((V) -oxo多氧甲基酸盐中间体的表征及其在氧转移反应中的特性
Alex M Khenkin1, Devesh Kumar, Sason Shaik
1Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100.
Journal of the American Chemical Society
|November 30, 2006
概括
这项研究研究了替代的多氧甲酸盐 (P2W17MnIII) 作为氧化催化剂. 尽管理论上预测了高反应性,但实验结果显示,由于溶剂对聚氧甲酸盐的电荷和的影响,催化速度较慢.
科学领域:
- 无机化学 无机化学
- 催化剂是一种催化剂.
- 材料科学 材料科学 材料科学
背景情况:
- 聚氧甲酸盐 (POMs) 是具有可调节性质的多功能无机集群.
- 与相替代的POM显示出作为氧化催化剂的前景.
- 了解活性位点的电子结构和反应性对于催化剂设计至关重要.
研究的目的:
- 为了研究 (III) 替代的多氧甲酸盐P2W17MnIII的催化活性,使用iodopentafluorobenzene bis (tifluoroacetate) (F5PhI (TFAc) 2) 作为单氧供体.
- 为了阐明在催化过程中形成的氧物种的电子结构和反应机制.
- 将实验反应率与理论预测进行比较,并确定限制催化性能的因素.
主要方法:
- 谱光特性 (19F NMR,31P NMR) 用于识别反应中间体和物种.
- 密度函数理论 (DFT) 计算以建模电子结构和过渡状态.
- 使用1-octene作为基质来确定反应速率和激活参数的动态测量.
主要成果:
- 观察到一个 ((V) -oxo物种 (P2W17MnV=O) 的形成.
- DFT计算预测了环氧化和氧化的低三重过渡状态,表明了高反应性.
- 实验动力学显示反应性低于预测,归因于激活的高度负.
结论:
- 在P2W17MnIII中, ((V) -oxo物种的反应性低于类似的氨酸复合物.
- 极性溶剂和水对高电荷的聚氧甲酸盐进行强烈的溶解,会对过渡状态产生重大影响.
- 溶剂分子的电阻和自由度的损失导致激活的负,降低了催化效率.
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