Multisite Reactivity of the Central Mo2CP Core in the Unsaturated Carbyne-Bridged Complex [Mo25-C5H5)2(μ-CPh)(μ-PCy2)(CO)2]

The title compound reacted with HBF4·OEt2 at room temperature to give a mixture of the agostic-like, phosphine-bridged complex [Mo2Cp2(μ-CPh)(μ-κ12-PHCy2)(CO)2]BF4 (major) and the carbene-bridged complex [Mo2Cp2(μ-η12-CHPh)(μ-PCy2)(CO)2]BF4 (minor). It readily added a molecule of HCCCO2Me or a single Se atom at its Mo2C(carbyne) center to give with high yield the corresponding propenylylidene- or selenoacyl-bridged derivatives [Mo2Cp2{μ-η23-CPhCHC(CO2Me)}(μ-PCy2)(CO)2] and [Mo2Cp2{μ-η,κ:η,κ-C(Ph)Se}(μ-PCy2)(CO)2], respectively. In contrast, the addition of a neat donor at the metal site can induce a reversible carbyne–carbonyl coupling, as observed in the reaction with N2CPh2 to give the ketenyl derivative [Mo2Cp2{μ-η12-C(Ph)CO}(μ-PCy2)(CO)(κ1-N2CPh2)].