Trapping of a 12-Valence-Electron Osmium Intermediate

The hydride−dihydrogen complex [OsH(η2-H2){κ3N,C,C-CH2CH-o-C5H4N}(PiPr3)2]BF4 (1) is a “functional equivalent” of the 12-valence-electron monohydride cation “[OsH(PiPr3)2]+”, which is trapped by aromatic solvents, such as toluene, benzene, and fluorobenzene to form the arene derivatives [OsH(η6-C6H5R)(PiPr3)2]BF4 (R = CH3 (2), H (3), F (4)). This “functional equivalent” can be also generated by protonation of the hexahydride OsH6(PiPr3)2 (5) with 1 equiv of HBF4 and subsequent release of three hydrogen molecules. The monohydride is also trapped by 5. The protonation of the latter with 0.5 equiv of HBF4 yields the heptahydride dimer [{OsH2(PiPr3)2}2(μ-H)3]BF4 (6), which does not undergo exchange of bridging and terminal hydrides.