AgS2O6CF3: the first trifluoromethylsulfonylsulfate(vi)

Abstract

We describe the synthetic route towards a novel class of salts, trifluoromethylsulfonylsulfates, as exemplified by the silver(I) derivative (AgS₂O₆CF₃). Formation proceeds via direct reaction between a triflate precursor, AgSO₃CF₃, and SO₃. The title compound crystallizes in the P2₁/c unit cell with a = 5.15746(14) Å, b = 25.8563(9) Å, c = 5.53970(14) Å and β = 101.1749(19)°. The structure is layered with the puckered [AgS₂O₆] 2D sheets; the terminal CF₃ groups are separated by the van der Waals gap, as seen also for related metal triflates. The compound is very fragile thermally and it decomposes endothermally to AgSO₃CF₃ with concomitant evolution of SO₃ even at 65 °C or upon grinding in an agate mortar; thus it may serve as a solid store of – otherwise volatile and corrosive – SO₃. The IR and Raman spectra of AgS₂O₆CF₃ have been tentatively assigned based on similarities to those of related Ag₂S₂O₇ and AgSO₃CF₃ and phonon calculations. Synthesis and properties of KS₂O₆CF₃ are also briefly described.