Thermochemistry of Nickel Trifluoride

The literature data on thermal behavior of crystalline nickel fluorides NiF 3 and Ni 2 F 5 in the higher oxidation states are analyzed. Their enthalpies of formation are calculated: Δ f H o (Ni[NiF 6 ](cr), 0 K) = -1399.6 ± 6 and Δ f H o (Ni 2 F 5 (cr), 0 K) = −1370.5 ± 8 kJ/mol. The partial saturated vapor pressures in the NiF 3 –Ni 2 F 5 and Ni 2 F 5 –NiF 2 systems over a broad temperature range are determined. The technical impossibility to achieve a measurable pressure of NiF 3 is shown. The findings are compared to the data for similar derivatives of 3d-block elements and ruthenium and platinum trifluorides. Ni 2 F 5 (cr) is suggested to be used as a fluorine accumulator.