Thermochemistry of Nickel Trifluoride

Abstract

The literature data on thermal behavior of crystalline nickel fluorides NiF₃ and Ni₂F₅ in the higher oxidation states are analyzed. Their enthalpies of formation are calculated: Δ_fH^o(Ni[NiF₆](cr), 0 K) = -1399.6 ± 6 and Δ_fH^o(Ni₂F₅(cr), 0 K) = −1370.5 ± 8 kJ/mol. The partial saturated vapor pressures in the NiF₃–Ni₂F₅ and Ni₂F₅–NiF₂ systems over a broad temperature range are determined. The technical impossibility to achieve a measurable pressure of NiF₃ is shown. The findings are compared to the data for similar derivatives of 3d-block elements and ruthenium and platinum trifluorides. Ni₂F₅(cr) is suggested to be used as a fluorine accumulator.