Tc(VII) oxyfluorides; Preparation and study by 99Tc NMR, raman spectroscopy and x-ray crystallography

Although TcO3F can be prepared by solvolysis of TcO4− in anhydrous HF and ReO2F3 and ReOF5 have been known for some time, the preparations of the higher oxyfluorides of Tc(VII) have not been reported.The noble-gas fluorides KrF2 and XeF6 are potent oxidative fluorinating agents and provide a ready means to the syntheses of the higher oxyfluorides of Tc(VII). Thus, XeF6 and KrF2 oxidative fluorinations of TcO3F in HF media lead to the stepwise elimination of O2 gas and fluorination of Tc(VII), resulting in the syntheses of TcO2F3 and Tc2O5F4. The latter is the subJect of a x-ray single crystal structure and vibrational study.Technetium-99 NMR spectroscopy has been used to monitor the above reactions and to characterize the diamagnetic Tc(VII) products in solution. Technetium-99 possesses a quadrupole moment, Q (I = 9/2). Quadrupole relaxation is expected to broaden 99Tc NMR signals, but due to the favorable magnitude of Q and large I, the extent of line broadening is not severe. In the case of TcO2F3, the line width is narrow enough in the non-cubic environment of 99Tc to permit the observation of the first 99Tc-19F spin-spin coupling.The fluoride ion donor properties of TcO3F are also reported, leading to the isolation of TcO3F·AsF5 from HF solution. 99Tc and 17O NMR studes confirm the presence of TcO3+ in solution. Solid stare Raman spectroscopy indicates that the TcO3+ cation is fluorine bridged to the AsF6− anion.