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)2and 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 and1H 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 Co2C2core 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-{pipe}{pipe}) bonding mode for the acetylene group in the former case and the μ3-η2, η2bonding mode in the latter one.