MnIII-Peroxo adduct supported by a new tetradentate ligand shows acid-sensitive aldehyde deformylation reactivity.
MnIII-Peroxo adduct supported by a new tetradentate ligand shows acid-sensitive aldehyde deformylation reactivity.
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由新的四齿配体支持的 MnIII-Peroxo 加合物显示出酸敏感的醛去甲酰化反应活性。
DOI：
10.1039/c8dt02300j
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Jackson,TimothyA
中科院分区：
文献类型：
--
作者：
Denler,MelissaC;Wijeratne,GayanB;Rice,DerekB;Colmer,HannahE;Day,VictorW;Jackson,TimothyA
合成了新的四齿配体L7BQ(L7BQ=1，4-二(喹啉-8-基)-1，4-二氮杂环戊烷)。[MnII(L7BQ)(OTf)2]配合物的X射线晶体结构表明，[MnII(L7BQ)(OTf)2]是一个单体的MnII中心，L7BQ配体在赤道场中提供了四个施主氮原子，两个三氟离子结合在轴向位置。当该物种在−40°C下用H_2O_2和Et_3N处理时，生成了[Mn_3(O_2)(L_7BQ)]+。这种新中间体的形成得到了多种光谱技术的支持，包括电子吸收、锰K边X射线吸收和电子顺磁共振方法。[MnIII(O2)(L7BQ)]+[MnIII(O2)(L7BQ)]+的扩展X射线吸收精细结构数据的评估结果表明，[MnIII(O2)(L7BQ)]+的Mn-O键距为1.85ó，这比以前报道的结晶学表征的MnIII-Peroxo加合物的结果要短。对[MnIII(O2)(L7BQ)]+的X射线前缘区域的分析表明，有20.8个单位的大前缘区域。含时密度泛函理论计算表明，前缘强度是由过氧基和L7BQ配体引起的中心对称性几何扭曲引起的Mn4p-3D混合引起的。通过与环己烷甲醛和2-苯丙醛的反应，考察了[MnIII(O2)(L7BQ)]+与醛的反应活性。根据这些实验，确定了在酸存在下，[MnIII(O2)(L7BQ)]+只与醛反应。具体地说，在[MnIII(O2)(L7BQ)]+中加入环己烷羧酸可以将MnIII-过氧基加合物转化为一种新的中间体，该中间体可能与所观察到的醛脱甲酰化活性有关。这些观察结果突显了在乙醛脱甲酰化反应中识别活性金属物种的挑战。
The new tetradentate L7BQ ligand (L7BQ = 1,4-di(quinoline-8-yl)-1,4-diazepane) has been synthesized and shown to support MnII and MnIII-peroxo complexes. X-ray crystallography of the [MnII(L7BQ)(OTf)2] complex shows a monomeric MnII center with the L7BQ ligand providing four donor nitrogen atoms in the equatorial field, with two triflate ions bound in the axial positions. When this species is treated with H2O2 and Et3N at −40 °C, a MnIII-peroxo adduct, [MnIII(O2)(L7BQ)]+ is formed. The formation of this new intermediate is supported by a variety of spectroscopic techniques, including electronic absorption, Mn K-edge X-ray absorption and electron paramagnetic resonance methods. Evaluation of extended X-ray absorption fine structure data for [MnIII(O2)(L7BQ)]+ resolved Mn–O bond distances of 1.85 Å, which are on the short end of those previously reported for crystallographically characterized MnIII-peroxo adducts. An analysis of the X-ray pre-edge region of [MnIII(O2)(L7BQ)]+ revealed a large pre-edge area of 20.8 units. Time-dependent density functional theory computations indicate that the pre-edge intensity is due to Mn 4p–3d mixing caused by geometric distortions from centrosymmetry induced by both the peroxo and L7BQ ligands. The reactivity of [MnIII(O2)(L7BQ)]+ towards aldehydes was assessed through reaction with cyclohexanecarboxaldehyde and 2-phenylpropionaldehyde. From these experiments, it was determined that [MnIII(O2)(L7BQ)]+ only reacts with aldehydes in the presence of acid. Specifically, the addition of cyclohexanecarboxylic acid to [MnIII(O2)(L7BQ)]+ converts the MnIII-peroxo adduct to a new intermediate that could be responsible for the observed aldehyde deformylation activity. These observations underscore the challenges in identifying the reactive metal species in aldehyde deformylation reactions.
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DOI：
10.1007/s00775-013-1067-4
发表时间：
2013
期刊：
JBIC Journal of Biological Inorganic Chemistry
影响因子：
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作者：
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影响因子：
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DOI：
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发表时间：
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DOI：
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发表时间：
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期刊：
Synlett : Accounts and Rapid Communications in Synthetic Organic Chemistry
影响因子：
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