Synthesis and molecular structure of hexaruthenium clusters containing unsaturated ring systems derived from 1-ethynylcyclopentanol, 1-ethynylcycloheptanol and 1-ethynylcyclooctanol

Six hexaruthenium compounds which are identified as [Ru6C(CO)13(μ-CO){μ3-η1,η2,η3-C5H7CCC(H)C5H8}] 1 (12%), [Ru6(CO)12(μ-CO)2{μ4-η1,η1,η2,η4-CC(H)C5H6}2] 2 (8%), [Ru6C(CO)14(μ-CO){μ2-η1,η3-C(H)C7H11}] 3 (8%), [Ru6(CO)14{μ4-η1,η1η2,η4-CC(H)C7H10}2] 4 (10%), [Ru6C(CO)13(μ-CO){μ3-η1,η2,η3-C8H12C(H)C(H)C(H)C(OH)C8H14}] 5 (16%), and [Ru6(CO)14{μ4-η1,η1η2,η4-CC(H)C8H12}2] 6 (8%) have been synthesised by reaction of HC≡C(C5H8OH), HC≡C(C7H12OH) and HC≡C(C8H14OH), respectively, with triruthenium dodecacarbonyl in cyclohexane under refluxing conditions. All these compounds have been fully characterised by spectroscopic and X-ray diffraction methods. The structures of 1, 3 and 5 are based on a Ru6 octahedral skeleton containing a μ6-carbide. Both clusters 1 and 5 involve the coupling of two functionalized alkyne molecules to give an unusual hexatetraene chain with the elimination of water molecules. Complex 3 consists of one alkyne moiety bonded to a Ru3 triangular face via one σ and a π-allyl bond. An interesting feature in clusters 2, 4 and 6 is the formation of a metallacyclic five-membered ring with a μ4-η1,η1,η2,η4 mode, which is derived from the C≡C triple bond and C≡H bond activations. Reaction of [Ru3(CO)10(NCMe)2] with 1-ethynylcyclopentanol affords another new cluster, [Ru3(CO)9(μ-CO)(μ3-η1,η1,η2-HCCC5H8OH)] 7, which consists of an alkyne ligand bound to the triruthenium cluster unit via a typical μ3-(η2-||) coordination mode