Nickel double salts

Nickel is one of the metals that can form Tutton's salts. The singly charged ion can be any of the full range of potassium, rubidium, cesium, ammonium (${\displaystyle {\ce {NH4}}}$), or thallium.^[1] As a mineral the ammonium nickel salt, (NH₄)₂Ni(SO₄)₂ · 6 H₂O, can be called nickelboussingaultite.^[2] With sodium, the double sulfate is nickelblödite Na₂Ni(SO₄)₂ · 4 H₂O from the blödite family. Nickel can be substituted by other divalent metals of similar sized to make mixtures that crystallise in the same form.^[3]

Nickel forms double salts with Tutton's salt structure with tetrafluoroberyllate with the range of cations of ammonia,^[4] potassium, rubidium, cesium,^[5] and thallium.^[6]

Anhydrous salts of the formula M₂Ni₂(SO₄)₃, which can be termed metal nickel trisulfates, belong to the family of langbeinites. The known salts include (NH₄)₂Ni₂(SO₄)₃, K₂Ni₂(SO₄)₃ and Rb₂Ni₂(SO₄)₃, and those of Tl and Cs are predicted to exist.

Some minerals are double salts, for example Nickelzippeite Ni₂(UO₂)₆(SO₄)₃(OH)₁₀ · 16H₂O which is isomorphic to cobaltzippeite, magnesiozippeite and zinczippeite, part of the zippeite group.^[7]

Double hydrides of nickel exist, such as Mg₂NiH₄.^[8]

formula	name	mol	struct	cell Å			°	V	Z	density	colour	refs
		wt		a	b	c	β	Å3		g/cm3
Li2[NiF(PO4)]	Lithium nickel fluorophosphate	186.56	orthorhombic	10.473	6.289	10.846		714.3	8	3.469		[9]
Na2[NiF(PO4)]	sodium nickel fluorophosphate	218.645	Pbcn				90	823.4				[10]
Na2Ni(SO4)2 · 4 H2O	nickelblödite	368.867	monoclinic	11.045	8.193	5.535	100.50			2.487	green	[11]
K2Ni2(SO4)3	potassium nickel trisulfate	483.77	orthorhombic	9.8436	9.8436	9.8436	90			3.369		[12]
Rb2Ni2(SO4)3	rubidium nickel trisulfate	576.51		9.9217	9.9217	9.9217	90			3.921		[13]
(NH4)2Ni2(SO4)3	ammonium nickel trisulfate	441.65	orthorhombic	9.904	9.904	9.904	90			3.02		[14]
(NH4)4Ni3(SO4)5	ammonium nickel pentasulfate	728.56									yellow	[15]
NiLa(SeO3)2Cl	nickel lanthanum diselenite chloride	486.977	hexagonal	8.666		18.662		1194.2	6		(153K)	[16]
NiNd10(SeO3)12Cl8	nickel Neodymium diselenite chloride		monoclinic	15.8175	1578,68	19.276	114.202	7407	4		(153K)	[17]
Ni6Fe3+2(SO4)(OH)16 · 4 H2O	honessite	904.08	trigonal	3.083		26.71		219.86	0.25	1.71	green	[18]
NiTi(SO4)3	nickel titanium sulfate		monoclinic	8.254	8.54	14.1444	124.967	817	4	3.21		[19]
Na2Ni(SeO4)2 · 2 H2O	sodium nickel selenate dihydrate		triclinic	5.507	5.905	7.172	α = 108.56 °, β = 99.07 °, γ = 106.35 °	204.2	1			[20]
K2Ni(SeO4)2 · 2 H2O	potassium nickel selenate dihydrate											[21]
K2Ni(SeO4)2 · 6 H2O	potassium nickel selenate Tuttons salt	527.52	monoclinic	a	b	c	104.45		4	2.559	bright green	[22]
Rb2Ni(SeO4)2 · 6 H2O	rubidium nickel selenate Tuttons salt	619.62	monoclinic	a	b	c	105.20		4	2.856	bright green	[22]
Cs2Ni(SeO4)2 · 6 H2O	caesium nickel selenate Tuttons salt	713.62	monoclinic	9.426	12.961	6.473	106.17	759.5	2	3.114	bright emerald green	[22][23]
(NH4)2Ni(SeO4)2 · 6 H2O	ammonium nickel selenate Tuttons salt	485.68	monoclinic	a	b	c	106.29		4	2.243	bright green	[22]
Tl2Ni(SeO4)2 · 6 H2O	thallium nickel selenate Tuttons salt		monoclinic	a	b	c	105.60		4	3.993	bright green	[24]
K2NiP2O7		310.85	monoclinic P21	9.230	17.540	8.32	91.44	1346.3	8	3.067		[25]
K6Sr2Ni5(P2O7)5		786.55	monoclinic P21/c	11.038	9.53	7.438	100.13	1578	2	3.309	yellow	[25]
NaNi2(SO4)2[(H2O)(OH)]			monoclinic C2/m Natrochalcite-type	8.605	6.185	7.336	114.78	354.5	2			[26]
BaNi2(PO4)2	barium nickel phosphate		Trigonal R-3	4.8112	4.8112	23.302		467.1	3		green	[27]
BaNi2(AsO4)2	barium nickel arsenate		Trigonal R-3	4.945	4.945	23.61		532.59	3	5.31		[27]
BaNi2(VO4)2	barium nickel vanadate		Trigonal R-3	5.0375	5.0375	22.33			3			[28]
Na4Ni7(AsO4)6	tetrasodium heptanickel hexaarsenate	1336.3	monoclinic C2/m	14.538	14.505	10.6120	118.299	1970.3	4		brown	[29]
K2Ni(CO3)2 · H2O	potassium nickel carbonate Potassium tetraaquadicarbonatonickelate		monoclinic Baylissite-type	6.755	6.156	12.2406	113.265	467.6	2	2.34		[30]
Rb2Ni(CO3)2 · H2O	Rubidium nickel carbonate		monoclinic Baylissite-type	6.971	6.348	12.2807	114.289	495.34	2	2.83		[31]
NiTh(NO3)6 · 8 H2O	nickel thorium nitrate		Monoclinic P21/c	9.089	8.728	13.565	96.65	1068.8(2)				[32]
K[NiGa2(PO4)3(H2O)2]	Potassium nickel(II) gallium phosphate hydrate	558.17	Monoclinic C2/c	13.209	10.173	8.813	107.68	1128.4	Z = 4			[33]
KNi3(PO4)P2O7	Potassium trinickel(II) orthophosphate diphosphate	484.14	Monoclinic	9.8591	9.3953	9.9778	118.965	808.63	4			[34]
KNiPO4	potassium nickel phosphate											[35]
KNiPO4 · 6 H2O	potassium nickel phosphate hexahydrate		monoclinic P21	6.8309	11.0610	6.1165	91.045	462.07	2			[36]
NiK4(P3O9)2 · 7 H2O	nickel potassium tricyclophosphate hydrate		orthorhombic Fm2m	23.03	11.882	8.732			4		blue	[37]
NiK4(P3O9)2	nickel potassium tricyclophosphate		triclinic P-1	6.143	6.80	12.80	α=102.8 β=89.7 γ=66.03	473.56	1			[37]
NaK5Ni5(P2O7)4	Sodium pentapotassium pentanickel tetra(diphosphate)	1207.80	triclinic	7.188	9.282	10.026(5)	α=109.31 β=90.02 γ=104.07	610.0	1			[38]
NH4NiPO4·H2O	ammonium nickel phosphate hydrate		orthorhombic	5.566	8.760	4.742		231.2				[39]
NH4NiPO4·6H2O	ammonium nickel phosphate hydrate Ni-struvite		Orthorhombic Pmn21	6.924	6.104	11.166		471.5	2			[40][41][42]
LiNiPO4	lithium nickel phosphate		orthorhombic	10.032	5.855	4.681		274.9	4		brown	[43]
NaNiPO4	sodium nickel phosphate		Pnma maricite structure	8.7839	6.7426	5.0368		298.31	4		yellow	[44]
NaNiPO4	sodium nickel phosphate		Pnma triphylite form	4.98	6.13	9.98		304.23				[45]
Na4Ni7(PO4)6			Cm	10.550	13.985	6.398	104.87	912.4	2	3.906		[44][46]
NaNiPO4 · 7 H2O	sodium nickel phosphate heptahydrate		tetrahedral P42/mmc	6.7390		10.9690		498.15	2			[36]
Na3NiP3O10 · 12 H2O	trisodium nickel triphosphate dodecahydrate		monoclinic (pseudoorthorhombic)	15.0236	9.1972	14.6654.	90.0492	2014.46		1.967	light green	[47]
Na5Ni2(PO4)3 · H2O	Pentasodium dinickel triphosphate hydrate		monoclinic space group P21/n	14.0395	5.185	16.4739	110.419					[48]
Na6Ni2(PO4)3OH			orthorhombic Pcmb	7.501	21.4661	7.173						[48]
Na2Ni3(OH)2(PO4)2	sodium nickel hydroxide phosphate		monoclinic	14.259	5.695	4.933	104.28		2	3.816		[49]
NiNa4(P3O9)2 · 6 H2O	nickel tetrasodium cyclotriphosphate hexahydrate		triclinic	6.157	6.820	10.918	α=80.21 β=97.8 γ=119.5	409.8	1			[50]
NiRb4(P3O9)2	nickel tetrarubidium cyclotriphosphate		P-31c	7.288	7.288	20.343			2			[51]
NiCs4(P3O9)2 · 6 H2O	nickel tetracaesium cyclotriphosphate hydrate		orthorhombic	19.992	6.500	18.445			4			[37]
NiCs4(PO3)6	nickel tetracaesium cyclotriphosphate		rhombohedral P-31c	11.602	11.602	9.078		1058.24	2			[37]
NiAg4(P3O9)2 · 6 H2O	nickel tetrasilver cyclotriphosphate hexahydrate		triclinic	9.209	8.053	6.841	α=89.15 β=102.94 γ=97.24		1			[52]
NiAg4(P3O9)2	nickel tetrasilver cyclotriphosphate		triclinic	6.100	6.783	10.764	α = 78.66 β=96.85 γ=113.36	401	1			[52]
Ni(NH4)4(P3O9)2 · 4 H2O	nickel tetraammonium cyclotriphosphate tetrahydrate		monoclinic						2			[53]
TlNi4(PO4)3	Thallium nickel triphosphate		orthorhombic Cmc21						4		pale yellow	[54]
Tl4Ni6(PO4)6	Thallium nickel hexaphosphate		monoclinic Cm						4		yellow brown	[54]
Tl2Ni4P2O7(PO4)2			monoclinic C2/c						8		brown	[54]
NiMnSb	Nickel manganese antimonide		cubic	5.945				210.1	4	7.57		[55]
NiMnSi	Nickel manganese silicide		Orthorhombic	5.8967	3.6124	6.9162		147.32	4			[56][57]
NiMnGe			orthorhombic Pnma	6.053	3.769	7.090		161.75	2			[58]
NiFeGe			hexagonal									[58]
TiNiSi			orthorhombic									[58]
NaNiIO6	sodium nickel periodate		orthorhombic	8.599	2.492	10.281		220.3				[59]
KNiIO6	potassium nickel periodate		orthorhombic	12.09	3.683	6.062		269.9				[59]
KNiIO6	potassium nickel periodate		triclinic	6.4203	5.075	4.223	α= 65.07 β= 92.717 γ=109.95	116.51				[59]

Double fluorides include the above-mentioned fluoroanion salts, and those fluoronickelates such as NiF₄ and NiF₆. Other odd ones include an apple green coloured KNiF₃·H₂O and NaNiF₃·H₂O, aluminium nickel pentafluoride AlNiF₅·7H₂O, ceric nickelous decafluoride Ce₂NiF₁₀·7H₂O, niobium nickel fluoride Ni₃H₄Nb₂F₂₀·19H₂O, vanadium nickel pentafluoride VNiF₅·7H₂O, vanadyl nickel tetrafluoride VONiF₄·7H₂O, chromic nickelous pentafluoride CrNiF₅·7H₂O, molybdenum nickel dioxytetrafluoride NiMoO₂F₄·6H₂O, tungsten nickel dioxytetrafluoride NiWO₂F₄·6H₂O and NiWO₂F₄·10H₂O, manganic nickel pentafluoride MnNiF₄·7H₂O, nickelous ferric fluoride FeNiF₅·7H₂O.^[60]

Nickel trichloride double salts exist which are polymers. Nickel is in octahedral coordination, with double halogen bridges. Examples of this include RbNiCl₃, pinkish tan coloured H₂NN(CH₃)₃NiCl₃.^[61] Other double trichlorides include potassium nickel trichloride KNiCl₃·5H₂O,^[62] yellow cesium nickel trichloride CsNiCl₃,^[62] lithium nickel trichloride LiNiCl₃·3H₂O,^[62] hyrdrazinium nickel tetrachloride,^[62] and nickel ammonium chloride hexahydrate NH₄NiCl₃·6H₂O.^[63]

The tetrachloronickelates contain a tetrahedral NiCl₄²⁻ and are dark blue. Some salts of organic bases are ionic liquids at standard conditions.^[64] tetramethylammonium nickel trichloride is pink and very insoluble.^[65] Other tetrachlorides include rubidium nickel tetrachloride, lithium nickel tetrachloride Li₂NiCl₄·4H₂O stable from 23 to 60°, stannous nickel tetrachloride SnCl₂•NiCl₂•6H₂O, stannic nickel hexachloride SnCl₄•NiCl₂•6H₂O is tetragonal.^[66]

Lithium nickel hexachloride Li₄NiCl₆·10H₂O is stable from 0 to 23°.

Copper nickel dioxychloride 2CuO·NiCl₂·6H₂O, and copper nickel trioxychloride 3CuO·NiCl₂·4H₂O.^[62]

Cadmium dinickel hexachloride, CdCl₂•2NiCl₂•12H₂O crystallises in hexagonal system, dicadmium dinickel hexachloride, 2CdCl₂•NiCl₂•12H₂O has rhombic crystals, and is pleochroic varying from light to dark green.^[66]

Thallic nickel octochloride 2TlCl₃•NiCl₂•8H₂O is bright green.^[66]

Double bromides include the tetrabromonickelates, and also caesium nickel tribromide, CsNiBr₃ copper nickel trioxybromide, 3CuO·NiBr₂·4H₂O mercuric nickel bromide, Hg₂NiBr6, HgNiBr₄. Aqueous nickel bromide reacting with mercuric oxide yields mercuric nickel oxybromide, 6NiO.NiBr₂•HgBr₂•20H₂O didymium nickel bromide, 2(Pr,Nd)Br₃•3NiBr₂•18H₂O is reddish brown (mixture of praseodymium and neodymium) Lanthanum nickel bromide, 2LaBr₃•3NiBr₂•18H₂O nickel stannic bromide (or nickel bromostannate) NiSnBr₆·8H₂O is apple green.^[67][68]

The tetraiodonickelates are blood red coloured salts of the NiI₄ ion with large cations. Double iodides known include mercuric nickel hexaiodide 2HgI₂•NiI₂ · 6 H₂O, mercuric nickel tetraiodide HgI₂•NiI₂ · 6 H₂O, and lead nickel hexaiodide I₂•2NiI₂ · 3 H₂O.^[69]

The diperiodatonickelates of nickel IV are strong oxidisers, and akali monoperiodatonickelates also are known.

Nickel forms double nitrates with the lighter rare earth elements. The solid crystals have the formula Ni₃Me₂(NO₃)₁₂•24H₂O. The metals include La Ce Pr Nd Sm Gd and the non rare earth Bi. Nickel can also be replaced by similar divalent ions, Mg, Mn Co Zn. For the nickel salts melting temperatures range from 110.5° for La, 108.5° for Ce, 108° for Pr, 105.6° for Nd, 92.2° for Sm and down to 72.5° for Gd The Bi salt melting at 69°. Crystal structure is hexagonal with Z=3.^[70] Ni₃La₂(NO₃)₁₂•24H₂O becomes ferromagnetic below 0.393 K.^[71] These double nickel nitrates have been used to separate the rare earth elements by fractional crystallization.^[72]

Nickel thorium nitrate has formula NiTh(NO₃)₆ · 8 H₂O. Nickel atoms can be substituted by other ions with radius 0.69 to 0.83 Å. The nitrates are coordinated on the thorium atom and the water to the nickel. Enthalp of solution of the octahydrate is 7 kJ/mol. Enthalpy of formation is -4360 kJ/mol. At 109° the octahydrate becomes NiTh(NO₃)₆•6H₂O, and at 190° NiTh(NO₃)₆•3H₂O and anhydrous at 215°.^[32] The hexahydrate has Pa3 cubic structure.^[32]

Various double amides containing nickel clusters have been made using liquid ammonia as a solvent. Substances made include red Li₃Ni₄(NH₂)₁₁·NH₃ (Pna21; Z = 4; a = 16.344(3) Å; b = 12.310(2) Å; c = 8.113(2) Å v=1631 D=1.942), and Cs₂Ni(NH₂)₄•NH₃ (P21/c; Z = 4; a =9.553(3) Å; b = 8.734(3) Å; c = 14.243(3) Å; β = 129.96(3)° V=910 D=2.960). These are called amidonickel compounds.^[73] Yet others include Li₄Ni₄(NH₂)₁₂·NH₃, Na₂Ni(NH₂)₄,^[74] orange red Na₂Ni(NH₂)₄•2NH₃,^[75] Na₂Ni(NH₂)₄•NH₃, K₂Ni(NH₂)₄•0.23KNH₂, and Rb₂Ni(NH₂)₄•0.23RbNH₂.^[73]

Nickel dihydrogen phosphide (Ni(PH₂)₂) can form orange, green or black double salts KNi(PH₂)₃) that crystallise from liquid ammonia. They are unstable above -78 °C, giving off ammonia, phosphine and hydrogen.^[76]