C-H bond oxidation catalyzed by an imine-based iron complex: A mechanistic insight
dc.contributor.author
dc.date.accessioned
2016-03-14T12:00:55Z
dc.date.available
2016-03-14T12:00:55Z
dc.date.issued
2015
dc.identifier.issn
0020-1669
dc.identifier.uri
dc.description.abstract
A family of imine-based nonheme iron(II) complexes (LX)2Fe(OTf)2 has been prepared, characterized, and employed as C-H oxidation catalysts. Ligands LX (X = 1, 2, 3, and 4) stand for tridentate imine ligands resulting from spontaneous condensation of 2-pycolyl-amine and 4-substituted-2-picolyl aldehydes. Fast and quantitative formation of the complex occurs just upon mixing aldehyde, amine, and Fe(OTf)2 in a 2:2:1 ratio in acetonitrile solution. The solid-state structures of (L1)2Fe(OTf)(ClO4) and (L3)2Fe(OTf)2 are reported, showing a low-spin octahedral iron center, with the ligands arranged in a meridional fashion. 1H NMR analyses indicate that the solid-state structure and spin state is retained in solution. These analyses also show the presence of an amine-imine tautomeric equilibrium. (LX)2Fe(OTf)2 efficiently catalyze the oxidation of alkyl C-H bonds employing H2O2 as a terminal oxidant. Manipulation of the electronic properties of the imine ligand has only a minor impact on efficiency and selectivity of the oxidative process. A mechanistic study is presented, providing evidence that C-H oxidations are metal-based. Reactions occur with stereoretention at the hydroxylated carbon and selectively at tertiary over secondary C-H bonds. Isotopic labeling analyses show that H2O2 is the dominant origin of the oxygen atoms inserted in the oxygenated product. Experimental evidence is provided that reactions involve initial oxidation of the complexes to the ferric state, and it is proposed that a ligand arm dissociates to enable hydrogen peroxide binding and activation. Selectivity patterns and isotopic labeling studies strongly suggest that activation of hydrogen peroxide occurs by heterolytic O-O cleavage, without the assistance of a cis-binding water or alkyl carboxylic acid. The sum of these observations provides sound evidence that controlled activation of H2O2 at (LX)2Fe(OTf)2 differs from that occurring in biomimetic iron catalysts described to dat
dc.description.sponsorship
This work was also partially supported by Università di Roma La Sapienza- Area Supporto alla Ricerca (Progetti di Ricerca 2014 and Avvio alla Ricerca 2014). M.C. acknowledges financial support from ERC-2009-StG-239910 (to M.C.), the Spanish Ministry of Science (Nos. CTQ2012-37420-C02-01/BQU and CSD2010-00065, to M.C.) and Generalitat de Catalunya (ICREA Academia Award and No. SGR-862
dc.format.mimetype
application/pdf
dc.language.iso
eng
dc.publisher
American Chemical Society (ACS)
dc.relation
MICINN/PN 2010-2016/CSD2010-00065
info:eu-repo/grantAgreement/MINECO//CTQ2012-37420-C02-01/ES/DISEÑO BIOINSPIRADO DE CATALIZADORES PARA LA OXIDACION DE ENLACES C-H, C=C Y AGUA/
AGAUR/2014-2016/2014 SGR-862
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Reproducció digital del document publicat a: http://dx.doi.org/10.1021/acs.inorgchem.5b01500
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© Inorganic Chemistry, 2015, vol. 54, núm. 21, p. 10141-10152
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Articles publicats (D-Q)
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Tots els drets reservats
dc.title
C-H bond oxidation catalyzed by an imine-based iron complex: A mechanistic insight
dc.type
info:eu-repo/semantics/article
dc.rights.accessRights
info:eu-repo/semantics/embargoedAccess
dc.embargo.terms
Cap
dc.date.embargoEndDate
info:eu-repo/date/embargoEnd/2026-01-01
dc.relation.projectID
info:eu-repo/grantAgreement/EC/FP7/239910/EU/Bio-inspired Design of Catalysts for Selective Oxidations of C-H and C=C Bonds/BIDECASEOX
dc.type.version
info:eu-repo/semantics/publishedVersion
dc.identifier.doi
dc.identifier.idgrec
023702
dc.contributor.funder
dc.relation.FundingProgramme
dc.relation.ProjectAcronym
dc.identifier.eissn
1520-510X