Three new acid M+ arsenates and phosphates with multiply protonated As/PO4 groups

Schwendtner, K.; Kolitsch, U.

doi:10.1107/S2053229619008489

research papers

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 75| Part 8| August 2019| Pages 1134-1141

https://doi.org/10.1107/S2053229619008489

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Three new acid M⁺ arsenates and phosphates with multiply protonated As/PO₄ groups

Karolina Schwendtner ^a ^* and Uwe Kolitsch ^b,^c

^aInstitute for Chemical Technology and Analytics, Division of Structural Chemistry, TU Wien, Getreidemarkt 9, Wien 1060, Austria, ^bMineralogisch-Petrographische Abteilung, Naturhistorisches Museum, Burgring 7, Wien 1010, Austria, and ^cInstitut für Mineralogie und Kristallographie, Universität Wien, Althanstrasse 14, Wien 1090, Austria
^*Correspondence e-mail: karolina.schwendtner@tuwien.ac.at

Edited by I. D. Williams, Hong Kong University of Science and Technology, Hong Kong (Received 18 December 2018; accepted 14 June 2019; online 25 July 2019)

The crystal structures of caesium dihydrogen arsenate(V) bis[trihydrogen arsenate(V)], Cs(H₂AsO₄)(H₃AsO₄)₂, ammonium dihydrogen arsenate(V) trihydrogen arsenate(V), NH₄(H₂AsO₄)(H₃AsO₄), and dilithium bis(dihydrogen phosphate), Li₂(H₂PO₄)₂, were solved from single-crystal X-ray diffraction data. NH₄(H₂AsO₄)(H₃AsO₄), which was hydrothermally synthesized (T = 493 K), is homeotypic with Rb(H₂AsO₄)(H₃AsO₄), while Cs(H₂AsO₄)(H₃AsO₄)₂ crystallizes in a novel structure type and Li₂(H₂PO₄)₂ represents a new polymorph of this composition. The Cs and Li compounds grew at room temperature from highly acidic aqueous solutions. Li₂(H₂PO₄)₂ forms a three-dimensional (3D) framework of PO₄ tetrahedra sharing corners with Li₂O₆ dimers built of edge-sharing LiO₄ groups, which is reinforced by hydrogen bonds. The two arsenate compounds are characterized by a 3D network of AsO₄ groups that are connected solely via multiple strong hydrogen bonds. A statistical evaluation of the As—O bond lengths in singly, doubly and triply protonated AsO₄ groups gave average values of 1.70 (2) Å for 199 As—OH bonds, 1.728 (19) Å for As—OH bonds in HAsO₄ groups, 1.714 (12) Å for As—OH bonds in H₂AsO₄ groups and 1.694 (16) Å for As—OH bonds in H₃AsO₄ groups, and a grand mean value of 1.667 (18) Å for As—O bonds to nonprotonated O atoms.

Keywords: arsenate; phosphate; caesium; lithium; ammonium; statistical evaluation; crystal structure; H₂PO₄; H₂AsO₄; H₃AsO₄; As—O bond lengths.

CCDC references: 1922991; 1922990; 1922989

1. Introduction

M⁺ phosphates and arsenates, and their crystal structures and physicochemical properties, have been extensively studied. Several compounds exhibit interesting properties, such as protonic conductivity (Chouchene et al., 2017a ,b ; Volkov et al., 1995 , 1997 ; Voronov et al., 2013 ; Dekhili et al., 2018 ) or nonlinear optical properties (Dhouib et al., 2014a , 2017 ; Kumaresan et al., 2008 ).

To further increase the knowledge about the possible compounds and structure types of M⁺–M³⁺ arsenates, a comprehensive study of the system M⁺–M³⁺–O–(H–)As/P⁵⁺ (M⁺ = Li, Na, K, Rb, Cs, Ag, Tl and NH₄; M³⁺ = Al, Ga, In, Sc, Fe, Cr and Tl) was undertaken, which led to a large number of new structure types that have been published (Schwendtner, 2006 ; Schwendtner & Kolitsch, 2004a ,b , 2005 , 2007a ,b ,c , 2017a ,b , 2018 ). The three compounds structurally characterized in the present article are by-products of this comprehensive study. The following paragraphs provide brief backgrounds to the families of materials to which the three compounds belong.

Lithium phosphates are rather common and the system Li–H–P–O has been widely studied because of the proton conductivity of compounds like LiH₂PO₄ (Catti & Ivaldi, 1978 ). The title compound Li₂(H₂PO₄)₂ is a new polymorph of this well-known compound. Other known compounds in the Li–H–P–O system, the majority containing polymerized phosphate groups, include Li₄H(PO₃)₅, LiH₂PO₂, Li₆(P₆O₁₈)(H₂O)₃, Li₄P₂O₈(H₂O)₄, Li₃(P₃O₉)(H₂O)₃, Li₆(P₆O₁₈)(H₂O)₅, Li₄(P₄O₁₂)(H₂O)₅, Li₆(P₆O₁₈)(H₂O)_8.24, Li₆(P₆O₁₈)(H₂O)_9.86, Li₃PO₄ and Li₄P₂O₇.

Known caesium arsenates include CsAs₃O₈ (Schwendtner & Kolitsch, 2007a), Cs₃AsO₄ (Emmerling et al., 2002 ), Cs₂(HAsO₄)(H₂O)₂ (Stöger & Weil, 2014 ), KDP-type Cs(H₂AsO₄) (Ferrari et al., 1956 ) and CsH₅(AsO₄)₂ (Naili et al., 2001 ). Ammonium arsenate compounds comprise (NH₄)(H₂AsO₄), for which a tetragonal KDP-type polymorph (Khan & Baur, 1972 ) and an orthorhombic low-temperature polymorph (Fukami, 1989 ) were reported, (NH₄)₂(HAsO₄) (Weil, 2012 ) and (NH₄)₃(AsO₄)(H₂O)₃ (Hseu & Lu, 1977 ).

Compounds containing H₃AsO₄ groups are relatively rare and mainly known from compounds containing organic groups (e.g. Dekola et al., 2011 ; Dhouib et al., 2014a,b , 2017; Ratajczak et al., 2000 ). Inorganic compounds containing arsenic acid (with clearly located H atoms of the H₃AsO₄ group) and with known crystal structures are restricted to only seven representatives: CuH₁₀(AsO₄)₄ (Tran Qui & Chiadmi, 1986 ) and isotypic ZnH₁₀(AsO₄)₄ (Sure & Guse, 1989 ) (the O—H bonds were not clearly identified in the latter structure determination), RbH₅(AsO₄)₂ (Naili & Mhiri, 2001 ), CsH₅(AsO₄)₂ (Naili et al., 2001), K₄(SO₄)(HSO₄)₂(H₃AsO₄) (Amri et al., 2007 ), Cs₄(SeO₄)(HSeO₄)₂(H₃AsO₄) (Amri et al., 2009 ) and isotypic Rb₄(SO₄)(HSO₄)₂(H₃AsO₄) (Belhaj Salah et al., 2018 ). (NH₄)₂(H₃AsO₄)(SO₄) (Boubia et al., 1985 ) also contains H₃AsO₄ groups, but the H atoms were not located, and for CdH₁₀(AsO₄)₄ (Tran Qui & Chiadmi, 1986), hydrogen-bond details were published, but no atomic coordinates.

2. Experimental

2.1. Synthesis and crystallization

Analytical grade chemicals were used for all syntheses. NH₄(H₂AsO₄)(H₃AsO₄) was grown by hydrothermal methods (T = 493 K, 7 d, Teflon-lined stainless steel autoclave) from a mixture of In₂O₃ and H₃AsO₄·0.5H₂O in an approximate volume ratio of 1:10 and 10 drops of NH₄(OH) (32%). No additional H₂O was added. The reaction product was a solid mass of colourless intergrown crystals with less than 10 vol% of a yellow unidentified material. The NH₄(H₂AsO₄)(H₃AsO₄) crystals are stable in air.

Cs(H₂AsO₄)(H₃AsO₄)₂ formed as the secondary product from further reaction of hydrothermally grown CsAs₃O₈ (Schwendtner & Kolitsch, 2007a). CsAs₃O₈ contains AsO₆ groups, is highly hygroscopic and, at room temperature, decomposes to a highly acidic liquid in which rounded prismatic glassy colourless crystals of Cs(H₂AsO₄)(H₃AsO₄)₂ grew within a few weeks.

Li₂(H₂PO₄)₂ was also a secondary product of a hydrothermal run (T = 493 K, 7 d, Teflon-lined stainless steel autoclave) from a mixture of Li₂CO₃, Ga₂O₃, phosphoric acid and distilled water. The initial and final pH values were both about 1. The hydrothermal synthesis yielded globular crystal aggregates of rounded hexagonal prisms of GaPO₄. From the remaining acidic liquid of the synthesis, Li₂(H₂PO₄)₂ grew as colourless crude block-shaped crystals by slow evaporation at room temperature.

2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. NH₄(H₂AsO₄)(H₃AsO₄) disintegrated (`melted') during the measurement, so only the first two sets or 65% of the Ewald sphere could be measured. Specifically, we note that out of the nine sets collected, the first two were fully usable (no decay visible); the decay only started with set 3, so we ignored sets 3–9. We did not observe any anomalous behaviour of the data set during scaling. The remaining sets showed a pseudocubic I-centred tetragonal unit cell, with approximate a and c values of 7.68 and 7.69 Å, respectively; possibly NH₄(H₂AsO₄)(H₃AsO₄) recrystallized to pseudocubic I $[\overline{4}]$ 2d-type (NH₄)H₂AsO₄ (Fukami, 1989). Nine reflections with negative intensities (blocked by the beam stop) were omitted from the refinement. All N—H and O—H bonds were restricted to 0.9 ± 0.2 Å, as was the O6—H6 bond in Cs(H₂AsO₄)(H₃AsO₄)₂. The O—H bonds in Li₂(H₂PO₄)₂ were not restrained as they refined to reasonable values for refinements based on the X-ray diffraction data sets.

Table 1
Experimental details

Experiments were carried out at 293 K with Mo Kα radiation using a Nonius KappaCCD single-crystal four-circle diffractometer. Absorption was corrected for by multi-scan methods (SCALEPACK; Otwinowski et al., 2003 ).

	Cs(H₂AsO₄)(H₃AsO₄)₂	(NH₄)(H₂AsO₄)(H₃AsO₄)	Li₂(H₂PO₄)₂
Crystal data
Chemical formula	Cs(H₂AsO₄)(H₃AsO₄)₂	(NH₄)(H₂AsO₄)(H₃AsO₄)	Li₂(H₂PO₄)₂
M_r	557.73	300.92	207.85
Crystal system, space group	Monoclinic, P2₁/c	Orthorhombic, Pbca	Monoclinic, P2₁/n
a, b, c (Å)	9.712 (2), 12.738 (3), 9.307 (2)	7.943 (2), 9.855 (2), 19.623 (4)	5.400 (1), 15.927 (3), 7.562 (2)
α, β, γ (°)	90, 90.91 (3), 90	90, 90, 90	90, 90.47 (3), 90
V (Å³)	1151.2 (4)	1536.1 (6)	650.4 (2)
Z	4	8	4
μ (mm⁻¹)	11.83	8.71	0.67
Crystal size (mm)	0.14 × 0.13 × 0.08	0.15 × 0.10 × 0.07	0.15 × 0.12 × 0.10

Data collection
T_min, T_max	0.288, 0.451	0.355, 0.581	0.906, 0.936
No. of measured, independent and observed [I > 2σ(I)] reflections	8200, 4186, 3411	1799, 1295, 905	5625, 2857, 2490
Completeness to 0.84 Å resolution	1.00	0.65	1.00
R_int	0.016	0.038	0.014
(sin θ/λ)_max (Å⁻¹)	0.758	0.676	0.806

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.054, 1.05	0.046, 0.109, 1.02	0.025, 0.072, 1.04
No. of reflections	4186	1295	2857
No. of parameters	178	136	126
No. of restraints	1	9	0
H-atom treatment	All H-atom parameters refined	Only H-atom coordinates refined	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.91, −1.60	0.74, −0.61	0.44, −0.38
Computer programs: COLLECT (Nonius, 2003 ), DENZO and SCALEPACK (Otwinowski et al., 2003), SHELXS97 (Sheldrick, 2008 ), SHELXL2016 (Sheldrick, 2015 ), DIAMOND (Brandenburg, 2005 ) and publCIF (Westrip, 2010 ).

3. Results and discussion

The asymmetric unit of Cs(H₂AsO₄)(H₃AsO₄)₂ contains one Cs, three As, 12 O and eight H atoms (Fig. 1). The Cs atom is 12-coordinated, with the Cs—O bond lengths varying between 3.1202 (17) and 3.934 (3) Å (Table 2). The average Cs—O bond length (3.458 Å) is considerably longer than the statistical average of 3.377 Å for 12-coordinated Cs atoms (Gagné & Hawthorne, 2016 ), explaining the low bond-valence sum (BVS; Gagné & Hawthorne, 2015 ) of 0.85 v.u. The As—O bond lengths are very similar for the doubly (As3) and triply protonated (As1 and As2) As atoms (1.683–1.681 Å) and slightly shorter than the statistical average of 1.687 Å (Gagné & Hawthorne, 2018a ). Since two/three O atoms of the coordination polyhedra are protonated, the As—O bond lengths are only slightly elongated compared to unprotonated O atoms. The BVSs of the three As atoms are between 5.06 and 5.09 v.u. and thus close to the expected value, whereas all O atoms are considerably underbonded, with BVSs ranging from 1.22 to 1.53 v.u., and are all either donors or acceptors of hydrogen bonds. The latter are strong (compared to the other H₃AsO₄-containing compounds cited above), with O—H⋯O distances in the range 2.524 (2)–2.664 (2) Å (Table 3) and connect the individual protonated AsO₄ tetrahedra into a three-dimensional (3D) network (Figs. 2a–c). In the [101] direction, the structure forms tunnels walled by AsO₄ tetrahedra in which the Cs atom is located (Fig. 2d).

Table 2
Selected bond lengths (Å) for Cs(H₂AsO₄)(H₃AsO₄)₂

Cs1—O6ⁱ	3.1202 (17)	As1—O1	1.6437 (15)
Cs1—O2ⁱⁱ	3.2184 (19)	As1—O2	1.6903 (17)
Cs1—O3ⁱⁱⁱ	3.2326 (19)	As1—O3	1.6970 (17)
Cs1—O4	3.2469 (17)	As1—O4	1.7025 (16)
Cs1—O5^iv	3.2536 (18)	As2—O5	1.6390 (16)
Cs1—O1^v	3.3579 (17)	As2—O6	1.6874 (16)
Cs1—O11^vi	3.359 (2)	As2—O7	1.6977 (19)
Cs1—O12	3.478 (2)	As2—O8	1.7004 (19)
Cs1—O9^vii	3.7056 (19)	As3—O9	1.6515 (16)
Cs1—O11^viii	3.755 (3)	As3—O10	1.6579 (17)
Cs1—O8	3.844 (2)	As3—O12	1.707 (2)
Cs1—O7^vii	3.924 (3)	As3—O11	1.7104 (19)
Symmetry codes: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iv) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (v) -x, -y+1, -z+1; (vi) -x+1, -y+1, -z+1; (vii) -x+1, -y+1, -z; (viii) x-1, y, z.

Table 3
Hydrogen-bond geometry (Å, °) for Cs(H₂AsO₄)(H₃AsO₄)₂

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O10^viii	0.83 (4)	1.70 (4)	2.524 (2)	171 (4)
O3—H3⋯O9^ix	0.79 (4)	1.76 (4)	2.553 (3)	172 (4)
O4—H4⋯O1ⁱⁱⁱ	0.92 (3)	1.70 (3)	2.609 (2)	170 (3)
O6—H6⋯O10	0.91 (2)	1.64 (2)	2.539 (2)	170 (4)
O7—H7⋯O9^vii	0.81 (4)	1.79 (4)	2.599 (3)	177 (4)
O11—H11⋯O1^vi	0.79 (4)	1.85 (4)	2.630 (3)	168 (4)
O8—H8⋯O5^iv	0.82 (4)	1.85 (4)	2.664 (2)	170 (4)
O12—H12⋯O5^iv	0.81 (4)	1.84 (4)	2.643 (3)	171 (4)
Symmetry codes: (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iv) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (vi) -x+1, -y+1, -z+1; (vii) -x+1, -y+1, -z; (viii) x-1, y, z; (ix) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 1
The principal building unit of Cs(H₂AsO₄)(H₃AsO₄)₂, shown as displacement ellipsoids at the 70% probability level. The symmetry codes are as defined in Table 2

Figure 2
Structural drawings of novel Cs(H₂AsO₄)(H₃AsO₄)₂, viewed along (a) a, (b) c, (c) b and (d) [101]. The unit cell is outlined. AsO₄ tetrahedra (yellow) are connected via multiple hydrogen bonds (blue) into a 3D network. The Cs⁺ cations lie between the AsO₄ tetrahedra.

The structure of (NH₄)(H₂AsO₄)(H₃AsO₄) is homeotypic with that of Rb(H₂AsO₄)(H₃AsO₄) (Naili & Mhiri, 2001); the Rb⁺ cation is replaced by an NH₄⁺ group providing additional hydrogen bonds to the atomic arrangement. This structure type is also closely related to that of CsH₅(AsO₄)₂ (Naili et al., 2001), which can be seen as a distorted version of the Rb(H₂AsO₄)(H₃AsO₄) structure type. The structure of (NH₄)(H₂AsO₄)(H₃AsO₄) is built of individual, doubly or triply protonated AsO₄ tetrahedra that are connected via strong hydrogen bonds into a 3D network (Figs. 3, 4a and 4b). The NH₄⁺ groups lie in voids and further reinforce the network via medium-to-weak strength hydrogen bonds. AsO₄ tetrahedra and NH₄⁺ cations are arranged in layers perpendicular to c (Fig. 4). The NH₄⁺ cation is ten-coordinated, with an average N—O bond distance of 3.112 Å (Table 4), leading to a BVS of 0.97 v.u. (García-Rodríguez et al., 2000 ). Both AsO₄ groups are overbonded (5.08 and 5.13 v.u. for As1 and As2, respectively), although the average As—O bond lengths (1.682 and 1.678 Å) are fairly close to the statistical average of 1.687 Å (Gagné & Hawthorne, 2018a). All O atoms are considerably underbonded and participate in a complex hydrogen-bonding network (Table 5). In Rb(H₂AsO₄)(H₃AsO₄) (Naili & Mhiri, 2001), there are some very strong hydrogen bonds present (2.432 Å) that connect the structure along the c axis. Hydrogen bonds with O—H⋯O distances < 2.5 Å are also present in many isostoichiometric M⁺H₅(PO₄)₂ compounds [see compilation in Naili & Mhiri (2001)]. In (NH₄)(H₂AsO₄)(H₃AsO₄), these O—H⋯O hydrogen bonds are still strong but considerably longer, ranging from 2.568 (8) to 2.653 (9) Å. This is probably due to a small shift of the atom positions in the two compounds, seen also from an inspection of the unit cells of the two homeotypic compounds. While unit-cell parameters a and b are quite similar and 0.003 and 0.033 Å longer, respectively, in the ammonium compound, unit-cell parameter c is considerably shorter [19.623 (4) Å; Table 1] in comparison with that of the rubidium compound [20.4226 (6) Å; Naili & Mhiri, 2001], leading also to a distinctly smaller unit-cell volume of (NH₄)(H₂AsO₄)(H₃AsO₄). This change is explained, unlike what is expected from the slightly different effective ionic radii of NH₄⁺ and Rb⁺ (the latter is slightly smaller), firstly, by the ability of the NH₄⁺ cation to form hydrogen bonds, and, secondly, by a slight shift of the As1 atoms in the b direction and a slight expansion in that direction. Hydrogen bonds connecting adjacent As2O₄ tetrahedra in the b direction in Rb(H₂AsO₄)(H₃AsO₄) are lost and replaced by hydrogen bonds connecting As1O₄ and As2O₄ along c in (NH₄)(H₂AsO₄)(H₃AsO₄) (Fig. 5), resulting in a compression of the whole structure along c.

Table 4
Selected bond lengths (Å) for (NH₄)(H₂AsO₄)(H₃AsO₄)

N—O5	2.869 (10)	N—O3ⁱ	3.283 (10)
N—O1ⁱ	2.947 (9)	As1—O1	1.648 (5)
N—O5ⁱ	3.032 (11)	As1—O2	1.662 (6)
N—O2ⁱⁱ	3.075 (9)	As1—O3	1.705 (6)
N—O4ⁱⁱⁱ	3.082 (9)	As1—O4	1.714 (5)
N—O6	3.148 (10)	As2—O5	1.632 (6)
N—O7^iv	3.194 (10)	As2—O8	1.692 (5)
N—O3	3.216 (10)	As2—O7	1.693 (5)
N—O8^v	3.272 (9)	As2—O6	1.696 (6)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ ; (ii) -x, -y+1, -z; (iii) -x+1, -y+1, -z; (iv) $[x+{\script{1\over 2}}, y, -z-{\script{1\over 2}}]$ ; (v) $[-x+1, y+{\script{1\over 2}}, -z-{\script{1\over 2}}]$ .

Table 5
Hydrogen-bond geometry (Å, °) for (NH₄)(H₂AsO₄)(H₃AsO₄)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N—H1⋯O4ⁱⁱⁱ	0.89 (2)	2.36 (8)	3.082 (9)	138 (10)
N—H1⋯O7^iv	0.89 (2)	2.54 (9)	3.194 (10)	130 (9)
N—H4⋯O5ⁱ	0.90 (2)	2.20 (7)	3.032 (11)	154 (14)
N—H3⋯O1ⁱ	0.89 (2)	2.10 (4)	2.947 (9)	159 (9)
N—H2⋯O5	0.91 (2)	1.96 (2)	2.869 (10)	174 (7)
O3—H5⋯O1^vi	0.89 (2)	2.13 (15)	2.616 (7)	113 (12)
O3—H5⋯O3ⁱⁱ	0.89 (2)	2.61 (11)	3.311 (12)	136 (13)
O6—H7⋯O2^vii	0.90 (2)	1.82 (10)	2.653 (9)	152 (19)
O4—H6⋯O1ⁱ	0.89 (2)	1.77 (3)	2.650 (8)	170 (7)
O7—H8⋯O2^viii	0.89 (2)	1.72 (4)	2.568 (8)	157 (8)
O8—H9⋯O5^iv	0.89 (2)	1.78 (6)	2.590 (7)	150 (11)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ ; (ii) -x, -y+1, -z; (iii) -x+1, -y+1, -z; (iv) $[x+{\script{1\over 2}}, y, -z-{\script{1\over 2}}]$ ; (vi) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]$ ; (vii) $[-x+{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (viii) $[x, -y+{\script{1\over 2}}]$ , $[z-{\script{1\over 2}}]$ .

Figure 3
The principal building unit of (NH₄)(H₂AsO₄)(H₃AsO₄), shown as displacement ellipsoids at the 70% probability level. Hydrogen bonds are shown as blue dashed lines.

Figure 4
Structural drawings of (NH₄)(H₂AsO₄)(H₃AsO₄), viewed along (a) [110] and (b) b. The unit cell is outlined. AsO₄ tetrahedra (yellow) are connected via multiple hydrogen bonds (blue dashed lines) into a 3D network. AsO₄ tetrahedra and NH₄⁺ cations are arranged in layers perpendicular to c. Additional hydrogen bonds of medium strength are provided by the NH₄⁺ cations.

Figure 5
Comparison of (a) homeotypic (NH₄)(H₂AsO₄)(H₃AsO₄) with (b) Rb(H₂AsO₄)(H₃AsO₄) (Naili & Mhiri, 2001

). A shift (arrows in figure) of As1 in the b direction leads to a compression of the whole structure along c, and results in a change of the hydrogen-bonding network. Hydrogen bonds connecting As2O₄ tetrahedra along b are lost in (NH₄)(H₂AsO₄)(H₃AsO₄), but new hydrogen bonds now connect As1O₄ and As2O₄ along c.

The asymmetric unit of monoclinic (P2₁/n) Li₂(H₂PO₄)₂ contains two Li, two P, eight O and four H atoms, all in general positions (Fig. 6). Li₂(H₂PO₄)₂ is built of LiO₄ tetrahedra that share edges with adjacent LiO₄ tetrahedra, thereby forming Li₂O₆ dimers (Fig. 7b). Each corner of the LiO₄ tetrahedra shares a corner with a PO₄ tetrahedron, thus connecting the Li₂O₆ dimers into a 3D network (Figs. 7a and 7b). This network is reinforced by hydrogen bonds of medium-to-high strength (Table 6). In the orthorhombic (Pna2₁) dimorph of Li(H₂PO₄) (Catti & Ivaldi, 1978), which is characterized by a high electrical (proton) conductivity (Hwan Oh et al., 2010 ), the LiO₄ tetrahedra share corners, thus forming chains that are connected by the PO₄ groups. In monoclinic Li₂(H₂PO₄)₂, the average (Table 7) Li—O (1.951 and 1.953 Å) and P—O (1.539 and 1.537 Å) bond lengths are very close to the statistical average of 1.972 Å (Gagné & Hawthorne, 2016) for Li—O and 1.537 Å (Gagné & Hawthorne, 2018b ) for P—O bond lengths. This is also reflected by the nearly ideal BVSs (Gagné & Hawthorne, 2015) of 1.01 and 1.00 v.u. for Li1 and Li2, respectively, and 4.98 and 5.00 v.u. for P1 and P2, respectively. The most underbonded O atoms (O3, O4, O7 and O8, with BVSs of 1.16–1.37 v.u.) form strong-to-medium hydrogen bonds (Table 6). A comparison of the X-ray densities of monoclinic Li₂(H₂PO₄)₂ (2.123 kg m⁻³) and its orthorhombic dimorph LiH₂PO₄ (Catti & Ivaldi, 1978) (2.09 kg m⁻³) suggests that monoclinic Li₂(H₂PO₄)₂ is slightly denser and therefore thermodynamically slightly more stable, at least under ambient conditions. Orthorhombic LiH₂PO₄ shows no phase transition between room temperature and 100 (Hwan Oh et al., 2010) or 17 K (Lee et al., 2008 ). We note that monoclinic Li₂(H₂PO₄)₂ most probably has an isotypic arsenate analogue, since Remy & Bachet (1967 ) were able to synthesize monoclinic Li₂(H₂AsO₄)₂, with a = 5.55, b = 16.36, c = 7.80 Å, β = 90.53° and space group P2₁/n, although they did not determine its crystal structure. Orthorhombic Li(H₂PO₄) also has an isotypic arsenate analogue, the crystal structure of which was reported by Fanchon et al. (1987 ), who pointed out a slight rearrangement in one of the two independent hydrogen bonds.

Table 6
Hydrogen-bond geometry (Å, °) for Li₂(H₂PO₄)₂

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H1⋯O7^vi	0.77 (2)	1.91 (2)	2.6769 (12)	171 (2)
O4—H2⋯O2^iv	0.84 (2)	1.99 (2)	2.8292 (14)	176 (2)
O7—H3⋯O6^vii	0.73 (2)	1.79 (2)	2.5210 (13)	172 (3)
O8—H4⋯O1^viii	0.79 (2)	1.79 (2)	2.5667 (12)	167 (2)
Symmetry codes: (iv) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (vi) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (vii) -x+2, -y+1, -z+1; (viii) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Table 7
Selected bond lengths (Å) for Li₂(H₂PO₄)₂

Li1—O5	1.888 (2)	Li2—P2^iv	3.077 (2)
Li1—O6ⁱ	1.902 (2)	P1—O1	1.4996 (9)
Li1—O8ⁱⁱ	1.967 (2)	P1—O2	1.5043 (8)
Li1—O2	2.045 (2)	P1—O3	1.5588 (9)
Li1—Li2ⁱⁱⁱ	2.611 (3)	P1—O4	1.5917 (8)
Li1—P2ⁱ	3.068 (2)	P2—O5	1.4944 (8)
Li2—O5^iv	1.919 (2)	P2—O6	1.5113 (8)
Li2—O1	1.944 (2)	P2—O7	1.5640 (9)
Li2—O4^v	1.973 (2)	P2—O8	1.5774 (8)
Li2—O2^iv	1.974 (2)
Symmetry codes: (i) x-1, y, z; (ii) -x+1, -y+1, -z+2; (iii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iv) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (v) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Figure 6
The principal building unit of Li₂(H₂PO₄)₂, shown with displacement ellipsoids at the 70% probability level. The symmetry codes are as defined in Table 7

Figure 7
Structural drawings of Li₂(H₂PO₄)₂, viewed along (a) a and (b) c. The unit cell is outlined. Phosphate tetrahedra are shown in pink and edge-sharing LiO₄ tetrahedra in green. The hydrogen bonds reinforcing the network are shown in blue.

4. Statistical evaluation of As—O bonds in protonated AsO₄ groups

Several statistical analyses of bond lengths in As⁵⁺O₄ polyhedra have been published recently. Gagné & Hawthorne (2018a) reported average As—O bond lengths of 1.687 (27) Å in AsO₄ and 1.830 (28) Å in AsO₆ groups, derived from 508 and 13 polyhedra, respectively. Schwendtner (2008 ) found similar values of 1.686 (29) and 1.827 (29) Å for a larger sample size of 704 AsO₄ and 40 AsO₆ polyhedra, respectively. An analysis of As—O bond lengths in minerals by Majzlan et al. (2014 ) gave a very similar value of 1.685 Å (no s.u. given) for the average As—O bond length and a value of 1.727 Å (no s.u. given) for As—OH bonds. Data for As—O bond lengths in multiply protonated As⁵⁺O_x (x = 4 and 6) polyhedra are scarce (especially those for H₃AsO₄ groups) due to the rare occurrence of compounds containing such polyhedra. An earlier attempt by Ichikawa (1988 ) to carry out a statistical analysis of the hydrogen-bond-length dependence of the distortion in H_nAsO₄ (n = 1–3) tetrahedra was severely hampered for the doubly and triply protonated representatives, since data for only six H₂AsO₄ and two H₃AsO₄ groups were available, and no pertinent conclusions were possible. As the number of synthetic compounds and minerals containing H_nAsO₄ (n = 1–3) groups has considerably increased in the last three decades, we were able to perform a detailed analysis of As—O/OH bonds in H_nAsO₄ (n = 1–3) groups using data from the ICSD database (FIZ, 2018 ) (conventional R value < 5, full occupancy of As and O sites), expanded by the published data for known H₃AsO₄-containing inorganic compounds mentioned in the Introduction (§1), and the two novel title arsenate compounds (Table 8 and Fig. 8).

Table 8
Statistical analysis of the As—O bond lengths (Å) in H_nAsO₄ (n = 1–3) groups

Bond lengths	Analysed number	Average	Minimum	Maximum
As—O/OH in H_nAsO₄ (average)	97	1.687 (6)	1.660	1.709
As—O/OH in H_nAsO₄ (individual)	388	1.687 (27)	1.614	1.801
As—OH in H_nAsO₄ (including split H-atom positions)	199	1.701 (23)	1.625	1.801
As—OH in H_nAsO₄ (no split H atoms)	117	1.714 (21)	1.625	1.801
As—OH in HAsO₄	43	1.728 (19)	1.689	1.801
As—OH in H₂AsO₄	41	1.714 (12)	1.688	1.749
As—OH in H₃AsO₄	33	1.694 (16)	1.625	1.712
As—OH/2 (split H atoms) in H_1–2AsO₄	82	1.683 (13)	1.656	1.714
As—O (no H atoms) in H_nAsO₄	189	1.671 (23)	1.614	1.755
As—O (no H/As*) in H_nAsO₄	174	1.667 (18)	1.614	1.735
Note: (*) no As—O—As bonds (see text).

Figure 8
Comparison of As—O distances in H_nAsO₄ (n = 1–3) groups, sorted by As—OH bonds into clouds for H₃AsO₄ (turquoise), H₂AsO₄ (yellow) and HAsO₄ (red) groups. As—OH bonds to split H-atom positions are shown in green, while all bonds to the remaining nonprotonated O atoms are shown in blue.

The average As—O/OH bond length for the 97 analysed H_nAsO₄ (n = 1–3) groups of 1.686 (27) Å is nearly identical to the value reported by Gagné & Hawthorne (2018a), but the individual bond lengths vary greatly with the number of As—OH bonds in the respective polyhedra. While the As—OH bonds are extremely elongated to 1.728 (19) Å in HAsO₄ groups and to 1.714 (12) Å in H₂AsO₄ groups, the average As—OH bond length is considerably shorter, with a value of 1.694 (16) Å in the rare H₃AsO₄ groups. This result is in agreement with the observation of Ferraris & Ivaldi (1984 ) that the average length of X—OH (X = As and P) bonds tends to decrease from mono- to triprotonated anions with the same X atom. We also find that the As bonds to nonprotonated O atoms in H₃AsO₄ groups are shortened to 1.671 (23) Å. If As—O bonds involving bridging O ligands (as present in the As₂O₇ groups in pyroarsenates), i.e. As—O—As bonds, are removed from the data set because they are known to be anomalously elongated due to As—As repulsion, the value is even shorter, i.e. 1.667 (18) Å. A special case are As—O bonds to half-occupied H-atom positions; these are actually shortened to 1.683 (13) Å. Excluding split H-atom positions, the grand mean average As—OH bond length in H_nAsO₄ (n = 1–3) groups is 1.714 (21) Å and thus considerably shorter than the value of 1.727 Å derived by Majzlan et al. (2014), whose evaluation was based mainly on H_1-2AsO₄ groups. A visual analysis of the individual As—O bond lengths compared to the averages of the H_nAsO₄ (n = 1–3) groups (Fig. 8) shows that they form clearly distributed clouds, depending on the number of H atoms. The average As—O/OH bond lengths of the polyhedra, as well as the individual As—OH bond lengths, are largest in HAsO₄ groups and show a narrower distribution in H₂AsO₄. The population of H₃AsO₄ groups is characterized by shorter individual As—OH bond lengths but also a shorter average As—OH bond length of the polyhedra. It can also be recognized that the whole data set shows a strong concentration of bonds at around ca 1.687 Å and that all the shortest bonds are to the nonprotonated O atoms of each H_nAsO₄ (n = 1–3) group (blue cloud in Fig. 8, cf. Table 8). This is expected because the As atom in each H_nAsO₄ tries to achieve a BVS of 5, and due to the elongation of all the bonds to protonated O atoms, the remaining As—O bonds have to shorten accordingly. This also explains why both the individual As—OH bond lengths and average As—O(H) bond lengths decrease with increasing protonation. In the case of singly protonated AsO₄ groups, the three As—O bonds need to become slightly shortened in order to still achieve a BVS of 5, at the expense of a high bond-length distortion in this tetrahedron. In agreement with the distortion theorem (Brown & Shannon, 1973 ), this results in a slightly higher value of the average As—O(H) bond length of 1.689 (6) Å in HAsO₄ groups (vertical range of red cloud in Fig. 8) versus a corresponding value of 1.688 (3) Å in H₂AsO₄ groups (vertical range of yellow cloud) and the notably lower value of 1.680 (7) Å in H₃AsO₄ groups (vertical range of turquoise cloud). This low value in the latter is a consequence of three competing As—OH bonds which can only be counteracted by one As—O bond. This leads to three similarly short As—OH bonds and one even shorter As—O bond, i.e. a small bond-length distortion.

The overall spread of values is a consequence of the variable strengths of the hydrogen bonds in the individual compounds. A conspicuous outlier in Fig. 8 (e.g. in the top-right corner) may be explained by the influence of a very strong hydrogen bond in Mg(HAsO₄)(H₂O)₇, with an O⋯O donor–acceptor distance of 2.491 Å (no s.u. given; Ferraris & Franchini-Angela, 1973 ).

Supporting information

CCDC references: 1922991; 1922990; 1922989

Crystal structure: contains datablocks CsH2AsO4H3AsO42, Li2H2PO42, NH4H2AsO4H3AsO4, global. DOI: https://doi.org/10.1107/S2053229619008489/qf3024sup1.cif

Structure factors: contains datablock CsH2AsO4H3AsO42. DOI: https://doi.org/10.1107/S2053229619008489/qf3024CsH2AsO4H3AsO42sup2.hkl

Structure factors: contains datablock Li2H2PO42. DOI: https://doi.org/10.1107/S2053229619008489/qf3024Li2H2PO42sup3.hkl

Structure factors: contains datablock NH4H2AsO4H3AsO4. DOI: https://doi.org/10.1107/S2053229619008489/qf3024NH4H2AsO4H3AsO4sup4.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2053229619008489/qf3024Li2H2PO42sup5.cml

Supporting information file. DOI: https://doi.org/10.1107/S2053229619008489/qf3024NH4H2AsO4H3AsO4sup6.cml

Computing details top

For all structures, data collection: COLLECT (Nonius, 2003); cell refinement: SCALEPACK (Otwinowski et al., 2003); data reduction: DENZO and SCALEPACK (Otwinowski et al., 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: publCIF (Westrip, 2010).

Caesium dihydrogen arsenate(V) bis[trihydrogen arsenate(V)] (CsH2AsO4H3AsO42) top

Crystal data top

Cs(H₂AsO₄)(H₃AsO₄)₂	F(000) = 1032
M_r = 557.73	D_x = 3.218 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.712 (2) Å	Cell parameters from 4360 reflections
b = 12.738 (3) Å	θ = 2.7–32.6°
c = 9.307 (2) Å	µ = 11.83 mm⁻¹
β = 90.91 (3)°	T = 293 K
V = 1151.2 (4) Å³	Rounded prisms, colourless
Z = 4	0.14 × 0.13 × 0.08 mm

Data collection top

Nonius KappaCCD single-crystal four-circle diffractometer	3411 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.016
φ and ω scans	θ_max = 32.6°, θ_min = 2.7°
Absorption correction: multi-scan (SCALEPACK; Otwinowski et al., 2003)	h = −14→14
T_min = 0.288, T_max = 0.451	k = −19→19
8200 measured reflections	l = −14→14
4186 independent reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.023	All H-atom parameters refined
wR(F²) = 0.054	w = 1/[σ²(F_o²) + (0.0217P)² + 1.0466P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max = 0.002
4186 reflections	Δρ_max = 0.91 e Å⁻³
178 parameters	Δρ_min = −1.60 e Å⁻³
1 restraint	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00340 (11)

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
Cs1	0.22962 (2)	0.51389 (2)	0.27149 (2)	0.03776 (6)
As1	0.00263 (2)	0.23648 (2)	0.48710 (2)	0.01694 (5)
As2	0.46332 (2)	0.24756 (2)	0.02338 (2)	0.01917 (6)
As3	0.73534 (2)	0.47250 (2)	0.25789 (2)	0.02105 (6)
O1	0.01202 (17)	0.31350 (12)	0.62862 (15)	0.0225 (3)
O2	−0.15805 (17)	0.21801 (14)	0.41934 (18)	0.0273 (3)
O3	0.0553 (2)	0.11305 (13)	0.5291 (2)	0.0298 (4)
O4	0.10335 (17)	0.28641 (13)	0.35555 (17)	0.0255 (3)
O5	0.42912 (18)	0.17618 (13)	−0.11930 (16)	0.0262 (3)
O6	0.60947 (17)	0.20728 (13)	0.10689 (19)	0.0277 (4)
O7	0.4908 (2)	0.37667 (14)	−0.0112 (2)	0.0411 (5)
O8	0.32988 (19)	0.23889 (17)	0.1389 (2)	0.0351 (4)
O9	0.73949 (17)	0.54949 (13)	0.11525 (18)	0.0284 (4)
O10	0.75902 (17)	0.34537 (13)	0.22914 (17)	0.0269 (4)
O11	0.8597 (2)	0.50491 (15)	0.3823 (2)	0.0405 (5)
O12	0.5816 (2)	0.49272 (15)	0.3400 (2)	0.0417 (5)
H2	−0.179 (4)	0.265 (3)	0.360 (4)	0.061 (12)*
H3	0.115 (4)	0.095 (3)	0.477 (4)	0.067 (12)*
H4	0.081 (4)	0.250 (3)	0.273 (4)	0.054 (10)*
H6	0.659 (4)	0.262 (2)	0.144 (4)	0.080 (14)*
H7	0.420 (4)	0.402 (3)	−0.044 (4)	0.059 (11)*
H8	0.353 (4)	0.262 (3)	0.218 (4)	0.060 (11)*
H11	0.888 (4)	0.563 (3)	0.378 (4)	0.076 (14)*
H12	0.543 (4)	0.437 (3)	0.350 (4)	0.062 (11)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cs1	0.04230 (11)	0.02498 (8)	0.04561 (11)	0.00032 (6)	−0.01130 (8)	−0.00318 (7)
As1	0.01957 (10)	0.01814 (10)	0.01307 (9)	−0.00029 (8)	−0.00091 (7)	−0.00053 (7)
As2	0.01818 (11)	0.01998 (10)	0.01925 (11)	0.00205 (8)	−0.00274 (8)	−0.00085 (8)
As3	0.02387 (11)	0.01600 (11)	0.02320 (11)	−0.00176 (8)	−0.00263 (8)	0.00363 (8)
O1	0.0306 (8)	0.0218 (7)	0.0152 (7)	−0.0005 (6)	−0.0010 (6)	−0.0031 (6)
O2	0.0224 (8)	0.0343 (9)	0.0251 (8)	−0.0062 (7)	−0.0048 (6)	0.0062 (7)
O3	0.0371 (10)	0.0213 (8)	0.0311 (9)	0.0077 (7)	0.0072 (8)	0.0037 (7)
O4	0.0271 (8)	0.0314 (8)	0.0179 (7)	−0.0088 (7)	0.0032 (6)	−0.0016 (6)
O5	0.0298 (9)	0.0305 (8)	0.0182 (7)	0.0036 (7)	−0.0013 (6)	−0.0046 (6)
O6	0.0231 (8)	0.0205 (8)	0.0392 (9)	0.0011 (6)	−0.0103 (7)	0.0019 (7)
O7	0.0416 (12)	0.0211 (8)	0.0601 (13)	0.0007 (8)	−0.0166 (10)	0.0085 (8)
O8	0.0244 (9)	0.0577 (13)	0.0233 (9)	0.0012 (8)	0.0031 (7)	−0.0088 (8)
O9	0.0260 (8)	0.0283 (8)	0.0308 (8)	−0.0016 (7)	0.0001 (7)	0.0126 (7)
O10	0.0316 (9)	0.0179 (7)	0.0307 (8)	0.0019 (6)	−0.0105 (7)	−0.0006 (6)
O11	0.0527 (13)	0.0260 (9)	0.0419 (11)	−0.0106 (9)	−0.0227 (9)	0.0034 (8)
O12	0.0441 (12)	0.0246 (9)	0.0570 (13)	0.0001 (8)	0.0238 (10)	0.0039 (9)

Geometric parameters (Å, º) top

Cs1—O6ⁱ	3.1202 (17)	Cs1—H3ⁱⁱⁱ	3.25 (4)
Cs1—O2ⁱⁱ	3.2184 (19)	Cs1—H6ⁱ	3.43 (4)
Cs1—O3ⁱⁱⁱ	3.2326 (19)	As1—O1	1.6437 (15)
Cs1—O4	3.2469 (17)	As1—O2	1.6903 (17)
Cs1—O5^iv	3.2536 (18)	As1—O3	1.6970 (17)
Cs1—O1^v	3.3579 (17)	As1—O4	1.7025 (16)
Cs1—O11^vi	3.359 (2)	As2—O5	1.6390 (16)
Cs1—O12	3.478 (2)	As2—O6	1.6874 (16)
Cs1—O9^vii	3.7056 (19)	As2—O7	1.6977 (19)
Cs1—O11^viii	3.755 (3)	As2—O8	1.7004 (19)
Cs1—O8	3.844 (2)	As3—O9	1.6515 (16)
Cs1—O7^vii	3.924 (3)	As3—O10	1.6579 (17)
Cs1—O12^vi	4.028 (3)	As3—O12	1.707 (2)
Cs1—O7	4.077 (3)	As3—O11	1.7104 (19)
Cs1—O3ⁱⁱ	4.103 (2)	O2—H2	0.83 (4)
Cs1—O10ⁱ	4.2239 (19)	O3—H3	0.79 (4)
Cs1—As1ⁱⁱ	4.3298 (9)	O4—H4	0.92 (3)
Cs1—As3^vi	4.3913 (10)	O6—H6	0.910 (18)
Cs1—As1^v	4.5175 (9)	O7—H7	0.81 (4)
Cs1—O2^v	4.527 (2)	O8—H8	0.82 (4)
Cs1—H8	3.46 (4)	O11—H11	0.79 (4)
Cs1—H12	3.27 (4)	O12—H12	0.81 (4)
Cs1—H2ⁱⁱ	3.45 (4)

O6ⁱ—Cs1—O2ⁱⁱ	70.42 (5)	As1ⁱⁱ—Cs1—H12	142.7 (7)
O6ⁱ—Cs1—O3ⁱⁱⁱ	154.40 (5)	As3^vi—Cs1—H12	74.4 (6)
O2ⁱⁱ—Cs1—O3ⁱⁱⁱ	85.00 (5)	As1^v—Cs1—H12	124.7 (6)
O6ⁱ—Cs1—O4	143.71 (4)	O2^v—Cs1—H12	103.5 (6)
O2ⁱⁱ—Cs1—O4	140.79 (5)	H8—Cs1—H12	55.5 (9)
O3ⁱⁱⁱ—Cs1—O4	61.72 (4)	O6ⁱ—Cs1—H2ⁱⁱ	57.7 (6)
O6ⁱ—Cs1—O5^iv	100.47 (5)	O2ⁱⁱ—Cs1—H2ⁱⁱ	13.8 (6)
O2ⁱⁱ—Cs1—O5^iv	153.62 (4)	O3ⁱⁱⁱ—Cs1—H2ⁱⁱ	98.4 (6)
O3ⁱⁱⁱ—Cs1—O5^iv	98.54 (5)	O4—Cs1—H2ⁱⁱ	149.2 (7)
O4—Cs1—O5^iv	59.07 (4)	O5^iv—Cs1—H2ⁱⁱ	151.5 (7)
O6ⁱ—Cs1—O1^v	74.39 (4)	O1^v—Cs1—H2ⁱⁱ	53.0 (7)
O2ⁱⁱ—Cs1—O1^v	58.54 (4)	O11^vi—Cs1—H2ⁱⁱ	111.7 (6)
O3ⁱⁱⁱ—Cs1—O1^v	99.22 (5)	O12—Cs1—H2ⁱⁱ	105.6 (7)
O4—Cs1—O1^v	104.44 (4)	O9^vii—Cs1—H2ⁱⁱ	82.5 (6)
O5^iv—Cs1—O1^v	144.69 (4)	O11^viii—Cs1—H2ⁱⁱ	89.7 (7)
O6ⁱ—Cs1—O11^vi	81.01 (5)	O8—Cs1—H2ⁱⁱ	139.8 (6)
O2ⁱⁱ—Cs1—O11^vi	122.02 (5)	O7^vii—Cs1—H2ⁱⁱ	63.1 (7)
O3ⁱⁱⁱ—Cs1—O11^vi	119.57 (5)	O12^vi—Cs1—H2ⁱⁱ	113.4 (6)
O4—Cs1—O11^vi	66.48 (4)	O7—Cs1—H2ⁱⁱ	104.7 (6)
O5^iv—Cs1—O11^vi	78.98 (5)	O3ⁱⁱ—Cs1—H2ⁱⁱ	51.9 (6)
O1^v—Cs1—O11^vi	65.72 (5)	O10ⁱ—Cs1—H2ⁱⁱ	22.8 (6)
O6ⁱ—Cs1—O12	60.63 (5)	As1ⁱⁱ—Cs1—H2ⁱⁱ	29.3 (6)
O2ⁱⁱ—Cs1—O12	111.52 (5)	As3^vi—Cs1—H2ⁱⁱ	109.0 (6)
O3ⁱⁱⁱ—Cs1—O12	126.27 (5)	As1^v—Cs1—H2ⁱⁱ	57.1 (6)
O4—Cs1—O12	105.10 (5)	O2^v—Cs1—H2ⁱⁱ	60.4 (6)
O5^iv—Cs1—O12	46.08 (4)	H8—Cs1—H2ⁱⁱ	148.5 (9)
O1^v—Cs1—O12	133.57 (4)	H12—Cs1—H2ⁱⁱ	118.8 (9)
O11^vi—Cs1—O12	94.97 (6)	O6ⁱ—Cs1—H3ⁱⁱⁱ	143.7 (7)
O6ⁱ—Cs1—O9^vii	118.46 (5)	O2ⁱⁱ—Cs1—H3ⁱⁱⁱ	79.2 (7)
O2ⁱⁱ—Cs1—O9^vii	70.13 (4)	O3ⁱⁱⁱ—Cs1—H3ⁱⁱⁱ	14.1 (7)
O3ⁱⁱⁱ—Cs1—O9^vii	42.49 (4)	O4—Cs1—H3ⁱⁱⁱ	72.3 (7)
O4—Cs1—O9^vii	94.38 (4)	O5^iv—Cs1—H3ⁱⁱⁱ	97.9 (7)
O5^iv—Cs1—O9^vii	94.84 (4)	O1^v—Cs1—H3ⁱⁱⁱ	106.4 (7)
O1^v—Cs1—O9^vii	118.64 (4)	O11^vi—Cs1—H3ⁱⁱⁱ	133.4 (7)
O11^vi—Cs1—O9^vii	160.46 (4)	O12—Cs1—H3ⁱⁱⁱ	116.3 (7)
O12—Cs1—O9^vii	93.83 (5)	O9^vii—Cs1—H3ⁱⁱⁱ	28.4 (7)
O6ⁱ—Cs1—O11^viii	113.59 (5)	O11^viii—Cs1—H3ⁱⁱⁱ	84.4 (7)
O2ⁱⁱ—Cs1—O11^viii	88.68 (5)	O8—Cs1—H3ⁱⁱⁱ	54.9 (7)
O3ⁱⁱⁱ—Cs1—O11^viii	71.56 (5)	O7^vii—Cs1—H3ⁱⁱⁱ	82.1 (7)
O4—Cs1—O11^viii	62.61 (4)	O12^vi—Cs1—H3ⁱⁱⁱ	153.0 (7)
O5^iv—Cs1—O11^viii	117.33 (4)	O7—Cs1—H3ⁱⁱⁱ	58.7 (7)
O1^v—Cs1—O11^viii	42.94 (4)	O3ⁱⁱ—Cs1—H3ⁱⁱⁱ	48.7 (7)
O11^vi—Cs1—O11^viii	58.10 (6)	O10ⁱ—Cs1—H3ⁱⁱⁱ	115.8 (7)
O12—Cs1—O11^viii	152.77 (5)	As1ⁱⁱ—Cs1—H3ⁱⁱⁱ	69.2 (7)
O9^vii—Cs1—O11^viii	110.65 (5)	As3^vi—Cs1—H3ⁱⁱⁱ	151.3 (7)
O6ⁱ—Cs1—O8	135.06 (4)	As1^v—Cs1—H3ⁱⁱⁱ	123.6 (7)
O2ⁱⁱ—Cs1—O8	127.77 (4)	O2^v—Cs1—H3ⁱⁱⁱ	143.6 (7)
O3ⁱⁱⁱ—Cs1—O8	56.82 (4)	H8—Cs1—H3ⁱⁱⁱ	66.2 (9)
O4—Cs1—O8	50.42 (4)	H12—Cs1—H3ⁱⁱⁱ	111.5 (9)
O5^iv—Cs1—O8	43.09 (4)	H2ⁱⁱ—Cs1—H3ⁱⁱⁱ	93.0 (9)
O1^v—Cs1—O8	150.13 (4)	O6ⁱ—Cs1—H6ⁱ	15.1 (4)
O11^vi—Cs1—O8	108.28 (5)	O2ⁱⁱ—Cs1—H6ⁱ	56.4 (5)
O12—Cs1—O8	74.64 (4)	O3ⁱⁱⁱ—Cs1—H6ⁱ	141.4 (5)
O9^vii—Cs1—O8	57.64 (4)	O4—Cs1—H6ⁱ	152.5 (7)
O11^viii—Cs1—O8	107.98 (4)	O5^iv—Cs1—H6ⁱ	115.4 (4)
O6ⁱ—Cs1—O7^vii	66.17 (5)	O1^v—Cs1—H6ⁱ	63.5 (6)
O2ⁱⁱ—Cs1—O7^vii	61.16 (4)	O11^vi—Cs1—H6ⁱ	86.1 (7)
O3ⁱⁱⁱ—Cs1—O7^vii	96.12 (5)	O12—Cs1—H6ⁱ	73.9 (5)
O4—Cs1—O7^vii	137.19 (4)	O9^vii—Cs1—H6ⁱ	113.1 (7)
O5^iv—Cs1—O7^vii	92.45 (4)	O11^viii—Cs1—H6ⁱ	105.4 (6)
O1^v—Cs1—O7^vii	115.59 (4)	O8—Cs1—H6ⁱ	146.3 (6)
O11^vi—Cs1—O7^vii	144.05 (5)	O7^vii—Cs1—H6ⁱ	66.0 (7)
O12—Cs1—O7^vii	56.84 (5)	O12^vi—Cs1—H6ⁱ	71.1 (5)
O9^vii—Cs1—O7^vii	53.85 (4)	O7—Cs1—H6ⁱ	110.1 (7)
O11^viii—Cs1—O7^vii	148.74 (4)	O3ⁱⁱ—Cs1—H6ⁱ	94.6 (4)
O8—Cs1—O7^vii	86.80 (4)	O10ⁱ—Cs1—H6ⁱ	21.7 (4)
O6ⁱ—Cs1—O12^vi	58.18 (4)	As1ⁱⁱ—Cs1—H6ⁱ	71.6 (4)
O2ⁱⁱ—Cs1—O12^vi	127.11 (4)	As3^vi—Cs1—H6ⁱ	73.5 (6)
O3ⁱⁱⁱ—Cs1—O12^vi	147.33 (4)	As1^v—Cs1—H6ⁱ	52.9 (7)
O4—Cs1—O12^vi	86.18 (4)	O2^v—Cs1—H6ⁱ	37.9 (7)
O5^iv—Cs1—O12^vi	56.21 (4)	H8—Cs1—H6ⁱ	141.1 (8)
O1^v—Cs1—O12^vi	94.31 (4)	H12—Cs1—H6ⁱ	86.2 (8)
O11^vi—Cs1—O12^vi	42.12 (5)	H2ⁱⁱ—Cs1—H6ⁱ	43.2 (8)
O12—Cs1—O12^vi	53.27 (6)	H3ⁱⁱⁱ—Cs1—H6ⁱ	133.6 (9)
O9^vii—Cs1—O12^vi	145.54 (4)	O1—As1—O2	114.91 (9)
O11^viii—Cs1—O12^vi	100.17 (5)	O1—As1—O3	110.85 (8)
O8—Cs1—O12^vi	98.93 (4)	O2—As1—O3	103.30 (9)
O7^vii—Cs1—O12^vi	104.61 (5)	O1—As1—O4	109.15 (8)
O6ⁱ—Cs1—O7	105.03 (5)	O2—As1—O4	108.74 (8)
O2ⁱⁱ—Cs1—O7	96.97 (4)	O3—As1—O4	109.70 (9)
O3ⁱⁱⁱ—Cs1—O7	70.09 (5)	O1—As1—Cs1^ix	149.10 (6)
O4—Cs1—O7	90.81 (4)	O2—As1—Cs1^ix	39.80 (6)
O5^iv—Cs1—O7	60.59 (4)	O3—As1—Cs1^ix	70.95 (7)
O1^v—Cs1—O7	154.70 (4)	O4—As1—Cs1^ix	98.34 (6)
O11^vi—Cs1—O7	139.58 (5)	O1—As1—Cs1^v	37.17 (6)
O12—Cs1—O7	57.68 (5)	O2—As1—Cs1^v	79.53 (6)
O9^vii—Cs1—O7	38.65 (4)	O3—As1—Cs1^v	133.54 (6)
O11^viii—Cs1—O7	140.53 (4)	O4—As1—Cs1^v	113.07 (6)
O8—Cs1—O7	40.44 (4)	Cs1^ix—As1—Cs1^v	118.527 (15)
O7^vii—Cs1—O7	46.38 (5)	O1—As1—Cs1	82.60 (6)
O12^vi—Cs1—O7	106.93 (4)	O2—As1—Cs1	112.76 (6)
O6ⁱ—Cs1—O3ⁱⁱ	109.44 (4)	O3—As1—Cs1	131.43 (7)
O2ⁱⁱ—Cs1—O3ⁱⁱ	40.33 (4)	O4—As1—Cs1	28.57 (6)
O3ⁱⁱⁱ—Cs1—O3ⁱⁱ	48.55 (5)	Cs1^ix—As1—Cs1	120.358 (14)
O4—Cs1—O3ⁱⁱ	100.71 (4)	Cs1^v—As1—Cs1	85.61 (2)
O5^iv—Cs1—O3ⁱⁱ	146.51 (4)	O1—As1—Cs1^iv	86.21 (6)
O1^v—Cs1—O3ⁱⁱ	61.34 (4)	O2—As1—Cs1^iv	122.72 (6)
O11^vi—Cs1—O3ⁱⁱ	119.62 (5)	O3—As1—Cs1^iv	25.83 (6)
O12—Cs1—O3ⁱⁱ	143.06 (5)	O4—As1—Cs1^iv	113.01 (6)
O9^vii—Cs1—O3ⁱⁱ	57.92 (4)	Cs1^ix—As1—Cs1^iv	96.02 (2)
O11^viii—Cs1—O3ⁱⁱ	63.81 (4)	Cs1^v—As1—Cs1^iv	115.679 (15)
O8—Cs1—O3ⁱⁱ	103.48 (4)	Cs1—As1—Cs1^iv	122.793 (14)
O7^vii—Cs1—O3ⁱⁱ	86.30 (4)	O5—As2—O6	111.26 (9)
O12^vi—Cs1—O3ⁱⁱ	155.60 (4)	O5—As2—O7	114.48 (10)
O7—Cs1—O3ⁱⁱ	96.43 (4)	O6—As2—O7	104.36 (9)
O6ⁱ—Cs1—O10ⁱ	36.71 (4)	O5—As2—O8	109.24 (9)
O2ⁱⁱ—Cs1—O10ⁱ	36.59 (4)	O6—As2—O8	109.46 (9)
O3ⁱⁱⁱ—Cs1—O10ⁱ	120.83 (4)	O7—As2—O8	107.84 (11)
O4—Cs1—O10ⁱ	154.48 (4)	O5—As2—Cs1^x	95.67 (6)
O5^iv—Cs1—O10ⁱ	136.79 (4)	O6—As2—Cs1^x	22.81 (6)
O1^v—Cs1—O10ⁱ	50.52 (4)	O7—As2—Cs1^x	126.99 (7)
O11^vi—Cs1—O10ⁱ	94.57 (4)	O8—As2—Cs1^x	101.01 (7)
O12—Cs1—O10ⁱ	92.99 (4)	O5—As2—Cs1ⁱⁱⁱ	26.12 (6)
O9^vii—Cs1—O10ⁱ	102.35 (3)	O6—As2—Cs1ⁱⁱⁱ	114.54 (6)
O11^viii—Cs1—O10ⁱ	93.21 (4)	O7—As2—Cs1ⁱⁱⁱ	132.54 (7)
O8—Cs1—O10ⁱ	154.64 (4)	O8—As2—Cs1ⁱⁱⁱ	84.33 (7)
O7^vii—Cs1—O10ⁱ	68.01 (4)	Cs1^x—As2—Cs1ⁱⁱⁱ	93.09 (2)
O12^vi—Cs1—O10ⁱ	90.61 (3)	O5—As2—Cs1	134.76 (6)
O7—Cs1—O10ⁱ	114.28 (4)	O6—As2—Cs1	113.69 (6)
O3ⁱⁱ—Cs1—O10ⁱ	73.06 (3)	O7—As2—Cs1	58.21 (8)
O6ⁱ—Cs1—As1ⁱⁱ	86.45 (4)	O8—As2—Cs1	50.09 (7)
O2ⁱⁱ—Cs1—As1ⁱⁱ	19.64 (3)	Cs1^x—As2—Cs1	125.199 (14)
O3ⁱⁱⁱ—Cs1—As1ⁱⁱ	71.16 (4)	Cs1ⁱⁱⁱ—As2—Cs1	121.926 (14)
O4—Cs1—As1ⁱⁱ	121.53 (3)	O5—As2—Cs1^vii	90.42 (6)
O5^iv—Cs1—As1ⁱⁱ	164.43 (3)	O6—As2—Cs1^vii	86.22 (6)
O1^v—Cs1—As1ⁱⁱ	50.57 (3)	O7—As2—Cs1^vii	39.15 (8)
O11^vi—Cs1—As1ⁱⁱ	116.08 (4)	O8—As2—Cs1^vii	146.97 (7)
O12—Cs1—As1ⁱⁱ	130.88 (4)	Cs1^x—As2—Cs1^vii	103.191 (16)
O9^vii—Cs1—As1ⁱⁱ	69.65 (3)	Cs1ⁱⁱⁱ—As2—Cs1^vii	116.209 (15)
O11^viii—Cs1—As1ⁱⁱ	71.36 (3)	Cs1—As2—Cs1^vii	97.20 (2)
O8—Cs1—As1ⁱⁱ	123.41 (3)	O9—As3—O10	116.43 (9)
O7^vii—Cs1—As1ⁱⁱ	77.50 (3)	O9—As3—O12	107.64 (10)
O12^vi—Cs1—As1ⁱⁱ	137.57 (3)	O10—As3—O12	110.13 (9)
O7—Cs1—As1ⁱⁱ	104.25 (3)	O9—As3—O11	112.01 (9)
O3ⁱⁱ—Cs1—As1ⁱⁱ	23.02 (2)	O10—As3—O11	104.28 (9)
O10ⁱ—Cs1—As1ⁱⁱ	50.06 (2)	O12—As3—O11	105.88 (12)
O6ⁱ—Cs1—As3^vi	64.95 (4)	O9—As3—Cs1^vi	140.88 (6)
O2ⁱⁱ—Cs1—As3^vi	122.08 (3)	O10—As3—Cs1^vi	101.00 (6)
O3ⁱⁱⁱ—Cs1—As3^vi	138.36 (4)	O12—As3—Cs1^vi	66.54 (9)
O4—Cs1—As3^vi	79.54 (3)	O11—As3—Cs1^vi	43.34 (8)
O5^iv—Cs1—As3^vi	71.42 (3)	O9—As3—Cs1^xi	85.37 (6)
O1^v—Cs1—As3^vi	75.01 (3)	O10—As3—Cs1^xi	88.31 (6)
O11^vi—Cs1—As3^vi	20.45 (4)	O12—As3—Cs1^xi	147.95 (8)
O12—Cs1—As3^vi	76.10 (5)	O11—As3—Cs1^xi	42.67 (9)
O9^vii—Cs1—As3^vi	166.23 (3)	Cs1^vi—As3—Cs1^xi	84.74 (3)
O11^viii—Cs1—As3^vi	77.68 (4)	O9—As3—Cs1	89.67 (6)
O8—Cs1—As3^vi	109.89 (3)	O10—As3—Cs1	104.40 (6)
O7^vii—Cs1—As3^vi	123.95 (4)	O12—As3—Cs1	25.37 (8)
O12^vi—Cs1—As3^vi	22.88 (3)	O11—As3—Cs1	130.41 (9)
O7—Cs1—As3^vi	128.41 (3)	Cs1^vi—As3—Cs1	91.81 (3)
O3ⁱⁱ—Cs1—As3^vi	135.12 (3)	Cs1^xi—As3—Cs1	167.258 (8)
O10ⁱ—Cs1—As3^vi	87.72 (2)	O9—As3—Cs1^vii	34.48 (6)
As1ⁱⁱ—Cs1—As3^vi	124.056 (16)	O10—As3—Cs1^vii	82.04 (6)
O6ⁱ—Cs1—As1^v	60.99 (4)	O12—As3—Cs1^vii	121.00 (9)
O2ⁱⁱ—Cs1—As1^v	66.46 (3)	O11—As3—Cs1^vii	127.34 (8)
O3ⁱⁱⁱ—Cs1—As1^v	116.05 (4)	Cs1^vi—As3—Cs1^vii	170.584 (8)
O4—Cs1—As1^v	108.35 (4)	Cs1^xi—As3—Cs1^vii	86.46 (3)
O5^iv—Cs1—As1^v	131.91 (3)	Cs1—As3—Cs1^vii	96.08 (3)
O1^v—Cs1—As1^v	17.20 (3)	As1—O1—Cs1^v	125.63 (8)
O11^vi—Cs1—As1^v	55.56 (4)	As1—O1—Cs1	77.18 (6)
O12—Cs1—As1^v	117.41 (4)	Cs1^v—O1—Cs1	99.42 (4)
O9^vii—Cs1—As1^v	133.25 (3)	As1—O1—Cs1^iv	74.03 (6)
O11^viii—Cs1—As1^v	52.95 (3)	Cs1^v—O1—Cs1^iv	142.21 (4)
O8—Cs1—As1^v	158.75 (3)	Cs1—O1—Cs1^iv	117.40 (4)
O7^vii—Cs1—As1^v	114.39 (3)	As1—O2—Cs1^ix	120.56 (9)
O12^vi—Cs1—As1^v	77.99 (3)	As1—O2—Cs1^v	78.93 (6)
O7—Cs1—As1^v	160.62 (3)	Cs1^ix—O2—Cs1^v	157.86 (5)
O3ⁱⁱ—Cs1—As1^v	77.62 (3)	As1—O2—H2	111 (3)
O10ⁱ—Cs1—As1^v	46.39 (3)	Cs1^ix—O2—H2	99 (3)
As1ⁱⁱ—Cs1—As1^v	63.620 (14)	Cs1^v—O2—H2	81 (3)
As3^vi—Cs1—As1^v	60.497 (15)	As1—O3—Cs1^iv	140.95 (9)
O6ⁱ—Cs1—O2^v	41.82 (4)	As1—O3—Cs1^ix	86.03 (7)
O2ⁱⁱ—Cs1—O2^v	72.98 (2)	Cs1^iv—O3—Cs1^ix	131.45 (5)
O3ⁱⁱⁱ—Cs1—O2^v	137.48 (4)	As1—O3—H3	110 (3)
O4—Cs1—O2^v	117.24 (4)	Cs1^iv—O3—H3	84 (3)
O5^iv—Cs1—O2^v	117.36 (4)	Cs1^ix—O3—H3	90 (3)
O1^v—Cs1—O2^v	38.27 (4)	As1—O4—Cs1	136.90 (8)
O11^vi—Cs1—O2^v	53.08 (4)	As1—O4—Cs1^ix	61.45 (5)
O12—Cs1—O2^v	95.87 (4)	Cs1—O4—Cs1^ix	145.93 (5)
O9^vii—Cs1—O2^v	142.89 (3)	As1—O4—H4	107 (2)
O11^viii—Cs1—O2^v	72.01 (4)	Cs1—O4—H4	109 (2)
O8—Cs1—O2^v	159.03 (4)	Cs1^ix—O4—H4	45 (2)
O7^vii—Cs1—O2^v	103.84 (4)	As2—O5—Cs1ⁱⁱⁱ	141.07 (8)
O12^vi—Cs1—O2^v	61.15 (4)	As2—O5—Cs1^x	65.44 (6)
O7—Cs1—O2^v	146.83 (4)	Cs1ⁱⁱⁱ—O5—Cs1^x	106.13 (4)
O3ⁱⁱ—Cs1—O2^v	95.30 (4)	As2—O6—Cs1^x	145.08 (8)
O10ⁱ—Cs1—O2^v	41.49 (3)	As2—O6—H6	112 (3)
As1ⁱⁱ—Cs1—O2^v	77.02 (3)	Cs1^x—O6—H6	102 (3)
As3^vi—Cs1—O2^v	49.19 (2)	As2—O7—Cs1^vii	125.00 (10)
As1^v—Cs1—O2^v	21.54 (2)	As2—O7—Cs1	101.06 (9)
O6ⁱ—Cs1—H8	127.7 (6)	Cs1^vii—O7—Cs1	133.62 (5)
O2ⁱⁱ—Cs1—H8	137.8 (6)	As2—O7—H7	108 (3)
O3ⁱⁱⁱ—Cs1—H8	67.3 (6)	Cs1^vii—O7—H7	103 (3)
O4—Cs1—H8	48.7 (6)	Cs1—O7—H7	63 (3)
O5^iv—Cs1—H8	31.8 (6)	As2—O8—Cs1	110.08 (9)
O1^v—Cs1—H8	153.0 (6)	As2—O8—Cs1ⁱⁱⁱ	74.96 (6)
O11^vi—Cs1—H8	99.6 (6)	Cs1—O8—Cs1ⁱⁱⁱ	142.44 (5)
O12—Cs1—H8	67.3 (6)	As2—O8—H8	110 (3)
O9^vii—Cs1—H8	67.9 (6)	Cs1—O8—H8	57 (3)
O11^viii—Cs1—H8	110.2 (6)	Cs1ⁱⁱⁱ—O8—H8	159 (3)
O8—Cs1—H8	11.4 (6)	As3—O9—Cs1^vii	130.90 (8)
O7^vii—Cs1—H8	89.8 (6)	As3—O9—Cs1^xi	75.31 (6)
O12^vi—Cs1—H8	87.5 (6)	Cs1^vii—O9—Cs1^xi	99.91 (4)
O7—Cs1—H8	44.8 (6)	As3—O10—Cs1^x	168.61 (9)
O3ⁱⁱ—Cs1—H8	114.7 (6)	As3—O10—Cs1^vi	59.93 (5)
O10ⁱ—Cs1—H8	156.5 (6)	Cs1^x—O10—Cs1^vi	111.15 (3)
As1ⁱⁱ—Cs1—H8	134.8 (6)	As3—O10—Cs1^vii	78.77 (6)
As3^vi—Cs1—H8	99.2 (6)	Cs1^x—O10—Cs1^vii	110.89 (3)
As1^v—Cs1—H8	154.2 (6)	Cs1^vi—O10—Cs1^vii	137.79 (4)
O2^v—Cs1—H8	148.0 (6)	As3—O10—Cs1^xi	72.57 (6)
O6ⁱ—Cs1—H12	72.2 (7)	Cs1^x—O10—Cs1^xi	113.62 (3)
O2ⁱⁱ—Cs1—H12	123.9 (7)	Cs1^vi—O10—Cs1^xi	76.59 (3)
O3ⁱⁱⁱ—Cs1—H12	118.9 (6)	Cs1^vii—O10—Cs1^xi	83.52 (4)
O4—Cs1—H12	91.9 (7)	As3—O11—Cs1^vi	116.21 (11)
O5^iv—Cs1—H12	32.8 (7)	As3—O11—Cs1^xi	119.34 (11)
O1^v—Cs1—H12	141.8 (6)	Cs1^vi—O11—Cs1^xi	121.90 (6)
O11^vi—Cs1—H12	91.0 (6)	As3—O11—H11	115 (3)
O12—Cs1—H12	13.3 (7)	Cs1^vi—O11—H11	102 (3)
O9^vii—Cs1—H12	93.7 (6)	Cs1^xi—O11—H11	68 (3)
O11^viii—Cs1—H12	145.1 (6)	As3—O12—Cs1	142.50 (11)
O8—Cs1—H12	63.9 (6)	As3—O12—Cs1^vi	90.58 (9)
O7^vii—Cs1—H12	66.1 (6)	Cs1—O12—Cs1^vi	126.73 (6)
O12^vi—Cs1—H12	51.9 (6)	As3—O12—H12	110 (3)
O7—Cs1—H12	55.3 (6)	Cs1—O12—H12	68 (3)
O3ⁱⁱ—Cs1—H12	149.4 (6)	Cs1^vi—O12—H12	95 (3)
O10ⁱ—Cs1—H12	105.9 (7)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O10^viii	0.83 (4)	1.70 (4)	2.524 (2)	171 (4)
O3—H3···O9^x	0.79 (4)	1.76 (4)	2.553 (3)	172 (4)
O4—H4···O1ⁱⁱⁱ	0.92 (3)	1.70 (3)	2.609 (2)	170 (3)
O6—H6···O10	0.91 (2)	1.64 (2)	2.539 (2)	170 (4)
O7—H7···O9^vii	0.81 (4)	1.79 (4)	2.599 (3)	177 (4)
O11—H11···O1^vi	0.79 (4)	1.85 (4)	2.630 (3)	168 (4)
O8—H8···O5^iv	0.82 (4)	1.85 (4)	2.664 (2)	170 (4)
O12—H12···O5^iv	0.81 (4)	1.84 (4)	2.643 (3)	171 (4)

Symmetry codes: (iii) x, −y+1/2, z−1/2; (iv) x, −y+1/2, z+1/2; (vi) −x+1, −y+1, −z+1; (vii) −x+1, −y+1, −z; (viii) x−1, y, z; (x) −x+1, y−1/2, −z+1/2.

Dilithium bis(dihydrogen phosphate) (Li2H2PO42) top

Crystal data top

Li₂(H₂PO₄)₂	F(000) = 416
M_r = 207.85	D_x = 2.123 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 5.400 (1) Å	Cell parameters from 2948 reflections
b = 15.927 (3) Å	θ = 2.6–34.9°
c = 7.562 (2) Å	µ = 0.67 mm⁻¹
β = 90.47 (3)°	T = 293 K
V = 650.4 (2) Å³	Crude blocky, colourless
Z = 4	0.15 × 0.12 × 0.10 mm

Data collection top

Nonius KappaCCD single-crystal four-circle diffractometer	2490 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.014
φ and ω scans	θ_max = 34.9°, θ_min = 2.6°
Absorption correction: multi-scan (SCALEPACK; Otwinowski et al., 2003)	h = −8→8
T_min = 0.906, T_max = 0.936	k = −25→25
5625 measured reflections	l = −12→12
2857 independent reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.025	All H-atom parameters refined
wR(F²) = 0.072	w = 1/[σ²(F_o²) + (0.0358P)² + 0.2847P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.001
2857 reflections	Δρ_max = 0.44 e Å⁻³
126 parameters	Δρ_min = −0.38 e Å⁻³
0 restraints	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.032 (2)

Special details top

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

	x	y	z	U_iso*/U_eq
Li1	0.3095 (4)	0.41644 (13)	0.8697 (3)	0.0180 (3)
Li2	0.2049 (4)	0.17789 (12)	0.3787 (3)	0.0188 (4)
P1	0.20738 (5)	0.22094 (2)	0.78828 (3)	0.01221 (6)
P2	0.82490 (4)	0.50113 (2)	0.75280 (3)	0.01103 (6)
O1	0.31754 (15)	0.18533 (5)	0.62305 (11)	0.02001 (15)
O2	0.35275 (14)	0.28897 (5)	0.88008 (11)	0.01756 (14)
O3	0.16657 (18)	0.15302 (6)	0.93356 (12)	0.02388 (18)
O4	−0.06014 (14)	0.25573 (6)	0.73730 (11)	0.01953 (15)
O5	0.64679 (14)	0.43820 (5)	0.82463 (11)	0.01765 (14)
O6	1.07946 (14)	0.46742 (5)	0.71115 (10)	0.01685 (14)
O7	0.71704 (16)	0.54689 (6)	0.58619 (11)	0.02046 (16)
O8	0.84346 (15)	0.57281 (5)	0.89622 (10)	0.01729 (14)
H1	0.057 (4)	0.1225 (14)	0.916 (3)	0.055 (7)*
H2	−0.089 (4)	0.2448 (15)	0.630 (3)	0.056 (6)*
H3	0.782 (5)	0.5391 (16)	0.503 (3)	0.064 (8)*
H4	0.950 (4)	0.6050 (14)	0.874 (3)	0.052 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Li1	0.0137 (8)	0.0215 (9)	0.0189 (8)	0.0019 (7)	0.0014 (6)	0.0024 (7)
Li2	0.0161 (8)	0.0181 (8)	0.0222 (9)	−0.0015 (6)	0.0007 (7)	−0.0005 (7)
P1	0.01114 (11)	0.01204 (11)	0.01341 (11)	0.00015 (7)	−0.00151 (8)	−0.00139 (8)
P2	0.01011 (11)	0.01230 (11)	0.01071 (11)	0.00059 (7)	0.00120 (7)	0.00032 (7)
O1	0.0202 (4)	0.0236 (4)	0.0162 (3)	0.0080 (3)	−0.0008 (3)	−0.0041 (3)
O2	0.0152 (3)	0.0149 (3)	0.0225 (4)	−0.0028 (2)	−0.0017 (3)	−0.0042 (3)
O3	0.0271 (4)	0.0227 (4)	0.0217 (4)	−0.0094 (3)	−0.0068 (3)	0.0077 (3)
O4	0.0137 (3)	0.0284 (4)	0.0164 (3)	0.0063 (3)	−0.0032 (2)	−0.0035 (3)
O5	0.0141 (3)	0.0152 (3)	0.0237 (4)	−0.0032 (2)	0.0036 (3)	0.0019 (3)
O6	0.0124 (3)	0.0245 (4)	0.0137 (3)	0.0057 (3)	0.0018 (2)	0.0025 (3)
O7	0.0208 (4)	0.0280 (4)	0.0126 (3)	0.0118 (3)	0.0016 (3)	0.0033 (3)
O8	0.0207 (4)	0.0166 (3)	0.0147 (3)	−0.0055 (3)	0.0046 (3)	−0.0041 (2)

Geometric parameters (Å, º) top

Li1—O5	1.888 (2)	P1—O2	1.5043 (8)
Li1—O6ⁱ	1.902 (2)	P1—O3	1.5588 (9)
Li1—O8ⁱⁱ	1.967 (2)	P1—O4	1.5917 (8)
Li1—O2	2.045 (2)	P2—O5	1.4944 (8)
Li1—Li2ⁱⁱⁱ	2.611 (3)	P2—O6	1.5113 (8)
Li1—P2ⁱ	3.068 (2)	P2—O7	1.5640 (9)
Li2—O5^iv	1.919 (2)	P2—O8	1.5774 (8)
Li2—O1	1.944 (2)	O3—H1	0.77 (2)
Li2—O4^v	1.973 (2)	O4—H2	0.84 (2)
Li2—O2^iv	1.974 (2)	O7—H3	0.73 (2)
Li2—P2^iv	3.077 (2)	O8—H4	0.79 (2)
P1—O1	1.4996 (9)

O5—Li1—O6ⁱ	115.73 (11)	O2—P1—O4	109.28 (5)
O5—Li1—O8ⁱⁱ	124.03 (11)	O3—P1—O4	106.20 (5)
O6ⁱ—Li1—O8ⁱⁱ	104.66 (10)	O5—P2—O6	115.26 (5)
O5—Li1—O2	94.55 (9)	O5—P2—O7	111.65 (5)
O6ⁱ—Li1—O2	121.45 (11)	O6—P2—O7	109.33 (5)
O8ⁱⁱ—Li1—O2	95.77 (9)	O5—P2—O8	105.84 (5)
O5—Li1—Li2ⁱⁱⁱ	47.19 (7)	O6—P2—O8	110.34 (5)
O6ⁱ—Li1—Li2ⁱⁱⁱ	142.36 (11)	O7—P2—O8	103.75 (5)
O8ⁱⁱ—Li1—Li2ⁱⁱⁱ	112.09 (10)	O5—P2—Li1^vi	98.65 (5)
O2—Li1—Li2ⁱⁱⁱ	48.30 (6)	O6—P2—Li1^vi	29.39 (5)
O5—Li1—P2ⁱ	133.57 (9)	O7—P2—Li1^vi	138.44 (5)
O6ⁱ—Li1—P2ⁱ	22.95 (4)	O8—P2—Li1^vi	94.06 (5)
O8ⁱⁱ—Li1—P2ⁱ	81.81 (7)	O5—P2—Li2ⁱⁱⁱ	29.33 (5)
O2—Li1—P2ⁱ	122.98 (9)	O6—P2—Li2ⁱⁱⁱ	85.96 (5)
Li2ⁱⁱⁱ—Li1—P2ⁱ	162.91 (9)	O7—P2—Li2ⁱⁱⁱ	127.10 (6)
O5^iv—Li2—O1	108.09 (10)	O8—P2—Li2ⁱⁱⁱ	118.06 (5)
O5^iv—Li2—O4^v	120.38 (11)	Li1^vi—P2—Li2ⁱⁱⁱ	71.62 (5)
O1—Li2—O4^v	106.56 (10)	P1—O1—Li2	133.78 (8)
O5^iv—Li2—O2^iv	95.90 (9)	P1—O2—Li2ⁱⁱⁱ	133.57 (8)
O1—Li2—O2^iv	105.81 (10)	P1—O2—Li1	129.67 (8)
O4^v—Li2—O2^iv	118.91 (11)	Li2ⁱⁱⁱ—O2—Li1	81.02 (8)
O5^iv—Li2—Li1^iv	46.19 (7)	P1—O3—H1	115.4 (17)
O1—Li2—Li1^iv	108.00 (10)	P1—O4—Li2^vii	129.92 (8)
O4^v—Li2—Li1^iv	145.44 (11)	P1—O4—H2	108.9 (16)
O2^iv—Li2—Li1^iv	50.68 (7)	Li2^vii—O4—H2	121.0 (16)
O5^iv—Li2—P2^iv	22.43 (4)	P2—O5—Li1	144.45 (8)
O1—Li2—P2^iv	106.59 (8)	P2—O5—Li2ⁱⁱⁱ	128.24 (8)
O4^v—Li2—P2^iv	101.01 (8)	Li1—O5—Li2ⁱⁱⁱ	86.62 (9)
O2^iv—Li2—P2^iv	117.05 (8)	P2—O6—Li1^vi	127.66 (8)
Li1^iv—Li2—P2^iv	68.47 (6)	P2—O7—H3	116 (2)
O1—P1—O2	116.61 (5)	P2—O8—Li1ⁱⁱ	131.07 (8)
O1—P1—O3	112.58 (5)	P2—O8—H4	111.6 (17)
O2—P1—O3	104.53 (5)	Li1ⁱⁱ—O8—H4	116.4 (17)
O1—P1—O4	107.18 (5)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O7^viii	0.77 (2)	1.91 (2)	2.6769 (12)	171 (2)
O4—H2···O2^iv	0.84 (2)	1.99 (2)	2.8292 (14)	176 (2)
O7—H3···O6^ix	0.73 (2)	1.79 (2)	2.5210 (13)	172 (3)
O8—H4···O1^x	0.79 (2)	1.79 (2)	2.5667 (12)	167 (2)

Symmetry codes: (iv) x−1/2, −y+1/2, z−1/2; (viii) −x+1/2, y−1/2, −z+3/2; (ix) −x+2, −y+1, −z+1; (x) −x+3/2, y+1/2, −z+3/2.

Ammonium dihydrogen arsenate(V) trihydrogen arsenate(V) (NH4H2AsO4H3AsO4) top

Crystal data top

(NH₄)(H₂AsO₄)(H₃AsO₄)	D_x = 2.602 Mg m⁻³
M_r = 300.92	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 793 reflections
a = 7.943 (2) Å	θ = 3.3–28.7°
b = 9.855 (2) Å	µ = 8.71 mm⁻¹
c = 19.623 (4) Å	T = 293 K
V = 1536.1 (6) Å³	Rounded prisms, colourless
Z = 8	0.15 × 0.10 × 0.07 mm
F(000) = 1168

Data collection top

Nonius KappaCCD single-crystal four-circle diffractometer	905 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.038
φ and ω scans	θ_max = 28.7°, θ_min = 3.3°
Absorption correction: multi-scan (SCALEPACK; Otwinowski et al., 2003)	h = −10→10
T_min = 0.355, T_max = 0.581	k = −13→12
1799 measured reflections	l = −25→26
1295 independent reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.046	Only H-atom coordinates refined
wR(F²) = 0.109	w = 1/[σ²(F_o²) + (0.0508P)² + 1.4516P] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max < 0.001
1295 reflections	Δρ_max = 0.74 e Å⁻³
136 parameters	Δρ_min = −0.61 e Å⁻³
9 restraints	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0011 (5)

Special details top

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

	x	y	z	U_iso*/U_eq
N	0.2990 (9)	0.5958 (9)	−0.1213 (4)	0.0333 (17)
As1	0.19665 (8)	0.31360 (8)	0.03568 (4)	0.0228 (2)
As2	0.26446 (8)	0.39549 (9)	−0.27893 (4)	0.0254 (3)
O1	0.2714 (6)	0.1598 (5)	0.0226 (3)	0.0266 (13)
O2	0.0736 (6)	0.3271 (5)	0.1038 (3)	0.0296 (13)
O3	0.0971 (6)	0.3697 (6)	−0.0359 (3)	0.0302 (13)
O4	0.3684 (6)	0.4183 (6)	0.0407 (3)	0.0305 (14)
O5	0.2149 (6)	0.3602 (6)	−0.2002 (3)	0.0287 (13)
O6	0.3472 (7)	0.5542 (6)	−0.2792 (3)	0.0351 (14)
O7	0.0911 (6)	0.3961 (6)	−0.3291 (3)	0.0344 (14)
O8	0.4036 (6)	0.2901 (6)	−0.3172 (3)	0.0364 (16)
H1	0.410 (3)	0.585 (11)	−0.121 (6)	0.08 (4)*
H2	0.264 (10)	0.522 (6)	−0.145 (4)	0.040*
H3	0.251 (11)	0.619 (11)	−0.082 (3)	0.06 (3)*
H4	0.260 (19)	0.667 (11)	−0.146 (7)	0.18 (9)*
H5	0.013 (13)	0.430 (12)	−0.039 (8)	0.16 (7)*
H7	0.37 (2)	0.57 (2)	−0.324 (2)	0.22 (9)*
H6	0.332 (8)	0.502 (4)	0.032 (4)	0.03 (2)*
H8	0.057 (10)	0.324 (6)	−0.352 (4)	0.05 (3)*
H9	0.494 (9)	0.333 (12)	−0.300 (6)	0.10 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N	0.035 (4)	0.039 (5)	0.026 (4)	−0.001 (3)	0.002 (3)	−0.009 (4)
As1	0.0201 (4)	0.0169 (4)	0.0313 (5)	0.0005 (3)	0.0001 (3)	−0.0001 (4)
As2	0.0228 (4)	0.0240 (5)	0.0292 (5)	−0.0018 (3)	0.0014 (3)	−0.0014 (4)
O1	0.025 (3)	0.017 (3)	0.038 (4)	−0.0009 (19)	0.006 (2)	−0.006 (3)
O2	0.027 (2)	0.025 (3)	0.036 (4)	0.005 (2)	0.003 (2)	−0.004 (3)
O3	0.025 (3)	0.032 (3)	0.033 (3)	0.003 (2)	−0.003 (2)	0.006 (3)
O4	0.022 (2)	0.018 (3)	0.051 (4)	−0.001 (2)	−0.003 (2)	0.002 (3)
O5	0.026 (3)	0.030 (3)	0.030 (3)	−0.003 (2)	0.004 (2)	0.002 (3)
O6	0.041 (3)	0.025 (3)	0.039 (4)	0.000 (2)	−0.003 (2)	−0.002 (3)
O7	0.024 (3)	0.039 (4)	0.040 (4)	0.000 (2)	−0.010 (2)	−0.003 (3)
O8	0.022 (3)	0.031 (3)	0.056 (5)	0.001 (2)	0.007 (2)	−0.012 (3)

Geometric parameters (Å, º) top

N—O5	2.869 (10)	N—H3	0.89 (2)
N—O1ⁱ	2.947 (9)	N—H4	0.90 (2)
N—O5ⁱ	3.032 (11)	As1—O1	1.648 (5)
N—O2ⁱⁱ	3.075 (9)	As1—O2	1.662 (6)
N—O4ⁱⁱⁱ	3.082 (9)	As1—O3	1.705 (6)
N—O6	3.148 (10)	As1—O4	1.714 (5)
N—O7^iv	3.194 (10)	As2—O5	1.632 (6)
N—O3	3.216 (10)	As2—O8	1.692 (5)
N—O8^v	3.272 (9)	As2—O7	1.693 (5)
N—O3ⁱ	3.283 (10)	As2—O6	1.696 (6)
N—O4	3.671 (11)	As2—H9	1.97 (10)
N—As2	3.679 (8)	O3—H5	0.89 (2)
N—As1ⁱ	3.755 (8)	O4—H6	0.89 (2)
N—O6^vi	4.106 (10)	O6—H7	0.90 (2)
N—As1	4.229 (9)	O7—H8	0.89 (2)
N—H1	0.89 (2)	O8—H9	0.89 (2)
N—H2	0.91 (2)

O5—N—O1ⁱ	130.2 (3)	O2—As1—O3	111.4 (3)
O5—N—O5ⁱ	114.3 (3)	O1—As1—O4	106.0 (2)
O1ⁱ—N—O5ⁱ	107.3 (3)	O2—As1—O4	111.9 (3)
O5—N—O2ⁱⁱ	92.1 (2)	O3—As1—O4	102.8 (3)
O1ⁱ—N—O2ⁱⁱ	70.0 (2)	O1—As1—N^vii	48.9 (2)
O5ⁱ—N—O2ⁱⁱ	79.0 (2)	O2—As1—N^vii	135.4 (2)
O5—N—O4ⁱⁱⁱ	116.1 (3)	O3—As1—N^vii	60.9 (2)
O1ⁱ—N—O4ⁱⁱⁱ	71.4 (2)	O4—As1—N^vii	112.6 (2)
O5ⁱ—N—O4ⁱⁱⁱ	109.4 (3)	O1—As1—N	114.9 (2)
O2ⁱⁱ—N—O4ⁱⁱⁱ	141.2 (3)	O2—As1—N	130.3 (2)
O5—N—O6	52.6 (2)	O3—As1—N	43.6 (2)
O1ⁱ—N—O6	173.6 (4)	O4—As1—N	59.5 (2)
O5ⁱ—N—O6	67.3 (2)	N^vii—As1—N	77.08 (15)
O2ⁱⁱ—N—O6	105.0 (3)	O1—As1—Nⁱⁱ	124.9 (2)
O4ⁱⁱⁱ—N—O6	113.3 (3)	O2—As1—Nⁱⁱ	31.2 (2)
O5—N—O7^iv	60.4 (2)	O3—As1—Nⁱⁱ	80.4 (2)
O1ⁱ—N—O7^iv	124.2 (3)	O4—As1—Nⁱⁱ	124.9 (2)
O5ⁱ—N—O7^iv	113.6 (3)	N^vii—As1—Nⁱⁱ	116.13 (17)
O2ⁱⁱ—N—O7^iv	152.3 (3)	N—As1—Nⁱⁱ	108.59 (12)
O4ⁱⁱⁱ—N—O7^iv	60.4 (2)	O1—As1—Nⁱⁱⁱ	85.3 (2)
O6—N—O7^iv	62.1 (2)	O2—As1—Nⁱⁱⁱ	102.1 (2)
O5—N—O3	66.7 (2)	O3—As1—Nⁱⁱⁱ	131.8 (2)
O1ⁱ—N—O3	63.5 (2)	O4—As1—Nⁱⁱⁱ	30.4 (2)
O5ⁱ—N—O3	147.5 (3)	N^vii—As1—Nⁱⁱⁱ	114.68 (18)
O2ⁱⁱ—N—O3	68.5 (2)	N—As1—Nⁱⁱⁱ	88.28 (16)
O4ⁱⁱⁱ—N—O3	97.4 (3)	Nⁱⁱ—As1—Nⁱⁱⁱ	128.79 (19)
O6—N—O3	118.9 (3)	O1—As1—N^viii	64.6 (2)
O7^iv—N—O3	95.4 (3)	O2—As1—N^viii	57.6 (2)
O5—N—O8^v	116.3 (3)	O3—As1—N^viii	103.2 (2)
O1ⁱ—N—O8^v	111.4 (3)	O4—As1—N^viii	154.0 (2)
O5ⁱ—N—O8^v	48.33 (18)	N^vii—As1—N^viii	80.41 (16)
O2ⁱⁱ—N—O8^v	126.3 (3)	N—As1—N^viii	146.26 (12)
O4ⁱⁱⁱ—N—O8^v	66.2 (2)	Nⁱⁱ—As1—N^viii	60.37 (8)
O6—N—O8^v	68.0 (2)	Nⁱⁱⁱ—As1—N^viii	124.17 (18)
O7^iv—N—O8^v	74.0 (2)	O5—As2—O8	116.5 (3)
O3—N—O8^v	163.3 (3)	O5—As2—O7	110.8 (3)
O5—N—O3ⁱ	177.9 (3)	O8—As2—O7	106.0 (3)
O1ⁱ—N—O3ⁱ	51.9 (2)	O5—As2—O6	107.0 (3)
O5ⁱ—N—O3ⁱ	64.1 (2)	O8—As2—O6	108.2 (3)
O2ⁱⁱ—N—O3ⁱ	89.0 (2)	O7—As2—O6	108.1 (3)
O4ⁱⁱⁱ—N—O3ⁱ	63.9 (2)	O5—As2—N	48.4 (2)
O6—N—O3ⁱ	125.4 (3)	O8—As2—N	130.8 (2)
O7^iv—N—O3ⁱ	118.7 (3)	O7—As2—N	123.2 (2)
O3—N—O3ⁱ	115.4 (3)	O6—As2—N	58.6 (3)
O8^v—N—O3ⁱ	61.7 (2)	O5—As2—N^vii	31.3 (2)
O5—N—O4	96.7 (3)	O8—As2—N^vii	88.5 (2)
O1ⁱ—N—O4	45.61 (18)	O7—As2—N^vii	108.9 (2)
O5ⁱ—N—O4	149.0 (3)	O6—As2—N^vii	132.8 (3)
O2ⁱⁱ—N—O4	99.5 (2)	N—As2—N^vii	76.88 (15)
O4ⁱⁱⁱ—N—O4	53.5 (2)	O5—As2—N^vi	107.4 (2)
O6—N—O4	140.5 (3)	O8—As2—N^vi	126.6 (2)
O7^iv—N—O4	82.0 (2)	O7—As2—N^vi	26.1 (2)
O3—N—O4	45.05 (17)	O6—As2—N^vi	85.1 (2)
O8^v—N—O4	119.3 (2)	N—As2—N^vi	100.7 (2)
O3ⁱ—N—O4	84.9 (2)	N^vii—As2—N^vi	120.20 (9)
O5—N—As2	25.19 (13)	O5—As2—N^ix	114.5 (2)
O1ⁱ—N—As2	155.0 (3)	O8—As2—N^ix	4.0 (2)
O5ⁱ—N—As2	91.7 (2)	O7—As2—N^ix	110.0 (2)
O2ⁱⁱ—N—As2	98.9 (2)	O6—As2—N^ix	106.1 (2)
O4ⁱⁱⁱ—N—As2	118.1 (3)	N—As2—N^ix	126.83 (8)
O6—N—As2	27.38 (13)	N^vii—As2—N^ix	87.52 (18)
O7^iv—N—As2	57.81 (17)	N^vi—As2—N^ix	130.26 (19)
O3—N—As2	91.7 (2)	O5—As2—N^iv	130.53 (19)
O8^v—N—As2	93.3 (2)	O8—As2—N^iv	61.4 (2)
O3ⁱ—N—As2	152.7 (3)	O7—As2—N^iv	117.1 (2)
O4—N—As2	118.9 (3)	O6—As2—N^iv	46.9 (2)
O5—N—As1ⁱ	155.1 (3)	N—As2—N^iv	93.05 (19)
O1ⁱ—N—As1ⁱ	24.94 (13)	N^vii—As2—N^iv	129.92 (9)
O5ⁱ—N—As1ⁱ	85.9 (2)	N^vi—As2—N^iv	109.85 (16)
O2ⁱⁱ—N—As1ⁱ	77.1 (2)	N^ix—As2—N^iv	59.62 (5)
O4ⁱⁱⁱ—N—As1ⁱ	66.22 (19)	O5—As2—N^x	91.4 (2)
O6—N—As1ⁱ	151.7 (3)	O8—As2—N^x	92.4 (2)
O7^iv—N—As1ⁱ	126.5 (3)	O7—As2—N^x	33.3 (2)
O3—N—As1ⁱ	88.5 (2)	O6—As2—N^x	141.2 (2)
O8^v—N—As1ⁱ	87.8 (2)	N—As2—N^x	128.63 (8)
O3ⁱ—N—As1ⁱ	26.98 (12)	N^vii—As2—N^x	78.44 (17)
O4—N—As1ⁱ	63.92 (16)	N^vi—As2—N^x	56.57 (5)
As2—N—As1ⁱ	175.6 (2)	N^ix—As2—N^x	96.01 (15)
O5—N—O6^vi	57.27 (18)	N^iv—As2—N^x	136.46 (17)
O1ⁱ—N—O6^vi	108.1 (2)	O5—As2—H9	111 (4)
O5ⁱ—N—O6^vi	79.1 (2)	O8—As2—H9	26.9 (19)
O2ⁱⁱ—N—O6^vi	40.23 (16)	O7—As2—H9	129 (3)
O4ⁱⁱⁱ—N—O6^vi	171.4 (3)	O6—As2—H9	86 (3)
O6—N—O6^vi	68.00 (18)	N—As2—H9	106 (2)
O7^iv—N—O6^vi	115.4 (3)	N^vii—As2—H9	93 (4)
O3—N—O6^vi	75.10 (19)	N^vi—As2—H9	142 (4)
O8^v—N—O6^vi	120.9 (3)	N^ix—As2—H9	23.3 (19)
O3ⁱ—N—O6^vi	123.0 (3)	N^iv—As2—H9	43 (4)
O4—N—O6^vi	119.7 (2)	N^x—As2—H9	119.3 (19)
As2—N—O6^vi	58.77 (14)	As1—O1—N^vii	106.1 (3)
As1ⁱ—N—O6^vi	117.1 (2)	As1—O1—Nⁱⁱⁱ	73.8 (2)
O5—N—As1	79.4 (2)	N^vii—O1—Nⁱⁱⁱ	131.0 (2)
O1ⁱ—N—As1	53.58 (17)	As1—O1—N^viii	97.7 (2)
O5ⁱ—N—As1	158.4 (3)	N^vii—O1—N^viii	97.1 (2)
O2ⁱⁱ—N—As1	84.0 (2)	Nⁱⁱⁱ—O1—N^viii	131.9 (2)
O4ⁱⁱⁱ—N—As1	76.2 (2)	As1—O1—N	48.2 (2)
O6—N—As1	130.9 (3)	N^vii—O1—N	70.2 (2)
O7^iv—N—As1	87.5 (2)	Nⁱⁱⁱ—O1—N	76.27 (17)
O3—N—As1	21.42 (11)	N^viii—O1—N	132.56 (18)
O8^v—N—As1	142.4 (3)	As1—O2—Nⁱⁱ	132.5 (3)
O3ⁱ—N—As1	102.5 (2)	As1—O2—N^viii	105.1 (2)
O4—N—As1	23.73 (9)	Nⁱⁱ—O2—N^viii	76.41 (15)
As2—N—As1	104.2 (2)	As1—O2—Nⁱⁱⁱ	59.12 (17)
As1ⁱ—N—As1	77.29 (15)	Nⁱⁱ—O2—Nⁱⁱⁱ	154.8 (3)
O6^vi—N—As1	96.48 (18)	N^viii—O2—Nⁱⁱⁱ	125.74 (19)
O5—N—H1	98 (7)	As1—O2—N^vii	31.33 (17)
O1ⁱ—N—H1	102 (7)	Nⁱⁱ—O2—N^vii	113.6 (2)
O5ⁱ—N—H1	98 (7)	N^viii—O2—N^vii	76.03 (17)
O2ⁱⁱ—N—H1	170 (7)	Nⁱⁱⁱ—O2—N^vii	85.99 (16)
O4ⁱⁱⁱ—N—H1	31 (7)	As1—O3—N	115.0 (3)
O6—N—H1	82 (7)	As1—O3—N^vii	92.1 (3)
O7^iv—N—H1	37 (7)	N—O3—N^vii	100.3 (2)
O3—N—H1	114 (8)	As1—O3—Nⁱⁱ	77.3 (2)
O8^v—N—H1	50 (7)	N—O3—Nⁱⁱ	131.7 (2)
O3ⁱ—N—H1	81 (7)	N^vii—O3—Nⁱⁱ	126.8 (2)
O4—N—H1	78 (8)	As1—O3—H5	128 (10)
As2—N—H1	91 (7)	N—O3—H5	83 (10)
As1ⁱ—N—H1	93 (7)	N^vii—O3—H5	135 (10)
O6^vi—N—H1	149 (7)	Nⁱⁱ—O3—H5	57 (10)
As1—N—H1	96 (8)	As1—O4—Nⁱⁱⁱ	133.2 (3)
O5—N—H2	4 (5)	As1—O4—N	96.7 (3)
O1ⁱ—N—H2	128 (6)	Nⁱⁱⁱ—O4—N	126.5 (2)
O5ⁱ—N—H2	114 (6)	As1—O4—N^vii	47.7 (2)
O2ⁱⁱ—N—H2	88 (5)	Nⁱⁱⁱ—O4—N^vii	124.1 (2)
O4ⁱⁱⁱ—N—H2	119 (6)	N—O4—N^vii	72.12 (17)
O6—N—H2	55 (6)	As1—O4—H6	107 (5)
O7^iv—N—H2	65 (5)	Nⁱⁱⁱ—O4—H6	115 (5)
O3—N—H2	64 (6)	N—O4—H6	49 (6)
O8^v—N—H2	120 (5)	N^vii—O4—H6	114 (6)
O3ⁱ—N—H2	177 (5)	As2—O5—N	106.4 (3)
O4—N—H2	97 (6)	As2—O5—N^vii	132.5 (3)
As2—N—H2	27 (6)	N—O5—N^vii	115.4 (3)
As1ⁱ—N—H2	152 (5)	As2—O6—N	94.0 (3)
O6^vi—N—H2	54 (5)	As2—O6—N^iv	115.6 (3)
As1—N—H2	78 (6)	N—O6—N^iv	124.1 (3)
H1—N—H2	102 (8)	As2—O6—N^vi	74.2 (2)
O5—N—H3	125 (7)	N—O6—N^vi	106.2 (3)
O1ⁱ—N—H3	15 (6)	N^iv—O6—N^vi	126.3 (2)
O5ⁱ—N—H3	102 (8)	As2—O6—H7	102 (10)
O2ⁱⁱ—N—H3	55 (6)	N—O6—H7	164 (10)
O4ⁱⁱⁱ—N—H3	86 (6)	N^iv—O6—H7	50 (10)
O6—N—H3	160 (7)	N^vi—O6—H7	76 (10)
O7^iv—N—H3	137 (7)	As2—O7—N^vi	140.4 (3)
O3—N—H3	61 (7)	As2—O7—N^x	134.4 (3)
O8^v—N—H3	119 (7)	N^vi—O7—N^x	80.52 (12)
O3ⁱ—N—H3	57 (7)	As2—O7—N	39.73 (19)
O4—N—H3	56 (7)	N^vi—O7—N	104.8 (3)
As2—N—H3	146 (7)	N^x—O7—N	134.77 (17)
As1ⁱ—N—H3	31 (7)	As2—O7—N^vii	52.8 (2)
O6^vi—N—H3	94 (6)	N^vi—O7—N^vii	136.37 (19)
As1—N—H3	57 (8)	N^x—O7—N^vii	84.68 (19)
H1—N—H3	117 (9)	N—O7—N^vii	60.22 (12)
H2—N—H3	122 (9)	As2—O7—H8	123 (6)
O5—N—H4	105 (10)	N^vi—O7—H8	97 (6)
O1ⁱ—N—H4	106 (10)	N^x—O7—H8	29 (5)
O5ⁱ—N—H4	18 (10)	N—O7—H8	150 (6)
O2ⁱⁱ—N—H4	62 (10)	N^vii—O7—H8	90 (6)
O4ⁱⁱⁱ—N—H4	127 (10)	As2—O8—N^ix	173.9 (3)
O6—N—H4	68 (10)	As2—O8—N^iv	99.4 (2)
O7^iv—N—H4	124 (10)	N^ix—O8—N^iv	77.87 (12)
O3—N—H4	130 (10)	As2—O8—N^vii	69.8 (2)
O8^v—N—H4	66 (10)	N^ix—O8—N^vii	108.5 (3)
O3ⁱ—N—H4	74 (10)	N^iv—O8—N^vii	138.29 (17)
O4—N—H4	152 (10)	As2—O8—N	34.20 (18)
As2—N—H4	87 (10)	N^ix—O8—N	139.75 (18)
As1ⁱ—N—H4	90 (10)	N^iv—O8—N	85.3 (2)
O6^vi—N—H4	62 (10)	N^vii—O8—N	62.91 (12)
As1—N—H4	146 (10)	As2—O8—H9	94 (8)
H1—N—H4	116 (10)	N^ix—O8—H9	80 (8)
H2—N—H4	104 (10)	N^iv—O8—H9	39 (9)
H3—N—H4	96 (10)	N^vii—O8—H9	100 (9)
O1—As1—O2	114.3 (3)	N—O8—H9	64 (8)
O1—As1—O3	109.7 (3)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N—H1···O4ⁱⁱⁱ	0.89 (2)	2.36 (8)	3.082 (9)	138 (10)
N—H1···O7^iv	0.89 (2)	2.54 (9)	3.194 (10)	130 (9)
N—H4···O5ⁱ	0.90 (2)	2.20 (7)	3.032 (11)	154 (14)
N—H3···O1ⁱ	0.89 (2)	2.10 (4)	2.947 (9)	159 (9)
N—H2···O5	0.91 (2)	1.96 (2)	2.869 (10)	174 (7)
O3—H5···O1^viii	0.89 (2)	2.13 (15)	2.616 (7)	113 (12)
O3—H5···O3ⁱⁱ	0.89 (2)	2.61 (11)	3.311 (12)	136 (13)
O6—H7···O2^xi	0.90 (2)	1.82 (10)	2.653 (9)	152 (19)
O4—H6···O1ⁱ	0.89 (2)	1.77 (3)	2.650 (8)	170 (7)
O7—H8···O2^xii	0.89 (2)	1.72 (4)	2.568 (8)	157 (8)
O8—H9···O5^iv	0.89 (2)	1.78 (6)	2.590 (7)	150 (11)

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

Statistical analysis of As—O bond lengths (Å) in H_nAsO₄ (n = 1–3) groups top

Bond lengths	Analysed number	Average	Min.	Max.
As—O/OH in H_nAsO₄ (average)	97	1.687 (6)	1.660	1.709
As—O/OH in H_nAsO₄ (individual)	388	1.687 (27)	1.614	1.801
As—OH in H_nAsO₄ (incl. split H positions)	199	1.701 (23)	1.625	1.801
As—OH in H_nAsO₄ (no split H)	117	1.714 (21)	1.625	1.801
As—OH in HAsO₄	43	1.728 (19)	1.689	1.801
As—OH in H₂AsO₄	41	1.714 (12)	1.688	1.749
As—OH in H₃AsO₄	33	1.694 (16)	1.625	1.712
As—OH/2 (split H) in H_1-2AsO₄	82	1.683 (13)	1.656	1.714
As—O (no H) in H_nAsO₄	189	1.671 (23)	1.614	1.755
As—O (no H/As*) in H_nAsO₄	174	1.667 (18)	1.614	1.735

Note: (*) no As—O—As bonds (see text).

Acknowledgements

Funding for this research was provided by: Austrian Academy of Sciences (award No. Doc fForte Fellowship to KS).

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Volume 75| Part 8| August 2019| Pages 1134-1141

https://doi.org/10.1107/S2053229619008489

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