He Peng, Guan Mu-Han, Hu Meng-Yang, Zhou Yuan-Jun, Huang Ming-Yao, Zhu Shou-Fei
Frontiers Science Center for New Organic Matter, State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China.
Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, 300192, China.
Angew Chem Int Ed Engl. 2024 May 21;63(21):e202402044. doi: 10.1002/anie.202402044. Epub 2024 Apr 3.
The nuanced role of spin effects remains a critical gap in designing proficient open-shell catalysts. This study elucidates an iron-catalyzed allylic C(sp)-H silylation/alkyne hydrosilylation reaction, in which the spin state of the open-shell iron catalyst dictates the reaction kinetics and pathway. Specifically, spin crossover led to alkyne hydrosilylation, whereas spin conservation resulted in a novel allylic C(sp)-H silylation reaction. This chemoselectivity, governed by the spin-crossover efficiency, reveals an unexpected dimension in spin effects and a first in the realm of transition-metal-catalyzed in situ silylation of allylic C(sp)-H bonds, which had been previously inhibited by the heightened reactivity of alkenes in hydrosilylation reactions. Furthermore, this spin crossover can either accelerate or hinder the reaction at different stages within a single catalytic reaction, a phenomenon scarcely documented. Moreover, we identify a substrate-assisted C-H activation mechanism, a departure from known ligand-assisted processes, offering a fresh perspective on C-H activation strategies.
自旋效应的细微作用在设计高效开壳催化剂方面仍然是一个关键空白。本研究阐明了一种铁催化的烯丙基C(sp)-H硅氢化/炔烃硅氢化反应，其中开壳铁催化剂的自旋态决定了反应动力学和反应途径。具体而言，自旋交叉导致炔烃硅氢化，而自旋守恒则产生了一种新型的烯丙基C(sp)-H硅氢化反应。这种由自旋交叉效率控制的化学选择性揭示了自旋效应中一个意想不到的方面，并且是过渡金属催化烯丙基C(sp)-H键原位硅氢化领域中的首次发现，该反应此前因硅氢化反应中烯烃的高反应性而受到抑制。此外，这种自旋交叉在单个催化反应的不同阶段既可以加速也可以阻碍反应，这一现象鲜有记载。此外，我们确定了一种底物辅助的C-H活化机制，这与已知的配体辅助过程不同，为C-H活化策略提供了新的视角。
