Fluoronickelate

The fluoronickelates are a class of chemical compounds containing an anion with nickel at its core, surrounded by fluoride ions which act as ligands. This makes it a fluoroanion. The nickel atom can be in a range of oxidation states from +2, +3 to +4. The hexafluoronickelate(IV)²⁻ ion NiF₆²⁻ contains nickel in the maximal +4 state, and is in octahedral coordination by the fluoride atoms. It forms a commercially available salt Potassium hexafluoronickelate(IV) K₂NiF₆. Solid double salts can also contain tetrafluoronickelate NiF₄ eg K₂NiF₄.

formula	name	Ni Ox	structure	Remarks	references
(NH4)2NiF4	ammonium tetrafluoronickelate	2		Fuse NiCl2 with NH4F, light green color	[1][2]
(NH4)2NiF4·2H2O	ammonium tetrafluoronickelate dihydrate	2		Formed from Ni(OH)2 and NH4F in water	[3]
K2NiF4	potassium tetrafluoronickelate	2			[1]
Rb2NiF4	rubidium tetrafluoronickelate	2			[1]
Ba2NiF6	barium nickel fluoride	2		yellow square plates cas=18115-49-6	[4]
Pb2NiF6	lead(II)nickel(II) fluoride	2		cas=27037-78-1	[4]
Li3NiF6		3	Pna2 C92v a=9.60 Å b=8.37 Å c=4.09 Å Z=4 density=3.27 / 3.24	formed at 500° 70 bar F2	[5][6]
Na3NiF6	sodium hexafluoronickelate	3		violet cas=22707-99-9	[4]
K3NiF6	potassium hexafluoronickelate	3		violet cas=14881-07-3	[4][7]
KCs2NiF6	dicesium potassium hexafluoronickelate	3		lilac colour cas=53479-35-9	[4]
Li2NiF6	lithium hexafluoronickelate	4	hexagonal a=8.321 Å c=4.598 Å V=275.7 Å3 Z=3	pink sol 0.5 g/100 g HF at 0°	[5][7]
(O2)2NiF6	dioxygenyl hexafluoronickelate			possibly existing, decompose 10°	[8][9]
(NO2)2NiF6	dinitronium hexafluoronickelate	4		ΔH=-471 kJ/mol, ΔH0f=-1120	[10]
Na2NiF6	sodium hexafluoronickelate	4	cubic; or tetragonal	purple red	[11]
K2NiF6	potassium hexafluoronickelate	4	K2PtCl6 structure	red cas=17218-47-2	[11]
CaNiF6	calcium hexafluoronickelate	4		ΔH=-363 kJ/mol, ΔH0f=-1951 kJ/mol sold as a fluorine source	[10]
Rb2NiF6	rubidium hexafluoronickelate	4	K2PtCl6 structure	red cas=17218-48-3	[11]
Cs2NiF6	Cesium hexafluoronickelate	4	K2PtCl6 structure	red cas=17218-49-4	[11]
SrNiF6	strontium hexafluoronickelate	4		red cas=66456-12-0	[11]
BaNiF6	barium hexafluoronickelate	4	K2PtCl6 structure	red cas=66456-13-1	[11]
(NF4)2NiF6	bis-tetrafluoroammonium hexafluoronickelate	4	tetragonal K2PtCl6 structure	red cas=63105-40-8	[11]
(ClF2O)NiF6	bis [difluorooxychlorine (V)] hexafluoronickelate (IV)	4		deep purple, stable to 60 °C	[12][13]