A boron–boron linked large metallacarborane cluster: Characterization and X-ray structure of 8,9′-[closo-{3-Co(η5-C5H5)-1,2-C2B9H10}]2

The 8,9′-[closo-{3-Co(η5-C5H5)-1,2-C2B9H10}]2 (1) species, in which two large closo-CoC2B9 sub-clusters are connected by a B–B bond, is unexpectedly obtained from the reaction of closo-[3-Co(η5-C5H5)-1,2-C2B9H11] with sulfur in the presence of aluminium chloride under reflux conditions. The solid state conformation of 1 seems to be the result of a pair of intramolecular C–H⋯H–B dihydrogen bonds between the protonic H atoms of the C5H5 fragment of a sub-cluster and the hydridic H atoms of the C2B9H11 fragment in the other sub-cluster in 1.