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

Abstract
Terminal nitrido complexes N⋮Mo(OC(CF3)2Me)3 (4), N⋮Mo(OC(CF3)2Me)3(NCMe) (4-NCMe), and N⋮Mo(OC(CF3)3)3(NCMe) (5-NCMe) react irreversibly with 3-hexyne at elevated temperature in hydrocarbon solution to form the corresponding propylidyne complexes EtC⋮Mo(OC(CF3)2Me)3 (3) and EtC⋮Mo(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.