OSMIUM TETRAFLUORIDE DIOXIDE, CIS-OSO2F4

The new osmium(VIII) oxo fluoride obtained from the reaction of KrF2 and 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 calculations 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 addition 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. The results from the density functional theoretical calculations show that for OsO2F4 the cis-structure of C2v symmetry is a true minimum and that, in accord with expectations for a d0 transition metal complex, the trans-D4h structure is not a minimum energy structure and distorts to a C2v structure.