Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride

Abstract

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH₄ )₂ [TcO(OTf)₅ ]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO₃ (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, (NH₄ )₂ [TcO(OTf)₅ ] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH₄ )₄ [{TcO(TcO₄ )₄ }₄ ] ⋅10 H₂ 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.