Biomimetic Oxidation of 3,5-Di-tert-butylcatechol by Dioxygen via Mn-Enhanced Base Catalysis

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• 作者：Imola Cs. Szigy&aacute ; rtó ; L&aacute ; szló ; I. Sim&aacute ; ndi ; L&aacute ; szló ; P&aacute ; rk&aacute ; nyi ; L&aacute ; szló ; Korecz ; Gitta Schlosser
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：September 4, 2006
• 年：2006
• 卷：45
• 期：18
• 页码：7480 - 7487
• 全文大小：152K
• 年卷期：v.45,no.18(September 4, 2006)
• ISSN：1520-510X

文摘

The 6-coordinate dioximatomanganese(II) complex [Mn(HL)(CH₃OH)]⁺ (2, where H₂L is [HON=C(CH₃)C(CH₃)=NCH₂CH₂]₂NH), formed by instant solvolysis of [Mn₂(HL)₂](BPh₄)₂ (1) in methanol, accelerates the triethylamine (TEA)-catalyzed oxidation of 3,5-di-tert-butylcatechol (H₂dtbc) by O₂ to the corresponding o-benzoquinone. Significantly,2 alone has no catalytic effect. The observed rate increase can be explained by the interaction of 2 with thehydroperoxo intermediate HdtbcO₂^- formed from Hdtbc^- and O₂ in the TEA-catalyzed oxidation. The kinetics ofthe TEA-catalyzed and Mn-enhanced reaction has been studied by gas-volumetric monitoring of the amount of O₂consumed. The initial rate of O₂ uptake (V_in) shows a first-order dependence on the concentration of 2 and O₂ andsaturation kinetics with respect to both H₂dtbc and TEA. The observed kinetic behavior is consistent with parallelTEA-catalyzed and Mn-enhanced oxidation paths. The 3,5-di-tert-butylsemiquinone anion radical is an intermediatedetectable by electron spin resonance (ESR) spectroscopy. The dimeric catalyst precursor has been characterizedby X-ray diffraction and electrospray ionization mass spectrometry and the monomeric catalyst by ESR spectroscopy.