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 [Ru3(CO)7(µ-CO)(µ3-η2∶η3∶η3-C28H34O3)] 1a (10%), [Ru3(CO)7(µ-CO)(µ3-η2∶η3∶η3-C28H34O3)] 1b (4%) and [Ru3(CO)8(µ3-η2∶η2∶η4-C28H32O2)] 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 Ru3 triangular skeleton containing a fragment of C8 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 C8 hydrocarbyl fragment. The organic moiety in 2 is formed by coupling of two diyne ligands and is co-ordinated to a bent Ru3 chain via a µ3-η2∶η2∶η4 bonding mode. Cluster 2 is found to exhibit a charge-separated, zwitterionic formulation. Reaction of [Ru3(CO)10(NCMe)2] with 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne afforded another new cluster [Ru3(CO)9(µ-CO)(µ3-η1∶η1∶η2-C14H18O2)] 3, which consists of a diyne ligand bound to the triruthenium cluster unit via a typical µ3-(η2-||) co-ordination mode. Thermolysis of 1a and 2, with 1,4-bis(1-hydroxycyclopentyl)-1,3-butadiyne and [Ru3CO)12], respectively, led to [Ru3(CO)5(µ3-η5∶η5∶η6-C43H49O5)] 4 and a tetraruthenium cluster [Ru4(CO)10(µ4-η2∶η2∶η4∶η4-C28H32O2)] 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 µ3-η1∶η3∶η3 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 η3-allyl bond is formed.