic Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem, 91904 (Israel), Fax: (+972) 2-658-4680
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  • Hajime Hirao Dr.,

    1. Department of Organic Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem, 91904 (Israel), Fax: (+972) 2-658-4680
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  • Lawrence Que Jr. Prof. Dr.

    1. Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455 (USA), Fax: (+1) 612-624-7029
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  • We thank the National Institutes of Health (GM-33162 to L.Q.), the University of Minnesota Graduate School (dissertation fellowship to E.J.K.), the Ministry of Education and Research within the Framework of the German–Israeli Project Cooperation (DIP; to S.S.), and the JSPS Postdoctoral Fellowship for Research Abroad (to H.H.) for support of this research.

Abstract

It's in the bond: The cleavage of C[BOND]H bonds by two related oxoiron(IV) complexes shows a range of kinetic isotope effect (KIE) values that exhibit an unusual dependence on the C[BOND]H bond strength. Large nonclassical KIEs are observed for bond strengths below 93 kcal mol−1, while semiclassical values are found above this value (see graph, DHA=9,10-dihydroanthracene). This nonintuitive behavior can be rationalized by invoking a two-state reactivity model.

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