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Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds

Oxidation of the iron(II) precursor [(L(1))Fe(II)Cl(2)], where L(1) is a tetradentate bispidine, with soluble iodosylbenzene ((s)PhIO) leads to the extremely reactive ferryl oxidant [(L(1))(Cl)Fe(IV)=O](+) with a cis disposition of the chlorido and oxido coligands, as observed in non‐heme halogenase...

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Autores principales: Bleher, Katharina, Comba, Peter, Faltermeier, Dieter, Gupta, Ashutosh, Kerscher, Marion, Krieg, Saskia, Martin, Bodo, Velmurugan, Gunasekaran, Yang, Shuyi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9300152/
https://www.ncbi.nlm.nih.gov/pubmed/34792224
http://dx.doi.org/10.1002/chem.202103452
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author Bleher, Katharina
Comba, Peter
Faltermeier, Dieter
Gupta, Ashutosh
Kerscher, Marion
Krieg, Saskia
Martin, Bodo
Velmurugan, Gunasekaran
Yang, Shuyi
author_facet Bleher, Katharina
Comba, Peter
Faltermeier, Dieter
Gupta, Ashutosh
Kerscher, Marion
Krieg, Saskia
Martin, Bodo
Velmurugan, Gunasekaran
Yang, Shuyi
author_sort Bleher, Katharina
collection PubMed
description Oxidation of the iron(II) precursor [(L(1))Fe(II)Cl(2)], where L(1) is a tetradentate bispidine, with soluble iodosylbenzene ((s)PhIO) leads to the extremely reactive ferryl oxidant [(L(1))(Cl)Fe(IV)=O](+) with a cis disposition of the chlorido and oxido coligands, as observed in non‐heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron‐bound Cl(−). The time‐resolved formation of the halogenation product indicates that this primarily results from (s)PhIO oxidation of an initially formed oxido‐bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe(2+) and Fe(3+) in comparison with [(L(1))Fe(II)Cl(2)] indicate a high complex stability of the bispidine‐iron complexes. DFT analysis shows that, due to a large driving force and small triplet‐quintet gap, [(L(1))(Cl)Fe(IV)=O](+) is the most reactive small‐molecule halogenase model, that the Fe(III)/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects.
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spelling pubmed-93001522022-07-21 Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds Bleher, Katharina Comba, Peter Faltermeier, Dieter Gupta, Ashutosh Kerscher, Marion Krieg, Saskia Martin, Bodo Velmurugan, Gunasekaran Yang, Shuyi Chemistry Full Papers Oxidation of the iron(II) precursor [(L(1))Fe(II)Cl(2)], where L(1) is a tetradentate bispidine, with soluble iodosylbenzene ((s)PhIO) leads to the extremely reactive ferryl oxidant [(L(1))(Cl)Fe(IV)=O](+) with a cis disposition of the chlorido and oxido coligands, as observed in non‐heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron‐bound Cl(−). The time‐resolved formation of the halogenation product indicates that this primarily results from (s)PhIO oxidation of an initially formed oxido‐bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe(2+) and Fe(3+) in comparison with [(L(1))Fe(II)Cl(2)] indicate a high complex stability of the bispidine‐iron complexes. DFT analysis shows that, due to a large driving force and small triplet‐quintet gap, [(L(1))(Cl)Fe(IV)=O](+) is the most reactive small‐molecule halogenase model, that the Fe(III)/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects. John Wiley and Sons Inc. 2021-12-07 2022-01-19 /pmc/articles/PMC9300152/ /pubmed/34792224 http://dx.doi.org/10.1002/chem.202103452 Text en © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ (https://creativecommons.org/licenses/by-nc-nd/4.0/) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
spellingShingle Full Papers
Bleher, Katharina
Comba, Peter
Faltermeier, Dieter
Gupta, Ashutosh
Kerscher, Marion
Krieg, Saskia
Martin, Bodo
Velmurugan, Gunasekaran
Yang, Shuyi
Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title_full Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title_fullStr Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title_full_unstemmed Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title_short Non‐Heme‐Iron‐Mediated Selective Halogenation of Unactivated Carbon−Hydrogen Bonds
title_sort non‐heme‐iron‐mediated selective halogenation of unactivated carbon−hydrogen bonds
topic Full Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9300152/
https://www.ncbi.nlm.nih.gov/pubmed/34792224
http://dx.doi.org/10.1002/chem.202103452
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