Redetermination of K2Mg3(OH)2(SO4)3(H2O)2 from single-crystal X-ray data revealing the correct hydrogen-atom positions

Weil, M.

doi:10.1107/S2056989020016217

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 77| Part 1| January 2021| Pages 62-65

https://doi.org/10.1107/S2056989020016217

Open

access

Redetermination of K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂ from single-crystal X-ray data revealing the correct hydrogen-atom positions

Matthias Weil ^a ^*

^aInstitute for Chemical Technologies and Analytics, Division of Structural Chemistry, TU Wien, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria
^*Correspondence e-mail: matthias.weil@tuwien.ac.at

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 10 December 2020; accepted 14 December 2020; online 1 January 2021)

In comparison with the previous structure determination of K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂, dipotassium trimagnesium dihydroxide tris(sulfate) dihydrate, from laboratory powder X-ray diffraction data [Kubel & Cabaret-Lampin (2013 ). Z. Anorg. Allg. Chem. 639, 1782–1786], the present redetermination against CCD single-crystal data has allowed for the modelling of all non-H atoms with anisotropic displacement parameters. As well as higher accuracy and precision in terms of bond lengths and angles, the clear localization of the H-atom positions leads also to a reasonable hydrogen-bonding scheme for this hydroxy hydrate. The structure consists of (100) sheets composed of corner- and edge-sharing [MgO₆] octahedra and sulfate tetrahedra. Adjacent sheets are linked by the potassium cations and a hydrogen bond of medium strength involving the water molecule. The title compound is isotypic with its Co^II and Mn^II analogues: the three K₂M₃(OH)₂(SO₄)₃(H₂O)₂ (M = Mg, Co, Mn) structures are quantitatively compared.

Keywords: crystal structure; redetermination; potassium magnesium sulfate; hydrogen bonding; structure comparison.

CCDC reference: 2050138

1. Chemical context

In our recent projects focused on hydrothermal phase-formation studies in the systems M/X^VI/Te^IV/O/H (X = S, Se), it was tested whether tetrahedral sulfate or selenate anions can be incorporated into oxidotellurates(IV) of different divalent metals M. So far, this concept proved to be successful for M = Hg (Weil & Shirkhanlou, 2015 ), M = Ca, Cd, Sr (Weil & Shirkhanlou, 2017a ), M = Pb (Weil & Shirkhanlou, 2017b ) as well as for M = Zn, Mg (Weil & Shirkhanlou, 2017c ). However, in nearly all cases multi-phase formation was observed under the given hydrothermal conditions, and the target compounds, i.e. metal oxidochalcogenates(IV,VI) with both oxidosulfate(VI) or oxidoselenate(VI) and oxidotellurate(IV) building units, appeared only as minority phases next to other different phases. The same holds for the Mg/S/Te/O/H system when working at pH ∼10 by using potassium hydroxide as a base. From one of the reaction batches, high-quality single crystals of the title compound, K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂, could be isolated as one of the products. A crystal-structure refinement of this phase has already been performed by Rietveld refinement against laboratory powder X-ray diffraction data (Kubel & Cabaret-Lampin, 2013). In the corresponding structure model, H-atom positions were estimated and optimized by energy minimization, but the resulting hydrogen-bonding pattern was not discussed in detail. A close check of this model revealed chemically implausible O—H bond lengths and O—H⋯O angles (Table 1). For example, H1 is more tightly bonded to O7 than to the actual hydroxide O atom (O8); the second hydroxyl group (O9) shows a too large O—H distance accompanied with large D⋯A distances or a too small O9—H2⋯O8 angle; the water molecule (O10) shows likewise either unreasonable H⋯A distances or D—H⋯A angles. Hence a redetermination of the crystal structure of K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂ to establish a more reasonable hydrogen-bonding pattern by using single crystal X-ray diffraction CCD data seemed appropriate and is reported here.

Table 1
Hydrogen-bond geometry (Å, °) from the previous model based on powder X-ray diffraction data and geometry-optimized H-atom positions (Kubel & Cabaret-Lampin, 2013)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O7—H1⋯O8ⁱ	0.82	2.54	3.258 (14)	147
O9—H2⋯O8	1.13	2.18	2.901 (14)	119
O9—H2⋯O6ⁱⁱ	1.13	2.52	3.506 (13)	145
O9—H2⋯O6ⁱⁱⁱ	1.13	2.52	3.506 (13)	145
O10—H3⋯O5^iv	0.85	2.41	3.066 (9)	134
O10—H3⋯O6^iv	0.85	2.55	3.038 (13)	118
O10—H3⋯O1	0.85	2.52	3.229 (9)	142
O10—H4⋯O2ⁱⁱⁱ	0.97	2.39	2.812 (8)	106
O10—H4⋯O3^v	0.97	1.77	2.698 (9)	158
Symmetry codes; (i) x, −y, z + $[{1\over 2}]$ ; (ii) −x, −y + 1, z + $[{1\over 2}]$ ; (iii) x, −y + 1, z + $[{1\over 2}]$ ; (iv) x, y, z + 1; (v) −x + $[{1\over 2}]$ , −y + $[{1\over 2}]$ , z + $[{1\over 2}]$ .

2. Structural commentary

Of the 19 atoms in the asymmetric unit (1 K, 2 Mg, 2 S, 10 O, 4 H), eight (Mg1, S2, O5, O7, O8, O9, H1 and H2) are located on a crystallographic mirror plane at x = 0 (Wyckoff position 4 a); all other atoms in the asymmetric unit are on general sites (8 b). Both Mg^II atoms are octahedrally coordinated by oxygen atoms. Mg1 is bonded to four O atoms belonging to sulfate groups (O5, O1 and its symmetry-related counterpart, O7) and to O atoms of two OH groups (O8, O9), whereas Mg2 is bonded to three sulfate O atoms (O4, O6, O2), two OH groups (O8, O9) and an O atom belonging to a water molecule (O10). Two [Mg2(H₂O)(OH)₂O₃] octahedra build up a {Mg2(H₂O)_1/1O_3/1(OH)_2/2}₂ dimer by edge-sharing the two OH groups. These dimers are linked to the [Mg1(OH)₂O₄] octahedra by corner-sharing the two OH groups, which leads to the formation of zigzag chains running parallel to [001]. Sulfate tetrahedra join neighbouring chains into sheets extending parallel to (100). Adjacent sheets are linked into a three-dimensional network by potassium cations (irregular nine-coordination), together with a hydrogen bond involving the water molecule (O10) and a sulfate O atom (O3) (Fig. 1).

Figure 1
The crystal structure of K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂ in a projection along [0 $[\overline{1}]$ 0]. Displacement ellipsoids are drawn at the 98% probability level for non-H atoms, and H atoms are given as spheres of arbitrary radius. Colour code: [MgO₆] octahedra are green, SO₄ tetrahedra are red; sulfate O atoms are white, O atoms of OH are yellow (O8) and blue (O9), and O atoms of water molecules are orange (O10). Hydrogen bonds involving the hydroxy group O8 are indicated by yellow lines and those involving the water molecule by orange lines.

The bond lengths for the two octahedral [MgO₆] groups, the tetrahedral sulfate groups and the nine-coordinate potassium cations, with mean values of 2.089, 1.474 and 2.964 Å, respectively, are in very good agreement with the expected values of 2.089 (59), 1.473 (7) and 2.955 (214) Å, provided recently by Gagné & Hawthorne (2016 , 2018 ). In terms of a comparison between the current single-crystal study and the previous powder study by Kubel & Cabaret-Lampin (2013), individual bond lengths as obtained from the single crystal study are, as expected, more precise and accurate, with the largest deviation of Δ = 0.092 Å for the Mg1—O5^iv bond (Table 2).

Table 2
Comparison of bond lengths (Å) from the current single-crystal X-ray study and the previous powder X-ray diffraction study (Kubel & Cabaret-Lampin, 2013)

Bond	single-crystal study	powder study
K1—O4ⁱ	2.8323 (15)	2.902 (7)
K1—O3ⁱ	2.8594 (15)	2.877 (8)
K1—O10ⁱⁱ	2.8704 (15)	2.874 (9)
K1—O2ⁱⁱⁱ	2.9436 (14)	2.948 (8)
K1—O6	2.9743 (15)	2.945 (8)
K1—O3ⁱⁱ	2.9915 (15)	3.016 (9)
K1—O2	3.0532 (15)	3.116 (9)
K1—O1ⁱⁱ	3.0740 (15)	3.118 (10)
K1—O1	3.0780 (15)	3.128 (11)
K1—O3	3.3068 (15)	3.311 (10)
Mg1—O9	2.067 (2)	2.139 (11)
Mg1—O8	2.071 (2)	2.104 (10)
Mg1—O5^iv	2.081 (2)	1.989 (10)
Mg1—O1^v	2.0976 (13)	2.049 (5)
Mg1—O1	2.0977 (13)	2.049 (5)
Mg1—O7	2.160 (2)	2.139 (11)
Mg2—O4	2.0220 (15)	2.012 (9)
Mg2—O6^vi	2.0796 (14)	2.099 (8)
Mg2—O2^vi	2.0924 (15)	2.117 (8)
Mg2—O8	2.0952 (14)	2.036 (7)
Mg2—O9^vii	2.1026 (14)	2.045 (9)
Mg2—O10	2.1064 (15)	2.163 (8)
S1—O4	1.4657 (14)	1.487 (10)
S1—O3	1.4659 (14)	1.463 (6)
S1—O2	1.4818 (14)	1.500 (10)
S1—O1	1.4818 (13)	1.476 (6)
S2—O7	1.469 (2)	1.483 (13)
S2—O6	1.4751 (14)	1.468 (8)
S2—O6^v	1.4751 (14)	1.468 (8)
S2—O5	1.4779 (19)	1.530 (12)
Symmetry codes: (i) −x + $[{1\over 2}]$ , −y + $[{1\over 2}]$ , z − $[{1\over 2}]$ ; (ii) x, −y, z − $[{1\over 2}]$ ; (iii) −x + $[{1\over 2}]$ , y − $[{1\over 2}]$ , z; (iv) −x, −y, z + $[{1\over 2}]$ ; (v) −x, y, z; (vi) x, −y + 1, z + $[{1\over 2}]$ ; (vii) −x, −y + 1, z + $[{1\over 2}]$ .

The hydrogen-bonding pattern derived from the single crystal study is chemically plausible (Table 3, Fig. 1). The water molecule (O10) participates in two nearly linear O—H⋯O hydrogen bonds to two sulfate O atoms. One is of weak nature to O5 as the acceptor atom [D⋯A = 3.009 (2) Å] within a sheet, the other of medium strength to O3 [D⋯A = 2.722 (2) Å] between adjacent layers. The hydroxy group involving O8 exhibits a weak hydrogen bond to a neighbouring sulfate O atom [O7; D⋯A = 3.068 (2) Å]. The other hydroxy group involving O9 appears not to be involved in hydrogen bonding: the next nearest O atoms that could act as acceptor atoms are two symmetry-related O6 atoms (−x, −y + 1, z + $[{1\over 2}]$ ; x, −y + 1, z + $[{1\over 2}]$ ), both at a distance of 3.405 (2) Å from O9. Such a long D⋯A distance is usually not considered as relevant for hydrogen bonding but was discussed for the K₂Co₃(OH)₂(SO₄)₃(H₂O)₂ structure as part of a bifurcated O—H⋯(O,O) hydrogen bond of very weak nature, here with D⋯A = 3.370 (9) Å (Effenberger & Langhof, 1984 ).

Table 3
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O8—H1⋯O7ⁱ	0.86 (4)	2.22 (4)	3.068 (2)	168 (3)
O9—H2	0.73 (5)	?	?	?
O10—H3⋯O5ⁱⁱ	0.79 (4)	2.22 (4)	3.009 (2)	171 (3)
O10—H3⋯O6ⁱⁱ	0.79 (4)	2.59 (3)	3.023 (2)	116 (3)
O10—H4⋯O3ⁱⁱⁱ	0.83 (4)	1.90 (4)	2.722 (2)	171 (4)
Symmetry codes: (i) $[-x, -y, z+{\script{1\over 2}}]$ ; (ii) x, y, z+1; (iii) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂ is isotypic with its Co (Effenberger & Langhof, 1984) and Mn (Yu et al., 2007 ) analogues. The three isotypic K₂M₃(OH)₂(SO₄)₃(H₂O)₂ (M = Mg, Co, Mn) structures were quantitatively compared using the compstru program (de la Flor et al., 2016 ), available at the Bilbao Crystallographic Server (Aroyo et al., 2006 ). For this purpose, the hydrogen atoms were not taken into account. In relation to the title Mg structure, the Co and Mn structures show the following values for evaluation of the structural similarity. Co: the degree of lattice distortion is 0.0034, the maximum displacement between atomic positions of paired atoms is 0.0553 Å for the pair O9, the arithmetic mean of the distance between paired atoms is 0.0295 Å, and the measure of similarity is 0.010. Corresponding values for the Mn structure are: 0.0126, 0.1343 Å for pair O2, 0.0768 Å and 0.013, respectively. The two value sets indicate a higher similarity between the Mg and Co structures compared to the Mn structure. This is most probably related to the ionic radii (Shannon, 1976 ) of the six-coordinate metal cations that differ only marginally for Mg (0.72 Å) and Co (0.745 Å, assuming a high-spin 3d⁷ configuration), whereas Mn (0.83 Å for a high-spin 3d⁵ state) is considerately greater.

3. Synthesis and crystallization

A mixture of 380 mg of MgSO₄·7H₂O, 100 mg of TeO₂ and 70 mg of KOH was placed in a 5 ml Teflon container that was subsequently filled with 2 ml of water and sealed with a Teflon lid. The closed container was placed in a steel autoclave and was heated at 413 K for one week at autogenous pressure and then cooled down to room temperature within 5 h. The recovered solids consisted of Mg₂Te₃O₈ (Lin et al., 2013 ) as the main product (checked by powder X-ray diffraction of the bulk), besides minor amounts of caminite, Mg₂(SO₄)(OH)₂ (Keefer et al., 1981 ), the sulfate tellurite Mg₃(SO₄)(TeO₃)(OH)₂(H₂O)₂ (Weil & Shirkhanlou, 2017c) and the title compound (the latter phases determined by single-crystal X-ray diffraction).

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 4. Atomic coordinates and labelling for the non-H atoms were adapted from the previous refinement from powder X-ray diffraction data (Kubel & Cabaret-Lampin, 2013). H atoms were clearly discernible in difference-Fourier maps and were refined freely. The Flack parameter (Table 4) indicates that the absolute structure has been determined correctly.

Table 4
Experimental details

Crystal data
Chemical formula	K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂
M_r	509.36
Crystal system, space group	Orthorhombic, Cmc2₁
Temperature (K)	100
a, b, c (Å)	17.8228 (19), 7.4879 (8), 9.7686 (10)
V (Å³)	1303.7 (2)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	1.45
Crystal size (mm)	0.10 × 0.08 × 0.01

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.668, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	31799, 2535, 2430
R_int	0.042
(sin θ/λ)_max (Å⁻¹)	0.768

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.017, 0.039, 1.07
No. of reflections	2535
No. of parameters	132
No. of restraints	1
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.30, −0.38
Absolute structure	Flack x determined using 1125 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	−0.010 (13)
Coordinates taken from previous refinement. Computer programs: APEX3 and SAINT (Bruker, 2015 ), SHELXL2014/7 (Sheldrick, 2015 ), ATOMS for Windows (Dowty, 2006 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2050138

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989020016217/hb7955sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020016217/hb7955Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2015); cell refinement: SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: coordinates taken from previous refinement; program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: Atoms for Windows (Dowty, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Dipotassium trimagnesium dihydroxide tris(sulfate) dihydrate top

Crystal data top

K₂Mg₃(OH)₂(SO₄)₃(H₂O)₂	D_x = 2.595 Mg m⁻³
M_r = 509.36	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmc2₁	Cell parameters from 9959 reflections
a = 17.8228 (19) Å	θ = 2.8–33.0°
b = 7.4879 (8) Å	µ = 1.45 mm⁻¹
c = 9.7686 (10) Å	T = 100 K
V = 1303.7 (2) Å³	Plate, colourless
Z = 4	0.10 × 0.08 × 0.01 mm
F(000) = 1024

Data collection top

Bruker APEXII CCD diffractometer	2430 reflections with I > 2σ(I)
ω– and φ–scans	R_int = 0.042
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θ_max = 33.1°, θ_min = 2.3°
T_min = 0.668, T_max = 0.747	h = −27→27
31799 measured reflections	k = −11→11
2535 independent reflections	l = −14→14

Refinement top

Refinement on F²	Hydrogen site location: difference Fourier map
Least-squares matrix: full	All H-atom parameters refined
R[F² > 2σ(F²)] = 0.017	w = 1/[σ²(F_o²) + (0.0167P)² + 0.9127P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.039	(Δ/σ)_max < 0.001
S = 1.07	Δρ_max = 0.30 e Å⁻³
2535 reflections	Δρ_min = −0.38 e Å⁻³
132 parameters	Absolute structure: Flack x determined using 1125 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
1 restraint	Absolute structure parameter: −0.010 (13)

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
K1	0.19321 (2)	0.04648 (5)	−0.26016 (4)	0.00947 (7)
Mg1	0.0000	0.19893 (11)	0.00487 (10)	0.00514 (15)
Mg2	0.08605 (4)	0.46648 (8)	0.28489 (7)	0.00532 (11)
S1	0.17492 (2)	0.30375 (5)	0.01513 (5)	0.00452 (7)
S2	0.0000	0.18319 (8)	−0.31682 (6)	0.00448 (10)
O1	0.11670 (7)	0.16279 (16)	0.00789 (16)	0.0074 (2)
O2	0.17476 (8)	0.40504 (19)	−0.11519 (14)	0.0075 (2)
O3	0.24837 (8)	0.21941 (17)	0.03462 (15)	0.0091 (2)
O4	0.15996 (8)	0.42187 (18)	0.13162 (14)	0.0079 (2)
O5	0.0000	0.0697 (2)	−0.44063 (19)	0.0067 (3)
O6	0.06775 (8)	0.29624 (17)	−0.32058 (15)	0.0086 (2)
O7	0.0000	0.0711 (2)	−0.1934 (2)	0.0087 (4)
O8	0.0000	0.3133 (2)	0.1979 (2)	0.0055 (3)
O9	0.0000	0.4505 (2)	−0.0823 (2)	0.0062 (3)
O10	0.12236 (8)	0.23658 (19)	0.39003 (15)	0.0084 (2)
H1	0.0000	0.213 (6)	0.241 (5)	0.023 (11)*
H2	0.0000	0.509 (7)	−0.023 (5)	0.031 (13)*
H3	0.092 (2)	0.182 (5)	0.433 (3)	0.030 (9)*
H4	0.159 (2)	0.246 (6)	0.441 (4)	0.046 (12)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
K1	0.01028 (16)	0.00894 (14)	0.00920 (15)	−0.00051 (13)	0.00151 (15)	−0.00034 (14)
Mg1	0.0061 (4)	0.0045 (3)	0.0048 (4)	0.000	0.000	0.0002 (3)
Mg2	0.0054 (3)	0.0052 (3)	0.0053 (2)	0.00037 (19)	0.0001 (2)	−0.0003 (2)
S1	0.00477 (16)	0.00458 (15)	0.00422 (16)	0.00040 (13)	−0.00005 (15)	0.00002 (15)
S2	0.0054 (2)	0.0040 (2)	0.0041 (2)	0.000	0.000	−0.00057 (19)
O1	0.0063 (5)	0.0060 (5)	0.0101 (6)	−0.0022 (4)	0.0003 (5)	−0.0007 (5)
O2	0.0087 (6)	0.0093 (6)	0.0044 (6)	−0.0004 (5)	−0.0007 (4)	0.0021 (4)
O3	0.0057 (5)	0.0100 (6)	0.0114 (6)	0.0025 (4)	0.0006 (5)	0.0013 (5)
O4	0.0092 (6)	0.0084 (6)	0.0061 (6)	−0.0016 (5)	0.0022 (5)	−0.0028 (4)
O5	0.0087 (8)	0.0062 (8)	0.0053 (8)	0.000	0.000	−0.0021 (6)
O6	0.0082 (6)	0.0082 (5)	0.0096 (6)	−0.0037 (4)	0.0018 (5)	−0.0028 (5)
O7	0.0144 (9)	0.0055 (8)	0.0061 (8)	0.000	0.000	0.0009 (6)
O8	0.0059 (8)	0.0048 (7)	0.0056 (8)	0.000	0.000	0.0006 (6)
O9	0.0081 (8)	0.0049 (7)	0.0056 (8)	0.000	0.000	−0.0005 (6)
O10	0.0077 (6)	0.0084 (6)	0.0093 (6)	−0.0006 (5)	−0.0008 (5)	0.0020 (5)

Geometric parameters (Å, º) top

K1—O4ⁱ	2.8323 (15)	Mg2—O4	2.0220 (15)
K1—O3ⁱ	2.8594 (15)	Mg2—O6^vi	2.0796 (14)
K1—O10ⁱⁱ	2.8704 (15)	Mg2—O2^vi	2.0924 (15)
K1—O2ⁱⁱⁱ	2.9436 (14)	Mg2—O8	2.0952 (14)
K1—O6	2.9743 (15)	Mg2—O9^vii	2.1026 (14)
K1—O3ⁱⁱ	2.9915 (15)	Mg2—O10	2.1064 (15)
K1—O2	3.0532 (15)	S1—O4	1.4657 (14)
K1—O1ⁱⁱ	3.0740 (15)	S1—O3	1.4659 (14)
K1—O1	3.0780 (15)	S1—O2	1.4818 (14)
K1—O3	3.3068 (15)	S1—O1	1.4818 (13)
Mg1—O9	2.067 (2)	S2—O7	1.469 (2)
Mg1—O8	2.071 (2)	S2—O6	1.4751 (14)
Mg1—O5^iv	2.081 (2)	S2—O6^v	1.4751 (14)
Mg1—O1^v	2.0976 (13)	S2—O5	1.4779 (19)
Mg1—O1	2.0977 (13)	O10—H3	0.79 (4)
Mg1—O7	2.160 (2)	O10—H4	0.83 (4)

O4ⁱ—K1—O3ⁱ	49.50 (4)	O4—Mg2—O9^vii	168.75 (7)
O4ⁱ—K1—O10ⁱⁱ	131.23 (4)	O6^vi—Mg2—O9^vii	86.48 (7)
O3ⁱ—K1—O10ⁱⁱ	166.22 (4)	O2^vi—Mg2—O9^vii	97.32 (6)
O4ⁱ—K1—O2ⁱⁱⁱ	58.07 (4)	O8—Mg2—O9^vii	83.00 (6)
O3ⁱ—K1—O2ⁱⁱⁱ	105.47 (4)	O4—Mg2—O10	91.48 (6)
O10ⁱⁱ—K1—O2ⁱⁱⁱ	80.80 (4)	O6^vi—Mg2—O10	171.10 (7)
O4ⁱ—K1—O6	124.61 (4)	O2^vi—Mg2—O10	85.19 (6)
O3ⁱ—K1—O6	75.47 (4)	O8—Mg2—O10	88.59 (7)
O10ⁱⁱ—K1—O6	103.59 (4)	O9^vii—Mg2—O10	99.50 (7)
O2ⁱⁱⁱ—K1—O6	157.33 (4)	O4—S1—O3	108.76 (8)
O4ⁱ—K1—O3ⁱⁱ	60.13 (4)	O4—S1—O2	110.97 (8)
O3ⁱ—K1—O3ⁱⁱ	79.54 (4)	O3—S1—O2	109.50 (8)
O10ⁱⁱ—K1—O3ⁱⁱ	89.75 (4)	O4—S1—O1	109.84 (8)
O2ⁱⁱⁱ—K1—O3ⁱⁱ	79.64 (4)	O3—S1—O1	108.94 (8)
O6—K1—O3ⁱⁱ	122.18 (4)	O2—S1—O1	108.80 (8)
O4ⁱ—K1—O2	101.48 (4)	O7—S2—O6	110.39 (7)
O3ⁱ—K1—O2	79.94 (4)	O7—S2—O6^v	110.39 (7)
O10ⁱⁱ—K1—O2	111.40 (4)	O6—S2—O6^v	109.88 (11)
O2ⁱⁱⁱ—K1—O2	100.33 (4)	O7—S2—O5	110.07 (11)
O6—K1—O2	57.19 (4)	O6—S2—O5	108.03 (7)
O3ⁱⁱ—K1—O2	158.66 (4)	O6^v—S2—O5	108.03 (7)
O4ⁱ—K1—O1ⁱⁱ	100.22 (4)	S1—O1—Mg1	127.09 (8)
O3ⁱ—K1—O1ⁱⁱ	87.55 (4)	S1—O1—K1^viii	90.99 (6)
O10ⁱⁱ—K1—O1ⁱⁱ	78.76 (4)	Mg1—O1—K1^viii	121.06 (6)
O2ⁱⁱⁱ—K1—O1ⁱⁱ	121.72 (4)	S1—O1—K1	86.09 (6)
O6—K1—O1ⁱⁱ	80.84 (4)	Mg1—O1—K1	117.63 (7)
O3ⁱⁱ—K1—O1ⁱⁱ	46.57 (4)	K1^viii—O1—K1	106.63 (4)
O2—K1—O1ⁱⁱ	137.93 (4)	S1—O2—Mg2^ix	129.61 (8)
O4ⁱ—K1—O1	134.68 (4)	S1—O2—K1^x	126.58 (7)
O3ⁱ—K1—O1	125.75 (4)	Mg2^ix—O2—K1^x	102.37 (5)
O10ⁱⁱ—K1—O1	65.12 (4)	S1—O2—K1	87.03 (6)
O2ⁱⁱⁱ—K1—O1	92.68 (4)	Mg2^ix—O2—K1	105.63 (5)
O6—K1—O1	69.99 (4)	K1^x—O2—K1	90.41 (4)
O3ⁱⁱ—K1—O1	154.68 (4)	S1—O3—K1^xi	98.75 (7)
O2—K1—O1	46.28 (3)	S1—O3—K1^viii	94.61 (7)
O1ⁱⁱ—K1—O1	125.08 (4)	K1^xi—O3—K1^viii	93.32 (4)
O4ⁱ—K1—O3	91.01 (4)	S1—O3—K1	77.88 (6)
O3ⁱ—K1—O3	105.201 (16)	K1^xi—O3—K1	163.50 (5)
O10ⁱⁱ—K1—O3	88.56 (4)	K1^viii—O3—K1	103.02 (4)
O2ⁱⁱⁱ—K1—O3	58.95 (4)	S1—O4—Mg2	142.48 (9)
O6—K1—O3	98.63 (4)	S1—O4—K1^xi	99.91 (7)
O3ⁱⁱ—K1—O3	138.28 (5)	Mg2—O4—K1^xi	108.16 (6)
O2—K1—O3	44.26 (3)	S2—O5—Mg1^xii	139.91 (12)
O1ⁱⁱ—K1—O3	166.75 (4)	S2—O6—Mg2^ix	127.33 (9)
O1—K1—O3	43.96 (4)	S2—O6—K1	104.45 (7)
O9—Mg1—O8	89.91 (8)	Mg2^ix—O6—K1	108.72 (6)
O9—Mg1—O5^iv	170.48 (9)	S2—O7—Mg1	118.84 (11)
O8—Mg1—O5^iv	99.61 (8)	Mg1—O8—Mg2	126.57 (6)
O9—Mg1—O1^v	97.08 (4)	Mg1—O8—Mg2^v	126.57 (6)
O8—Mg1—O1^v	92.32 (5)	Mg2—O8—Mg2^v	94.11 (8)
O5^iv—Mg1—O1^v	82.63 (4)	Mg1—O8—H1	95 (3)
O9—Mg1—O1	97.08 (4)	Mg2—O8—H1	106.4 (19)
O8—Mg1—O1	92.32 (5)	Mg2^v—O8—H1	106.4 (19)
O5^iv—Mg1—O1	82.63 (4)	Mg1—O9—Mg2^xiii	121.58 (6)
O1^v—Mg1—O1	165.09 (8)	Mg1—O9—Mg2^ix	121.58 (6)
O9—Mg1—O7	91.97 (8)	Mg2^xiii—O9—Mg2^ix	93.68 (8)
O8—Mg1—O7	178.12 (9)	Mg1—O9—H2	103 (4)
O5^iv—Mg1—O7	78.51 (8)	Mg2^xiii—O9—H2	108 (3)
O1^v—Mg1—O7	87.44 (5)	Mg2^ix—O9—H2	108 (3)
O1—Mg1—O7	87.44 (5)	Mg2—O10—K1^viii	119.30 (6)
O4—Mg2—O6^vi	82.90 (6)	Mg2—O10—H3	118 (3)
O4—Mg2—O2^vi	85.94 (6)	K1^viii—O10—H3	101 (2)
O6^vi—Mg2—O2^vi	87.52 (6)	Mg2—O10—H4	118 (3)
O4—Mg2—O8	94.94 (6)	K1^viii—O10—H4	92 (3)
O6^vi—Mg2—O8	98.73 (7)	H3—O10—H4	105 (4)
O2^vi—Mg2—O8	173.74 (7)

Symmetry codes: (i) −x+1/2, −y+1/2, z−1/2; (ii) x, −y, z−1/2; (iii) −x+1/2, y−1/2, z; (iv) −x, −y, z+1/2; (v) −x, y, z; (vi) x, −y+1, z+1/2; (vii) −x, −y+1, z+1/2; (viii) x, −y, z+1/2; (ix) x, −y+1, z−1/2; (x) −x+1/2, y+1/2, z; (xi) −x+1/2, −y+1/2, z+1/2; (xii) −x, −y, z−1/2; (xiii) −x, −y+1, z−1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O8—H1···O7^iv	0.86 (4)	2.22 (4)	3.068 (2)	168 (3)
O9—H2	0.73 (5)	?	?	?
O10—H3···O5^xiv	0.79 (4)	2.22 (4)	3.009 (2)	171 (3)
O10—H3···O6^xiv	0.79 (4)	2.59 (3)	3.023 (2)	116 (3)
O10—H4···O3^xi	0.83 (4)	1.90 (4)	2.722 (2)	171 (4)

Symmetry codes: (iv) −x, −y, z+1/2; (xi) −x+1/2, −y+1/2, z+1/2; (xiv) x, y, z+1.

Hydrogen-bond geometry (Å, °) from the previous model based on powder X-ray diffraction data and geometry-optimized H-atom positions (Kubel & Cabaret-Lampin, 2013) top

D—H···A	D—H	H···A	D···A	D—H···A
O7—H1···O8ⁱ	0.82	2.54	3.258 (14)	147
O9—H2···O8	1.13	2.18	2.901 (14)	119
O9—H2···O6ⁱⁱ	1.13	2.52	3.506 (13)	145
O9—H2···O6ⁱⁱⁱ	1.13	2.52	3.506 (13)	145
O10—H3···O5^iv	0.85	2.41	3.066 (9)	134
O10—H3···O6^iv	0.85	2.55	3.038 (13)	118
O10—H3···O1	0.85	2.52	3.229 (9)	142
O10—H4···O2ⁱⁱⁱ	0.97	2.39	2.812 (8)	106
O10—H4···O3^v	0.97	1.77	2.698 (9)	158

Symmetry codes; (i) x, -y, z + 1/2; (ii) -x, -y + 1, z + 1/2; (iii) x, -y+1, z + 1/2; (iv) x, y, z + 1; (v) -x + 1/2, -y + 1/2, z + 1/2.

Comparison of bond lengths (Å) from the current single crystal X-ray study and the previous powder X-ray diffraction study (Kubel & Cabaret-Lampin, 2013) top

Bond	single crystal study	powder study
K1—O4ⁱ	2.8323 (15)	2.902 (7)
K1—O3ⁱ	2.8594 (15)	2.877 (8)
K1—O10ⁱⁱ	2.8704 (15)	2.874 (9)
K1—O2ⁱⁱⁱ	2.9436 (14)	2.948 (8)
K1—O6	2.9743 (15)	2.945 (8)
K1—O3ⁱⁱ	2.9915 (15)	3.016 (9)
K1—O2	3.0532 (15)	3.116 (9)
K1—O1ⁱⁱ	3.0740 (15)	3.118 (10)
K1—O1	3.0780 (15)	3.128 (11)
K1—O3	3.3068 (15)	3.311 (10)
Mg1—O9	2.067 (2)	2.139 (11)
Mg1—O8	2.071 (2)	2.104 (10)
Mg1—O5^iv	2.081 (2)	1.989 (10)
Mg1—O1^v	2.0976 (13)	2.049 (5)
Mg1—O1	2.0977 (13)	2.049 (5)
Mg1—O7	2.160 (2)	2.139 (11)
Mg2—O4	2.0220 (15)	2.012 (9)
Mg2—O6^vi	2.0796 (14)	2.099 (8)
Mg2—O2^vi	2.0924 (15)	2.117 (8)
Mg2—O8	2.0952 (14)	2.036 (7)
Mg2—O9^vii	2.1026 (14)	2.045 (9)
Mg2—O10	2.1064 (15)	2.163 (8)
S1—O4	1.4657 (14)	1.487 (10)
S1—O3	1.4659 (14)	1.463 (6)
S1—O2	1.4818 (14)	1.500 (10)
S1—O1	1.4818 (13)	1.476 (6)
S2—O7	1.469 (2)	1.483 (13)
S2—O6	1.4751 (14)	1.468 (8)
S2—O6^v	1.4751 (14)	1.468 (8)
S2—O5	1.4779 (19)	1.530 (12)

Symmetry codes: (i) -x + 1/2, -y + 1/2, z - 1/2; (ii) x, -y, z - 1/2; (iii) -x + 1/2, y -1/2, z; (iv) -x, -y, z + 1/2; (v) -x, y, z; (vi) x, -y + 1, z + 1/2; (vii) -x, -y + 1, z + 1/2.

Acknowledgements

The X-ray centre of TU Wien is acknowledged for financial support and for providing access to the powder and single-crystal diffractometers.

References

Aroyo, M. I., Perez-Mato, J. M., Capillas, C., Kroumova, E., Ivantchev, S., Madariaga, G., Kirov, A. & Wondratschek, H. (2006). Z. Kristallogr. 221, 15–27. Web of Science CrossRef CAS Google Scholar
Bruker (2015). APEX3 and SAINT. Bruker AXS Inc. Madison, Wisconsin, USA Google Scholar
Dowty, E. (2006). ATOMS. Shape Software, Kingsport, Tennessee, USA. Google Scholar
Effenberger, H. & Langhof, H. (1984). Monatsh. Chem. 115, 165–177. CrossRef ICSD CAS Web of Science Google Scholar
Flor, G. de la, Orobengoa, D., Tasci, E., Perez-Mato, J. M. & Aroyo, M. I. (2016). J. Appl. Cryst. 49, 653–664. Web of Science CrossRef IUCr Journals Google Scholar
Gagné, O. C. & Hawthorne, F. C. (2016). Acta Cryst. B72, 602–625. Web of Science CrossRef IUCr Journals Google Scholar
Gagné, O. C. & Hawthorne, F. C. (2018). Acta Cryst. B74, 79–96. Web of Science CrossRef IUCr Journals Google Scholar
Keefer, K. D., Hochella, M. F. Jr & de Jong, B. H. W. S. (1981). Acta Cryst. B37, 1003–1006. CrossRef ICSD CAS IUCr Journals Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef ICSD CAS IUCr Journals Google Scholar
Kubel, F. & Cabaret-Lampin, M. (2013). Z. Anorg. Allg. Chem. 639, 1782–1786. CrossRef ICSD CAS Google Scholar
Lin, W.-F., Xing, Q.-J., Ma, J., Zou, J.-P., Lei, S.-L., Luo, X.-B. & Guo, G.-C. (2013). Z. Anorg. Allg. Chem. 639, 31–34. Web of Science CrossRef ICSD CAS Google Scholar
Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259. Web of Science CrossRef CAS IUCr Journals Google Scholar
Shannon, R. D. (1976). Acta Cryst. A32, 751–767. CrossRef CAS IUCr Journals Web of Science Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Weil, M. & Shirkhanlou, M. (2015). Z. Anorg. Allg. Chem. 641, 1459–1466. Web of Science CrossRef ICSD CAS Google Scholar
Weil, M. & Shirkhanlou, M. (2017a). Z. Anorg. Allg. Chem. 643, 330–339. Web of Science CrossRef CAS Google Scholar
Weil, M. & Shirkhanlou, M. (2017b). Z. Anorg. Allg. Chem. 643, 757–765. Web of Science CrossRef CAS Google Scholar
Weil, M. & Shirkhanlou, M. (2017c). Z. Anorg. Allg. Chem. 643, 749–756. CrossRef CAS Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yu, J.-H., Ye, L., Ding, H., Chen, Y., Hou, Q., Zhang, X. & Xu, J. Q. (2007). Inorg. Chem. Commun. 10, 159–162. CrossRef ICSD CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.