The Elusive Fluoropolysulfates [FS2O6]- and [FS3O9]-, a New Class of Weakly Coordinating Anions.

Abstract

The isolation and structural characterization of the fluorodi- and fluorotrisulfate anions, [FS2O6]- and [FS3O9]- are reported. The [FS2O6]- anion has been obtained from reactions of SO3 with XeF2 in the presence of PbF2 as the salt Pb[FSO3][FS2O6] (triclinic, P 1 ¯ , Z = 2, a = 508.65(3), b = 909.67(5), c = 969.67(5) pm, α = 89.494(2)°, β = 77.373(2)°, γ = 76.466(2)° and V = 424.99(4) Å3). The [FS3O9]- ion forms in the reaction of K[FSO3] with SO3 at room temperature as the potassium salt K[FS3O9] (monoclinic, P21/c, Z = 4, a = 1048.69(8), b = 786.39(6), c = 969.58(7) pm, β = 90.431(2)° and V = 799.6(1) Å3). The use of the [FS3O9]- ion as a weakly coordinating anion was demonstrated with the isolation of [Se4][FS3O9]2 (monoclinic, P21/n, Z = 2, a = 719.2(1), b = 1576.0(2), c = 897.7(1) pm, β = 113.015(5)° and V = 936.5(2) Å3), obtained from the reaction of selenium, SO3 and XeF2 at 80°C. We investigated the anions quantum chemically concerning their molecular electrostatic potentials and the electronic energies of formation. The non-covalent interactions in [Se4][FS3O9]2 were analysed using Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital Analysis (NBO).

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