Treatment of (C5Me5)2Os2Br 4 with LiAlH4 in Et2O followed by addition of MeOH at -78°C affords two products: the osmium(VI) pentahydride (C 5Me5)OsH5 and the dinuclear osmium(III) tetrahydride (C5Me5)2Os2H 4. The X-ray crystal structures reveal that (C5Me 5)OsH5 adopts a pseudo-octahedral geometry with one axial and four equatorial hydride ligands, whereas all four hydride ligands in (C 5Me5)2Os2H4 bridge the osmium-osmium axis. Treatment of (C5Me5)OsH5 with HBF4·Et2O affords the osmium-(VIII) hexahydride [(C5Me5)OsH6][BF4], which evidently adopts a classical polyhydride structure, as judged from variable-temperature T1 studies. Treatment of (C5Me 5)OsH5 with tert-butyllithium in the presence of N,N,N′,N″,N″-pentamethyldiethylenetriamine (pmdeta) affords the osmium(IV) tetrahydride salt [Li(pmdeta)][(C5Me 5)OsH4], which is proposed to adopt a four-legged piano stool geometry. IR and NMR studies of the Os-D analogues of these new osmium hydrides are also discussed.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry