Binuclear cyclopentadienylosmium hydride chemistry: A stable quadruply bridged structure

The quadruply bridged structure Cp2Os2(μ-H)4 is shown to be the lowest energy Cp2Os2H4 structure. For the other Cp2Os2Hn systems (n = 8, 6, 2) the lowest energy structures contain doubly bridged Cp2Os2(μ-H)2 units. Bridging cyclopentadienyl rings are found in low-energy Cp2Os2H2 and Cp2Os2 structures. For Cp2Os2, two structures, each with a bridging μ-Cp ring, are shown to lie more than 14 kcal/mol in energy below singlet and triplet unbridged isomers.