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제107회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Robust and Efficient Amide-Based Nonheme Manganese(III) Hydrocarbon Oxidation Catalysts: Substrate and Solvent Effects on Involvement and Partition of Multiple Active Oxidants

2011년 2월 15일 17시 58분 32초
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금 <발표Ⅲ>
저자 및
이홍규, 김진훈, 김 철1
서울과학기술대학교 생무기연구실, Korea
1서울과학기술대학교 정밀화학과 친환경소재제품센터, Korea
Mononuclear nonheme manganese(III) complexes, [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 B, 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, H218O-exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. In addition, it has been observed that the participation of MnV=O, MnIV=O, and MnIII-OOR can be controlled by changing the substrate concentration. Moreover, partitioning between heterolysis and homolysis of the O-O bond of a Mn-acylperoxo intermediate (Mn-OOC(O)R) was significantly affected by the nature of solvent, and the O-O bond of the Mn-OOC(O)R proceeded predominantly by heterolytic cleavage in protic solvent. Therefore, a discrete MnV=O intermediate appeared to be the dominant reactive species in protic solvent. Furthermore, we have observed close similarities between these nonheme MnIII complex systems and Mn(saloph) catalysts previously reported, indicating 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.