Zemva, B; Lutar, K; Chacon, L; Felebeuermann, M; Allman, J; Shen, C; Bartlett, N; ,
F- accepters (BF3, AsF5, SbF5, or BiF5) added to solutions of NiF62- salts in anhydrous hydrogen fluoride (aHF) below -65 degrees C precipitate the tan solid NiF4. This solid, preserved at less than or equal to-65 degrees C, is quantitatively converted, by 2 equiv of F- donor (XeF6 or KF) in aHF, to dissolved NiF62-. Dry NiF4 loses F-2 above -60 degrees C, the decomposition to nearly black NiF3 becoming rapid at similar to 0 degrees C. When the dry NiF4 is prepared from K2NiF6, inclusion of some K+ leads, on thermolysis at 0 degrees C, to a pyrochlore form of NiF3 (P-NiF3). P-NiF3 contains K+ in the open channels, with KxNiF3, x approximate to 0.1. The nearly cubic P-NiF3 unit cell is rhombohedral: a(0) = 9.933(3) Angstrom, alpha = 91.01(3)degrees, V = 980 Angstrom(3), z = 16, with absent reflections coincident with those of the cubic space group O-h(7)-Fd3m, appropriate for pyrochlore. Decomposition of NiF4 in aHF begins at -65 degrees C and is rapid at 0 degrees C, giving black rhombohedral NiF3 (R-NiF3) with a(0) = 5.168(2) Angstrom, alpha = 55.46(3)degrees, V = 87.3 Angstrom(3), z = 2. When the NiF4 is made and decomposed at similar to 20 degrees C, with Kf present, a hexagonal tungsten bronze form of NiF3 is precipated (H-NiF3), with a(0) = 7.074(6) Angstrom, c(0) = 7.193(6) Angstrom, V = 312 Angstrom(3), z = 6. R- and H-NiF3 can also be made by mixing solutions of Ni2+ salts [e.g., Ni(AsF6)(2)] With NiF62- salts (e.g. K2NiF6) in aHF. All forms of the trifluoride (R, H, and P) lose F-2 on warming (R > 39 degrees, H > 72 degrees and P > 138 degrees C) to yield NiF2, but an intermediate red-brown phase is observed for R-NiF3. R-NiF3 at similar to 20 degrees C, oxidizes Xe to Xe(VI), perfluoropropene, C3F6, to perfluoropropane, C3F8, and solid LiCl with incandescence. H-NiF3 and P-NiF3 interact similarly but less energetically.