Synthesis, Characterization, and Molecular Structure of the First closo-Hydrido Complexes of Osmium with Carborane Ligands: closo-3,3-(PPh3)2-3-H-3-Cl-3,1,2-OsC2B9H11 and closo-3,3-(PPh3)2-3,3-H2-1,2-Me2-3,1,2-OsC2B9H9

Novel 12-vertex closo-hydridometallacarboranes 3,1,2-[(PPh3)2OsHXC2B9H11] (1a,b: X = Cl, H) and 3,1,2-[(PPh3)2OsH2-1,2-Me2C2B9H9] (1c) have been synthesized via oxidative addition of K+ salts of the nido-carborane anions [nido-7,8-R2-7,8-C2B9H10]- (R = H, Me), respectively, to OsCl2(PPh3)3 and characterized by spectroscopic (NMR and IR) as well as by single-crystal X-ray diffraction studies of 1a,c.