Reactions of three-electron ση 2 -prop-2-ynyl ligands formed by deprotonation of four-electron η 2 -alkyne molybdenum complexes

Reaction of [MoBr(η2-MeC2R)2(η-C5H5)](R = Me, or Ph) with Li[N(SiMe3)2] leads to a dehydrohalogenation reaction and unexpected formation or the three-electron σ,η2-prop-2-ynyl complexes [Mo(σ,η2-CH2C2R)(η2-MeC2R)(η-C5H5)]; treatment of these reactive molcules with the proton source CF3CO2H affords the bis-alkyne complexes [Mo(O2CCF3)(η2-MeC2R)2(η2-MeC2R)2(η-C5H5)], whereas reaction with carbon monoxide leads to a novel carbon–carbon bone forming reaction, and formation of the X-ray crystallographically identified complex [Mo{η2,η3-[graphic omitted]–CH2}(CO)(η-C5H5)].