research communications
of a new tripotassium hexanickel iron hexaphosphate
aLaboratoire de Chimie Appliquée des Matŕiaux, Centre des Sciences des Matériaux, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Batouta, BP 1014, Rabat, Morocco
*Correspondence e-mail: saidouaatta87@gmail.com
A new potassium-nickel iron phosphate, K3Ni6Fe(PO4)6, has been synthesized by solid-state reaction and structurally characterized by single-crystal X-ray diffraction and qualitative energy dispersive (EDS) analysis. The structure is built up by [FeO6], [PO4], and [NiO6] coordination polyhedra, which are linked to each other by edge and corner sharing to form zigzag layers parallel to the ab plane. These layers are interconnected by [PO4] tetrahedra and [NiO6] octahedra via common corners, leading to a three-dimensional framework delimiting large channels running along the [100] direction in which the K+ cations are localized.
Keywords: crystal structure; crystal growth; β-xenophyllite structure; K3Ni6Fe(PO4)6; X-ray diffraction; othophosphate; solid-state reaction synthesis.
CCDC reference: 1898755
1. Chemical context
Iron-based phosphates are widely studied materials today. They present a promising field for various applications such as electronics (Saw et al., 2014), (Lazoryak et al., 2004), magnetic materials (Hatert et al., 2004; Essehli et al., 2015) and catalytic processes (Moffat, 1978). The introduction of alkali metals into these phosphates materials can be of great interest to improve the ion-conduction properties for applications in rechargeable alkaline batteries (La Parola et al., 2018; Orikasa et al., 2016). The present work is part of our activity devoted particularly to the investigation of new materials based on phosphates belonging to the A2O–MO–Fe2O3–P2O5 (A = an alkali metal; M = divalent cation) quaternary system, which could have interesting or magnetic proprieties. We report herein on the synthesis and structural characterization by single crystal X-ray diffraction of a new potassium nickel iron phosphate with formula K3Ni6Fe(PO4)6.
2. Structural commentary
The 3Ni6Fe(PO4)6, consists of two [NiO6] octahedra, one [FeO6] octahedron, two [PO4] tetrahedra, and three K atoms, as shown in Fig. 1. One Ni2+, Fe3+, P5+, two K+ cations and two of the seven oxygen atoms lie on special positions. The Ni2 atom occupies 4g (2), the Fe atom is localized on the 2a (2/m) P2, K1, K3, O6 and O7 are positioned on 4i (m) sites. The octahedral coordination sphere of the nickel(II) cation is more distorted than that of the iron(III) atom, with average <Ni—O> distances of 2.066 and 2.119 Å for Ni1 and Ni2, respectively. The mean <P—O> distance in the two PO4 tetrahedra is equal to 1.547 Å for P1 and 1.543 Å for P2. The Fe atoms are coordinated octahedrally with an average <Fe—O> distance of 2.038 Å. The structure of the title compound is built up from two types of nickel sites and one iron site, each with an octahedral coordination environment, [Ni1O6], [Ni2O6] and [FeO6], besides two independent phosphor tetrahedra [P1O4] and [P2O4]. Edge-sharing [Ni2O6] octahedra build up a dimeric [Ni22O10] unit. Two [P2O6] octahedra are connected to the [Ni22O10] dimer by sharing edges to form an [Ni(2)2P(2)2O12] unit, which alternates with an [FeO6] octahedron to establish an infinite chain along the [100] direction (Fig. 2). In addition, the association between the [P1O4] tetrahedra and the [Ni1O6] octahedra by means of edge-sharing allows the formation of a zigzag chain running parallel to the [100] direction. Each of the P1O4 tetrahedra and Ni1O6 octahedra, both belonging to the same layer, share vertices with Ni1O6 and P1O4, respectively, of the adjacent one (Fig. 3). The two types of chain linkages lead to the formation of layers parallel to the ab plane (Fig. 4). One vertex of an Ni1O6 octahedron belonging to one layer is shared with a P1O4 vertex of the neighbouring layer. This configuration leads to a three-dimensional centrosymmetric framework, delimiting hexagonal tunnels along the [100] direction, in which the K+ cations are located (Fig. 5). The potassium cations are distributed over three independent crystallographic positions with partial occupancies
of the title compound, K3. Database survey
The investigated compound is a new member of the β-xenophyllite family that includes Na4Ni7(PO4)6 (Moring & Kostiner, 1986), Na4Co7(PO4)6 (Kobashi et al., 1998), K4Ni7(AsO4)6 (Ben Smail et al., 1999), Na4Co5.63Al0.91(AsO4)6 (Marzouki et al., 2010), Na4Li0.62Co5.67Al0.71(AsO4)6 (Marzouki et al., 2013), Ag4Co7(AsO4)6 (Marzouki et al., 2014) and Na4Co7(AsO4)6 (Ben Smida et al., 2016). The phosphates of these compounds crystallize in the non-centrosymmetric Cm while the arsenates adopt the C2/m space group.
4. Synthesis and crystallization
Single crystals of K3Ni6Fe(PO4)6 were prepared by solid-state reaction in air. A mixture of K2CO3, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and H3PO4 (85 wt.%) reagents with a K:Ni:Fe:P molar ratio of 2:2:1:3 was dissolved in 50 mL of distilled water. The resulting solution was stirred without heating for 24 h and was subsequently evaporated to dryness at 343 K. The obtained dry residue was progressively heated in a platinum crucible up to 673 K in order to eliminate volatile products. In a second step, the powder was homogenized in an agate mortar and then progressively heated to 1303 K. Kept at this temperature for 2 h, the reaction mixture then underwent slow cooling at a rate of 5 Kh−1 to 1103 K and then to room temperature with the furnace inertia. After washing with distilled water, the obtained crystals were brown with block-type shape. A qualitative EDX analysis (energy dispersive X-ray spectroscopy) detected the presence of the expected chemical elements corresponding to K, Ni, Fe, P and O atoms (see Fig. 6).
5. Refinement
Crystal data, data collection and structure 3Ni6Fe(PO4)6 are summarized in Table 1. The highest peak and the deepest hole in the final Fourier map are at 0.71 and 0.59 Å, respectively, from atom K2.
details of KSupporting information
CCDC reference: 1898755
https://doi.org/10.1107/S2056989019002706/vn2144sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019002706/vn2144Isup2.hkl
Data collection: APEX3 (Bruker, 2016); cell
SAINT-Plus (Bruker, 2016); data reduction: SAINT-Plus (Bruker, 2016); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).K3Ni6Fe(PO4)6 | F(000) = 1066 |
Mr = 1095.23 | Dx = 3.797 Mg m−3 |
Monoclinic, C2/m | Mo Kα radiation, λ = 0.71073 Å |
a = 10.6853 (4) Å | Cell parameters from 1981 reflections |
b = 14.1009 (5) Å | θ = 2.4–33.7° |
c = 6.5481 (2) Å | µ = 7.79 mm−1 |
β = 103.842 (1)° | T = 296 K |
V = 957.97 (6) Å3 | Block, brown |
Z = 2 | 0.36 × 0.27 × 0.20 mm |
Bruker D8 VENTURE Super DUO diffractometer | 1981 independent reflections |
Radiation source: INCOATEC IµS micro-focus source | 1891 reflections with I > 2σ(I) |
HELIOS mirror optics monochromator | Rint = 0.021 |
Detector resolution: 10.4167 pixels mm-1 | θmax = 33.7°, θmin = 2.4° |
φ and ω scans | h = −14→16 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −22→22 |
Tmin = 0.638, Tmax = 0.746 | l = −10→10 |
13870 measured reflections |
Refinement on F2 | 112 parameters |
Least-squares matrix: full | 0 restraints |
R[F2 > 2σ(F2)] = 0.024 | w = 1/[σ2(Fo2) + (0.0262P)2 + 6.1957P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.062 | (Δ/σ)max = 0.001 |
S = 1.07 | Δρmax = 2.34 e Å−3 |
1981 reflections | Δρmin = −1.16 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ni1 | 0.33034 (2) | 0.69342 (2) | 0.18429 (4) | 0.00599 (6) | |
Ni2 | 0.500000 | 0.87799 (2) | 1.000000 | 0.00683 (7) | |
Fe1 | 0.500000 | 0.500000 | 0.000000 | 0.00327 (9) | |
K1 | 0.40983 (18) | 0.500000 | 0.4730 (2) | 0.0200 (3) | 0.472 |
K2 | 0.38224 (13) | 0.90311 (11) | 0.48618 (19) | 0.0242 (3) | 0.417 |
K3 | 0.1849 (7) | 0.500000 | 0.4893 (8) | 0.0560 (19) | 0.192 |
P1 | 0.41063 (4) | 0.69522 (3) | 0.72442 (7) | 0.00485 (8) | |
P2 | 0.19569 (6) | 0.500000 | −0.01061 (10) | 0.00557 (11) | |
O1 | 0.31025 (13) | 0.70594 (10) | 0.8587 (2) | 0.0072 (2) | |
O2 | 0.34525 (14) | 0.68172 (11) | 0.4959 (2) | 0.0102 (2) | |
O3 | 0.50488 (13) | 0.60977 (10) | 0.7970 (2) | 0.0069 (2) | |
O4 | 0.50525 (13) | 0.78185 (10) | 0.7692 (2) | 0.0082 (2) | |
O5 | 0.19430 (13) | 0.58983 (10) | 0.1265 (2) | 0.0085 (2) | |
O6 | 0.06136 (18) | 0.500000 | −0.1681 (3) | 0.0087 (3) | |
O7 | 0.30728 (19) | 0.500000 | −0.1148 (3) | 0.0103 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ni1 | 0.00441 (10) | 0.00697 (10) | 0.00638 (10) | 0.00038 (7) | 0.00088 (7) | −0.00015 (7) |
Ni2 | 0.00519 (13) | 0.00602 (14) | 0.00944 (14) | 0.000 | 0.00207 (10) | 0.000 |
Fe1 | 0.00218 (18) | 0.00293 (18) | 0.00478 (19) | 0.000 | 0.00099 (15) | 0.000 |
K1 | 0.0413 (9) | 0.0080 (5) | 0.0103 (5) | 0.000 | 0.0055 (5) | 0.000 |
K2 | 0.0259 (6) | 0.0332 (7) | 0.0122 (4) | −0.0107 (5) | 0.0018 (4) | 0.0082 (4) |
K3 | 0.056 (4) | 0.100 (6) | 0.0100 (17) | 0.000 | 0.005 (2) | 0.000 |
P1 | 0.00395 (17) | 0.00570 (18) | 0.00483 (18) | 0.00067 (13) | 0.00093 (14) | −0.00035 (13) |
P2 | 0.0033 (2) | 0.0049 (2) | 0.0082 (3) | 0.000 | 0.00071 (19) | 0.000 |
O1 | 0.0055 (5) | 0.0095 (5) | 0.0072 (5) | 0.0022 (4) | 0.0028 (4) | 0.0009 (4) |
O2 | 0.0091 (6) | 0.0162 (6) | 0.0048 (5) | 0.0011 (5) | 0.0003 (4) | 0.0002 (4) |
O3 | 0.0049 (5) | 0.0070 (5) | 0.0089 (5) | 0.0014 (4) | 0.0018 (4) | 0.0012 (4) |
O4 | 0.0069 (5) | 0.0072 (5) | 0.0110 (6) | −0.0012 (4) | 0.0031 (4) | −0.0022 (4) |
O5 | 0.0071 (5) | 0.0067 (5) | 0.0120 (6) | −0.0012 (4) | 0.0027 (4) | −0.0031 (4) |
O6 | 0.0045 (7) | 0.0124 (8) | 0.0081 (8) | 0.000 | −0.0005 (6) | 0.000 |
O7 | 0.0056 (7) | 0.0088 (8) | 0.0181 (9) | 0.000 | 0.0060 (7) | 0.000 |
Ni1—O2 | 2.0153 (14) | K1—O7xi | 3.146 (3) |
Ni1—O5 | 2.0314 (14) | K2—O4 | 2.631 (2) |
Ni1—O1i | 2.0366 (13) | K2—O6xii | 2.677 (2) |
Ni1—O3ii | 2.0984 (14) | K2—O2i | 2.737 (2) |
Ni1—O1iii | 2.0988 (14) | K2—O5i | 2.8470 (19) |
Ni1—O4ii | 2.1161 (14) | K2—O4ii | 2.851 (2) |
Ni2—O4 | 2.0411 (14) | K2—O6vi | 2.929 (2) |
Ni2—O4iv | 2.0411 (14) | K2—O1i | 3.0776 (19) |
Ni2—O5v | 2.0928 (14) | K2—O7xii | 3.086 (2) |
Ni2—O5i | 2.0928 (14) | K2—O2 | 3.149 (2) |
Ni2—O6i | 2.2241 (13) | K3—O7xi | 2.609 (6) |
Ni2—O6vi | 2.2241 (13) | K3—O5 | 2.715 (5) |
Fe1—O7 | 2.016 (2) | K3—O5x | 2.715 (5) |
Fe1—O7vii | 2.016 (2) | K3—O6xi | 2.862 (6) |
Fe1—O3viii | 2.0490 (13) | K3—O6xiii | 2.949 (7) |
Fe1—O3ii | 2.0490 (13) | K3—O2 | 3.077 (4) |
Fe1—O3ix | 2.0490 (13) | K3—O2x | 3.077 (4) |
Fe1—O3iii | 2.0490 (13) | P1—O2 | 1.5042 (15) |
K1—O3 | 2.6263 (18) | P1—O1 | 1.5482 (14) |
K1—O3x | 2.6264 (18) | P1—O4 | 1.5679 (14) |
K1—O2 | 2.6673 (16) | P1—O3 | 1.5694 (14) |
K1—O2x | 2.6673 (16) | P2—O7 | 1.509 (2) |
K1—O3ix | 2.6691 (19) | P2—O6 | 1.554 (2) |
K1—O3ii | 2.6691 (19) | P2—O5x | 1.5546 (14) |
K1—O5 | 3.091 (2) | P2—O5 | 1.5546 (14) |
K1—O5x | 3.091 (2) | ||
O2—Ni1—O5 | 90.55 (6) | O3ix—K1—O5 | 93.66 (6) |
O2—Ni1—O1i | 94.23 (6) | O3ii—K1—O5 | 65.70 (5) |
O5—Ni1—O1i | 90.23 (6) | O3—K1—O5x | 155.60 (8) |
O2—Ni1—O3ii | 91.89 (6) | O3x—K1—O5x | 115.32 (5) |
O5—Ni1—O3ii | 99.19 (5) | O2—K1—O5x | 106.12 (6) |
O1i—Ni1—O3ii | 168.72 (5) | O2x—K1—O5x | 59.36 (5) |
O2—Ni1—O1iii | 178.70 (6) | O3ix—K1—O5x | 65.70 (5) |
O5—Ni1—O1iii | 88.65 (6) | O3ii—K1—O5x | 93.66 (6) |
O1i—Ni1—O1iii | 84.74 (6) | O5—K1—O5x | 48.38 (6) |
O3ii—Ni1—O1iii | 89.25 (5) | O3—K1—O7xi | 56.89 (5) |
O2—Ni1—O4ii | 92.33 (6) | O3x—K1—O7xi | 56.89 (5) |
O5—Ni1—O4ii | 169.40 (5) | O2—K1—O7xi | 78.69 (5) |
O1i—Ni1—O4ii | 99.72 (5) | O2x—K1—O7xi | 78.69 (5) |
O3ii—Ni1—O4ii | 70.53 (5) | O3ix—K1—O7xi | 144.33 (3) |
O1iii—Ni1—O4ii | 88.64 (5) | O3ii—K1—O7xi | 144.33 (3) |
O4—Ni2—O4iv | 96.75 (8) | O5—K1—O7xi | 106.17 (7) |
O4—Ni2—O5v | 103.69 (6) | O5x—K1—O7xi | 106.17 (7) |
O4iv—Ni2—O5v | 92.95 (5) | O4—K2—O6xii | 135.41 (8) |
O4—Ni2—O5i | 92.95 (5) | O4—K2—O2i | 89.14 (6) |
O4iv—Ni2—O5i | 103.69 (6) | O6xii—K2—O2i | 128.60 (7) |
O5v—Ni2—O5i | 154.96 (8) | O4—K2—O5i | 66.22 (5) |
O4—Ni2—O6i | 160.71 (6) | O6xii—K2—O5i | 147.28 (7) |
O4iv—Ni2—O6i | 94.81 (6) | O2i—K2—O5i | 61.95 (5) |
O5v—Ni2—O6i | 91.06 (6) | O4—K2—O4ii | 79.26 (7) |
O5i—Ni2—O6i | 69.28 (6) | O6xii—K2—O4ii | 69.19 (5) |
O4—Ni2—O6vi | 94.80 (6) | K2xiv—K2—O4ii | 126.86 (4) |
O4iv—Ni2—O6vi | 160.71 (6) | O2i—K2—O4ii | 105.45 (6) |
O5v—Ni2—O6vi | 69.28 (6) | O5i—K2—O4ii | 142.65 (7) |
O5i—Ni2—O6vi | 91.06 (6) | O4—K2—O6vi | 68.58 (5) |
O6i—Ni2—O6vi | 78.66 (8) | O6xii—K2—O6vi | 97.82 (7) |
O7—Fe1—O7vii | 180.0 | O2i—K2—O6vi | 126.41 (7) |
O7—Fe1—O3viii | 86.58 (5) | O5i—K2—O6vi | 64.47 (5) |
O7vii—Fe1—O3viii | 93.42 (5) | O4ii—K2—O6vi | 116.35 (6) |
O7—Fe1—O3ii | 93.42 (5) | O4—K2—O1i | 109.01 (6) |
O7vii—Fe1—O3ii | 86.58 (5) | O6xii—K2—O1i | 85.38 (5) |
O3viii—Fe1—O3ii | 180.00 (8) | O2i—K2—O1i | 50.84 (4) |
O7—Fe1—O3ix | 93.42 (5) | O5i—K2—O1i | 112.77 (6) |
O7vii—Fe1—O3ix | 86.58 (5) | O4ii—K2—O1i | 64.63 (5) |
O3viii—Fe1—O3ix | 81.87 (8) | O6vi—K2—O1i | 176.79 (6) |
O3ii—Fe1—O3ix | 98.13 (8) | O4—K2—O7xii | 165.00 (7) |
O7—Fe1—O3iii | 86.58 (5) | O6xii—K2—O7xii | 52.30 (6) |
O7vii—Fe1—O3iii | 93.42 (5) | O2i—K2—O7xii | 78.76 (5) |
O3viii—Fe1—O3iii | 98.13 (8) | O5i—K2—O7xii | 114.35 (7) |
O3ii—Fe1—O3iii | 81.87 (8) | O4ii—K2—O7xii | 95.32 (5) |
O3ix—Fe1—O3iii | 180.00 (5) | O6vi—K2—O7xii | 125.92 (6) |
O2—P1—O1 | 110.92 (8) | O1i—K2—O7xii | 56.34 (4) |
O2—P1—O4 | 114.19 (8) | O4—K2—O2 | 52.08 (5) |
O1—P1—O4 | 108.73 (8) | O6xii—K2—O2 | 125.05 (6) |
O2—P1—O3 | 108.41 (8) | O2i—K2—O2 | 56.55 (6) |
O1—P1—O3 | 112.61 (8) | O5i—K2—O2 | 87.27 (5) |
O4—P1—O3 | 101.72 (8) | O4ii—K2—O2 | 59.33 (5) |
O7—P2—O6 | 113.84 (12) | O6vi—K2—O2 | 120.57 (5) |
O7—P2—O5x | 112.26 (7) | O1i—K2—O2 | 56.94 (4) |
O6—P2—O5x | 104.37 (7) | O7xii—K2—O2 | 113.14 (5) |
O7—P2—O5 | 112.26 (7) | O7xi—K3—O5 | 139.0 (2) |
O6—P2—O5 | 104.37 (7) | O7xi—K3—O5x | 139.0 (2) |
O5x—P2—O5 | 109.14 (11) | O5—K3—O5x | 55.61 (11) |
O3—K1—O3x | 72.22 (7) | O7xi—K3—O6xi | 55.72 (11) |
O3—K1—O2 | 56.19 (4) | O5—K3—O6xi | 143.7 (2) |
O3x—K1—O2 | 125.17 (6) | O5x—K3—O6xi | 143.7 (2) |
O3—K1—O2x | 125.17 (6) | O7xi—K3—O6xiii | 149.1 (3) |
O3x—K1—O2x | 56.19 (4) | O5—K3—O6xiii | 65.77 (12) |
O2—K1—O2x | 147.77 (10) | O5x—K3—O6xiii | 65.77 (12) |
O3—K1—O3ix | 138.56 (8) | O6xi—K3—O6xiii | 93.4 (2) |
O3x—K1—O3ix | 93.79 (6) | O7xi—K3—O2 | 80.84 (14) |
O2—K1—O3ix | 136.75 (7) | O5—K3—O2 | 59.12 (9) |
O2x—K1—O3ix | 67.30 (4) | O5x—K3—O2 | 105.29 (19) |
O3—K1—O3ii | 93.79 (6) | O6xi—K3—O2 | 110.40 (11) |
O3x—K1—O3ii | 138.56 (8) | O6xiii—K3—O2 | 114.13 (11) |
O2—K1—O3ii | 67.30 (4) | O7xi—K3—O2x | 80.84 (14) |
O2x—K1—O3ii | 136.75 (7) | O5—K3—O2x | 105.29 (19) |
O3ix—K1—O3ii | 70.89 (7) | O5x—K3—O2x | 59.12 (9) |
O3—K1—O5 | 115.32 (5) | O6xi—K3—O2x | 110.40 (11) |
O3x—K1—O5 | 155.60 (8) | O6xiii—K3—O2x | 114.13 (11) |
O2—K1—O5 | 59.36 (5) | O2—K3—O2x | 112.8 (2) |
O2x—K1—O5 | 106.12 (6) |
Symmetry codes: (i) −x+1/2, −y+3/2, −z+1; (ii) −x+1, y, −z+1; (iii) x, y, z−1; (iv) −x+1, y, −z+2; (v) x+1/2, −y+3/2, z+1; (vi) x+1/2, y+1/2, z+1; (vii) −x+1, −y+1, −z; (viii) x, −y+1, z−1; (ix) −x+1, −y+1, −z+1; (x) x, −y+1, z; (xi) x, y, z+1; (xii) −x+1/2, −y+3/2, −z; (xiii) −x, −y+1, −z; (xiv) x, −y+2, z. |
Acknowledgements
The authors thank the Faculty of Science of the Mohammed V University in Rabat, Morocco, for the X-ray measurements.
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