Fluoride Ion affinities of GeF₄ and BF₃ from thermodynamic and structural data for (SF₃)₂GeF₆, C1O₂GeF₅, and C1O₂BF₄

(SF₃)₂GeF₆ is orthorhombic with a = 6.142 (1)Å,b = 9.593 (1) Å, c = 7.458 (1)Å, V= 439.4 (2)ų, and ρcalcd = 2.756 g cm^-3. Full-matrix least-squares refinement using 299 independent observations (Mo Kα, graphite monochromator) in space group Pmnn (No. 58) yielded weighted R = 0.025 (unweighted R = 0.016) from which SF₃⁺ ions are seen to have ~C₃v symmetry with S-F = 1.515 (2), 1.519 (2) Å and F-S-F = 96.2 (1)°. Each SF₃⁺ makes close contact with one F atom from each of three GeF₆^2- ions to give a distorted octahedron of F about S. The GeF₆^2- ions are almost octahedral with Ge-F = 1.783 (1), 1.787 (1) Å and cis F-Ge-F angles within 3σ of 90°, each F ligand being 2.37-2.42 Å from an S atom of an SF₃⁺. Lattice energy calculation gives ΔH°(2SF₃⁺(g) + GeF₆^2-(g) = (SF₃⁺)₂GeF₆^2-)) =-383 (12) kcal mol^-1. From dissociative pressure dependence on temperature, ΔH°((SF₃)₂GeF₆(s) = 2SF₄(g) + GeF₄(g)) = 42.9 (6) kcal mol^-1 and ΔSH° = 125 (2) cal mol^-1 K^-1. Similarly, ΔH°(C1O₂GeF₅(s) = ClO₂F(g) + GeF₄(g)) = 29.1 (4) kcal mol^-1 and ΔS° = 90(1) cal mol^-1 K^-1. Calculation of ΔH°(C1O₂+(g) + GeF₅^-(g) = C1O₂+GeF₅^-(s)) gives-146 (5) kcal mol^-1. The derived enthalpy changes are ΔH°(GeF₄(g) + F^-(g) = GeF₅^-(g, polymer)) =-100 (6) kcal mol^-1 and ΔH°(GeF₄(g) + 2F(g) = GeF₆^2-(g)) =-82 (18) kcal mol^-1. C1O₂BF₄ is monoclinic with a = 5.522 (1) Å, b = 8.646 (1) Å, c = 9.549 (2) Å, β = 98.01 (1)◦, V = 451.4 (2) ų, and ρcalcd = 2.269 g cm^-1. The structure was refined in space group Cc (No. 9) to yield a weighted R = 0.032 (unweighted R = 0.023) from 577 independent reflections. All four fluorine atoms of the tetrahedral BF₄^- ion form van der Waals contacts with the chlorine atoms of neighboring C1O₂⁺ ions. The closest of these contacts are nearly perpendicular to the plane defined by the centers of the chlorine and oxygen atoms. From measurements of the dissociation pressure of C1O₂⁺BF₄^- the previously reported value¹ of ΔH°(C1O₂F(g) + BF₃(g) = C1O₂BF₄(s)) =-24 (1) kcal mol^-1 has been confirmed. Lattice energy calculations have provided for evaluation of the following enthalpy changes: ΔH°(BF₃(g) + F^-(g) = BF₄^-(g)) =-92 (6) kcal mol^-1; ΔH°(SF₄(g) = SF₃⁺(g) + F^-(g))= 211 (8) kcal mol^-1; ΔH°(UF₆(g) + e^- = UF₆^-(g)) =-133 (6) kcal mol^-1.