Reactivity of multi-site bound allenylidene towards alkynes and silica gel

Heating the allenylidene species [Ru₃(CO)₉(μ-CO)(μ₃-C=C=CPh₂ )] in the presence of alkynes RC₂R (R = Me or Ph) led to formation of the novel complexes [Ru₃(CO)₉{μ₃C(R)C(R)C₂CPh ₂}] (R = Me or Ph) and [Ru₄(CO)₁₂-{μ₄-C(Ph)C(Ph)CCCPh₂ }], shown by X-ray diffraction to contain C₅ ligands formed through carbon-carbon bond formation with the α-carbon of the allenylidene unit. Adsorption of [Ru₃(CO)₉(μ-CO)(μ₃-C=C=CPh₂ )] onto silica gel at room temperature leads to formation of the acetylide species [Ru₃(CO)₉(μH){μ₃-C=CC(Ph) ₂OH}], whereas reaction of [Ru₃(CO)₉(μCO){μ₃-C=C=C(Ph)Me}] with silica gel affords [Ru₃(CO)₉(μ-H){μ₃-C=CC(Ph)=CH ₂}], containing an ene-yne ligand. Some insights into the mechanisms by which the transformations take place are given.