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Robust and efficient amide-based nonheme manganese(III) hydrocarbon oxidation catalysts: Substrate and solvent effects on involvement and partition of multiple active oxidants

Title
Robust and efficient amide-based nonheme manganese(III) hydrocarbon oxidation catalysts: Substrate and solvent effects on involvement and partition of multiple active oxidants
Authors
Song Y.J.Lee S.H.Park H.M.Kim S.H.Goo H.G.Eom G.H.Lee J.H.Lah M.S.Kim Y.Kim S.-J.Lee J.E.Lee H.-I.Kim C.
Ewha Authors
김성진김영미
SCOPUS Author ID
김성진scopus; 김영미scopus
Issue Date
2011
Journal Title
Chemistry - A European Journal
ISSN
0947-6539JCR Link
Citation
vol. 17, no. 26, pp. 7336 - 7344
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Two new mononuclear nonheme manganese(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Mn(bpc)Cl(H2O)] (1) and [Mn(Me2bpb)Cl(H2O)]·CH3OH (2), were prepared and characterized. Complex 2 has also been characterized by X-ray crystallography. Magnetic measurements revealed that the complexes are high spin (S=5/2) MnIII species with typical magnetic moments of 4.76 and 4.95 μB, respectively. These nonheme MnIII complexes efficiently catalyzed olefin epoxidation and alcohol oxidation upon treatment with MCPBA under mild experimental conditions. Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants MnV=O, MnIV=O, and MnIII-OO(O)CR. Evidence for this approach was derived from reactivity and Hammett studies, KIE (kH/kD) values, H2 18O-exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. In addition, it has been proposed that the participation of MnV=O, MnIV=O, and MnIII-OOR could be controlled by changing the substrate concentration, and that partitioning between heterolysis and homolysis of the O-O bond of a Mn-acylperoxo intermediate (Mn-OOC(O)R) might be significantly affected by the nature of solvent, and that the O-O bond of the Mn-OOC(O)R might proceed predominantly by heterolytic cleavage in protic solvent. Therefore, a discrete MnV=O intermediate appeared to be the dominant reactive species in protic solvents. Furthermore, we have observed close similarities between these nonheme MnIII complex systems and Mn(saloph) catalysts previously reported, suggesting that this simultaneous operation of the three active oxidants might prevail in all the manganese-catalyzed olefin epoxidations, including Mn(salen), Mn(nonheme), and even Mn(porphyrin) complexes. This mechanism provides the greatest congruity with related oxidation reactions by using certain Mn complexes as catalysts. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOI
10.1002/chem.201003202
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자연과학대학 > 화학·나노과학전공 > Journal papers
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