Osmium dioxide tetrafluoride, cis-OsO2F4, reacts with the strong fluoride ion accepters AsF5 and SbF5 in anhydrous HF and SbF5 solutions to form orange salts. Raman spectra are consistent with the formation of the fluorine-bridged diosmium cation F(cis-OsO2F3)(2)(+), as the AsF6- and Sb2F11- salts, respectively. The F-19 NMR spectra of the salts in HF solution are exchange-averaged singlets occurring at higher frequency than those of the fluorine environments of cis-OsO2F4. The F(cis-OsO2F3)(2)(Sb2F11-)-Sb-+ salt crystallizes in the orthorhombic space group Imma. At -107 degrees C, a = 12.838(3) Angstrom, b = 10.667(2) Angstrom, c = 11.323(2) Angstrom, V = 1550.7(8) Angstrom(3), and Z = 4. Refinement converged with R = 0.0469 [R(w) = 0.0500]. The crystal structure consists of discrete fluorine-bridged F(cisOsO(2)F(3))(2)(+) and Sb2F11- ions in which the fluorine bridge of the F(cis-OsO2F3)(2)(+) cation is trans to an oxygen atom (Os-O 1.676 Angstrom) of each OsO2F3 group. The angle at the bridge is 155.2(8)degrees with a bridging Os-F-b distance of 2.086(3) Angstrom. Two terminal fluorine atoms (Os-F 1.821 Angstrom) are cis to the two oxygen atoms (Os-O 1.750 Angstrom), and two terminal fluorine atoms of the OsO2F3 group are trans to one another (1.813 Angstrom). The OsO2F3+ cation was characterized by F-19 NMR and by Raman spectroscopy in neat SbF5 solution but was not isolable in the solid state. The NMR and Raman spectroscopic findings are consistent with a trigonal bipyramidal cation in which the oxygen atoms and a fluorine atom occupy the equatorial plane and two fluorine atoms are in axial positions. Density functional theory calculations show that the crystallographic structure of F(Cis-OSO2F3)(2)(+) is the energy-minimized structure and the energy-minimized structures of the OsO2F3+ cation and ReO2F3 are trigonal bipyramidal having C-2 nu point symmetry. Attempts to prepare the OsOF5+ cation by oxidative fluorination of cis-OsO2F4 with KrF(+)ASF(6)(-) in anhydrous HF proved unsuccessful.