Highly Active Molybdenum−Alkylidyne Catalysts for Alkyne Metathesis: Synthesis from the Nitrides by Metathesis with Alkynes

Terminal nitrido complexes NMo(OC(CF3)2Me)3 (4), NMo(OC(CF3)2Me)3(NCMe) (4-NCMe), and NMo(OC(CF3)3)3(NCMe) (5-NCMe) react irreversibly with 3-hexyne at elevated temperature in hydrocarbon solution to form the corresponding propylidyne complexes EtCMo(OC(CF3)2Me)3 (3) and EtCMo(OC(CF3)3)3 (6), long known as exceptionally active catalysts for alkyne metathesis. The propylidyne complexes are isolated as the more readily crystallized 1,2-dimethoxyethane (DME) adducts for convenience; 3-DME is isolated in 61% yield on a multigram scale.