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.