Synthesis and structural characterisation of ruthenium carbonyl clusters containing hydrocarbyl ligands derived from (hydroxy)alkynes HC≡CC(H)(OH)CH₃

Five new ruthenium ketonic clusters [Ru4(CO)12{μ4-η1:η1:η2:η2-CH3C(H)CCC(H)CH2C(O)CH3}] 1 (10%), [Ru5(CO)14(μ-H)2{μ4-η1:η1:η2:η2-CC(H)C(O)CH3}] 2 (15%), [Ru6(CO)16{μ4-η1:η1:η2:η2-CC(H)C(O)CH3}2] 3 (15%), [Ru7(CO)19{μ4-η1:η1:η2:η2-CC(H)C(O)CH3}{μ5-η1:η1:η1:η1:η2-CCC(H)CH3}] 4 (8%), and [Ru5(CO)12(μ-CO){μ4-η1:η1:η2:η2-CC(H)C(O)CH3}(μ4-η2-HCCCH2CH3)] 5 (10%) have been synthesised by reaction of but-3-yn-2-ol with triruthenium dodecacarbonyl, in cyclohexane, under reflux. All the compounds have been fully characterised by spectroscopic and X-ray diffraction methods. The structure of 1 is based on a Ru4butterfly skeleton containing a fragment of C8ketonic chain which arises from the coupling of two ligand molecules with the elimination of a water molecule. An interesting feature in clusters 2, 3, 4 and 5 is the formation of a metallocycloketonic ring with a μ4-η1:η1:η2:η2coordination mode which is derived from the activation of the C≡C triple bond. Both 2 and 5 consist of a wingtip bridged butterfly core, which is also bonded with two bridged hydrides in 2 and a μ4-η2acetylide fragment in 5 respectively. Cluster 2 is also closely related to cluster 3, in that it seems to be a monomeric unit of 3 forming a six atom raft geometry with two metallocycloketonic rings. The metal core of 4 is similar to 3, except that one Ru-Ru bond in 4 is broken to form two more metal-metal bonds with an additional Ru atom to give a novel Ru7core, which is best described as a distorted Ru4square plane sharing an edge with an edge-bridged butterfly. Moreover, one of the metallocycloketonic rings in 3 is replaced by an allenyl CCC(H)CH3ligand, which is coordinated to an edge-bridged butterfly in 4.