洞察科希-雅各布森-卡茨木催化系统中的烯酸复合物的结构和反应性. 一个密度功能研究研究
Ilja V Khavrutskii1, Djamaladdin G Musaev, Keiji Morokuma
1Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia, 30322.
Journal of the American Chemical Society
|November 6, 2003
概括
密度函数理论揭示了O-O键裂解在酸复合体中的两个途径,这些复合体是科希-雅各布森-卡茨基反应中的关键中间体. 复合物2的cis(O,N) 异构体表现出最低能量通路,涉及异质的O-O键裂变.
科学领域:
- 有机金属化学 有机金属化学
- 计算化学计算化学
- 反应机制 反应机制
背景情况:
- 乙烯氧复合物是科奇-雅各布森-卡茨基反应中的关键中间体,这是氧化反应的关键过程.
- 了解这些中间体的结构性质和反应性对于阐明反应机制至关重要.
- 之前的研究集中在实验观测上,因此需要对反应途径进行理论研究.
研究的目的:
- 为了研究乙烯氧复合物的结构性质[{Sal}Mn{III}RCO{3) ] (2) 和[{Salen}Mn{IV}RCO{3) ] (3).
- 通过密度函数理论阐明这些复合体中的O-O键裂解机制.
- 确定参与科奇-雅各布森-卡茨基反应的最有利的反应途径和中间体.
主要方法:
- 密度函数理论 (DFT) 的计算被用来研究复合体的结构性质和潜在能量表面 (PES).
- 四个不同的同位素 (cis(O,N),cis(N,O),cis(N,N,和trans) 位于两个复合体2和3.
- 进行了O-O键裂解路径的分析,包括异质和同质裂解,以及旋转交叉现象.
主要成果:
- 最低能量的异构体被确定为2-cis(O,N) (五重奏基态) 和几乎退化的3-cis(O,N)/3-cis(N,O) (四重奏基态).
- 复合体3显示了惰性O-O键,而复合体2则通过两个不同的路径显示了O-O键裂解.
- 在复合体2中最有利的途径涉及具有低激活屏障 (14.9 kcal/mol) 和外热性质 (-15.6 kcal/mol) 的五重奏PES上的异质O-O键分裂.
结论:
- O-O 键裂变主要发生在复合物 2 的 cis 同位体中.
- 反应可以通过高旋转路径或涉及三重状态的旋转交叉路径进行,从而导致oxo物种.
- 理论发现为科奇-雅各布森-卡茨基反应的机制和复合物的作用提供了关键的见解.
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