动态机制可能避免高氧化状态的Ir(V) -H中间体和协调复合物在和中通过阴离子Ir(III) 激活
Ryan Carlsen1, Nathan Wohlgemuth1, Lily Carlson1
1Department of Chemistry and Biochemistry , Brigham Young University , Provo , Utah 84602 , United States.
Journal of the American Chemical Society
|August 2, 2018
概括
密度函数理论可能无法完全捕捉有机金属反应动态. 直接动力学模拟显示中介物被绕过在C-H激活, 模糊机械路径.
科学领域:
- 有机金属化学
- 计算化学
- 反应动力学
背景情况:
- 密度函数理论 (DFT) 通常用于模拟有机金属反应机制,假设最小能量路径准确地表示反应动态.
- 对于C-H激活反应,通常使用标准的两步氧化添加/减少消除机制.
研究的目的:
- 研究甲和的C-H激活的详细反应动态.
- 为了确定中间体,如IrV-H,在反应过程中暂时形成或绕过.
- 阐明机械路径,区分协调和阶段性过程.
主要方法:
- 用近古典的直接动力学模拟来建模反应轨迹.
- 模拟是从氧化添加过渡状态的振动平均速度分布开始的.
- 分析的重点是中间体的命运和产品形成的性质.
主要成果:
- 很大一部分生产反应轨迹绕过了拟议的IrV-H中间体.
- 观察到的动态类似于发生在氧化添加/减少消除能量表面的西格玛键转化路径.
- 在通过减排过渡状态时观察到和产物从中心完全解离,绕过弱协调复合物.
结论:
- 这项研究挑战了DFT衍生的最小能量路径完全描述有机金属反应动态的假设.
- 这些发现表明C-H激活的两步和一步机制之间的界限模糊.
- 在降解后观察到的弱C-H协调复合物可能是溶剂的产物,而不是真正的反应中间体.
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