Chemical applications of 99Tc NMR spectroscopy: preparation of novel Tc(VII) species and their characterization by multinuclear NMR spectroscopy

The 99Tc NMR parameters of a number of Tc(VII) and one Tc(V) species have been determined. The anion TcO4- (ω = 22.508 311 MHz in H2O) was chosen as the standard for 99Tc NMR spectroscopy. A 99Tc-17O coupling constant of 131.4 Hz was obtained from a 17O- and 18O-enriched sample of TcO4- whose 99Tc spectrum also showed an isotopic shift of 0.22 ppm/mass number arising from a statistical distribution of 16O/17O/18O isotopic isomers. Technetium-99 and proton NMR provided definitive proof for the existence of the stereochemically nonrigid TcH92- anion. Both TcO3F and the novel TcO3+ cation were synthesized and characterized by 99Tc, 17O, and 19F NMR spectroscopy. Preliminary results on two new technetium(VII) oxyfluorides tentatively identified as F2O2TcOTcO2F2 and TcO2F3 are also reported. The diagmagnetic d2 anion, TcO2(CN)43-, represents the most deshielded 99Tc environment encountered in the present study