Synthesis, Characterization and Crystal Structures of Some Metal Carbonyl Linking Clusters of Osmium, Ruthenium and Cobalt Derived from Diethynylarenes

The use of various diethynylarene ligands in the synthesis of some metal carbonyl linking clusters is established. New dimeric complexes of osmium [{(μ-CO)Os₃(CO)₉}₂(μ₃-η²-diyne)], ruthenium [{(μ-H)Ru₃(CO)₉}₂(μ₃-η²,η²-diyne)] or [{(μ-CO)Ru₃(CO)₉}₂(μ₃-η²-diyne)] and cobalt [{Co₂(CO)₆}₂(η²-diyne)] (diyne = HC≡CArC≡CH, Ar = 2,7-fluorene, 2,7-fluoren-9-one, bithiazole or bithiophene) have been prepared in good yields from the reaction of [Os₃(CO)₁₀(NCMe)₂], [Ru₃(CO)₁₂] or [Ru₃(CO)₁₀(NCMe)₂] and [Co₂(CO)₈] with half an equivalent of the appropriate diethynylarene ligand, respectively. All these cluster compounds have been characterized by IR and ¹H NMR spectroscopies and mass spectrometry. The molecular structures of three of them have been determined by X-ray crystallography. For the group 8 osmium and ruthenium analogues, the hexanuclear carbonyl clusters consist of two trinuclear metal cores with the exhibition of the μ₃-(η²-||) bonding mode for the acetylene groups when [M₃(CO)₁₀(NCMe)₂] (M = Ru, Os) was used and the μ₃-η²,η² bonding mode when [Ru₃(CO)₁₂] served as the starting cluster. The tetracobalt species possesses two Co₂C₂ cores adopting the pseudo-tetrahedral geometry having the alkyne bond lying perpendicular to the Co–Co vector in each core. Density functional theory was also used to study the electronic structures of selected molecules.