使用O2的Cp*Ir (III) (NHC) (Me) (Cl) 的氧功能化:识别了一种罕见的双金属Ir (IV) μ-oxo中间体
Matthew C Lehman1, Dale R Pahls2, Joseph M Meredith3
1‡Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States.
Journal of the American Chemical Society
|February 22, 2015
概括
这项研究详细介绍了利用空气作为氧化剂从复合物中形成甲醇的过程. 一个关键的中间体,一个带有Ir(IV) -O-Ir(IV) 核心的二金属复合物,被分离和表征.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 无机化学 无机化学
背景情况:
- 复合物是有机合成中的有价值的催化剂.
- 了解反应机制对于催化剂的开发至关重要.
- 涉及金属复合物的氧化反应通常通过复杂的中间体进行.
研究的目的:
- 研究从特定的复合物中形成甲醇的机制.
- 为了分离和描述反应中间体.
- 阐明双金属物种在催化循环中的作用.
主要方法:
- 在室温下进行定量反应监测.
- 使用光谱学 (NMR,UV-Vis) 和X射线晶体学,对二金属复合物的分离和表征.
- 计算研究 (DFT,MCSCF) 用于分析电子结构.
- 同位素标记研究和激素捕捉实验.
主要成果:
- 甲醇是从[Cp*Ir(III) ((NHC) Me ((CD2Cl2)) ](+) 与O2和乙醇中定量形成的.
- 作为一个关键的中间体,分离出了一种新型的二金属复合物,[(Cp*Ir(NHC) Me) 2 (((μ-O) ]][(BAr(F) 4) [2] (3),作为一个关键的中间体.
- 综合体3有一个Ir(IV) -O-Ir(IV) 核心,有一个非线性μ-oxo桥,以促进氧原子的转移.
- 计算分析揭示了Ir中心与oxo/oxyl中间体的电子结构之间的通信.
- 从3中形成甲醇被TEMPO抑制,而3的形成则没有.
结论:
- 该机制涉及一个Ir oxo/oxyl中间体和一个稳定的二金属复合体.
- 复合体3中的μ-oxo桥和非线性几何结构对于氧原子转移至关重要.
- 在整个反应过程中,Cp*和NHC连接体保持完整.
- 这项工作提供了对氧化反应中复合物的反应性和机械路径的洞察.
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