Synthesis, structural characterisation and electrochemistry of ruthenium carbonyl clusters derived from ferrocenyl(formyl)acetylene

Abstract

Two new ferrocenyl ruthenium carbonyl clusters, [Ru 4(CO) 12(μ 4-η 1,η 1,η 2,η 2-{(C 5H 5)Fe(C 5H 4CCCHO)})] 1 (20%) and [Ru 3(CO) 8(μ 3-η 1,η 2,η 4-{(C 5H 5)Fe(C 5H 4CCCHO)} 2)] 2 (10%), have been synthesised by reaction of (C 5H 5)Fe(C 5H 4C≡CCHO) with triruthenium dodecacarbonyl in cyclohexane under refluxing conditions. Thermolysis of 1 in refluxing toluene led to the formation of [Ru 5(CO) 13(μ-H)(μ 5-C)(μ 2-η 1,η 1-{(C 5H 5)Fe(C 5H 4C)})] 3 (10%). Reaction of [Ru 3(CO) 10(NCMe) 2] with ferrocenyl(formyl)acetylene afforded the triruthenium cluster [Ru 3(CO) 9(μ-CO)(μ 3-η 1,η 1,η 2-{(C 5H 5)Fe(C 5H 4CCCHO)})] 4 (30%). All these new compounds have been characterised fully by conventional spectroscopic and X-ray diffraction methods. The structure of 1 consists of a ferrocenyl carboxaldehyde bound to the Ru 4 butterfly skeleton via a typical μ 4-η 1, η 1, η 2, η 2 coordination mode. Cluster 2 is based upon an Ru 3 closed triangle bearing a metallacyclopentadiene ring that arises from the coupling of two ligand molecules with the formation of O→Ru dative bond. Thermolysis of 1 afforded a rare pentanuclear ruthenium cluster containing a carboferrocenyl fragment with a μ 2-η 1,η 1 mode. Both fluxional and electrochemical behaviour of cluster 3 have been studied. Compound 4 consists of an alkyne ligand bound to the triruthenium cluster unit via a typical μ 3-(η 2-∣∣) coordination mode.