Constrained-geometry ruthenium carboranyl complexes and their unique chemical properties

By utilizing the unique electronic and steric properties of the icosahedral carboranyl moiety, a new class of constrained-geometry ruthenium complexes bearing linked cyclopentadienyl-carboranyl ligands has been achieved. They exhibit interesting reactivity patterns, of which some are different from conventional cyclopentadienyl ruthenium complexes. For example, the Cp in the constrained-geometry [eta(5):sigma(C)-Me(2)C(C(5)H(4))C(2)B(10)H(10)]Ru systems is active and participates in reactions to give C-C coupling products whereas the "CpRu" moiety in CpRu-X is inert and remains intact in the same reactions. The constrained-geometry ligands can also stabilize mononuclear Ru bis(vinylidene) complexes and furnish the Ru-C(cage) to Ru-B(cage) conversion in the presence of H(2). This account provides an overview of our recent work in this area.