Crystal structures of Na2SeO4·1.5H2O and Na2SeO4·10H2O

Weil, M.; Bonneau, B.

doi:10.1107/S1600536814011799

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Volume 70| Part 8| August 2014| Pages 54-57

doi:10.1107/S1600536814011799

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Crystal structures of Na₂SeO₄·1.5H₂O and Na₂SeO₄·10H₂O

Matthias Weil ^a ^* and Barbara Bonneau ^b

^aInstitute for Chemical Technologies and Analytics, Division of Structural Chemistry, Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria, and ^bIUT Bordeaux 1, 15 Rue Naudet, 33175 Gradignan, France
^*Correspondence e-mail: mweil@mail.zserv.tuwien.ac.at

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 2 May 2014; accepted 21 May 2014; online 19 July 2014)

The crystal structures of Na₂SeO₄·1.5H₂O (sodium selenate sesquihydrate) and Na₂SeO₄·10H₂O (sodium selenate decahydrate) are isotypic with those of Na₂CrO₄·1.5H₂O and Na₂XSeO₄·10H₂O (X = S, Cr), respectively. The asymmetric unit of the sesquihydrate contains two Na⁺ cations, one SeO₄ tetrahedron and one and a half water molecules, the other half being generated by twofold rotation symmetry. The coordination polyhedra of the cations are a distorted monocapped octahedron and a square pyramid; these [NaO_x] polyhedra are linked through common edges and corners into a three-dimensional framework structure, the voids of which are filled with the Se atoms of the SeO₄ tetrahedra. The structure is consolidated by O—H⋯O hydrogen bonds between coordinating water molecules and framework O atoms. The asymmetric unit of the decahydrate consists of two Na⁺ cations, one SeO₄ tetrahedron and ten water molecules. Both Na⁺ cations are octahedrally surrounded by water molecules and by edge-sharing condensed into zigzag chains extending parallel to [001]. The SeO₄ tetrahedra and two uncoordinating water molecules are situated between the chains and are connected to the chains through an intricate network of medium-strength O—H⋯O hydrogen bonds.

Keywords: isotypism; sodium selenate; salt hydrates; crystal structure.

CCDC references: 1004274; 1004275

1. Chemical context

Based on recent studies in the system Na/Se/O/H that revealed dimorphism of the phases NaHSeO₄ and Na₅H₃(SeO₄)₄(H₂O)₂ (Pollitt & Weil, 2014 ), we became interested in the structure determination of hydrous phases of Na₂SeO₄. Although the first report of the decahydrate of Na₂SeO₄ dates back to 1827 (Mitscherlich, 1827 ), a detailed structure report for this compound has not been published so far. Mitscherlich (1827) also recognized an isomorphic relationship of Na₂SeO₄·10H₂O with Na₂SO₄·10H₂O (Glauber's salt or mirabilite as a mineral species). This relation was later confirmed by Rosický (1908 ) and by Ruben et al. (1961 ) on the basis of unit-cell determinations using diffraction methods. Another hydrous phase of Na₂SeO₄ reported in the literature is the metastable heptahydrate that crystallized from supersaturated Na₂SeO₄ solutions only when seeded with Na₂SO₄·7H₂O nuclei below 293 K (Belarew, 1965 ).

During crystallization studies of aqueous Na₂SeO₄ solutions under different temperature conditions, we were able to isolate crystals not only of the decahydrate, but also of the sesquihydrate, the crystal structures of which are reported here.

2. Structural commentary

Na₂SeO₄·1.5H₂O is isotypic with the corresponding chromate (Kahlenberg, 2012 ) and is the second example of the Na₂XO₄·1.5H₂O structure family. The main building blocks of this structure type are distorted [NaO₅(H₂O)₂] (Na1) monocapped octahedra, distorted [NaO₄(H₂O)] square pyramids (Na2) (Fig. 1) and rather regular XO₄ (X = Se, Cr) tetrahedra. These building blocks are linked through common corners and edges into a three-dimensional framework structure (Fig. 2). Hydrogen bonds of the type O—H⋯O between the coordinating water molecules and parts of the framework O atoms provide additional stabilization (Table 1). The bond lengths (Table 2) and angles within the individual building blocks of the selenate and chromate structures are more or less identical with mean distances of SeO₄ = 1.641; CrO₄ = 1.651; Na1O₇ = 2.514 (selenate), 2.505 (chromate); Na2O₅ = 2.350 (selenate), 2.360 Å (chromate).

Table 1
Hydrogen-bond geometry (Å, °) for 1.5-hydrate

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OW5—H1⋯O4^viii	0.82 (1)	2.13 (1)	2.922 (2)	164 (3)
OW5—H2⋯O3^ix	0.82 (1)	2.08 (1)	2.891 (2)	169 (3)
OW6—H3⋯O1^vi	0.82 (1)	1.90 (1)	2.703 (2)	167 (4)
Symmetry codes: (vi) $[x, -y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (viii) $[x+{\script{1\over 2}}, y-{\script{1\over 2}}, z]$ ; (ix) $[x+{\script{3\over 4}}, y-{\script{1\over 4}}, -z+{\script{1\over 4}}]$ .

Table 2
Selected bond lengths (Å) for 1.5-hydrate

Na1—OW5	2.3660 (18)	Na2—O2^iv	2.3301 (18)
Na1—O3ⁱ	2.4157 (19)	Na2—OW6^v	2.3480 (18)
Na1—O1	2.4379 (18)	Na2—O4^vi	2.3651 (19)
Na1—O3ⁱⁱ	2.4594 (16)	Na2—O1^vii	2.4103 (18)
Na1—OW5ⁱ	2.465 (2)	Se1—O2	1.6350 (14)
Na1—O4ⁱⁱⁱ	2.6057 (19)	Se1—O3	1.6367 (14)
Na1—O2ⁱⁱ	2.8475 (17)	Se1—O4	1.6451 (16)
Na2—O2	2.298 (2)	Se1—O1	1.6481 (15)
Symmetry codes: (i) $[x+{\script{1\over 4}}, y+{\script{1\over 4}}, -z+{\script{1\over 4}}]$ ; (ii) $[x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ ; (iii) x+1, y, z; (iv) $[x-{\script{1\over 2}}, -y, -z+{\script{1\over 2}}]$ ; (v) x-1, y, z; (vi) $[x, -y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vii) $[x-{\script{1\over 2}}, y-{\script{1\over 2}}, z]$ .

Figure 1
The NaO₇ and NaO₅ polyhedra in the structure of Na₂SO₄·1.5H₂O. Displacement parameters are drawn at the 99% probability level. [Symmetry codes: (i) $[x+{\script{1\over 4}}]$ , $[y+{\script{1\over 4}}]$ , $[-z+{\script{1\over 4}}]$ ; (ii) $[x+{\script{1\over 2}}]$ , $[y+{\script{1\over 2}}]$ , z; (iii) x+1, y, z; (iv) $[x-{\script{1\over 2}}]$ , -y, $[-z+{\script{1\over 2}}]$ ; (v) x-1, y, z; (vi) x, $[-y+{\script{1\over 2}}]$ , $[-z+{\script{1\over 2}}]$ ; (vii) $[x-{\script{1\over 2}}]$ , $[y-{\script{1\over 2}}]$ , z.]

Figure 2
The crystal structure of Na₂SO₄·1.5H₂O in a projection along [110]. NaO₅ polyhedra are turquoise, NaO₇ polyhedra are blue, SeO₄ tetrahedra are red and H atoms are grey. Hydrogen bonds have been omitted for clarity.

Isotypism has been reported for several Na₂XO₄·10H₂O (X = S, Se, Cr, W, Mo) phases (Ruben et al., 1961), but only the structures of X = S (Levy & Lisensky, 1978 ; Prescott et al., 2001 ) and Cr (Kahlenberg, 2012) have been determined so far. As expected, the general structural set-up in the isotypic Na₂XO₄·10H₂O structures is very similar. Each of the two Na⁺ cations is octahedrally surrounded [mean Na—O distance of the two octahedra is 2.420 Å (see Table 3); sulfate analogue (Prescott et al., 2001): 2.415 Å; chromate analogue (Kahlenberg, 2012): 2.423 Å]. The [NaO₆] octahedra are linked via edge-sharing into zigzag chains (Fig. 3) running parallel to [001]. These chains are linked with neighbouring chains and intermediate SeO₄ tetrahedra (mean Se—O distance 1.639; sulfate 1.488, chromate 1.647 Å) and non-coordinating lattice water molecules through O—H⋯O hydrogen bonds of medium strength (Table 4) to build up the crystal structure (Fig. 4). The most important difference between the structures of the three Na₂XO₄·10H₂O (X = S, Se, Cr) phases is the missing disorder of the XO₄ tetrahedron in the selenate compound that has been observed in the sulfate compound on the basis of single-crystal neutron data (Levy & Lisensky, 1978) and single-crystal X-ray data (Prescott et al., 2001), or for the chromate compound on the basis of single-crystal X-ray data (Kahlenberg, 2012).

Table 3
Selected bond lengths (Å) for 10-hydrate

Na1—OW5	2.3776 (6)	Na2—OW7	2.3935 (6)
Na1—OW6ⁱ	2.4181 (6)	Na2—OW9	2.4325 (6)
Na1—OW11	2.4184 (6)	Na2—OW6	2.4415 (6)
Na1—OW10	2.4194 (6)	Na2—OW10ⁱⁱ	2.4667 (6)
Na1—OW8ⁱ	2.4473 (6)	Se1—O41	1.6335 (5)
Na1—OW9ⁱ	2.4507 (6)	Se1—O31	1.6394 (5)
Na2—OW12	2.3814 (6)	Se1—O1	1.6398 (5)
Na2—OW5ⁱⁱ	2.3891 (6)	Se1—O21	1.6421 (5)
Symmetry codes: (i) x, y, z+1; (ii) $[x, -y-{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Table 4
Hydrogen-bond geometry (Å, °) for 10-hydrate

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OW5—H5A⋯O41	0.82 (1)	1.96 (1)	2.7570 (7)	164 (1)
OW5—H5B⋯OW13ⁱⁱⁱ	0.82 (1)	2.00 (1)	2.7980 (7)	165 (1)
OW6—H6A⋯OW14	0.82 (1)	2.02 (1)	2.8301 (7)	168 (1)
OW6—H6B⋯O41ⁱⁱ	0.82 (1)	1.98 (1)	2.7791 (7)	166 (2)
OW7—H7A⋯O1^iv	0.82 (1)	1.97 (1)	2.7727 (7)	166 (1)
OW7—H7B⋯OW8^v	0.82 (1)	1.95 (1)	2.7542 (7)	168 (1)
OW8—H8A⋯O41ⁱⁱ	0.82 (1)	1.95 (1)	2.7544 (7)	166 (1)
OW8—H8B⋯OW7^vi	0.82 (1)	1.99 (1)	2.8076 (7)	178 (1)
OW9—H9A⋯O1^vii	0.82 (1)	2.11 (1)	2.9152 (7)	168 (1)
OW9—H9B⋯OW13^viii	0.82 (1)	2.04 (1)	2.8596 (7)	177 (1)
OW10—H10A⋯OW14^ix	0.82 (1)	2.05 (1)	2.8686 (7)	178 (2)
OW10—H10B⋯O31^x	0.82 (1)	2.08 (1)	2.8920 (7)	174 (1)
OW11—H11A⋯O31	0.82 (1)	2.05 (1)	2.8604 (7)	171 (1)
OW11—H11B⋯OW12ⁱ	0.82 (1)	1.96 (1)	2.7716 (8)	168 (1)
OW12—H12A⋯O21^iv	0.82 (1)	1.92 (1)	2.7359 (7)	179 (1)
OW12—H12B⋯OW11^viii	0.82 (1)	1.97 (1)	2.7818 (7)	173 (1)
OW13—H13A⋯O1^xi	0.82 (1)	1.98 (1)	2.7932 (7)	172 (1)
OW13—H13B⋯O21^x	0.82 (1)	1.98 (1)	2.7931 (7)	170 (1)
OW14—H14A⋯O21^xii	0.82 (1)	1.98 (1)	2.8002 (7)	174 (1)
OW14—H14B⋯O31^viii	0.82 (1)	2.00 (1)	2.8061 (7)	169 (1)
Symmetry codes: (i) x, y, z+1; (ii) $[x, -y-{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) x+1, y, z; (iv) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (v) $[x, -y-{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (vi) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vii) -x+2, -y, -z+1; (viii) -x+1, -y, -z+1; (ix) -x+1, -y-1, -z+1; (x) $[-x+1, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (xi) -x+1, -y, -z+2; (xii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 3
A chain of edge-sharing NaO₆ octahedra in the crystal structure of Na₂SO₄·10H₂O. Displacement parameters are drawn at the 99% probability level. [Symmetry code: (i) x, −y − $[{1\over 2}]$ , z − $[{1\over 2}]$ .]

Figure 4
The crystal structure of Na₂SO₄·10H₂O in a projection along [110]. NaO₆ polyhedra are light blue, SeO₄ tetrahedra are red, O atoms are white and H atoms are grey. Hydrogen bonds have been omitted for clarity.

3. Synthesis and crystallization

Anhydrous Na₂SeO₄ was prepared according to the method compiled by Brauer (1963 ) by adding a half-concentrated aqueous selenic acid solution (ca 60 wt%) to an excess of an Na₂CO₃ solution. The resulting solution was heated until a considerable amount of the neutralization product had crystallized. The crystal mush was then separated by suction filtration of the still-hot solution and dried in air. X-ray powder diffraction revealed a single-phase material. The Na₂SeO₄ crystals were then dissolved in small amounts of water and kept at ca 300, 293 and 280 K until complete evaporation of the solvent. According to Rietveld refinements using TOPAS (Bruker, 2013 ) the product crystallized at 300 K consisted of Na₂SeO₄ and Na₂SeO₄·1.5H₂O in an approximate 9:1 weight ratio, the product crystallized at 290 K consisted of Na₂SeO₄ and Na₂SeO₄·1.5H₂O in an approximate 5:1 ratio, and the product crystallized at 280 K consisted of Na₂SeO₄, Na₂SeO₄·1.5H₂O and Na₂SeO₄·10H₂O in an approximate 5:4:1 ratio. The crystal forms of the three obtained phases were different and were used for separation. Crystals of the anhydrous phase had mainly a lath-like form, of the sesquihydrate a plate-like form, and of the decahydrate a pinacoidal form. All obtained hydrate phases tend to weather when stored under ambient conditions.

4. Refinement

Unit-cell determinations revealed isotypic relationships with the corresponding chromate phases (Kahlenberg, 2012). For better comparison of the isotypic structures, atom labels and the setting of the unit cells of the selenate compounds were retained, and the coordinates of the non-H atoms of the chromate structure were used as starting parameters for refinement [note that the unit cell of Na₂CrO₄·1.5H₂O is given in the non-standard setting F2dd of space group No. 43 (standard setting Fdd2)]. The H atoms of the water molecules were located from difference maps and were refined with a common U_iso parameter and a fixed O—H distance of 0.82 Å. Experimental details are given in Table 1.

Table 5
Experimental details

	1.5-hydrate	10-hydrate
Crystal data
Chemical formula	Na₂SeO₄·1.5H₂O	Na₂O₄Se·10H₂O
M_r	215.96	369.10
Crystal system, space group	Orthorhombic, F2dd	Monoclinic, P2₁/c
Temperature (K)	100	100
a, b, c (Å)	6.7533 (8), 8.6299 (10), 35.206 (4)	11.5758 (6), 10.4911 (5), 12.9570 (7)
α, β, γ (°)	90, 90, 90	90, 107.995 (3), 90
V (Å³)	2051.8 (4)	1496.56 (13)
Z	16	4
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	7.43	2.62
Crystal size (mm)	0.20 × 0.15 × 0.10	0.32 × 0.18 × 0.09

Data collection
Diffractometer	Bruker SMART CCD	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2008 )	Multi-scan (SADABS; Bruker, 2013)
T_min, T_max	0.488, 0.584	0.642, 0.749
No. of measured, independent and observed [I > 2σ(I)] reflections	8363, 1824, 1723	213856, 11218, 9196
R_int	0.032	0.054
(sin θ/λ)_max (Å⁻¹)	0.762	0.965

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.019, 0.042, 0.99	0.021, 0.046, 1.05
No. of reflections	1824	11218
No. of parameters	89	215
No. of restraints	4	20
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.91, −0.37	0.48, −0.52
Absolute structure	Flack (1983 ), 823 Friedel pairs	–
Absolute structure parameter	0.025 (8)	–
Computer programs: SMART, SAINT, SAINT-Plus and APEX2 (Bruker, 2013, 2013), SHELXS97 and SHELXL97 (Sheldrick, 2008 ), ATOMS (Dowty, 2006 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 1004274; 1004275

Crystal structure: contains datablocks 1.5-hydrate, 10-hydrate, global. DOI: 10.1107/S1600536814011799/hb0010sup1.cif

Structure factors: contains datablock 1.5-hydrate. DOI: 10.1107/S1600536814011799/hb00101.5-hydratesup2.hkl

checkCIF report

Chemical context top

Based on recent studies in the system Na/Se/O/H that revealed dimorphism of the phases NaHSeO₄ and Na₅H₃(SeO₄)₄(H₂O)₂ (Pollitt & Weil, 2014), we became interested in the structure determination of hydrous phases of Na₂SeO₄. Although the first report of the decahydrate of Na₂SeO₄ dates back to 1827 (Mitscherlich, 1827), a detailed structure report for this compound has not been published so far. Mitscherlich (1827) also recognized an isomorphic relationship of Na₂SeO₄.10H₂O with Na₂SO₄.10H₂O (Glauber's salt or mirabilite as a mineral species). This relation was later confirmed by Rosický (1908) and by Ruben et al. (1961) on the basis of unit-cell determinations using diffraction methods. Another hydrous phase of Na₂SeO₄ reported in the literature is the metastable heptahydrate that crystallized from supersaturated Na₂SeO₄ solutions only when seeded with Na₂SO₄.7H₂O nuclei below 293 K (Belarew, 1965).

Structural commentary top

Na₂SeO₄.1.5H₂O is isotypic with the corresponding chromate (Kahlenberg, 2012) and is the second example of the Na₂XO₄.1.5H₂O structure family. The main building blocks of this structure type are distorted [NaO₅(H₂O)₂] (Na1) monocapped octahedra, distorted [NaO₄(H₂O)] square pyramids (Na2) (Fig. 1) and rather regular XO₄ (X = Se, Cr) tetrahedra. These building blocks are linked through common corners and edges into a three-dimensional framework structure (Fig. 2). Hydrogen bonds of the type O—H···O between the coordinating water molecules and parts of the framework O atoms provide additional stabilization (Table 1). The bond lengths (Table 2) and angles within the individual building blocks of the selenate and chromate structures are more or less identical with mean distances of SeO₄ = 1.641; CrO₄ = 1.651; Na1O₇ = 2.514 (selenate), 2.505 (chromate); Na2O₅ = 2.350 (selenate), 2.360 Å (chromate).

Isotypism has been reported for several Na₂XO₄.10H₂O (X = S, Se, Cr, W, Mo) phases (Ruben et al., 1961), but only the structures of X = S (Levy & Lisensky, 1978; Prescott et al., 2001) and Cr (Kahlenberg, 2012) have been determined so far. As expected, the general structural set-up in the isotypic Na₂XO₄.10H₂O structures is very similar. Each of the two Na⁺ cations is octahedrally surrounded [mean Na—O distance of the two octahedra is 2.420 Å (see Table 3); sulfate analogue (Prescott et al., 2001): 2.415 Å; chromate analogue (Kahlenberg, 2012): 2.423 Å]. The [NaO₆] octahedra are linked via edge-sharing into zigzag chains (Fig. 3) running parallel to [001]. These chains are linked with neighbouring chains and intermediate SeO₄ tetrahedra (mean Se—O distance 1.639; sulfate 1.488, chromate 1.647 Å) and non-coordinating lattice water molecules through O—H···O hydrogen bonds of medium strength (Table 4) to build up the crystal structure (Fig. 4). The most important difference between the structures of the three Na₂XO₄.10H₂O (X = S, Se, Cr) phases is the missing disorder of the XO₄ tetrahedron in the selenate compound that has been observed in the sulfate compound on basis of single-crystal neutron data (Levy & Lisensky, 1978) and single-crystal X-ray data (Prescott et al., 2001), or for the chromate compound on basis of single-crystal X-ray data (Kahlenberg, 2012).

Synthesis and crystallization top

Anhydrous Na₂SeO₄ was prepared according to the method compiled by Brauer (1963) by adding a half-concentrated aqueous selenic acid solution (ca 60 wt%) to an excess of an Na₂CO₃ solution. The resulting solution was heated until a considerable amount of the neutralization product had crystallized. The crystal mush was then separated by suction filtration of the still hot solution and dried in air. X-ray powder diffraction revealed a single-phase material. The Na₂SeO₄ crystals were then dissolved in small amounts of water and kept at ca 300, 293 and 280 K until complete evaporation of the solvent. According to Rietveld refinements using TOPAS (Bruker, 2013) the product crystallized at 300 K consisted of Na₂SeO₄ and Na₂SeO₄.1.5H₂O in an approximate 9:1 ratio, the product crystallized at 290 K consisted of Na₂SeO₄ and Na₂SeO₄.1.5H₂O in an approximate 5:1 ratio, and the product crystallized at 280 K consisted of Na₂SeO₄, Na₂SeO₄.1.5H₂O and Na₂SeO₄.10H₂O in an approximate 5:4:1 ratio. The crystal forms of the three obtained phases were different and were used for separation. Crystals of the anhydrous phase had mainly a lath-like form, of the sesquihydrate a plate-like form, and of the decahydrate a pinacoidal form. All obtained hydrate phases tend to weather when stored under ambient conditions.

Refinement top

Unit-cell determinations revealed isotypic relationships with the corresponding chromate phases (Kahlenberg, 2012). For better comparison of the isotypic structures, atom labels and the setting of the unit cells of the selenate compounds were retained, and the coordinates of the non-H atoms of the chromate structure were used as starting parameters for refinement [note that the unit cell of Na₂CrO₄.1.5H₂O is given in the non-standard setting F2dd of space group No. 43 (standard setting Fdd2)]. The H atoms of the water molecules were located from difference maps and were refined with a common U_iso parameter and a fixed O—H distance of 0.82 Å.

Related literature top

For related literature, see: Belarew (1965); Brauer (1963); Bruker (2013); Kahlenberg (2012); Levy & Lisensky (1978); Mitscherlich (1827); Pollitt & Weil (2014); Prescott et al. (2001); Rosický (1908); Ruben et al. (1961).

Computing details top

Data collection: SMART (Bruker, 2008) for 1.5-hydrate; APEX2 (Bruker, 2013) for 10-hydrate. Cell refinement: SAINT (Bruker, 2008) for 1.5-hydrate; SAINT-Plus (Bruker, 2013) for 10-hydrate. Data reduction: SAINT (Bruker, 2008) for 1.5-hydrate; SAINT-Plus (Bruker, 2013) for 10-hydrate. For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. The NaO₅ and NaO₇ polyhedra in the structure of Na₂SO₄·1.5H₂O. Displacement parameters are drawn at the 99% probability level. [Symmetry codes: (i) x + 1/4, y + 1/4, -z + 1/4; (ii) x + 1/2, y + 1/2, z; (iii) x + 1, y, z; (iv) x - 1/2, -y, -z + 1/2; (v) x - 1, y, z; (vi) x, -y + 1/2, -z + 1/2; (vii) x - 1/2, y - 1/2, z.]
	Fig. 2. The crystal structure of Na₂SO₄·1.5H₂O in a projection along [110]. NaO₅ polyhedra are turquoise, NaO₇ polyhedra are blue, SeO₄ tetrahedra are red and H atoms are grey. Hydrogen bonds have been omitted for clarity.
	Fig. 3. A chain of edge-sharing NaO₆ octahedra in the crystal structure of Na₂SO₄.10H₂O. Displacement parameters are drawn at the 99% probability level. [Symmetry code: (i) x, -y - 1/2, z - 1/2.]
	Fig. 4. The crystal structure of Na₂SO₄.10H₂O in a projection along [110]. NaO₆ polyhedra are light blue, SeO₄ tetrahedra are red, O atoms are white and H atoms are grey. Hydrogen bonds have been omitted for clarity.

(1.5-hydrate) Sodium selenate sesquihydrate top

Crystal data top

Na₂SeO₄·1.5H₂O	F(000) = 1648
M_r = 215.96	D_x = 2.797 Mg m⁻³
Orthorhombic, F2dd	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: F -2d 2	Cell parameters from 4199 reflections
a = 6.7533 (8) Å	θ = 3.9–32.8°
b = 8.6299 (10) Å	µ = 7.43 mm⁻¹
c = 35.206 (4) Å	T = 100 K
V = 2051.8 (4) Å³	Fragment, colourless
Z = 16	0.20 × 0.15 × 0.10 mm

Data collection top

Bruker SMART CCD diffractometer	1824 independent reflections
Radiation source: fine-focus sealed tube	1723 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.032
ω scan	θ_max = 32.8°, θ_min = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −10→9
T_min = 0.488, T_max = 0.584	k = −12→12
8363 measured reflections	l = −53→53

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.019	H-atom parameters constrained
wR(F²) = 0.042	w = 1/[σ²(F_o²) + (0.0148P)²] where P = (F_o² + 2F_c²)/3
S = 0.99	(Δ/σ)_max < 0.001
1824 reflections	Δρ_max = 0.91 e Å⁻³
89 parameters	Δρ_min = −0.37 e Å⁻³
4 restraints	Absolute structure: Flack (1983), 823 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.025 (8)

Crystal data top

Na₂SeO₄·1.5H₂O	V = 2051.8 (4) Å³
M_r = 215.96	Z = 16
Orthorhombic, F2dd	Mo Kα radiation
a = 6.7533 (8) Å	µ = 7.43 mm⁻¹
b = 8.6299 (10) Å	T = 100 K
c = 35.206 (4) Å	0.20 × 0.15 × 0.10 mm

Data collection top

Bruker SMART CCD diffractometer	1824 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	1723 reflections with I > 2σ(I)
T_min = 0.488, T_max = 0.584	R_int = 0.032
8363 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.019	H-atom parameters constrained
wR(F²) = 0.042	Δρ_max = 0.91 e Å⁻³
S = 0.99	Δρ_min = −0.37 e Å⁻³
1824 reflections	Absolute structure: Flack (1983), 823 Friedel pairs
89 parameters	Absolute structure parameter: 0.025 (8)
4 restraints

Special details top

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	U_iso*/U_eq
Se1	0.45783 (6)	0.26019 (2)	0.188204 (5)	0.00624 (5)
Na1	0.94725 (16)	0.40728 (9)	0.15499 (2)	0.01065 (16)
Na2	0.14581 (15)	0.04335 (11)	0.24656 (3)	0.01009 (18)
O1	0.6662 (2)	0.35383 (19)	0.19642 (4)	0.0091 (3)
O2	0.4372 (3)	0.11507 (17)	0.21780 (4)	0.0097 (3)
O3	0.4561 (3)	0.18930 (16)	0.14509 (4)	0.0096 (3)
O4	0.2752 (2)	0.38446 (19)	0.19358 (5)	0.0095 (3)
OW5	0.9382 (3)	0.13500 (18)	0.14734 (4)	0.0119 (3)
OW6	0.9204 (3)	0.2500	0.2500	0.0122 (5)
H1	0.898 (5)	0.076 (3)	0.1639 (7)	0.033 (6)*
H2	1.026 (4)	0.088 (4)	0.1364 (8)	0.033 (6)*
H3	0.844 (4)	0.232 (4)	0.2676 (7)	0.033 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.00707 (8)	0.00585 (8)	0.00581 (7)	−0.00002 (8)	0.00015 (9)	−0.00019 (7)
Na1	0.0128 (4)	0.0089 (4)	0.0103 (4)	−0.0009 (4)	0.0007 (4)	0.0004 (3)
Na2	0.0106 (4)	0.0103 (4)	0.0094 (4)	−0.0018 (3)	0.0014 (3)	−0.0007 (3)
O1	0.0081 (8)	0.0091 (7)	0.0100 (7)	−0.0028 (6)	0.0001 (6)	−0.0007 (6)
O2	0.0106 (8)	0.0081 (6)	0.0106 (6)	−0.0013 (6)	−0.0004 (6)	0.0046 (5)
O3	0.0128 (7)	0.0093 (6)	0.0068 (6)	−0.0010 (8)	−0.0005 (7)	−0.0033 (5)
O4	0.0101 (7)	0.0093 (7)	0.0091 (7)	0.0035 (6)	0.0010 (6)	−0.0011 (6)
OW5	0.0131 (9)	0.0096 (7)	0.0129 (7)	0.0004 (7)	0.0036 (7)	0.0014 (5)
OW6	0.0112 (15)	0.0156 (11)	0.0097 (9)	0.000	0.000	0.0036 (8)

Geometric parameters (Å, º) top

Na1—OW5	2.3660 (18)	Na2—O2^iv	2.3301 (18)
Na1—O3ⁱ	2.4157 (19)	Na2—OW6^v	2.3480 (18)
Na1—O1	2.4379 (18)	Na2—O4^vi	2.3651 (19)
Na1—O3ⁱⁱ	2.4594 (16)	Na2—O1^vii	2.4103 (18)
Na1—OW5ⁱ	2.465 (2)	Se1—O2	1.6350 (14)
Na1—O4ⁱⁱⁱ	2.6057 (19)	Se1—O3	1.6367 (14)
Na1—O2ⁱⁱ	2.8475 (17)	Se1—O4	1.6451 (16)
Na2—O2	2.298 (2)	Se1—O1	1.6481 (15)

O2—Se1—O3	107.70 (7)	O2^iv—Na2—O4^vi	84.15 (6)
O2—Se1—O4	111.23 (9)	OW6^v—Na2—O4^vi	89.63 (6)
O3—Se1—O4	110.19 (9)	O2—Na2—O1^vii	79.12 (6)
O2—Se1—O1	109.66 (8)	O2^iv—Na2—O1^vii	91.76 (6)
O3—Se1—O1	110.61 (9)	OW6^v—Na2—O1^vii	126.16 (6)
O4—Se1—O1	107.47 (8)	O4^vi—Na2—O1^vii	144.12 (7)
OW5—Na1—O3ⁱ	90.74 (6)	Se1—O1—Na2ⁱⁱ	114.37 (8)
OW5—Na1—O1	81.96 (6)	Se1—O1—Na1	130.73 (9)
O3ⁱ—Na1—O1	86.18 (7)	Na2ⁱⁱ—O1—Na1	110.74 (7)
OW5—Na1—O3ⁱⁱ	165.30 (6)	Se1—O2—Na2	124.06 (9)
O3ⁱ—Na1—O3ⁱⁱ	78.45 (5)	Se1—O2—Na2^viii	137.82 (10)
O1—Na1—O3ⁱⁱ	106.93 (7)	Na2—O2—Na2^viii	97.03 (5)
OW5—Na1—OW5ⁱ	81.63 (6)	Se1—O2—Na1^vii	89.17 (6)
O3ⁱ—Na1—OW5ⁱ	84.75 (6)	Na2—O2—Na1^vii	101.13 (6)
O1—Na1—OW5ⁱ	161.11 (7)	Na2^viii—O2—Na1^vii	91.96 (6)
O3ⁱⁱ—Na1—OW5ⁱ	87.43 (6)	Se1—O3—Na1^ix	135.64 (11)
OW5—Na1—O4ⁱⁱⁱ	90.36 (7)	Se1—O3—Na1^vii	103.80 (7)
O3ⁱ—Na1—O4ⁱⁱⁱ	164.16 (7)	Na1^ix—O3—Na1^vii	90.39 (6)
O1—Na1—O4ⁱⁱⁱ	109.61 (5)	Se1—O4—Na2^vi	123.44 (9)
O3ⁱⁱ—Na1—O4ⁱⁱⁱ	97.35 (7)	Se1—O4—Na1^v	128.80 (9)
OW5ⁱ—Na1—O4ⁱⁱⁱ	79.79 (6)	Na2^vi—O4—Na1^v	97.50 (6)
OW5—Na1—O2ⁱⁱ	135.50 (6)	Na1—OW5—Na1^ix	91.42 (7)
O3ⁱ—Na1—O2ⁱⁱ	118.59 (6)	Na1—OW5—H1	123 (2)
O1—Na1—O2ⁱⁱ	68.66 (5)	Na1^ix—OW5—H1	111 (2)
O3ⁱⁱ—Na1—O2ⁱⁱ	59.17 (5)	Na1—OW5—H2	122 (3)
OW5ⁱ—Na1—O2ⁱⁱ	130.17 (6)	Na1^ix—OW5—H2	100 (2)
O4ⁱⁱⁱ—Na1—O2ⁱⁱ	70.31 (5)	H1—OW5—H2	106 (3)
O2—Na2—O2^iv	155.95 (7)	Na2^x—OW6—Na2ⁱⁱⁱ	99.15 (10)
O2—Na2—OW6^v	111.92 (6)	Na2^x—OW6—H3	121 (3)
O2^iv—Na2—OW6^v	91.48 (6)	Na2ⁱⁱⁱ—OW6—H3	108 (3)
O2—Na2—O4^vi	90.30 (7)

Symmetry codes: (i) x+1/4, y+1/4, −z+1/4; (ii) x+1/2, y+1/2, z; (iii) x+1, y, z; (iv) x−1/2, −y, −z+1/2; (v) x−1, y, z; (vi) x, −y+1/2, −z+1/2; (vii) x−1/2, y−1/2, z; (viii) x+1/2, −y, −z+1/2; (ix) x−1/4, y−1/4, −z+1/4; (x) x+1, −y+1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OW5—H1···O4^xi	0.82 (1)	2.13 (1)	2.922 (2)	164 (3)
OW5—H2···O3^xii	0.82 (1)	2.08 (1)	2.891 (2)	169 (3)
OW6—H3···O1^vi	0.82 (1)	1.90 (1)	2.703 (2)	167 (4)

Symmetry codes: (vi) x, −y+1/2, −z+1/2; (xi) x+1/2, y−1/2, z; (xii) x+3/4, y−1/4, −z+1/4.

(10-hydrate) Sodium selenate decahydrate top

Crystal data top

Na₂O₄Se·10H₂O	F(000) = 752
M_r = 369.10	D_x = 1.638 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9719 reflections
a = 11.5758 (6) Å	θ = 2.7–40.1°
b = 10.4911 (5) Å	µ = 2.62 mm⁻¹
c = 12.9570 (7) Å	T = 100 K
β = 107.995 (3)°	Fragment, colourless
V = 1496.56 (13) Å³	0.32 × 0.18 × 0.09 mm
Z = 4

Data collection top

Bruker APEXII CCD diffractometer	11218 independent reflections
Radiation source: fine-focus sealed tube	9196 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.054
ω and ϕ scans	θ_max = 43.3°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2013)	h = −22→22
T_min = 0.642, T_max = 0.749	k = −20→20
213856 measured reflections	l = −24→24

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.021	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.046	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.017P)² + 0.2899P] where P = (F_o² + 2F_c²)/3
11218 reflections	(Δ/σ)_max = 0.006
215 parameters	Δρ_max = 0.48 e Å⁻³
20 restraints	Δρ_min = −0.52 e Å⁻³

Crystal data top

Na₂O₄Se·10H₂O	V = 1496.56 (13) Å³
M_r = 369.10	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.5758 (6) Å	µ = 2.62 mm⁻¹
b = 10.4911 (5) Å	T = 100 K
c = 12.9570 (7) Å	0.32 × 0.18 × 0.09 mm
β = 107.995 (3)°

Data collection top

Bruker APEXII CCD diffractometer	11218 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2013)	9196 reflections with I > 2σ(I)
T_min = 0.642, T_max = 0.749	R_int = 0.054
213856 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.021	20 restraints
wR(F²) = 0.046	H-atom parameters constrained
S = 1.05	Δρ_max = 0.48 e Å⁻³
11218 reflections	Δρ_min = −0.52 e Å⁻³
215 parameters

Special details top

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

	x	y	z	U_iso*/U_eq
Se1	0.752121 (5)	0.139467 (5)	0.740658 (4)	0.00723 (1)
Na1	0.74307 (2)	−0.24486 (3)	0.97851 (2)	0.01112 (5)
Na2	0.75630 (2)	−0.11228 (3)	0.23666 (2)	0.01081 (4)
O1	0.86910 (4)	0.19770 (5)	0.83551 (4)	0.01211 (7)
O21	0.73195 (4)	0.21974 (4)	0.62765 (4)	0.01245 (8)
O31	0.63136 (4)	0.15034 (5)	0.78083 (4)	0.01257 (7)
O41	0.77699 (5)	−0.00971 (4)	0.71826 (4)	0.01330 (8)
OW5	0.85363 (4)	−0.21683 (5)	0.85304 (4)	0.01236 (7)
OW6	0.64473 (4)	−0.27987 (5)	0.11583 (4)	0.01269 (8)
OW7	0.87675 (5)	0.03985 (5)	0.36196 (4)	0.01443 (8)
OW8	0.87052 (5)	−0.42968 (5)	0.05311 (4)	0.01472 (8)
OW9	0.88112 (4)	−0.10907 (5)	0.11623 (4)	0.01306 (8)
OW10	0.61813 (4)	−0.39325 (5)	0.84832 (4)	0.01310 (8)
OW11	0.61541 (5)	−0.06034 (5)	0.91589 (4)	0.01584 (9)
OW12	0.63321 (5)	0.04187 (5)	0.11747 (4)	0.01397 (8)
OW13	0.09783 (5)	−0.14961 (5)	0.94520 (4)	0.01473 (8)
OW14	0.39997 (5)	−0.34873 (5)	0.08502 (4)	0.01467 (8)
H5A	0.8345 (13)	−0.1472 (6)	0.8240 (11)	0.0412 (9)*
H5B	0.9267 (3)	−0.2110 (14)	0.8845 (10)	0.0412 (9)*
H6A	0.5712 (2)	−0.2905 (14)	0.1003 (11)	0.0412 (9)*
H6B	0.6722 (13)	−0.3481 (7)	0.1436 (11)	0.0412 (9)*
H7A	0.8618 (13)	0.1162 (3)	0.3535 (12)	0.0412 (9)*
H7B	0.8709 (12)	0.0169 (13)	0.4206 (5)	0.0412 (9)*
H8A	0.8415 (11)	−0.4602 (12)	0.0978 (8)	0.0412 (9)*
H8B	0.9440 (2)	−0.4401 (13)	0.0788 (10)	0.0412 (9)*
H9A	0.9508 (4)	−0.1364 (12)	0.1394 (11)	0.0412 (9)*
H9B	0.8892 (13)	−0.0359 (5)	0.0973 (11)	0.0412 (9)*
H10A	0.6143 (13)	−0.4669 (4)	0.8683 (11)	0.0412 (9)*
H10B	0.5473 (4)	−0.3767 (12)	0.8146 (10)	0.0412 (9)*
H11A	0.6205 (12)	−0.0062 (10)	0.8719 (8)	0.0412 (9)*
H11B	0.6254 (12)	−0.0213 (11)	0.9728 (6)	0.0412 (9)*
H12A	0.6618 (12)	0.1138 (5)	0.1205 (12)	0.0412 (9)*
H12B	0.5615 (3)	0.0506 (13)	0.1131 (11)	0.0412 (9)*
H13A	0.1146 (13)	−0.1610 (13)	1.0108 (2)	0.0412 (9)*
H13B	0.1423 (10)	−0.1952 (11)	0.9226 (10)	0.0412 (9)*
H14A	0.3586 (11)	−0.3337 (13)	0.0224 (4)	0.0412 (9)*
H14B	0.3809 (12)	−0.2944 (10)	0.1223 (9)	0.0412 (9)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.00796 (2)	0.00652 (2)	0.00716 (2)	0.00002 (2)	0.00228 (1)	0.00003 (2)
Na1	0.01190 (11)	0.01128 (11)	0.01052 (11)	−0.00036 (9)	0.00396 (9)	−0.00045 (8)
Na2	0.01176 (11)	0.01011 (10)	0.01050 (10)	0.00016 (9)	0.00333 (8)	0.00013 (8)
O1	0.00993 (17)	0.01300 (18)	0.01144 (17)	−0.00124 (14)	0.00041 (14)	−0.00188 (14)
O21	0.0162 (2)	0.01156 (18)	0.00963 (17)	0.00085 (15)	0.00404 (15)	0.00315 (14)
O31	0.00980 (17)	0.0156 (2)	0.01373 (18)	−0.00012 (15)	0.00571 (14)	−0.00071 (15)
O41	0.0190 (2)	0.00658 (16)	0.01498 (19)	0.00140 (15)	0.00617 (16)	−0.00054 (14)
OW5	0.01162 (18)	0.01215 (18)	0.01230 (18)	−0.00102 (15)	0.00222 (14)	0.00144 (14)
OW6	0.01137 (18)	0.01229 (19)	0.01431 (19)	−0.00005 (15)	0.00381 (15)	0.00107 (14)
OW7	0.0160 (2)	0.01212 (19)	0.01404 (19)	−0.00039 (16)	0.00291 (16)	0.00042 (15)
OW8	0.01307 (19)	0.0172 (2)	0.0149 (2)	0.00141 (16)	0.00583 (16)	0.00232 (16)
OW9	0.01073 (18)	0.01301 (18)	0.0154 (2)	0.00022 (14)	0.00393 (15)	0.00012 (15)
OW10	0.01081 (18)	0.01338 (18)	0.01408 (19)	−0.00065 (15)	0.00237 (15)	0.00038 (15)
OW11	0.0166 (2)	0.0150 (2)	0.0176 (2)	0.00205 (17)	0.00788 (17)	0.00367 (16)
OW12	0.01201 (19)	0.01201 (19)	0.0171 (2)	−0.00065 (15)	0.00339 (16)	0.00122 (15)
OW13	0.01312 (19)	0.0176 (2)	0.01342 (19)	0.00137 (16)	0.00410 (15)	0.00051 (16)
OW14	0.0148 (2)	0.0152 (2)	0.01333 (19)	0.00127 (16)	0.00335 (15)	−0.00077 (15)

Geometric parameters (Å, º) top

Na1—OW5	2.3776 (6)	Na2—OW7	2.3935 (6)
Na1—OW6ⁱ	2.4181 (6)	Na2—OW9	2.4325 (6)
Na1—OW11	2.4184 (6)	Na2—OW6	2.4415 (6)
Na1—OW10	2.4194 (6)	Na2—OW10ⁱⁱ	2.4667 (6)
Na1—OW8ⁱ	2.4473 (6)	Se1—O41	1.6335 (5)
Na1—OW9ⁱ	2.4507 (6)	Se1—O31	1.6394 (5)
Na2—OW12	2.3814 (6)	Se1—O1	1.6398 (5)
Na2—OW5ⁱⁱ	2.3891 (6)	Se1—O21	1.6421 (5)

O41—Se1—O31	109.72 (2)	Na1—OW5—H5A	107.3 (10)
O41—Se1—O1	109.88 (3)	Na2ⁱⁱⁱ—OW5—H5A	111.8 (10)
O31—Se1—O1	108.89 (2)	Na1—OW5—H5B	111.1 (10)
O41—Se1—O21	108.50 (2)	Na2ⁱⁱⁱ—OW5—H5B	125.7 (10)
O31—Se1—O21	110.31 (2)	H5A—OW5—H5B	104.6 (14)
O1—Se1—O21	109.53 (2)	Na1^iv—OW6—Na2	94.959 (19)
OW5—Na1—OW6ⁱ	175.60 (2)	Na1^iv—OW6—H6A	122.0 (10)
OW5—Na1—OW11	94.230 (19)	Na2—OW6—H6A	124.0 (10)
OW6ⁱ—Na1—OW11	89.467 (19)	Na1^iv—OW6—H6B	104.4 (10)
OW5—Na1—OW10	86.270 (19)	Na2—OW6—H6B	106.9 (10)
OW6ⁱ—Na1—OW10	95.70 (2)	H6A—OW6—H6B	102.8 (13)
OW11—Na1—OW10	96.28 (2)	Na2—OW7—H7A	120.4 (10)
OW5—Na1—OW8ⁱ	88.961 (19)	Na2—OW7—H7B	103.6 (10)
OW6ⁱ—Na1—OW8ⁱ	87.276 (19)	H7A—OW7—H7B	109.7 (14)
OW11—Na1—OW8ⁱ	176.39 (2)	Na1^iv—OW8—H8A	105.1 (10)
OW10—Na1—OW8ⁱ	85.59 (2)	Na1^iv—OW8—H8B	133.6 (10)
OW5—Na1—OW9ⁱ	93.341 (19)	H8A—OW8—H8B	105.2 (13)
OW6ⁱ—Na1—OW9ⁱ	84.368 (19)	Na2—OW9—Na1^iv	94.36 (2)
OW11—Na1—OW9ⁱ	88.42 (2)	Na2—OW9—H9A	118.2 (10)
OW10—Na1—OW9ⁱ	175.30 (2)	Na1^iv—OW9—H9A	114.2 (10)
OW8ⁱ—Na1—OW9ⁱ	89.72 (2)	Na2—OW9—H9B	110.5 (10)
OW12—Na2—OW5ⁱⁱ	171.87 (2)	Na1^iv—OW9—H9B	115.8 (10)
OW12—Na2—OW7	95.37 (2)	H9A—OW9—H9B	104.3 (13)
OW5ⁱⁱ—Na2—OW7	90.57 (2)	Na1—OW10—Na2ⁱⁱⁱ	92.153 (19)
OW12—Na2—OW9	85.96 (2)	Na1—OW10—H10A	117.7 (10)
OW5ⁱⁱ—Na2—OW9	99.063 (19)	Na2ⁱⁱⁱ—OW10—H10A	108.3 (10)
OW7—Na2—OW9	95.10 (2)	Na1—OW10—H10B	121.3 (10)
OW12—Na2—OW6	88.92 (2)	Na2ⁱⁱⁱ—OW10—H10B	113.9 (10)
OW5ⁱⁱ—Na2—OW6	85.252 (19)	H10A—OW10—H10B	103.0 (13)
OW7—Na2—OW6	175.61 (2)	Na1—OW11—H11A	128.3 (10)
OW9—Na2—OW6	84.260 (19)	Na1—OW11—H11B	101.3 (10)
OW12—Na2—OW10ⁱⁱ	89.884 (19)	H11A—OW11—H11B	105.1 (13)
OW5ⁱⁱ—Na2—OW10ⁱⁱ	84.965 (19)	Na2—OW12—H12A	116.2 (10)
OW7—Na2—OW10ⁱⁱ	86.209 (19)	Na2—OW12—H12B	120.7 (10)
OW9—Na2—OW10ⁱⁱ	175.74 (2)	H12A—OW12—H12B	106.6 (13)
OW6—Na2—OW10ⁱⁱ	94.743 (19)	H13A—OW13—H13B	108.1 (13)
Na1—OW5—Na2ⁱⁱⁱ	95.178 (19)	H14A—OW14—H14B	105.5 (13)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OW5—H5A···O41	0.82 (1)	1.96 (1)	2.7570 (7)	164 (1)
OW5—H5B···OW13^v	0.82 (1)	2.00 (1)	2.7980 (7)	165 (1)
OW6—H6A···OW14	0.82 (1)	2.02 (1)	2.8301 (7)	168 (1)
OW6—H6B···O41ⁱⁱ	0.82 (1)	1.98 (1)	2.7791 (7)	166 (2)
OW7—H7A···O1^vi	0.82 (1)	1.97 (1)	2.7727 (7)	166 (1)
OW7—H7B···OW8ⁱⁱⁱ	0.82 (1)	1.95 (1)	2.7542 (7)	168 (1)
OW8—H8A···O41ⁱⁱ	0.82 (1)	1.95 (1)	2.7544 (7)	166 (1)
OW8—H8B···OW7^vii	0.82 (1)	1.99 (1)	2.8076 (7)	178 (1)
OW9—H9A···O1^viii	0.82 (1)	2.11 (1)	2.9152 (7)	168 (1)
OW9—H9B···OW13^ix	0.82 (1)	2.04 (1)	2.8596 (7)	177 (1)
OW10—H10A···OW14^x	0.82 (1)	2.05 (1)	2.8686 (7)	178 (2)
OW10—H10B···O31^xi	0.82 (1)	2.08 (1)	2.8920 (7)	174 (1)
OW11—H11A···O31	0.82 (1)	2.05 (1)	2.8604 (7)	171 (1)
OW11—H11B···OW12ⁱ	0.82 (1)	1.96 (1)	2.7716 (8)	168 (1)
OW12—H12A···O21^vi	0.82 (1)	1.92 (1)	2.7359 (7)	179 (1)
OW12—H12B···OW11^ix	0.82 (1)	1.97 (1)	2.7818 (7)	173 (1)
OW13—H13A···O1^xii	0.82 (1)	1.98 (1)	2.7932 (7)	172 (1)
OW13—H13B···O21^xi	0.82 (1)	1.98 (1)	2.7931 (7)	170 (1)
OW14—H14A···O21^xiii	0.82 (1)	1.98 (1)	2.8002 (7)	174 (1)
OW14—H14B···O31^ix	0.82 (1)	2.00 (1)	2.8061 (7)	169 (1)

Symmetry codes: (i) x, y, z+1; (ii) x, −y−1/2, z−1/2; (iii) x, −y−1/2, z+1/2; (v) x+1, y, z; (vi) x, −y+1/2, z−1/2; (vii) −x+2, y−1/2, −z+1/2; (viii) −x+2, −y, −z+1; (ix) −x+1, −y, −z+1; (x) −x+1, −y−1, −z+1; (xi) −x+1, y−1/2, −z+3/2; (xii) −x+1, −y, −z+2; (xiii) −x+1, y−1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) for (1.5-hydrate) top

D—H···A	D—H	H···A	D···A	D—H···A
OW5—H1···O4^viii	0.8199 (10)	2.125 (9)	2.922 (2)	164 (3)
OW5—H2···O3^ix	0.8200 (10)	2.082 (7)	2.891 (2)	169 (3)
OW6—H3···O1^vi	0.8201 (10)	1.898 (8)	2.703 (2)	167 (4)

Symmetry codes: (vi) x, −y+1/2, −z+1/2; (viii) x+1/2, y−1/2, z; (ix) x+3/4, y−1/4, −z+1/4.

Selected bond lengths (Å) for (1.5-hydrate) top

Na1—OW5	2.3660 (18)	Na2—O2^iv	2.3301 (18)
Na1—O3ⁱ	2.4157 (19)	Na2—OW6^v	2.3480 (18)
Na1—O1	2.4379 (18)	Na2—O4^vi	2.3651 (19)
Na1—O3ⁱⁱ	2.4594 (16)	Na2—O1^vii	2.4103 (18)
Na1—OW5ⁱ	2.465 (2)	Se1—O2	1.6350 (14)
Na1—O4ⁱⁱⁱ	2.6057 (19)	Se1—O3	1.6367 (14)
Na1—O2ⁱⁱ	2.8475 (17)	Se1—O4	1.6451 (16)
Na2—O2	2.298 (2)	Se1—O1	1.6481 (15)

Symmetry codes: (i) x+1/4, y+1/4, −z+1/4; (ii) x+1/2, y+1/2, z; (iii) x+1, y, z; (iv) x−1/2, −y, −z+1/2; (v) x−1, y, z; (vi) x, −y+1/2, −z+1/2; (vii) x−1/2, y−1/2, z.

Selected bond lengths (Å) for (10-hydrate) top

Na1—OW5	2.3776 (6)	Na2—OW7	2.3935 (6)
Na1—OW6ⁱ	2.4181 (6)	Na2—OW9	2.4325 (6)
Na1—OW11	2.4184 (6)	Na2—OW6	2.4415 (6)
Na1—OW10	2.4194 (6)	Na2—OW10ⁱⁱ	2.4667 (6)
Na1—OW8ⁱ	2.4473 (6)	Se1—O41	1.6335 (5)
Na1—OW9ⁱ	2.4507 (6)	Se1—O31	1.6394 (5)
Na2—OW12	2.3814 (6)	Se1—O1	1.6398 (5)
Na2—OW5ⁱⁱ	2.3891 (6)	Se1—O21	1.6421 (5)

Symmetry codes: (i) x, y, z+1; (ii) x, −y−1/2, z−1/2.

Hydrogen-bond geometry (Å, º) for (10-hydrate) top

D—H···A	D—H	H···A	D···A	D—H···A
OW5—H5A···O41	0.8197 (10)	1.959 (4)	2.7570 (7)	164.1 (14)
OW5—H5B···OW13ⁱⁱⁱ	0.8198 (10)	1.999 (4)	2.7980 (7)	164.7 (14)
OW6—H6A···OW14	0.8198 (10)	2.024 (3)	2.8301 (7)	167.5 (14)
OW6—H6B···O41ⁱⁱ	0.8199 (10)	1.977 (4)	2.7791 (7)	165.9 (15)
OW7—H7A···O1^iv	0.8198 (10)	1.971 (4)	2.7727 (7)	165.6 (14)
OW7—H7B···OW8^v	0.8198 (10)	1.946 (3)	2.7542 (7)	168.3 (14)
OW8—H8A···O41ⁱⁱ	0.8198 (10)	1.952 (4)	2.7544 (7)	165.9 (14)
OW8—H8B···OW7^vi	0.8197 (10)	1.9883 (13)	2.8076 (7)	178.0 (14)
OW9—H9A···O1^vii	0.8201 (10)	2.109 (3)	2.9152 (7)	167.5 (14)
OW9—H9B···OW13^viii	0.8199 (10)	2.0408 (15)	2.8596 (7)	176.6 (14)
OW10—H10A···OW14^ix	0.8199 (10)	2.0489 (13)	2.8686 (7)	178.3 (15)
OW10—H10B···O31^x	0.8199 (10)	2.0750 (18)	2.8920 (7)	174.4 (14)
OW11—H11A···O31	0.8198 (10)	2.049 (3)	2.8604 (7)	170.5 (14)
OW11—H11B···OW12ⁱ	0.8199 (10)	1.964 (3)	2.7716 (8)	168.4 (14)
OW12—H12A···O21^iv	0.8199 (10)	1.9161 (13)	2.7359 (7)	178.7 (14)
OW12—H12B···OW11^viii	0.8198 (10)	1.967 (2)	2.7818 (7)	172.5 (14)
OW13—H13A···O1^xi	0.8197 (10)	1.979 (2)	2.7932 (7)	171.7 (14)
OW13—H13B···O21^x	0.8199 (10)	1.981 (3)	2.7931 (7)	170.4 (14)
OW14—H14A···O21^xii	0.8197 (10)	1.9837 (19)	2.8002 (7)	174.0 (14)
OW14—H14B···O31^viii	0.8199 (10)	1.998 (3)	2.8061 (7)	168.5 (14)

Symmetry codes: (i) x, y, z+1; (ii) x, −y−1/2, z−1/2; (iii) x+1, y, z; (iv) x, −y+1/2, z−1/2; (v) x, −y−1/2, z+1/2; (vi) −x+2, y−1/2, −z+1/2; (vii) −x+2, −y, −z+1; (viii) −x+1, −y, −z+1; (ix) −x+1, −y−1, −z+1; (x) −x+1, y−1/2, −z+3/2; (xi) −x+1, −y, −z+2; (xii) −x+1, y−1/2, −z+1/2.

Experimental details

	(1.5-hydrate)	(10-hydrate)
Crystal data
Chemical formula	Na₂SeO₄·1.5H₂O	Na₂O₄Se·10H₂O
M_r	215.96	369.10
Crystal system, space group	Orthorhombic, F2dd	Monoclinic, P2₁/c
Temperature (K)	100	100
a, b, c (Å)	6.7533 (8), 8.6299 (10), 35.206 (4)	11.5758 (6), 10.4911 (5), 12.9570 (7)
α, β, γ (°)	90, 90, 90	90, 107.995 (3), 90
V (Å³)	2051.8 (4)	1496.56 (13)
Z	16	4
Radiation type	Mo Kα	Mo Kα
µ (mm⁻¹)	7.43	2.62
Crystal size (mm)	0.20 × 0.15 × 0.10	0.32 × 0.18 × 0.09

Data collection
Diffractometer	Bruker SMART CCD diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)	Multi-scan (SADABS; Bruker, 2013)
T_min, T_max	0.488, 0.584	0.642, 0.749
No. of measured, independent and observed [I > 2σ(I)] reflections	8363, 1824, 1723	213856, 11218, 9196
R_int	0.032	0.054
(sin θ/λ)_max (Å⁻¹)	0.762	0.965

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.019, 0.042, 0.99	0.021, 0.046, 1.05
No. of reflections	1824	11218
No. of parameters	89	215
No. of restraints	4	20
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.91, −0.37	0.48, −0.52
Absolute structure	Flack (1983), 823 Friedel pairs	?
Absolute structure parameter	0.025 (8)	?

Computer programs: SMART (Bruker, 2008), APEX2 (Bruker, 2013), SAINT (Bruker, 2008), SAINT-Plus (Bruker, 2013), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ATOMS (Dowty, 2006), publCIF (Westrip, 2010).

Acknowledgements

The X-ray centre of the Vienna University of Technology is acknowledged for providing access to the single-crystal and powder diffractometers. BB acknowledges the French government for a grant during a student exchange programme.

References

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Volume 70| Part 8| August 2014| Pages 54-57

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