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

Heating the allenylidene species [Ru-3(CO)(9)(mu -CO)(mu (3)-C=C=CPh2)] in the presence of alkynes RC2R (R=Me or Ph) led to formation of the novel com plexes [Ru-3(CO)(9){mu (3)-C(R)C(R)C2CPh2}] (R=Me or Ph) and [Ru-4(CO)(12){ mu (4)-C(Ph)C(Ph)CCCPh2}], shown by X-ray diffraction to contain C-5 ligand s formed through carbon-carbon bond formation with the alpha -carbon of the allenylidene unit. Adsorption of [Ru-3(CO)(9)(mu -CO)(mu (3)-C=C=CPh2)] on to silica gel at room temperature leads to formation of the acetylide speci es [Ru-3(CO)(9)(mu -H){mu (3)-C=CC(Ph)(2)OH}], whereas reaction of [Ru-3(CO )(9)(mu -CO){mu (3)-C=C=C(Ph)Me}] with silica gel affords [Ru-3(CO)(9)(mu - H){mu (3)-C=CC(Ph)=CH2}], containing an ene-yne ligand. Some insights into the mechanisms by which the transformations take place are given.