Theoretical Investigation of Alkyne Metathesis Catalyzed by W/Mo Alkylidyne Complexes

In this paper, the mechanism of alkyne metathesis catalyzed by W/Mo alkylidyne complexes has been theoretically investigated with the aid of density functional theory calculations. Calculations on various model alkylidyne complexes M(⋮CMe)(OR) 3 (M = W, Mo; R = Me, CH 2 F), W(⋮CMe)(NMe 2 ) 3, and W(⋮CMe)(Cl) 3 allow us to examine the factors that influence the reaction barriers. In the reaction mechanism, metallacyclobutadienes are initially formed from a ring-closing step between alkynes and alkylidyne complexes. A ring-opening step then gives the metathesis products. The factors that determine the metathesis reaction barriers have been examined. The reaction paths leading to the formation of Cp complexes, a possible path deactivating catalytic activity, were also studied.