The crystal structure of barium manganese(II) iron(III) fluoride BaMnFeF7

The crystal structure of the monoclinic compound BaMnFeF₇ has been determined: a = 553.2(1), b = 1098.0(2), c = 918.3(1) pm, β = 94.67(1)°, V = 555.9(3) × 10^?24 cm³, Z = 4. All atoms are in general positions of space group $\text{P2}{}_1\text{c}$, weighted R = 0.031, using 1771 independent single-crystal reflections with I > 2σ(I). The structure consists of edge-sharing dinuclear Mn₂F^6?₁₀ units (MnMn = 322.2 pm), linked via corners by intermediate FeF₆ octahedra, at which two cis ligands remain unbridged. The average distances in the distorted octahedra are MnF = 211.6 pm and FeF = 192.7 pm. The barium atoms are irregularly 12-coordinated with a mean distance BaF = 290.5 pm. The structure is discussed in relation to the trigonal weberite Na₂MnFeF₇ and others.     

Die Kristallstrukturen der Weberite Na2CuScF7 und Na2ZnAlF7

The Crystal Structures of the Weberites Na₂CuScF₇ and Na₂ZnAlF₇ At single crystals of the orthorhombic weberites Na₂CuScF₇ (Pmnb, Z = 4) and Na₂ZnAlF₇ (Imma, Z = 4) X-ray structure determinations were performed. Na₂CuScF₇ (Na₂ZnAlF₇): a = 726.0 (709.2), b = 1053.4 (1009.2), c = 765.8 (733.7) pm; R1 = 0.030 (0.042) for 887 (363) observed and independent reflections. The resulting average distances of the octahedrally coordinated metal atoms are: Cu? F = 200.7 pm, Sc? F = 201.7 pm; Zn? F = 198.8 pm, Al? F = 180.1 pm. Some structural relations and the variation in the bridge angles of the corner-sharing octahedra are discussed.     

Structure of Na2Fe2F7 and structural relations in the family of weberites Na2MIIMIIIF7

The mixed valence compound Na₂Fe₂F₇ crystallizes in the monoclinic weberite structure of the Na₂CuFeF₇-II type (M-II), space group C2/c, Z = 16, a = 12.676, b = 7.422, c = 24.710 Å, β = 99.97°. Refinement on F² led to wR(F²) = 0.117 for all 2 645 reflections, R = 0.057 for 1 258 refl. with F_o > 4σ(F). On the basis of this and other recent single crystal investigations the structures of weberites Na₂M^IIM^IIIF₇ are classified in four main structure types: O-I is the ‘classical’ orthorhombic weberite type (S.G. Imma) encountered e.g. in the mineral Na₂MgAlF₇, from which two lower symmetric variants O-II (Na₂CuCrF₇ type) and O-III (Na₂NiInF₇) are deriving. The second M-I and third M-II basic type are monoclinic (e. g. Na₂CuFeF₇-I and -II), the fourth type T is trigonal (Na₂MnFeF₇). The structural relations within the weberite family are discussed and the connections established, which allow to regard these weberites as well as the pyrochlores as subtraction derivatives of the fluorite type.     

Kristallstrukturbestimmungen an vier monoklinen Weberiten Na2MIIMIIIF7 (MII = Fe,Co; MIII = V,Cr)

Crystal Structure Determinations of Four Monoclinic Weberites Na₂M^IIM^IIIF₇ (M^II = Fe, Co; M^III = V, Cr) By solid state reaction of the binary fluorides single crystals of the following weberites were prepared and their monoclinic structure (space group C2/c, Z = 16) determined by X-ray methods: Na₂FeVF₇ (a = 1 271.0(3), b = 742.9(1), c = 2 471.6(5) pm, β = 100.03(3)°; R₁ = 0.043 (1 545 Reflexe); Fe? F = 203.8, V? F = 193.0 pm); Na₂FeCrF₇ (a = 1 262.5(3), b = 739.1(1), c = 2 460.5(5) pm, β = 99.93(3)°; R₁ = 0.029 (2 340); Fe? F = 203.6, Cr? F = 190.5 pm); Na₂CoVF₇ (a = 1 270.3(5), b = 739.1(3), c = 2 465.1(10) pm, β = 100.02(3)°; R₁ = 0.028 (2 250); Co? F = 201.6, V? F = 193.6 pm); Na₂CoCrF₇ (a = 1 257.8(3), b = 733.5(1), c = 2 441.5(5) pm, β = 99.64(3)°; R₁ = 0.030 (2 227); Co? F = 201.2, Cr? F = 190.2 pm). Concerning the above average distances within the distorted [MF₆] octahedra and the shape of [NaF₈] coordination details are given and discussed.     

Die Kryolithstruktur von Na3ScF6 und die Oktaederkippung in isostrukturellen Natriumhexafluorometallaten Na3MF6

The Cryolite Structure of Na₃ScF₆ and the Tilting of Octahedra in Isostructural Sodium Hexafluorometallates Na₃MF₆ X-ray studies at single crystals of Na₃ScF₆ confirmed the monoclinic cryolite type structure of this compound: a = 559.5, b = 580.2, c = 811.6 pm, β = 90.72°, Z = 2, space group P2₁/n; R1 = 0.021 for 512 symmetry independent reflections. The octahedra of [ScF₆] (average Sc? F = 200.7 pm), as well as those of [NaF₆] (Na1? F = 229.1 pm) linked to them, are titled by about 20° with respect to the axes of the perovskite-like pseudocell. This tilting of octahedra is discussed in comparison with other cryolites and with orthorhombic perovskites NaMF₃; there results a correlation between tilt angle and tolerance factor t ? 0.88 of these compounds, the [NaF₈] coordination of which invariably exhibits a constant mean value of Na2? F = 231.5 ± 1 pm for the four shortest distances.     

Copper Weberites: Crystal Structure and Magnetic Investigation of Na2CuGaF7 and Na2CuInF7

The crystal structures of two new copper weberites Na₂CuGaF₇ and Na₂CuInF₇ have been determined. Na₂CuGaF₇ has the monoclinic space group C2/c: a = 1232.5(5) pm, b = 731.8(1) pm, c = 1278.0(5) pm, β = 109.29(2)° and Z = 8. Na₂CuInF₇ crystallizes in the orthorhombic space group Pmnb: a = 731.8(1) pm, b = 1060.2(2) pm, c = 771.2(1) pm and Z = 4. The structures have been refined from 1175 reflections to R = 0.043 (wR = 0.035) for Na₂CuGaF₇, and from 1917 reflections to R = 0.034 (wR = 0.025) for Na₂CuInF₇. The structures consist of [CuF₅]_n^3n? chains which are parallel the a-axis in Na₂CuInF₇ and oriented in two alternating directions in Na₂CuGaF₇. Sodium atoms exhibit either seven-fold or eight-fold coordination. Although strong antiferromagnetic interactions are observed inside the chains, there is no evidence for three-dimensional ordering.     

Über röntgenographische Einkristalluntersuchungen an Na2FeAlF7, Na2MIIGaF7 (MII = Ni,Zn) und Na2ZnFeF7 und die Strukturchemie der Weberite

On X-Ray Single Crystal Studies of Na₂FeAlF₇, Na₂M^IIGaF₇ (M^II = Ni, Zn), and Na₂ZnFeF₇ and the Structural Chemistry of Weberites At single crystals of the orthorhombic weberite Na₂NiGaF₇ (a = 716.1, b = 1021.6, c = 740.9 pm; Imma, Z = 4) and of the monoclinic variants (C2/c, Z = 16) Na₂FeAlF₇ (a = 1242.6, b = 727.8, c = 2420.6 pm, β = 99.99°), Na₂ZnGaF₇ (a = 1251.9, b = 730.3, c = 2435.3 pm, β = 99.74°) and Na₂ZnFeF₇ (a = 1261.0, b = 7.359, c = 2453.8 pm, β = 99.70°) complete X-ray structure determinations were performed. The results and the influence of radii on the bridge angles M^II–F–M^II and M^II–F–M^III are discussed in connection with general features within the structural chemistry of 28 weberites.     

Darstellung sowie Kristall- und Molekülstruktur von Triphenylphosphinoxidhydrogenfluorid, (C6H5)3PO · HF

Preparation, Crystal and Molecular Structure of Triphenylphosphineoxide Hydrogen - fluoride (C₆H₅)₃PO · HF (C₆H₅)₃PO · HF was prepared from hydrofluoric acid (40%) and (C₆H₅)₃PO in benzene. It crystallizes in the monoclinic space group P2₁/c with a = 1 032.8(3), b = 1 051.0(7), c = 1695.5(2) pm, β = 121.95(2)° and Z = 4; d (calc./obs.) 1.27/1.26 g ° cm^?3. The structure was determined by direct methods from 2 709 independent reflections and has been refined by full matrix least squares methods to R = 0.049. In the compound HF and (C₆H₅)₃PO are linked by a short H-bond. Some distances: O? F 238.4(5), O? H 142.3, H? F 99.8, P? O 149.5(4) pm. Angle O? H? F 159.8°.     

Die Kristallstrukturen der Vanadium-Weberite Na2MIIVIIIF7 (MII  Mn,Ni, Cu) und von NaVF4

The Crystal Structures of the Vanadium Weberites Na₂M^IIV^IIIF₇ (M^II ? Mn, Ni, Cu) and of NaVF₄ At single crystals of the vanadium(III) compounds NaVF₄ (a = 790.1, b = 531.7, c = 754.0 pm, β = 101.7°; P2₁/c, Z = 4), Na₂NiVF₇ (a = 726.0, b = 1031.9, c = 744.6 pm; Imma, Z = 4) and Na₂CuVF₇ (a = 717.6, b = 1043.5, c = 754.6 pm; Pmnb, Z = 4) X-ray structure determinations were performed, at Na₂MnVF₇ (a = 746.7, c = 1821.6 pm; P3₂21, Z = 6) a new refinement. NaVF₄ crystallizes in the layer structure type of NaNbO₂F₂. The fluorides Na₂M^IIVF₇ represent new orthorhombic (M^II ? Ni; Cu) resp. trigonal (M^II ? Mn) weberites. The average distances within the [VF₆] octahedra of the four compounds are in good agreement with each other and with data of related fluorides (V? F: 193.3 pm). The differences between mean bond lengths of terminal and bridging F ligands are 5% in NaVF₄, but less than 1% in the weberites. Details and data for comparison are discussed.     

Ternäre Halogenide vom Typ A3MX6. III [1, 2]. Synthese,Strukturen und Ionenleitfähigkeit der Halogenide Na3MX6 (X = Cl,Br)

Ternary Halides of the A₃MX₆ Type. III [1, 2]. Synthesis, Structures, and Ionic Conductivity of the Halides Na₃MX₆ (X = Cl, Br) The bromides Na₃MBr₆ crystallize with the stuffed LiSbF₆-type structure (type I; M = Sm? Gd) or with the structure of the mineral cryolite (type II; M = Gd? Lu). The structure types were refined from single crystal X-ray data (Na₃SmBr₆: trigonal, space group R3 , a = 740.8(2) pm, c = 1 998.9(8) pm, Z = 3; Na₃YBr₆: monoclinic, space group P2₁/n, a = 721.3(4) pm, b = 769.9(2) pm, c = 1 074.8(4) pm, β = 90.60(4)°, Z = 2). Reversible phase transitions from one structure to the other occur. The phase transition temperatures were determined for the bromides as well as for the chlorides Na₃MCl₆ (M = Eu? Lu). The refinement of both structures for one compound was possible for Na₃GdBr₆ (I: trigonal, space group R3 , a = 737.1(5) pm, c = 1 887(2) pm, Z = 3; II: monoclinic, space group P2₁/n, a = 725.2(1) pm, b = 774.1(3) pm, c = 1 080.1(3) pm, β = 90.76(3)°, Z = 2). All compounds exhibit ionic conductivity of the sodium ions which decreases with the change from type I to type II. The conductivity of the bromides is always higher when compared with the respective chlorides.     

Die Kristallstruktur der Verbindungen BaCaGaF7 und BaCaCrF7

Crystal Structure of the Compounds BaCaGaF₇ and BaCaCrF₇ The isostructural fluorides BaCaGaF₇ and BaCaCrF₇ (values in parentheses) crystallize monoclinically in space group P2/n, Z = 4: a = 539.0 (539.8), b = 541.0 (542.2), c = 1897.8 (1900.6) pm, β = 92.33 (92.10)°. Complete X-ray single crystal structure determinations showed, that the compounds are built up from triple layers [CaF_8/2 · MF₃]^2?, which consist of a central sheet of edge-sharing CaF_8/2^2? polyhedra (distorted square antiprisms) with M^IIIF₆octahedra condensed on it at both sides and which are held together by 12-coordinated barium ions. The resulting average distances are: Ga? F = 187.8 (Cr? F = 189.4) pm, Ca ? F = 236.2 (236.2) pm, Ba? F = 289.4 (289.4) pm. Some relations to the structures of other fluorides are discussed.     

Kristallstrukturen von MgCr2O4-Typ Li2VCl4 und Spinell-Typ Li2MgCl4 und Li2CdCl4

Crystal Structures of MgCrO₄-type Li₂VCl₄ and Spinel-type Li₂MgCl₄ and Li₂CdCl₄ The crystal structures of the ternary lithium chlorides Li₂MCl₄ (M = Mg, V, Cd) have been determined firstly by X-ray single-crystal experiments. Li₂MgCl₄ and Li₂CdCl₄ crystallize in an inverse spinel structure (space group Fd3 m, Z = 8, a = 1 040.1(2) and 1 062.06(9) pm, structural parameters u = 0.25699(2) and 0.2550(1), R = 1.7 and 3.7% for 218 and 211 unique reflections). The Li? Cl distances of the tetrahedrally coordinated Li⁺ ions are significantly greater than calculated with Shannon's crystal radii ( > 238 ± 1 instead of 233 pm). Contrary to the results of X-ray powder data reported in the literature, Li₂VCl₄ crystallizes in the distorted spinel structure of MgCr₂O₄ type (space group F4 3m, Z = 8, a = 1 037.49(2) pm, R = 5.9% for 217 unique reflections). The decrease of the site symmetry of the octahedrally coordinated ions (V²⁺, Li⁺) from 3 m to 3m resulting in contracted and widened tetrahedral M₄ entities of the spinel structure is obviously caused by V? V metal—metal bonds (shortest V? V distance 366.2(7) pm).     

Die Kristall- und Molekülstrukturen von Chlorotrispyridinium-bis-(tetrachloroaluminat(III)) und einer weiteren Modifikation von Pyridiniumchlorid

Crystal- and Molecular Structures of Chlorotrispyridinium-bis-(tetrachloroaluminate(III)) and a New Modification of Pyridinium Chloride The compounds PyHCl and ((PyH)₃Cl)(AlCl₄)₂ are formed by hydrolysis during the synthesis of adducts in the system AlCl₃/pyridine. The second room temperature modification of PyHCl crystallizes in the space group P2₁/c with the lattice constants a = 847.9(3), b = 1770.2(3), c = 801.9(3) pm, β = 95.23(3)°, Z = 8. The atomic parameters were refined from 4471 measured intensities to R(F) = 6,9%. The N? Cl distances are 306.8(7) and 311.0(8) pm. The unit cell of ((PyH)₃Cl)(AlCl₄)₂ is orthorhombic (space group Pbca) and has the lattice constants a = 1306.3(4), b = 1589.4(4), c = 2708.6(7) pm, Z = 8. The crystal structure was refined from 7226 measured intensities to R(F) = 6.7%. The cation shows three pyridinium ions to have NH…?Cl hydrogen bonds to a central positioned chloride ion with N? Cl distances of 301.4(7), 305(1) and 306(1) pm.     

Na3F[WO4]: A Sodium Fluoride Ortho‐Oxotungstate(VI) with Strands of Face‐Shared Fluoride‐Centred Sodium Octahedra According to $^{1}_{\infty}\rm \{[FNa_{6/2}]^{2+}\}$

During the reaction of Na₂[WO₄] with YF₃ purposed to yield fluoride‐derivatized yttrium oxotungstates(VI), colourless platelet‐shaped single crystals of Na₃F[WO₄] emerged as main product. The title compound crystallizes orthorhombically in the space group Pnma (a = 559.59(5), b = 751.02(7), c = 1285.98(9) pm) with four formula units per unit cell. Besides isolated ortho‐oxotungstate units [WO₄]^2? (d(W–O) = 176–178 pm) the crystal structure contains two crystallographically independent Na⁺ cations which are both octahedrally coordinated by four oxygen atoms and two fluoride anions. The F^? anions are surrounded by six sodium cations (d(F–Na) = 224–242 pm) also in an octahedral fashion. These octahedra built up chains along [100] by sharing trans‐oriented faces according to , which are stacked according to a hexagonal closest rod‐packing. The cationic strands are surrounded, interconnected and charge‐balanced by isolated [WO₄]^2? tetrahedra with almost ideal shape and every O^2? ligand is terminally coordinated by three Na⁺ cations.     

Struktur‐ und magnetochemische Untersuchungen an KCuGaF6

Structural and Magnetochemical Studies on KCuGaF₆ The crystal structure of KCuGaF₆ was determined on the base of X‐ray single crystal data (wR₂ = 0.084 for 2476 independent reflections). The compound crystallizes with a = 728.56(4), b = 989.51(6), c = 676.27(3) pm, β = 93.120(5)°, Z = 4 in space group P2₁/c of the pyrochlore related KCuCrF₆ type. The octahedral coordinations [GaF₆] and [CuF₆] are slightly resp. strongly distorted (mean values Ga‐F: 188.2 pm resp. Cu‐F: 188.2/200.1/227.6 pm). The longest distances Ga‐F and the shortest ones Cu‐F are found within octahedral chains of these two kinds of atoms, running along [100] and [001], resp., and being mutually bridged as well (M‐F‐M in between 114 and 145°). The magnetic mole susceptibilities measured at powders and at a single crystal follow the isotropic Heisenberg model for S = ¹/₂, if effects of chain disrupture are considered in the form of some paramagnetic portion. No indication of threedimensional magnetic order is observed down to T = 2 K and low magnetic fields H < 100 G. KCuGaF₆ (J/k = —71 K for the powder) is distinguished this way from the chain structure compounds KCuAlF₆ und Na₂CuScF₇ (J/k = —76 resp. —59 K) which were also magnetically studied and yield similar antiferromagnetic exchange constants J/k.     

Erdalkali-Fluoromanganate(III): BaMnF5 · H2O und SrMnF5 · H2O

Alkaline Earth Fluoromanganates(III): BaMnF₅ · H₂O and SrMnF₅ · H₂O Solid BaF₂ or SrF₂ forms with solutions of Mn³⁺ in aqueous hydrofluoric acid precipitates of hitherto unknown BaMnF₅ · H₂ and SrMnF₅ · H₂O respectively. X-ray structure determination on single crystals of both isotypic compounds (space group P2₁/m, Z = 2; BaMnF₅ · H₂O: a = 537.0(3), b = 817.2(2), c = 628.0(4) pm β = 111.17(5)°, R_w = 0.035 for 1403 reflections; SrMnF₅ · H₂O: a = 510.8(1), b = 792.0(2), c = 610.6(1) pm, β = 110.24(1)° R_w = 0.068 for 539 reflections) reveal pure [MnF₆]^3? octahedra connected with each other to infinite chains by sharing trans corners. The H₂O molecules are coordinated to the alkaline earth ions only and form weak O? H…F hydrogen bonds. The pronounced weakening of the Mn? F bonds within the chain direction (Mn? F 2X 212.7(1)/210.8(5) pm, 2X 183.8(3)/181.8(9) pm, 2X 186.9(2)/187.2(8) pm) may be due by halves to the Jahn-Teller-effect as can be deduced by bond valence calculations.     

Röntgenographische Einkristallstrukturbestimmungen an den Kalium-Kupfer(II)-Fluoriden K2CuF4 und K3Cu2F7

X-Ray Single Crystal Structure Determinations of the Potassium Copper(II) Fluorides K₂CuF₄ and K₃Cu₂F₇ With single crystals of the tetragonal compounds K₂CuF₄ (a = 414.7(2), c = 1273(3) pm) and K₃Cu₂F₇ (a = 415.6(3), c = 2052(3) pm), showing no superstructure reflections, crystal structure determinations were based on space group I4/mmm of the K₂NiF₄ and Sr₃Ti₂O₇ type, resp. The shape of F₀-Fourier maxima at the positions of linking fluorine atoms within the layers of octahedra suggested disorder of bridging ligands caused by multidomain structure, which could be refined assuming half occupation of higherfold positions. The results confirmed the Jahn-Teller-distortions of octahedra being elongated with a significant orthorhombic component: Cu? F = 190.9(7)/193.9(2)/223.8(7) pm in K₂CuF₄ (R_W = 0.020) and 190.0(7)/194.7/225.6(7) pm in K₃Cu₂F₇ (R_W = 0.023). In the acentric octahedra of the latter compound the intermediate distance is averaged from the splitted lengths 192.7(4)/196.8(1) pm of axes along the c direction.     

Zur kenntnis ‚Kationen-reicher’︁ Tantalate und Niobate Über Na5TaO5 und Na5NbO5

On Tantalates and Niobates ‘rich in Cations’. On Na₅TaO₅ and Na₅NbO₅ Colourless, transparent single crystals of Na₅TaO₅ [annealed mixtures of Na₂O, Li₂O, and Ta₂O₅, Na : Li : Ta = 6.6 : 1.1 : 1, Ni-cylinder, 1000°C, 75 d] as well as Na₅NbO₅ [annealed mixtures of Na₂O, Li₂O, and Nb₂O₅, Na : Li : Nb = 6.6 : 1.1 : 1, Ni-cylinder, 1000°C, 75 d] have been prepared. Single crystal data show that both isotypic oxides represent a deformed variant of the NaCl-type of structure [Na₅TaO₅: 1154 from 1250 I₀ (hkl), four-cycle diffractometer Philips PW 1100, ω2-θ scan, Ag? Kα , R = 4.88%, space group c2/c with a = 629.3(1) pm, b = 1025.4(2) pm, c = 1004.6(2) pm, b? 106.80(2)°, z = 4 and Na₅NbO₅: 998 from 1247 I₀(hkl), four-cycle diffractometer Philips PW 1100, ω-2θ scan, Ag? Kα , R = 8.58% and R_w = 7.67%, space group C2/2 with a = 629.1(1) pm, b = 1024.4(2) pm, c = 1004.2(2) pm, b? = 106.80(2)°, Z = 4]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Effective Fictive Ionic Radii, MEFIR, as well as Charge Distribution, CHARDI, are calculated.     

Strukturen caesiumhaltiger Fluoride. VIII. Cs7Ni4F15 und Cs7Co4F15: Die Kristallstrukturbestimmung an den bisher caesiumreichsten Verbindungen in den zugehörigen Systemen CsF/MF2

Structures of Cesium-containing Fluorides. VIII. Cs₇Ni₄F₁₅ and Cs₇Co₄F₁₅: Crystal Structure Determination of the Hitherto Cesium-richest Compounds in the Corresponding Systems CsF/MF₂ . The only nickel-containing phase we could identify after solid state reaction 2 CsF + NiF₂ was the compound Cs₇Ni₄F₁₅. The single crystal structure determination of this monoclinic fluoride (and its cobalt analog Cs₇Co₄F₁₅) yielded a = 787.2 (788.3), b = 1089.7 (1096.6), c = 1149.5 (1164.9) pm, β = 92.74 (92.59)°, space group P2₁/c, Z = 2, R_g = 0.045 (0.058) for 2543 (2716) independent reflections. The resulting strongly puckered layer structure rather than of single octahedra consists of face-sharing M₂F₉ units, which are connected via the half of their remaining corners. The M? F distances vary from 195.1 to 212.0 (196.7 to 217.0) pm and show unusual high mean values of 203.7 (206.5) pm. Data for comparison and further details are discussed.     

Strukturen caesiumhaltiger Fluoride. VII. Cs6Ni5F16 – eine neue Verbindung im System CsF/NiF2 und ihre Kristallstruktur

Structures of Caesium-containing Fluorides. VII. Cs₆Ni₅F₁₆ – a New Compound in the System CsF/NiF₂ and its Crystal Structure Single crystals of a more caesium-containing phase of composition Cs₆Ni₅F₁₆, forming in the course of solid state CsNiF₃ preparation, could be isolated and their structure determined: a = 618.4(1), b = 1. 455.5(2), c = 2145.1(2) pm, space group Cmca, Z = 4, R = 0.030 (1936 independent reflections). The structure contains chains of five face-sharing octahedra, which are connected at their ends via corners to form a zig-zag layer. The Ni? Ni distances within the chains are 264.1 and 270.2 pm, the average Ni? F distance is 202.0 pm. The caesium atoms exhibit 10-, 11-, and 12-coordination. The structural relations to 2L? CsNiF₃ and Cs₄Ni₃F₁₀ are discussed.