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Amide-based nonheme cobalt(III) olefin epoxidation catalyst: Partition of multiple active oxidants Co V=O, Co IV=O, and Co III-OO(O)CR

Title
Amide-based nonheme cobalt(III) olefin epoxidation catalyst: Partition of multiple active oxidants Co V=O, Co IV=O, and Co III-OO(O)CR
Authors
Song Y.J.Hyun M.Y.Lee J.H.Lee H.G.Kim J.H.Jang S.P.Noh J.Y.Kim Y.Kim S.-J.Lee S.J.Kim C.
Ewha Authors
김성진김영미
SCOPUS Author ID
김성진scopus; 김영미scopus
Issue Date
2012
Journal Title
Chemistry - A European Journal
ISSN
0947-6539JCR Link
Citation
vol. 18, no. 19, pp. 6094 - 6101
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
A mononuclear nonheme cobalt(III) complex of a tetradentate ligand containing two deprotonated amide moieties, [Co(bpc)Cl 2][Et 4N] (1; H 2bpc=4,5-dichloro-1,2-bis(2-pyridine-2- carboxamido)benzene), was prepared and then characterized by elemental analysis, IR, UV/Vis, and EPR spectroscopy, and X-ray crystallography. This nonheme Co III complex catalyzes olefin epoxidation upon treatment with meta-chloroperbenzoic acid. It is proposed that complex 1 shows partitioning between the heterolytic and homolytic cleavage of an O-O bond to afford Co V=O (3) and Co IV=O (4) intermediates, proposed to be responsible for the stereospecific olefin epoxidation and radical-type oxidations, respectively. Moreover, under extreme conditions, in which the concentration of an active substrate is very high, the Co-OOC(O)R (2) species is a possible reactive species for epoxidation. Furthermore, partitioning between heterolysis and homolysis of the O-O bond of the intermediate 2 might be very sensitive to the nature of the solvent, and the O-O bond of the Co-OOC(O)R species might proceed predominantly by heterolytic cleavage, even in the presence of small amounts of protic solvent, to produce a discrete Co V=O intermediate as the dominant reactive species. Evidence for these multiple active oxidants was derived from product analysis, the use of peroxyphenylacetic acid as the peracid, and EPR measurements. The results suggest that a less accessible Co V=O moiety can form in a system in which the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOI
10.1002/chem.201103916
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자연과학대학 > 화학·나노과학전공 > Journal papers
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