ß-H Abstraction/1,3-CH Bond Addition as a Mechanism for the Activation of CH Bonds at Early Transition Metal Centers
ß-H Abstraction/1,3-CH Bond Addition as a Mechanism for the Activation of CH Bonds at Early Transition Metal Centers
复制标题
-H 抽象/1,3-CH 键加成作为早期过渡金属中心 CH 键激活的机制
作者：
Hu Y
本文描述了一个被忽视的在早期过渡金属中心活化CH键的机制，即在η - 2-烯烃中间的1,3-CH键加成。x射线表征的[Cp2Zr(c-C3H5)2]通过β-H抽离反应去除环丙烷，生成瞬态η - 2-环丙烯[Cp2Zr(η2-c-C3H4)]中间体a。迅速裂解呋喃和噻吩的CH键，得到呋喃基和噻吩基配合物[Cp2Zr(c-C3H5)(2-C4H3X)] （X = 0， S）。苯的活性较弱。包括动力学研究、同位素标记和反应谱的DFT计算在内的机理研究都证实，通过Zr（η - 2-烯烃）键的快速立体特异性1,3- ch键加成遵循速率决定的β-H萃取反应。DFT计算还表明，[Cp2Zr(c-C3H5)2]的α-CC球形旋体有助于环丙烷的β-H萃取。用NBO分析方法讨论了α-CC有机相互作用的性质。
This article describes the generalization of an overlooked mechanism for CH bond activation at early transition metal centers, namely 1,3-CH bond addition at an η2-alkene intermediate. The X-ray-characterized [Cp2Zr(c-C3H5)2] eliminates cyclopropane by a β-H abstraction reaction to generate the transient η2-cyclopropene [Cp2Zr(η2-c-C3H4)] intermediateA.Arapidly cleaves the CH bond of furan and thiophene to give the furyl and thienyl complexes [Cp2Zr(c-C3H5)(2-C4H3X)] (X = O, S), respectively. Benzene is less cleanly activated. Mechanistic investigations including kinetic studies, isotope labeling, and DFT computation of the reaction profile all confirm that rapid stereospecific 1,3-CH bond addition across the Zr(η2-alkene) bond ofAfollows the rate-determining β-H abstraction reaction. DFT computations also suggest that an α-CC agostic rotamer of [Cp2Zr(c-C3H5)2] assists the β-H abstraction of cyclopropane. The nature of the α-CC agostic interaction is discussed in the light of an NBO analysis.