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.