Opening of Carborane Cages by Metal Cluster Complexes: The Reaction of a Thiolate-Substituted Carborane with Triosmium Carbonyl Cluster Complexes

The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)­C2B10H11 has yielded the
complex Os3(CO)9[μ3-η3-C2B10H9(SCH3)]­(μ-H)2, 1, by the loss of the two NCMe ligands and
one CO ligand from the Os3 cluster and the coordination
of the sulfur atom and the activation of two B–H bonds with
transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(μ-H)­[(μ3-η3-1,4,5-μ3-η3-6,10,11-C2B10H8S­(CH3)]­Os3(CO)9(μ-H)2, 2, that contains two triosmium triangles attached to the same
carborane cage. The carborane cage was opened by cleavage of two B–C
bonds and one B–B bond. The B–H group that was pulled
out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B–B
bonds. When heated to 150 °C, 2 was transformed
into the complex Os3(CO)9(μ-H)­[(μ3-η3-μ3-η3-C2B10H7S­(CH3)]­Os3(CO)9(μ-H), 3, by the loss of
two hydrogen atoms and a rearrangement that led to further opening
of the carborane cage. Reaction of 1 with a second equivalent
of closo-o-(1-SCH3)­C2B10H11 has yielded the complex Os3(CO)6)­(μ3-η3-C2B10H9-R-SCH3) (μ3-η3-C2B10H10-S-SCH3)­(μ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound
Os3(CO)6(μ3-η3-C2B10H9-R-SCH3)­(μ3-η3-C2B10H10-R-SCH3)­(μ-H)3, 4b, by an inversion of stereochemistry at one
of the sulfur atoms by heating to 174 °C.