Crystal structure of a new tripotassium hexa­nickel iron hexa­phosphate

Ouaatta, S.; Assani, A.; Saadi, M.; El Ammari, L.

doi:10.1107/S2056989019002706

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ISSN: 2056-9890

Volume 75| Part 3| March 2019| Pages 402-404

https://doi.org/10.1107/S2056989019002706

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Crystal structure of a new tripotassium hexanickel iron hexaphosphate

Said Ouaatta,^a ^* Abderrazzak Assani,^a Mohamed Saadi ^a and Lahcen El Ammari ^a

^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

Edited by A. Van der Lee, Université de Montpellier II, France (Received 18 February 2019; accepted 21 February 2019; online 26 February 2019)

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 X-ray spectroscopy (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 ), ferroelectrics (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 ionic conductivity 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 asymmetric unit of the title compound, K₃Ni₆Fe(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 Wyckoff position 4g (2), the Fe atom is localized on the 2a (2/m) Wyckoff position, 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

Figure 1
Molecular structure of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) −x + $[{1\over 2}]$ , −y + $[{3\over 2}]$ , −z + 1; (ii) −x + 1, y, −z + 1; (iii) x, y, z − 1; (iv) −x + 1, y, −z + 2; (v) x + $[{1\over 2}]$ , −y + $[{3\over 2}]$ , z + 1; (vi) x + $[{1\over 2}]$ , y + $[{1\over 2}]$ , 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 + $[{1\over 2}]$ , −y + $[{3\over 2}]$ , −z; (xiii) −x, −y + 1, −z; (xiv) x, −y + 2, z.

Figure 2
A chain formed by sharing edges and corners of [Ni2₂O₁₀] dimers, [P2O₄] tetrahedra and [FeO₆] octahedra along the [100] direction

Figure 3
Corner- and edge-sharing [P1O₄] tetrahedra and [Ni1O₆] octahedra forming a zigzag shape chain running parallel to [100]

Figure 4
View along the c axis of corner- and edge-sharing [PO₄] tetrahedra and [NiO₆] octahedra forming a layer parallel to the ab plane.

Figure 5
Polyhedral representation of the crystal structure of K₃Ni₆Fe(PO₄)₆ showing large tunnels running along the [100] direction that contain the K⁺ cations.

3. 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 ), Na₄Co_5.63Al_0.91(AsO₄)₆ (Marzouki et al., 2010 ), Na₄Li_0.62Co_5.67Al_0.71(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 space group 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 refinement details of K₃Ni₆Fe(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.

Table 1
Experimental details

Crystal data
Chemical formula	K₃Ni₆Fe(PO₄)₆
M_r	1095.23
Crystal system, space group	Monoclinic, C2/m
Temperature (K)	296
a, b, c (Å)	10.6853 (4), 14.1009 (5), 6.5481 (2)
β (°)	103.842 (1)
V (Å³)	957.97 (6)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	7.79
Crystal size (mm)	0.36 × 0.27 × 0.20

Data collection
Diffractometer	Bruker D8 VENTURE Super DUO
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.638, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	13870, 1981, 1891
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.781

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.024, 0.062, 1.07
No. of reflections	1981
No. of parameters	112
Δρ_max, Δρ_min (e Å⁻³)	2.34, −1.16
Computer programs: APEX3 and SAINT-Plus (Bruker, 2016 ), SHELXT2014 (Sheldrick, 2015a ), SHELXL2016 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ), DIAMOND (Brandenburg, 2006 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1898755

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989019002706/vn2144sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019002706/vn2144Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2016); cell refinement: 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).

Tripotassium hexanickel iron hexaphosphate top

Crystal data top

K₃Ni₆Fe(PO₄)₆	F(000) = 1066
M_r = 1095.23	D_x = 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

Data collection top

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	R_int = 0.021
Detector resolution: 10.4167 pixels mm^-1	θ_max = 33.7°, θ_min = 2.4°
φ and ω scans	h = −14→16
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −22→22
T_min = 0.638, T_max = 0.746	l = −10→10
13870 measured reflections

Refinement top

Refinement on F²	112 parameters
Least-squares matrix: full	0 restraints
R[F² > 2σ(F²)] = 0.024	w = 1/[σ²(F_o²) + (0.0262P)² + 6.1957P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.062	(Δ/σ)_max = 0.001
S = 1.07	Δρ_max = 2.34 e Å⁻³
1981 reflections	Δρ_min = −1.16 e Å⁻³

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	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)

Atomic displacement parameters (Å²) top

	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

Geometric parameters (Å, º) top

Ni1—O2	2.0153 (14)	K1—O7^xi	3.146 (3)
Ni1—O5	2.0314 (14)	K2—O4	2.631 (2)
Ni1—O1ⁱ	2.0366 (13)	K2—O6^xii	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—O6^vi	2.929 (2)
Ni2—O4^iv	2.0411 (14)	K2—O1ⁱ	3.0776 (19)
Ni2—O5^v	2.0928 (14)	K2—O7^xii	3.086 (2)
Ni2—O5ⁱ	2.0928 (14)	K2—O2	3.149 (2)
Ni2—O6ⁱ	2.2241 (13)	K3—O7^xi	2.609 (6)
Ni2—O6^vi	2.2241 (13)	K3—O5	2.715 (5)
Fe1—O7	2.016 (2)	K3—O5^x	2.715 (5)
Fe1—O7^vii	2.016 (2)	K3—O6^xi	2.862 (6)
Fe1—O3^viii	2.0490 (13)	K3—O6^xiii	2.949 (7)
Fe1—O3ⁱⁱ	2.0490 (13)	K3—O2	3.077 (4)
Fe1—O3^ix	2.0490 (13)	K3—O2^x	3.077 (4)
Fe1—O3ⁱⁱⁱ	2.0490 (13)	P1—O2	1.5042 (15)
K1—O3	2.6263 (18)	P1—O1	1.5482 (14)
K1—O3^x	2.6264 (18)	P1—O4	1.5679 (14)
K1—O2	2.6673 (16)	P1—O3	1.5694 (14)
K1—O2^x	2.6673 (16)	P2—O7	1.509 (2)
K1—O3^ix	2.6691 (19)	P2—O6	1.554 (2)
K1—O3ⁱⁱ	2.6691 (19)	P2—O5^x	1.5546 (14)
K1—O5	3.091 (2)	P2—O5	1.5546 (14)
K1—O5^x	3.091 (2)

O2—Ni1—O5	90.55 (6)	O3^ix—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—O5^x	155.60 (8)
O2—Ni1—O3ⁱⁱ	91.89 (6)	O3^x—K1—O5^x	115.32 (5)
O5—Ni1—O3ⁱⁱ	99.19 (5)	O2—K1—O5^x	106.12 (6)
O1ⁱ—Ni1—O3ⁱⁱ	168.72 (5)	O2^x—K1—O5^x	59.36 (5)
O2—Ni1—O1ⁱⁱⁱ	178.70 (6)	O3^ix—K1—O5^x	65.70 (5)
O5—Ni1—O1ⁱⁱⁱ	88.65 (6)	O3ⁱⁱ—K1—O5^x	93.66 (6)
O1ⁱ—Ni1—O1ⁱⁱⁱ	84.74 (6)	O5—K1—O5^x	48.38 (6)
O3ⁱⁱ—Ni1—O1ⁱⁱⁱ	89.25 (5)	O3—K1—O7^xi	56.89 (5)
O2—Ni1—O4ⁱⁱ	92.33 (6)	O3^x—K1—O7^xi	56.89 (5)
O5—Ni1—O4ⁱⁱ	169.40 (5)	O2—K1—O7^xi	78.69 (5)
O1ⁱ—Ni1—O4ⁱⁱ	99.72 (5)	O2^x—K1—O7^xi	78.69 (5)
O3ⁱⁱ—Ni1—O4ⁱⁱ	70.53 (5)	O3^ix—K1—O7^xi	144.33 (3)
O1ⁱⁱⁱ—Ni1—O4ⁱⁱ	88.64 (5)	O3ⁱⁱ—K1—O7^xi	144.33 (3)
O4—Ni2—O4^iv	96.75 (8)	O5—K1—O7^xi	106.17 (7)
O4—Ni2—O5^v	103.69 (6)	O5^x—K1—O7^xi	106.17 (7)
O4^iv—Ni2—O5^v	92.95 (5)	O4—K2—O6^xii	135.41 (8)
O4—Ni2—O5ⁱ	92.95 (5)	O4—K2—O2ⁱ	89.14 (6)
O4^iv—Ni2—O5ⁱ	103.69 (6)	O6^xii—K2—O2ⁱ	128.60 (7)
O5^v—Ni2—O5ⁱ	154.96 (8)	O4—K2—O5ⁱ	66.22 (5)
O4—Ni2—O6ⁱ	160.71 (6)	O6^xii—K2—O5ⁱ	147.28 (7)
O4^iv—Ni2—O6ⁱ	94.81 (6)	O2ⁱ—K2—O5ⁱ	61.95 (5)
O5^v—Ni2—O6ⁱ	91.06 (6)	O4—K2—O4ⁱⁱ	79.26 (7)
O5ⁱ—Ni2—O6ⁱ	69.28 (6)	O6^xii—K2—O4ⁱⁱ	69.19 (5)
O4—Ni2—O6^vi	94.80 (6)	K2^xiv—K2—O4ⁱⁱ	126.86 (4)
O4^iv—Ni2—O6^vi	160.71 (6)	O2ⁱ—K2—O4ⁱⁱ	105.45 (6)
O5^v—Ni2—O6^vi	69.28 (6)	O5ⁱ—K2—O4ⁱⁱ	142.65 (7)
O5ⁱ—Ni2—O6^vi	91.06 (6)	O4—K2—O6^vi	68.58 (5)
O6ⁱ—Ni2—O6^vi	78.66 (8)	O6^xii—K2—O6^vi	97.82 (7)
O7—Fe1—O7^vii	180.0	O2ⁱ—K2—O6^vi	126.41 (7)
O7—Fe1—O3^viii	86.58 (5)	O5ⁱ—K2—O6^vi	64.47 (5)
O7^vii—Fe1—O3^viii	93.42 (5)	O4ⁱⁱ—K2—O6^vi	116.35 (6)
O7—Fe1—O3ⁱⁱ	93.42 (5)	O4—K2—O1ⁱ	109.01 (6)
O7^vii—Fe1—O3ⁱⁱ	86.58 (5)	O6^xii—K2—O1ⁱ	85.38 (5)
O3^viii—Fe1—O3ⁱⁱ	180.00 (8)	O2ⁱ—K2—O1ⁱ	50.84 (4)
O7—Fe1—O3^ix	93.42 (5)	O5ⁱ—K2—O1ⁱ	112.77 (6)
O7^vii—Fe1—O3^ix	86.58 (5)	O4ⁱⁱ—K2—O1ⁱ	64.63 (5)
O3^viii—Fe1—O3^ix	81.87 (8)	O6^vi—K2—O1ⁱ	176.79 (6)
O3ⁱⁱ—Fe1—O3^ix	98.13 (8)	O4—K2—O7^xii	165.00 (7)
O7—Fe1—O3ⁱⁱⁱ	86.58 (5)	O6^xii—K2—O7^xii	52.30 (6)
O7^vii—Fe1—O3ⁱⁱⁱ	93.42 (5)	O2ⁱ—K2—O7^xii	78.76 (5)
O3^viii—Fe1—O3ⁱⁱⁱ	98.13 (8)	O5ⁱ—K2—O7^xii	114.35 (7)
O3ⁱⁱ—Fe1—O3ⁱⁱⁱ	81.87 (8)	O4ⁱⁱ—K2—O7^xii	95.32 (5)
O3^ix—Fe1—O3ⁱⁱⁱ	180.00 (5)	O6^vi—K2—O7^xii	125.92 (6)
O2—P1—O1	110.92 (8)	O1ⁱ—K2—O7^xii	56.34 (4)
O2—P1—O4	114.19 (8)	O4—K2—O2	52.08 (5)
O1—P1—O4	108.73 (8)	O6^xii—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)	O6^vi—K2—O2	120.57 (5)
O7—P2—O5^x	112.26 (7)	O1ⁱ—K2—O2	56.94 (4)
O6—P2—O5^x	104.37 (7)	O7^xii—K2—O2	113.14 (5)
O7—P2—O5	112.26 (7)	O7^xi—K3—O5	139.0 (2)
O6—P2—O5	104.37 (7)	O7^xi—K3—O5^x	139.0 (2)
O5^x—P2—O5	109.14 (11)	O5—K3—O5^x	55.61 (11)
O3—K1—O3^x	72.22 (7)	O7^xi—K3—O6^xi	55.72 (11)
O3—K1—O2	56.19 (4)	O5—K3—O6^xi	143.7 (2)
O3^x—K1—O2	125.17 (6)	O5^x—K3—O6^xi	143.7 (2)
O3—K1—O2^x	125.17 (6)	O7^xi—K3—O6^xiii	149.1 (3)
O3^x—K1—O2^x	56.19 (4)	O5—K3—O6^xiii	65.77 (12)
O2—K1—O2^x	147.77 (10)	O5^x—K3—O6^xiii	65.77 (12)
O3—K1—O3^ix	138.56 (8)	O6^xi—K3—O6^xiii	93.4 (2)
O3^x—K1—O3^ix	93.79 (6)	O7^xi—K3—O2	80.84 (14)
O2—K1—O3^ix	136.75 (7)	O5—K3—O2	59.12 (9)
O2^x—K1—O3^ix	67.30 (4)	O5^x—K3—O2	105.29 (19)
O3—K1—O3ⁱⁱ	93.79 (6)	O6^xi—K3—O2	110.40 (11)
O3^x—K1—O3ⁱⁱ	138.56 (8)	O6^xiii—K3—O2	114.13 (11)
O2—K1—O3ⁱⁱ	67.30 (4)	O7^xi—K3—O2^x	80.84 (14)
O2^x—K1—O3ⁱⁱ	136.75 (7)	O5—K3—O2^x	105.29 (19)
O3^ix—K1—O3ⁱⁱ	70.89 (7)	O5^x—K3—O2^x	59.12 (9)
O3—K1—O5	115.32 (5)	O6^xi—K3—O2^x	110.40 (11)
O3^x—K1—O5	155.60 (8)	O6^xiii—K3—O2^x	114.13 (11)
O2—K1—O5	59.36 (5)	O2—K3—O2^x	112.8 (2)
O2^x—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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