The Activation Mechanism of Ru–Indenylidene Complexes in Olefin Metathesis

Olefin metathesis is a powerful tool
for the formation of carbon–carbon
double bonds. Several families of well-defined ruthenium (Ru) catalysts
have been developed during the past 20 years; however, the reaction
mechanism for all such complexes was assumed to be the same. In the
present study, the initiation mechanism of Ru–indenylidene
complexes was examined and compared with that of benzylidene counterparts.
It was discovered that not all indenylidene complexes followed the
same mechanism, highlighting the importance of steric and electronic
properties of so-called spectator ligands, and that there is no single
mechanism for the Ru-based olefin metathesis reaction. The experimental
findings are supported quantitatively by DFT calculations.

烯烃复分解反应（Olefin metathesis）是构建碳-碳双键的强有力工具。近二十年来，已有多系列结构明确的钌(Ru)催化剂被开发出来；但此前学界普遍认为，这类钌配合物的反应机制均为同一套路径。本研究针对钌基茚亚基配合物的引发机制展开探究，并与亚苄基对应配合物的机制进行对比分析。研究发现，并非所有茚亚基配合物均遵循相同的反应机制，这凸显了所谓“旁观配体(spectator ligands)”的空间位阻与电子性质的重要性，同时也证实钌基烯烃复分解反应并无统一的反应机制。该实验结论通过密度泛函理论(DFT)计算得到了定量验证。