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The OsO4F-, OsO4F22-, and OsO3F3- Anions, Their Study by Vibrational and NMR Spectroscopy and Density Functional Theory Calculations, and the X-ray Crystal Structures of [N(CH3)4][OsO4F] and [N(CH3)4][OsO3F3]

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journal contribution
posted on 23.08.2000 by Michael Gerken, David A. Dixon, Gary J. Schrobilgen
The fluoride ion acceptor properties of OsO4 and OsO3F2 were investigated. The salts [N(CH3)4][OsO4F] and [N(CH3)4]2[OsO4F2] were prepared by the reactions of OsO4 with stoichiometric amounts of [N(CH3)4][F] in CH3CN solvent. The salts [N(CH3)4][OsO3F3] and [NO][OsO3F3] were prepared by the reactions of OsO3F2 with a stoichiometric amount of [N(CH3)4][F] in CH3CN solvent and with excess NOF, respectively. The OsO4F- anion was fully structurally characterized in the solid state by vibrational spectroscopy and by a single-crystal X-ray diffraction study of [N(CH3)4][OsO4F]:  Abm2, a = 7.017(1) Å, b = 11.401(2) Å, c = 10.925(2) Å, V = 874.1(3) Å3, Z = 4, and R = 0.0282 at −50 °C. The cis-OsO4F22- anion was characterized in the solid state by vibrational spectroscopy, and previous claims regarding the cis-OsO4F22- anion are shown to be erroneous. The fac-OsO3F3- anion was fully structurally characterized in CH3CN solution by 19F NMR spectroscopy and in the solid state by vibrational spectroscopy of its N(CH3)4+ and NO+ salts and by a single-crystal X-ray diffraction study of [N(CH3)4][OsO3F3]:  C2/c, a = 16.347(4) Å, b = 13.475(3) Å, c = 11.436(3) Å, β = 134.128(4)°, V = 1808.1(7) Å3, Z = 8, and R = 0.0614 at −117 °C. The geometrical parameters and vibrational frequencies of OsO4F-, cis-OsO4F22-, monomeric OsO3F2, and fac-OsO3F3- and the fluoride affinities of OsO4 and monomeric OsO3F2 were calculated using density functional theory methods.

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