Chalkogenfluoride in niedrigen Oxydationsstufen. V. Die ungewöhnlichen chemischen Gleichgewichte F3S?SF ⇌ 2SF2 und CF3SF2?SCF3 ⇌ 2 CF3SF

Lower Chalcogen Fluorides V. Unusual Chemical Equilibria F₃S? SF ? 2 SF₂ and CF₃SF₂? SCF₃ ? 2 CF₃SF SF₂ and CF₃SF form unusual chemical equilibria with their dimers F₃SSF and CF₃SF₂ SCF₃ involving two different bonds (SF and SS). The equilibrium between F₃SSF and SF₂ is disturbed by a decomposition reaction of these compounds yielding SF₄ and SSF₂ · K_p (298) = 2.5 · 10^?3atm, ΔH°₂₉₈ = 68.5 kJ/mol for the system F₃SSF ? 2SF₂ and K_p(298) = 1.3 × 10³ atm, δH₂₉₈ = 42.5 kJ/mol for the system CF₃SF₂SCF₃ ? 2CF₃SF have been determined as the equilibrium constants and the dissociation enthalpies. In both systems kinetic hindrance delays the achievement of the equilibrium. The rates for dissociation and decomposition are strongly surface dependent. Under favourable conditions the half-lives at 298 K for the dissociation of F₃SSF and CF₃SF₂SCF₃ are found to be ca. 8 h and ca. 2 h respectively, and for the decomposition of SF₂ and CF₃SF (p ～ 13 mbar) the values are ca. 10 h and 1 year respectively.