An Unusual Dicarbenium Fulvalene Complex, [FvMo2(CO)4(μ-η3:η3-CH2C⋮CCH2)][BF4]2 (Fv = Fulvalene), Which Exhibits Reactivity toward Weak Nucleophiles

The title compound was prepared and characterized by spectroscopic methods. The complex [FvMo2(CO)4(μ-η3:η3-CH2C⋮CCH2)][BF4]2 (3) exhibits reactivity toward weak nucleophiles such as MeOH, H2O, and PhOMe, affording the monocarbenium ions [FvMo2(CO)4(μ-η2:η3-MeOCH2C⋮CCH2)][BF4] (4), [FvMo2(CO)4(μ-η2:η3-HOCH2C⋮CCH2)][BF4] (5), and [FvMo2(CO)4(μ-η2:η3-CH2C⋮CCH2C6H4OMe)][BF4] (6a,b; para:ortho 55:45), respectively. When 3 was treated with strong nucleophiles such as pyridine and triphenylphosphine, double nucleophilic attack occurred, yielding the complexes [FvMo2(CO)4(μ-η2:η3-C5H5NCH2C⋮CCH2NC5H5))][BF4]2 (7) and [FvMo2(CO)4(μ-η2:η3-PPh3CH2C⋮CCH2PPh3)][BF4]2 (8), respectively. The reactivity of the fulvalenyl-bridged dimolybdenum propargyl dication complex 3 is compared to that of the related cyclopentadienyl system and discussed.