OSMIUM TETRAFLUORIDE DIOXIDE, CIS-OSO2F4

The new osmium(VIII) oxo fluoride obtained from the reaction of KrF2 a nd OsO4 in anhydrous HF solution and originally identified as OsOF6 is shown by quantitative material balance, electron diffraction, NMR and vibrational spectroscopy, and density functional theory calculations to be cis-OsO2F4. The combined electron diffraction study and DFT calc ulations result in the following geometry: r(Os)=0 = 1.674(4) angstrom , r(Os-F)e 1.883(3) angstrom, r(Os-F)a = 1.843(3) angstrom, angle O=Os =O = 103.5(25)degrees, angle F(e)-Os-F(e) = 77.3(26)degrees, angle F(a )-Os-F(a) = 172.0(3)degrees, angle O=Os-F(a) = 92.4(17)degrees. In add ition to the F-19 NMR spectrum, the Os-187 chemical shift was measured for cis-OsO2F4 from its F-19{Os-187} inverse correlation spectrum. Th e results from the density functional theoretical calculations show th at for OsO2F4 the cis-structure of C2v symmetry is a true minimum and that, in accord with expectations for a d0 transition metal complex, t he trans-D4h structure is not a minimum energy structure and distorts to a C2v structure.