Langbeinite-related K₂FeSn(PO₄)₃ from single-crystal data

Crystals of dipotassium iron(III) tin(IV) tris­(orthophosphate) were grown from a self-flux in the system K₂O–P₂O₅–Fe₂O₃–SnO₂. The title compound is isotypic with the mineral langbeinite, K₂Mg₂(SO₄)₃. Its three-dimensional [M₂(PO₄)₃]_∞ framework is composed of [MO₆] (M = Sn, Fe) octa­hedra and [PO₄] tetra­hedra inter­linked via vertices. In comparison with the previous refinement from X-ray powder data [Aatiq, Haggouch, Bakri, Lakhdar & Saadoune. (2006). Powder Diffr. 21, 214–219], the present reinvestigation from single-crystal data allows a more precise determination of the distribution of the Fe and Sn atoms over two crystallographic positions and a revision of the P—O and M—O [M = K, (Fe, Sn)] bond lengths. For the two K⁺ cations, two different polyhedra with coordination numbers of 9 and 12 are observed. The (Fe, Sn) and K atoms are located on threefold axes.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](P-O) = 0.002 Å
• Disorder in main residue
• R factor = 0.021
• wR factor = 0.045
• Data-to-parameter ratio = 22.8

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...         -4
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...         -4
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...         -4
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...          m
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...          m
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...          m

Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.99
PLAT141_ALERT_4_C su on a - Axis Small or Missing (x 100000) .....          7 Ang.
PLAT301_ALERT_3_C Main Residue  Disorder .........................      11.00 Perc.

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           34.99
           From the CIF: _reflns_number_total               1434
           Count of symmetry unique reflns          812
           Completeness (_total/calc)            176.60%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       622
           Fraction of Friedel pairs measured     0.766
           Are heavy atom types Z>Si present        yes
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          3

   0 ALERT level A = In general: serious problem
   6 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   4 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   6 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Langbeinite-type frameworks [M₂(PO₄)₃]_∞ can be composed from various types of tetravalent and bi- or trivalent metal pairs. For example, the structures of K₂M_0.5Ti_1.5(PO₄)₃ (M = Ni, Co, Mn) (Ogorodnyk et al., 2006; 2007a), K₂MTi(PO₄)₃ (M = Y, Yb, Er) (Norberg, 2002), K₂FeZr(PO₄)₃ (Orlova et al., 2003) and K₂LuZr(PO₄)₃ (Ogorodnyk et al., 2007b) have been investigated in the past years. Among other langbeinite-related compounds, the structures of only two tin(IV)-containing phosphates, viz. K₂MSn(PO₄)₃ (M = Fe, Yb) refined from X-ray powder data, were previously reported (Aatiq et al., 2006). Herein we report the single-crystal growth and re-investigation of K₂FeSn(PO₄)₃ (I), a structure that is isotypic with the mineral langbeinite, K₂Mg₂(SO₄)₃ (Zemann, & Zemann, 1957).

Sn and Fe atoms are statistically distributed over two octahedrally coordinated positions with an insignificant priority of the M1 site occupation by Sn and of the M2 site by Fe. The {Sn(Fe)1-Sn(Fe)2-K1—K2} sequence runs along [111] (Fig. 1). K1 atoms are coordinated by 9 O atoms, while K2 atoms are surrounded by 12 O atoms (Fig. 2), with K—O bond lengths ranging from 2.852 (2) to 3.243 (2) Å.

Comparing the results from the single-crystal study with the results of the previous powder study, the following points are noteable. The distribution of two type of metals (Fe and Sn) over two octahedrally coordinated positions are close to those reported earlier, but the accuracy of single-crystal refinement is more precise. The values of corresponding Fe/Sn—O bond lengths insignificantly differs from one another in each type of octahedron in the present structure model, while the values found by Rietveld refinement differs a lot. Actually, the new results of the single-crystal refinement suggest a lower degree of distortion of the [(Fe,Sn)O₆] polyhedra. Moreover, in contrast to the results of the powder refinement with each of the K⁺ cations in 9-fold coordination, we assume that K1 is 9-coordinate, while K2 is 12-coordinate, which agrees with the most of earlier discussed structures of langbeinite-related phosphates.

Related literature

For the previous powder study of the title compound, see Aatiq et al. (2006). The crystal structure of the mineral langbeinite was determined by Zemann & Zemann (1957). Other phosphates with langbeinite-type structure have been investigated by Norberg (2002), Ogorodnyk et al. (2006), Ogorodnyk, Zatovsky & Slobodyanik (2007), Ogorodnyk, Zatovsky, Baumer et al. (2007), and Orlova et al. (2003).

S2. Experimental

Crystals of (I) were obtained in the pseudo-quaternary system K₂O—P₂O₅—SnO₂—Fe₂O₃ using the high-temperature flux crystallization technique. A well ground mixture of 0.9 g SnO₂ (6.0 mmol), 1,44 g Fe₂O₃ (9.0 mmol), 6,63 g KPO₃ (56.2 mmol) and 1,03 g K₄P₂O₇ (3.1 mmol) was placed into a platinum crucible, and was heated up to 1373 K. The melt was exposed during 6 h at this temperature to dissolve the metal oxides, and then was cooled down 1013 K at a rate 25 K/h. At the final stage of crystallization the melt was sustained under isothermal conditions for 1 h to gain equilibrium, and was then poured out onto a copper sheet for quenching. Yellow-brownish crystals with mostly tetrahedral shape were recovered from the remaining flux by leaching out with deionized water.

S3. Refinement

As suggested from the previous powder refinement (Aatiq et al., 2006), the Fe and Sn atoms are statistically distributed. Their coordinates and displacement ellipsoids were constrained. Three additional restraints were applied, viz. two for full occupancies of the Fe/Sn sites and one for the total charge of iron and tin (charge sum = 7.00). The highest peak in the final Fourier map is located 0.87 Å from atom P1, and the deepest hole is 1.05 Å from atom Sn1.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999).

Figures

	Fig. 1. A part of the crystal structure of (I), displayed with ellipsoids at the 70% probability level. The blue line shows the [111] direction.
	Fig. 2. Arrangement of [MO6] octahedra and [PO4] tetrahedra forming cavities around the K^+ cations (70% probability displacement ellipsoids). [M1O6] octahedra are light brown, [M2O6] octahedra are dark red, and [PO4] tetrahedra are purple.

dipotassium iron(III) tin(IV) tris(orthophosphate)

Crystal data

K2FeSn(PO4)3	Dx = 3.664 Mg m^−3
Mr = 537.65	Mo Kα radiation, λ = 0.71073 Å
Cubic, P213	Cell parameters from 5809 reflections
Hall symbol: P 2ac 2ab 3	θ = 2.9–35.0°
a = 9.91473 (7) Å	µ = 5.47 mm^−1
V = 974.64 (1) Å^3	T = 293 K
Z = 4	Tetrahedron, yellow brown
F(000) = 1020	0.08 × 0.06 × 0.05 mm

Data collection

XCalibur-3 diffractometer	1434 independent reflections
Radiation source: fine focus sealed tube	1338 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ϕ and ω scans	θmax = 35.0°, θmin = 2.9°
Absorption correction: multi-scan (Blessing; 1995)	h = −13→16
Tmin = 0.669, Tmax = 0.772	k = −15→15
5809 measured reflections	l = −15→16

Refinement

Refinement on F^2	w = 1/[σ^2(Fo^2) + (0.0194P)^2 + 0.5777P] where P = (Fo^2 + 2Fc^2)/3
Least-squares matrix: full	(Δ/σ)max < 0.001
R[F^2 > 2σ(F^2)] = 0.021	Δρmax = 0.50 e Å^−3
wR(F^2) = 0.045	Δρmin = −0.57 e Å^−3
S = 1.1	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1434 reflections	Extinction coefficient: 0.0058 (5)
63 parameters	Absolute structure: Flack (1983), 621 Friedel Pairs
3 restraints	Absolute structure parameter: −0.03 (2)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
K1	0.70742 (8)	0.70742 (8)	0.70742 (8)	0.0278 (3)
K2	0.93262 (6)	0.93262 (6)	0.93262 (6)	0.0220 (2)
Fe1	0.14686 (2)	0.14686 (2)	0.14686 (2)	0.00732 (8)	0.4464 (11)
Fe2	0.41421 (2)	0.41421 (2)	0.41421 (2)	0.00737 (8)	0.5538 (12)
Sn1	0.14686 (2)	0.14686 (2)	0.14686 (2)	0.00732 (8)	0.5536 (11)
Sn2	0.41421 (2)	0.41421 (2)	0.41421 (2)	0.00737 (8)	0.4462 (11)
P1	0.46113 (6)	0.22920 (6)	0.12592 (6)	0.00634 (10)
O1	0.31483 (18)	0.2389 (2)	0.0776 (2)	0.0154 (4)
O2	0.5516 (2)	0.2973 (2)	0.0223 (2)	0.0180 (4)
O3	0.5006 (2)	0.08280 (19)	0.1516 (2)	0.0172 (3)
O4	0.4825 (2)	0.3057 (2)	0.2572 (2)	0.0203 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
K1	0.0278 (3)	0.0278 (3)	0.0278 (3)	−0.0001 (3)	−0.0001 (3)	−0.0001 (3)
K2	0.0220 (2)	0.0220 (2)	0.0220 (2)	−0.0026 (2)	−0.0026 (2)	−0.0026 (2)
Fe1	0.00732 (8)	0.00732 (8)	0.00732 (8)	−0.00009 (7)	−0.00009 (7)	−0.00009 (7)
Fe2	0.00737 (8)	0.00737 (8)	0.00737 (8)	−0.00050 (7)	−0.00050 (7)	−0.00050 (7)
Sn1	0.00732 (8)	0.00732 (8)	0.00732 (8)	−0.00009 (7)	−0.00009 (7)	−0.00009 (7)
Sn2	0.00737 (8)	0.00737 (8)	0.00737 (8)	−0.00050 (7)	−0.00050 (7)	−0.00050 (7)
P1	0.0061 (2)	0.0066 (2)	0.0063 (2)	−0.00007 (18)	0.00116 (17)	−0.00006 (17)
O1	0.0068 (7)	0.0201 (9)	0.0194 (9)	−0.0031 (6)	−0.0024 (7)	0.0086 (8)
O2	0.0155 (9)	0.0211 (10)	0.0174 (9)	−0.0008 (7)	0.0091 (7)	0.0087 (8)
O3	0.0220 (9)	0.0078 (7)	0.0219 (9)	0.0063 (7)	0.0031 (8)	0.0032 (8)
O4	0.0240 (11)	0.0235 (11)	0.0135 (9)	−0.0030 (8)	0.0022 (8)	−0.0117 (8)

Geometric parameters (Å, º)

K1—O1^i	2.852 (2)	Fe1—O1^xiv	2.0195 (19)
K1—O1^ii	2.852 (2)	Fe1—K2^xv	3.6790 (12)
K1—O1^iii	2.852 (2)	Fe1—K1^xvi	3.8453 (6)
K1—O2^iv	3.013 (2)	Fe1—K1^xvii	3.8453 (6)
K1—O2^v	3.013 (2)	Fe1—K1^xviii	3.8453 (6)
K1—O2^vi	3.013 (2)	Fe2—O3^i	1.9830 (19)
K1—O4^iv	3.117 (2)	Fe2—O3^ii	1.9830 (19)
K1—O4^v	3.117 (2)	Fe2—O3^iii	1.9830 (19)
K1—O4^vi	3.117 (2)	Fe2—O4	2.010 (2)
K1—P1^iv	3.4419 (9)	Fe2—O4^xiv	2.010 (2)
K1—P1^v	3.4419 (9)	Fe2—O4^xiii	2.010 (2)
K1—P1^vi	3.4419 (9)	Fe2—K2^xix	3.7636 (4)
K2—O3^iv	2.868 (2)	Fe2—K2^xx	3.7636 (4)
K2—O3^vi	2.868 (2)	Fe2—K2^xxi	3.7636 (4)
K2—O3^v	2.868 (2)	P1—O4	1.521 (2)
K2—O2^vii	2.960 (2)	P1—O2	1.521 (2)
K2—O2^viii	2.960 (2)	P1—O3	1.525 (2)
K2—O2^ix	2.960 (2)	P1—O1	1.5306 (19)
K2—O4^iv	3.053 (3)	O1—K1^xvi	2.852 (2)
K2—O4^v	3.053 (3)	O2—Sn1^xxii	2.0032 (19)
K2—O4^vi	3.053 (3)	O2—Fe1^xxii	2.0032 (19)
K2—O4^vii	3.243 (2)	O2—K2^xix	2.960 (2)
K2—O4^viii	3.243 (2)	O2—K1^xxi	3.013 (2)
K2—O4^ix	3.243 (2)	O3—Sn2^xvi	1.9830 (19)
Fe1—O2^x	2.0032 (19)	O3—Fe2^xvi	1.9830 (19)
Fe1—O2^xi	2.0032 (19)	O3—K2^xxi	2.868 (2)
Fe1—O2^xii	2.0032 (19)	O4—K2^xxi	3.053 (3)
Fe1—O1^xiii	2.0195 (19)	O4—K1^xxi	3.117 (2)
Fe1—O1	2.0195 (19)	O4—K2^xix	3.243 (2)
O1^i—K1—O1^ii	92.31 (7)	O3^v—K2—O4^viii	86.13 (6)
O1^i—K1—O1^iii	92.31 (7)	O2^vii—K2—O4^viii	88.43 (6)
O1^ii—K1—O1^iii	92.31 (7)	O2^viii—K2—O4^viii	45.82 (5)
O1^i—K1—O2^iv	57.28 (5)	O2^ix—K2—O4^viii	100.56 (6)
O1^ii—K1—O2^iv	81.42 (6)	O4^iv—K2—O4^viii	137.22 (4)
O1^iii—K1—O2^iv	148.35 (7)	O4^v—K2—O4^viii	54.34 (8)
O1^i—K1—O2^v	148.35 (7)	O4^vi—K2—O4^viii	104.276 (11)
O1^ii—K1—O2^v	57.28 (5)	O4^vii—K2—O4^viii	115.51 (3)
O1^iii—K1—O2^v	81.42 (6)	O3^iv—K2—O4^ix	86.13 (6)
O2^iv—K1—O2^v	119.065 (15)	O3^vi—K2—O4^ix	156.82 (6)
O1^i—K1—O2^vi	81.42 (6)	O3^v—K2—O4^ix	56.20 (5)
O1^ii—K1—O2^vi	148.35 (7)	O2^vii—K2—O4^ix	100.56 (6)
O1^iii—K1—O2^vi	57.28 (5)	O2^viii—K2—O4^ix	88.43 (6)
O2^iv—K1—O2^vi	119.065 (15)	O2^ix—K2—O4^ix	45.82 (5)
O2^v—K1—O2^vi	119.065 (15)	O4^iv—K2—O4^ix	54.34 (8)
O1^i—K1—O4^iv	103.75 (6)	O4^v—K2—O4^ix	104.276 (11)
O1^ii—K1—O4^iv	82.12 (6)	O4^vi—K2—O4^ix	137.22 (4)
O1^iii—K1—O4^iv	163.15 (6)	O4^vii—K2—O4^ix	115.51 (3)
O2^iv—K1—O4^iv	46.64 (6)	O4^viii—K2—O4^ix	115.51 (3)
O2^v—K1—O4^iv	82.20 (6)	O2^x—Fe1—O2^xi	88.12 (9)
O2^vi—K1—O4^iv	129.53 (7)	O2^x—Fe1—O2^xii	88.12 (9)
O1^i—K1—O4^v	163.15 (6)	O2^xi—Fe1—O2^xii	88.12 (9)
O1^ii—K1—O4^v	103.75 (6)	O2^x—Fe1—O1^xiii	88.81 (8)
O1^iii—K1—O4^v	82.12 (6)	O2^xi—Fe1—O1^xiii	176.13 (9)
O2^iv—K1—O4^v	129.53 (7)	O2^xii—Fe1—O1^xiii	89.43 (9)
O2^v—K1—O4^v	46.64 (6)	O2^x—Fe1—O1	89.43 (9)
O2^vi—K1—O4^v	82.20 (6)	O2^xi—Fe1—O1	88.81 (8)
O4^iv—K1—O4^v	83.78 (7)	O2^xii—Fe1—O1	176.13 (9)
O1^i—K1—O4^vi	82.12 (6)	O1^xiii—Fe1—O1	93.51 (9)
O1^ii—K1—O4^vi	163.15 (6)	O2^x—Fe1—O1^xiv	176.13 (9)
O1^iii—K1—O4^vi	103.75 (6)	O2^xi—Fe1—O1^xiv	89.43 (9)
O2^iv—K1—O4^vi	82.20 (6)	O2^xii—Fe1—O1^xiv	88.81 (8)
O2^v—K1—O4^vi	129.53 (7)	O1^xiii—Fe1—O1^xiv	93.51 (9)
O2^vi—K1—O4^vi	46.64 (6)	O1—Fe1—O1^xiv	93.51 (9)
O4^iv—K1—O4^vi	83.78 (7)	O3^i—Fe2—O3^ii	93.35 (9)
O4^v—K1—O4^vi	83.78 (7)	O3^i—Fe2—O3^iii	93.35 (9)
O3^iv—K2—O3^vi	100.64 (6)	O3^ii—Fe2—O3^iii	93.35 (9)
O3^iv—K2—O3^v	100.64 (6)	O3^i—Fe2—O4	172.59 (9)
O3^vi—K2—O3^v	100.64 (6)	O3^ii—Fe2—O4	93.04 (9)
O3^iv—K2—O2^vii	95.91 (6)	O3^iii—Fe2—O4	82.53 (9)
O3^vi—K2—O2^vii	100.74 (6)	O3^i—Fe2—O4^xiv	93.04 (9)
O3^v—K2—O2^vii	149.93 (6)	O3^ii—Fe2—O4^xiv	82.53 (9)
O3^iv—K2—O2^viii	149.93 (6)	O3^iii—Fe2—O4^xiv	172.59 (9)
O3^vi—K2—O2^viii	95.91 (6)	O4—Fe2—O4^xiv	91.52 (9)
O3^v—K2—O2^viii	100.74 (6)	O3^i—Fe2—O4^xiii	82.53 (9)
O2^vii—K2—O2^viii	56.14 (6)	O3^ii—Fe2—O4^xiii	172.59 (9)
O3^iv—K2—O2^ix	100.74 (6)	O3^iii—Fe2—O4^xiii	93.04 (9)
O3^vi—K2—O2^ix	149.93 (6)	O4—Fe2—O4^xiii	91.52 (9)
O3^v—K2—O2^ix	95.91 (6)	O4^xiv—Fe2—O4^xiii	91.52 (9)
O2^vii—K2—O2^ix	56.14 (6)	O4—P1—O2	105.93 (13)
O2^viii—K2—O2^ix	56.14 (6)	O4—P1—O3	107.23 (13)
O3^iv—K2—O4^iv	48.81 (5)	O2—P1—O3	112.54 (12)
O3^vi—K2—O4^iv	114.59 (7)	O4—P1—O1	111.60 (13)
O3^v—K2—O4^iv	52.71 (6)	O2—P1—O1	108.63 (12)
O2^vii—K2—O4^iv	132.57 (6)	O3—P1—O1	110.83 (12)
O2^viii—K2—O4^iv	141.48 (6)	P1—O1—Fe1	130.29 (12)
O2^ix—K2—O4^iv	95.42 (6)	P1—O1—K1^xvi	112.12 (11)
O3^iv—K2—O4^v	114.59 (7)	Fe1—O1—K1^xvi	102.92 (7)
O3^vi—K2—O4^v	52.71 (6)	P1—O2—Sn1^xxii	165.01 (15)
O3^v—K2—O4^v	48.81 (5)	P1—O2—Fe1^xxii	165.01 (15)
O2^vii—K2—O4^v	141.48 (6)	P1—O2—K2^xix	93.70 (9)
O2^viii—K2—O4^v	95.42 (6)	Sn1^xxii—O2—K2^xix	93.67 (8)
O2^ix—K2—O4^v	132.57 (6)	Fe1^xxii—O2—K2^xix	93.67 (8)
O4^iv—K2—O4^v	85.96 (7)	P1—O2—K1^xxi	92.83 (10)
O3^iv—K2—O4^vi	52.71 (6)	Sn1^xxii—O2—K1^xxi	98.07 (8)
O3^vi—K2—O4^vi	48.81 (5)	Fe1^xxii—O2—K1^xxi	98.07 (8)
O3^v—K2—O4^vi	114.59 (7)	K2^xix—O2—K1^xxi	103.77 (7)
O2^vii—K2—O4^vi	95.42 (6)	P1—O3—Sn2^xvi	148.98 (14)
O2^viii—K2—O4^vi	132.57 (6)	P1—O3—Fe2^xvi	148.98 (14)
O2^ix—K2—O4^vi	141.48 (6)	P1—O3—K2^xxi	105.79 (11)
O4^iv—K2—O4^vi	85.96 (7)	Sn2^xvi—O3—K2^xxi	100.16 (8)
O4^v—K2—O4^vi	85.96 (7)	Fe2^xvi—O3—K2^xxi	100.16 (8)
O3^iv—K2—O4^vii	56.20 (5)	P1—O4—Fe2	151.99 (15)
O3^vi—K2—O4^vii	86.13 (6)	P1—O4—K2^xxi	98.04 (10)
O3^v—K2—O4^vii	156.82 (6)	Fe2—O4—K2^xxi	93.77 (8)
O2^vii—K2—O4^vii	45.82 (5)	P1—O4—K1^xxi	88.91 (9)
O2^viii—K2—O4^vii	100.56 (6)	Fe2—O4—K1^xxi	118.50 (9)
O2^ix—K2—O4^vii	88.43 (6)	K2^xxi—O4—K1^xxi	77.63 (6)
O4^iv—K2—O4^vii	104.276 (11)	P1—O4—K2^xix	83.19 (10)
O4^v—K2—O4^vii	137.22 (4)	Fe2—O4—K2^xix	88.28 (8)
O4^vi—K2—O4^vii	54.34 (8)	K2^xxi—O4—K2^xix	172.75 (8)
O3^iv—K2—O4^viii	156.82 (6)	K1^xxi—O4—K2^xix	95.28 (7)
O3^vi—K2—O4^viii	56.20 (5)

Symmetry codes: (i) −z+1/2, −x+1, y+1/2; (ii) −x+1, y+1/2, −z+1/2; (iii) y+1/2, −z+1/2, −x+1; (iv) z+1/2, −x+3/2, −y+1; (v) −x+3/2, −y+1, z+1/2; (vi) −y+1, z+1/2, −x+3/2; (vii) −z+1, x+1/2, −y+3/2; (viii) −y+3/2, −z+1, x+1/2; (ix) x+1/2, −y+3/2, −z+1; (x) −y+1/2, −z, x−1/2; (xi) x−1/2, −y+1/2, −z; (xii) −z, x−1/2, −y+1/2; (xiii) y, z, x; (xiv) z, x, y; (xv) x−1, y−1, z−1; (xvi) −x+1, y−1/2, −z+1/2; (xvii) x−1/2, −y+1/2, −z+1; (xviii) −x+1/2, −y+1, z−1/2; (xix) x−1/2, −y+3/2, −z+1; (xx) −x+1, y−1/2, −z+3/2; (xxi) −x+3/2, −y+1, z−1/2; (xxii) x+1/2, −y+1/2, −z.