Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warszawa, Poland.
Phys Chem Chem Phys. 2020 Jun 21;22(23):13062-13069. doi: 10.1039/d0cp01798a. Epub 2020 Jun 1.
A relatively fast degradation of ruthenium catalysts in the presence of selected olefins, and ethylene in particular, is one of the bottlenecks in their use in metathesis reactions. Here we explore the structure-activity relationships between the rate of degradation of Hoveyda-Grubbs catalysts and the structure of olefins by means of DFT calculations. We show that (Z)-1,2-dichloroethene can't form stable complexes with a 14-electron active complex due to a strong inductive electron withdrawal effect. Hoveyda-Grubbs catalysts can be, however, used to convert (Z)-1,2-dichloroethene to (E)-1,2-dichloroethene due to differences in crucial barriers in the catalytic cycle for E/Z isomers. Hoveyda-Grubbs catalysts in the presence of both isomers of 1,2-dimethoxyethene and 1,2-dichloroethene are predicted to be very stable in the unproductive metathesis, while for monosubstituted olefins the methoxyethene presence gives relatively low barriers for crucial degradation transition states and can readily undergo decomposition.
在某些烯烃特别是乙烯存在的情况下，钌催化剂的相对快速降解是其在交叉复分解反应中应用的瓶颈之一。在这里，我们通过密度泛函理论（DFT）计算来探究 Hoveyda-Grubbs 催化剂的降解速率与烯烃结构之间的构效关系。我们表明，（Z）-1,2-二氯乙烯由于强烈的诱导电子拉电子效应而不能与 14 电子活性配合物形成稳定的配合物。然而，由于 E/Z 异构体催化循环中关键势垒的差异，Hoveyda-Grubbs 催化剂可用于将（Z）-1,2-二氯乙烯转化为（E）-1,2-二氯乙烯。预测在 1,2-二甲氧基乙烷和 1,2-二氯乙烯两种异构体以及甲氧基乙烷存在的情况下，Hoveyda-Grubbs 催化剂在非生产性交叉复分解中非常稳定，而对于单取代烯烃，甲氧基乙烷的存在为关键降解过渡态提供了相对较低的势垒，并且很容易发生分解。
