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

Thomas E. Mallouk, Guy L. Rosenthal, Gerhard MÜLler, Raymond Brusasco, Neil Bartlett

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Abstract

(SF3)2GeF6 is orthorhombic with a = 6.142 (1)Å,b = 9.593 (1) Å, c = 7.458 (1)Å, V= 439.4 (2)Å3, 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 GeF62- ions to give a distorted octahedron of F about S. The GeF62- 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) + GeF62-(g) = (SF3+)2GeF62-)) =-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) = GeF62-(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) Å3, 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.

Original languageEnglish (US)
Pages (from-to)3167-3173
Number of pages7
JournalInorganic chemistry
Volume23
Issue number20
DOIs
StatePublished - Jan 1984

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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