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.