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

Abstract

Five new ruthenium ketonic clusters [Ru 4(CO) 12{μ 4-η 1:η 1:η 2:η 2-CH 3C(H)CCC(H)CH 2C(O)CH 3}] 1 (10%), [Ru 5(CO) 14(μ-H) 2{μ 4-η 1:η 1:η 2:η 2-CC(H)C(O)CH 3}] 2 (15%), [Ru 6(CO) 16{μ 4-η 1:η 1:η 2:η 2-CC(H)C(O)CH 3} 2] 3 (15%), [Ru 7(CO) 19{μ 4-η 1:η 1:η 2:η 2-CC(H)C(O)CH 3}{μ 5-η 1:η 1:η 1:η 1:η 2-CCC(H)CH 3}] 4 (8%), and [Ru 5(CO) 12(μ-CO){μ 4-η 1:η 1:η 2:η 2-CC(H)C(O)CH 3}(μ 4-η 2-HCCCH 2CH 3)] 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 Ru 4 butterfly skeleton containing a fragment of C 8 ketonic 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 μ 4-η 1:η 1:η 2:η 2 coordination 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 μ 4-η 2 acetylide 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 Ru 7 core, which is best described as a distorted Ru 4 square plane sharing an edge with an edge-bridged butterfly. Moreover, one of the metallocycloketonic rings in 3 is replaced by an allenyl CCC(H)CH 3 ligand, which is coordinated to an edge-bridged butterfly in 4.