C−C Coupling of a Permetalated Ethene, (μ₄-CC)Ru₂(FeCp*)₂(CO)₁₀, with Alkynes, and Isolation of a Labile MeCN Adduct, (μ₄-CC)Ru₂(FeCp*)₂(CO)₈(NCMe)₂

A tetranuclear C₂ (dicarbide) cluster complex with a permetallated ethene structure, (μ₄-CC)Ru₂(FeCp*)₂(CO)₁₀ (2), reacts with alkynes in refluxing THF to give a variety of adducts resulting from C−C coupling and oxidative metallacyclization with the C₂ ligand in addition to a unique μ₄-dicarbyne complex with a dimetallacyclobutatriene core, (μ₄-C−C)Ru₂(FeCp*)₂(CO)₆(μ-η²:η²-PhC⋮CPh). The reactions are initiated by decarbonylation, as confirmed by the reactions of an isolated, labile species lightly stabilized by MeCN, (μ₄-CC)Ru₂(FeCp*)₂(CO)₈(NCMe)₂, which undergoes the reactions at room temperature and provides the same types of products as those obtained from 2.