Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH(4))(2)[TcO(OTf)(5)]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO(3)(OTf)], and intermediate Tc(VI) species. (99)Tc nuclear magnetic resonance (NMR) has been used to study the Tc(VII) compound and electron paramagnetic resonance (EPR), (99)Tc NMR and X‐ray absorption near‐edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH(4))(2)[TcO(OTf)(5)] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH(4))(4)[{TcO(TcO(4))(4)}(4)] ⋅10 H(2)O. Single‐crystal X‐ray crystallography was used to determine the solid‐state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species.