Synthesis, Characterization and Crystal Structures of Some Linked Metal Carbonyl Clusters Derived from Diethynyl-Substituted Silane and Disilane Ligands

The use of diethynylsilane, diethynyldisilane and diethynyldisiloxane in the synthesis of some linked metal carbonyl clusters is demonstrated. New dimeric η2-diyne complexes of cobalt [{Co2(CO)6}2(η2-diyne)], ruthenium [{(μ-H)Ru3(CO)9}2(μ3-η2,η2-diyne)] and osmium [{(μ-CO)Os3(CO)9}2(μ3-η2-diyne)] {diyne=HC≡CSi(CH3)2C≡CH, HC≡CSi(CH3)2–Si(CH3)2C≡CH, HC≡CSi(CH3)2–O–Si(CH3)2C≡CH or HC≡CSi(Ph)2C≡CH} have been prepared in good yields from the reaction of [Co2(CO)8], [Ru3(CO)12] and [Os3(CO)10(NCMe)2] with half an equivalent of the appropriate diyne ligand, respectively. All the twelve compounds have been characterized by IR and 1H NMR spectroscopies and mass spectrometry. The molecular structures of eight of them have been determined by X-ray crystallography. Structurally, each of the tetracobalt species displays two Co2C2 cores adopting the pseudo-tetrahedral geometry with the alkyne bond lying essentially perpendicular to the Co–Co vector. For the group 8 ruthenium and osmium analogues, the hexanuclear carbonyl clusters consist of two trinuclear metal cores with the μ3-η2,η2 bonding mode for the acetylene groups in the former case and μ3-(η2-||) bonding mode in the latter one. Density functional theory was employed to study the electronic structures of these molecules in terms of the nature of the silyl or disilyl unit and its substituents.