Synthesis of Vanadium Oxo Alkylidene Complex and Its Reactivity in Ring-Closing Olefin Metathesis Reactions

V imido alkylidenes have been applied for the ring-opening metathesis polymerization involving cyclic olefins. However, those complexes found limited application in reactions with acyclic terminal olefins due to instability toward ethylene. Experimental and theoretical studies show that the β-hydride elimination from unsubstituted metallacyclobutene is the primary decomposition pathway in those systems. Herein, we report the synthesis of the first catalytically active V oxo alkylidene, VO­(CHSiMe3)­(PEt3)2Cl, which exhibits the highest reported productivity with various terminal olefins in ring-closing metathesis reactions among known V catalysts. Presented DFT studies indicate that β-hydride elimination is significantly disfavored for V oxo species.钒亚胺亚烷基配合物（V imido alkylidenes）已被应用于涉及环烯烃的开环易位聚合（ring-opening metathesis polymerization）反应。然而，这类配合物在与非环端烯烃的反应中应用受限，原因在于其对乙烯不稳定。实验与理论研究表明，在该类体系中，未取代金属环丁烯（metallacyclobutene）的β-氢消除（β-hydride elimination）是主要的分解路径。本文报道了首例具有催化活性的钒氧亚烷基配合物VO(CHSiMe3)(PEt3)2Cl的合成；在已知的钒基催化剂中，该配合物针对各类端烯烃的闭环易位（ring-closing metathesis）反应展现出已报道的最高催化效能。本文呈现的密度泛函理论（DFT）研究表明，钒氧类物种的β-氢消除过程显著受阻。