Synthesis, Characterization and Structural Properties of Some Heterobimetallic Carbonyl Clusters Derived from Diethynylsilane and Diethynyldisilane Ligands

We report the synthesis of some heterobimetallic carbonyl clusters of groups 8 and 9 derived from diethynylsilane and diethynyldisilane ligands. The triosmium carbonyl clusters containing a pendant acetylene unit (μ-CO)Os₃(CO)₉(μ₃-η²-HC≡C-E-C≡CH)] E = Si(CH₃)₂, Si(CH₃)₂–Si(CH₃)₂ and SiPh₂] were prepared and subsequently used for mixed-metal cluster formation. New diyne complexes of the type {(μ-CO)Os₃(CO)₉}{Co₂(CO)₆}(μ₃-η²:η²-diyne)] and {(μ-CO)Os₃(CO)₉}{(μ-H)Ru₃(CO)₉}(μ₃-η²:μ₃-η², η²-diyne)] diyne = HC≡CSi(CH₃)₂C≡CH, HC≡CSi(CH₃)₂–Si(CH₃)₂C≡CH or HC≡CSi(Ph)₂C≡CH] have been prepared in good yields from the reaction of (μ-CO)Os₃(CO)₉(μ₃-η²-HC≡C-E-C≡CH)] with a molar equivalent of Co₂(CO)₈] and Ru₃(CO)₁₂], respectively. All the new heterobimetallic compounds have been characterized by IR and ¹H NMR spectroscopy and mass spectrometry. The X-ray crystal structures and computational analyses based on density functional theory of these three molecules have been studied. Structurally, the dicobalt species adopts a pseudo-tetrahedral Co₂C₂ core with the alkyne bond which lies essentially perpendicular to the Co–Co vector. For the mixed osmium–ruthenium analogue, the hexanuclear carbonyl cluster consist of two trinuclear metal cores with the μ₃-(η²-||) bonding mode for the acetylene group in the former case and the μ₃-η², η² bonding mode in the latter one.