Substituent Effects and Supramolecular Interactions of Titanocene(III) Chloride: Implications for Catalysis in Single Electron Steps
Substituent Effects and Supramolecular Interactions of Titanocene(III) Chloride: Implications for Catalysis in Single Electron Steps
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DOI：
10.1021/ja4121567
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发表时间：
2014-01-29
影响因子：
15
通讯作者：
Flowers, Robert A., II
中科院分区：
文献类型：
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作者：
Gansaeuer, Andreas;Kube, Christian;Flowers, Robert A., II
用循环伏安(CV)和计算方法研究了二茂钛(III)配合物在四氢呋喃中的电化学性质及其在氯化物添加剂存在和不存在的情况下的稳定性。与Cp2TiCl相比，通过在环戊二烯基环上引入一个吸电子取代基(CO2Me或CN)，钛茂化合物的氧化峰电位可降低0.47V。首次证明了在催化应用条件下，低价茂钛化合物可以通过失去取代配体而分解。通过循环伏安、动力学和计算分析了新近发现的氯化物添加剂稳定茂钛(III)催化剂的效果。通过可逆氢键，[(C5H4R)(2)TiCl2](-)与盐酸阳离子发生了前所未有的超分子相互作用，这是添加剂的作用机理之一。这项研究为合理设计钛茂催化的单电子步骤反应提供了必要的关键信息。
The electrochemical properties of titanocene(III) complexes and their stability in THF in the presence and absence of chloride additives were studied by cyclic voltammetry (CV) and computational methods. The anodic peak potentials of the titanocenes can be decreased by as much as 0.47 V through the addition of an electron-withdrawing substituent (CO2Me or CN) to the cyclopentadienyl ring when compared with Cp2TiCl. For the first time, it is demonstrated that under the conditions of catalytic applications low-valent titanocenes can decompose by loss of the substituted ligand. The recently discovered effect of stabilizing titanocene(III) catalysts by chloride additives was analyzed by CV, kinetic, and computational studies. An unprecedented supramolecular interaction between [(C5H4R)(2)TiCl2](-) and hydrochloride cations through reversible hydrogen bonding is proposed as a mechanism for the action of the additives. This study provides the critical information required for the rational design of titanocene-catalyzed reactions in single electron steps.