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.
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