Cyclohexa-1,4-diene in a bridging coordination mode: synthesis and structural characterisation of Ru 5C(CO) 13(μ 2-η 2:η 2-C 6H 8-1,4) and Ru 5C(CO) 11(μ 2-η 2:η 2-C 6H 8-1,4) 2

Abstract

Reaction of the square-pyramidal cluster [Ru 5C(CO) 15] with cyclohexa-1,4-diene and Me 3NO in CH 2Cl 2 affords the organometallic cluster [Ru 5C(CO) 13(μ 2-η 2:η 2-C 6H 8-1,4)] ( 1). Further reaction of 1 with cyclohexa-1,4-diene and Me 3NO in CH 2Cl 2 yields [Ru 5C(CO) 11(μ 2-η 2:η 2-C 6H 8-1,4) 2] ( 2). The molecular structures of both 1 and 2 have been established by single crystal X-ray analysis. In 1 the diene ligand occupies a radial position bridging two metal atoms on the square base of the cluster, while in 2 the second diene substitutes two axial carbonyl groups on consecutive basal ruthenium atoms. In both clusters, the 1,4-topology of the diene ligand is maintained. Studies of the variation in the 1H NMR spectrum of 2 with temperature have revealed that as the temperature is raised the two different C 6H 8 ligands equilibrate.