Supported oxo alkylidenes were proposed to be catalytically active species in Shell olefin process and olefin conversion technology, both responsible for more than a million ton a year production of hydrocarbons used in detergent and polymer chemistry. Later, well-defined catalysts based on molybdenum, tungsten, and rhenium oxo alkylidenes were discovered and investigated. The metathesis catalysts are known to decompose by two major pathways: bimolecular decomposition and beta-hydride elimination in metallacyclobutane intermediate. The barrier for beta-hydride elimination in oxo intermediates was shown to be much higher than in imido. However, the chemistry of oxo alkylidenes is much less explored and no general method of synthesis is known.<br/>Recently, our group reported a method of promoting alpha-hydrogen abstraction from vanadium trialkyl complexes by using phosphonium chlorides to obtain vanadium chloride alkylidene phosphine complexes in good yields. In this work we apply similar transformation to afford vanadium oxo alkylidene complex. The complex is a rare example of vanadium oxo alkylidene, and the first one that is active in olefin metathesis reaction.<br/>We showed for the first time that vanadium oxo alkylidene complex can be used to catalyze synthetically useful ring closing metathesis and cross-metathesis reactions. The catalyst can tolerate some common functional groups (e.g. ester, amido, amino). The decomposition of a catalyst under reaction conditions is investigated.

First vanadium oxo alkylidene catalyst for olefin metathesis

ACS Fall 2021

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