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

Abstract

Heating the allenylidene species [Ru₃(CO)₉(μ-CO)(μ₃-CCCPh₂)] in the presence of alkynes RC₂R (R = Me or Ph) led to formation of the novel complexes [Ru₃(CO)₉{μ₃-C(R)C(R)C₂CPh₂}] (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-CCCPh₂)] onto silica gel at room temperature leads to formation of the acetylide species [Ru₃(CO)₉(μ-H){μ₃-CCC(Ph)₂OH}], whereas reaction of [Ru₃(CO)₉(μ-CO){μ₃-CCC(Ph)Me}] with silica gel affords [Ru₃(CO)₉(μ-H){μ₃-CCC(Ph)CH₂}], containing an ene-yne ligand. Some insights into the mechanisms by which the transformations take place are given.

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