Synthesis and structural characterisation of trinuclear and tetranuclear ruthenium clusters containing diyne ligands derived from 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne

Abstract

Three new ruthenium diyne clusters [Ru 3(CO)2(μ-CO)(μ 3-η 2:η 3:η 3-C 28H 34O 3)] 1a (10%), [Ru 3(CO) 7(μ-CO)(μ 3-η 2:η 3:η 3-C 28H 34O 3)] 1b (4%) and [Ru 3(CO) 8(μ 3-η 2:η 2:η 4-C 28H 32O 2)] 2 (12%) have been synthesized by reaction of 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne with triruthenium dodecacarbonyl in chloroform under refluxing conditions. All have been fully characterised by spectroscopic and X-ray diffraction methods. The structures of 1a and 1b are based on a Ru 3 triangular skeleton containing a fragment of C 8 chain, which arises from the coupling of two diyne molecules with the formation of a ruthenacyclopentadienyl ring and a furyl ring. Complexes 1a and 1b are isomeric to each other and differ only in the spatial position of the pendant alkyne moiety in the C 8 hydrocarbyl fragment. The organic moiety in 2 is formed by coupling of two diyne ligands and is co-ordinated to a bent Ru 3 chain via a μ 3-η 2:η 2:η 4 bonding mode. Cluster 2 is found to exhibit a charge-separated, zwitterionic formulation. Reaction of [Ru 3(CO) 10(NCMe) 2] with 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne afforded another new cluster [Ru 3(CO) 9(μ-CO)(μ 3-η 1:η 1:η 2-C 14H 18O 2)] 3, which consists of a diyne ligand bound to the triruthenium cluster unit via a typical μ 3-(η 2-∥) co-ordination mode. Thermolysis of 1a and 2, with 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne and [Ru 3CO) 12], respectively, led to [Ru 3(CO) 5(μ 3-η 5:η 5:η 6-C 43H 49O 5)] 4 and a tetraruthenium cluster [Ru 4(CO) 10(μ 4-η 2:η 2:η 4:η 4-C 28H 32O 2)] 5. Cluster 4 is closely related to 1a by the coupling of one more diyne ligand to the triruthenium skeleton of 1a, resulting in an unusual μ 3-η 1:η 3:η 3 mode. The co-ordination mode of the organic ligand in 5 is very similar to that in 2, except that one more metal atom is involved, and one η 3-allyl bond is formed.