Rock salt-urea-water (1/1/1) at 293 and 117 K

The crystal structure of NaCl·CH₄N₂O·H₂O has been determined at 117 K and redetermined at room temperature. It can be described as consisting of alternating `organic' and `inorganic' planar layers. While at room temperature the structure belongs to the space group I2, the low-temperature structure belongs to the space group Pn2₁m. All water O atoms are located on positions with crystallographic symmetry 2 (m) in the room-temperature (low-temperature) structure, which means that the water mol­ecules belong, in both cases, to point group mm2. During the phase transition, half of the urea mol­ecules per unit cell perform a 90° rotation about their respective C-O axes. The other half and the inorganic parts of the structure remain unaltered. The relationship between the two phases is remarkable, inasmuch as no obvious reason for the transition to occur could be found; the internal structures of all components of the two phases remain unaltered and even the inter­actions between the different parts seem to be the same before and after the transition (at least when looked at from an energetic point of view).

S1. Comment

In the Georg-Kerschensteiner-Gymnasium Müllheim there is a 30 year tradition of growing crystals by pupils (Georg-Kerschensteiner-Gymnasium Müllheim, 2008). In searching for more crystal growth experiments performable by grammar school students – and being aware of the existence of rock salt–glucose–water (1/2/1) crystals (Ferguson et al., 1991) – we have tried to grow crystals from aqueous solutions containing rock salt and urea. The growth experiments led to large single-crystal plates of which we determined the structure at ambient temperature and at 117 K. Structure analysis showed the crystals to be composed of rock salt, urea and water in the molar relation 1:1:1. Actually, NaCl.CH₄N₂O.H₂O, (I) (or NCUREA), crystals have been known for a long time (see Kleber et al., 1950); their three-dimensional structure at ambient conditions was determined by Palm & MacGillavry (1963) from two Weissenberg zero-level photographs. Our own X-ray experiments confirm and refine the results of Palm & MacGillavry (1963) but show that the structure at 117 K is different from that at room temperature.

While in principle our room-temperature structure of (I) is equal to the I2 structure described by Palm and MacGillavry (1963) there are, not surprisingly, some differences in detail. For example, the short Cl—N distance of 3.05 Å mentioned by Palm & MacGillavry (1963) is replaced by the more reasonable distance of 3.35 Å in our investigation. Furthermore, the quality of our data allowed us to localize all H atoms in the difference Fourier maps (but see the Experimental section) and to determine the correct absolute configuration.

Palm & MacGillavry (1963) have already described the structure and its relationship to the structures of urea and NaCl. In addition to their view we would like to picture the structure (Fig. 1a) as a stacking of toothed alternating `inorganic' and `organic' (001) layers (Fig. 2). The former consist of Na⁺ ions, Cl^- ions and H₂O molecules, forming infinite –Na(µ₂-OH₂)Na([µ₂-Cl]₂,µ₂-OH₂)Na– chains parallel to [100] with vicinal chains connected by O—H···Cl hydrogen bonds (Fig. 3). The Cl atoms form the `teeth' of these layers. The organic layers simply contain the urea molecules with the O3 atoms acting as `teeth'. The interface between the two different layers is stabilized by Na—O3 bonds, by four different N—H···Cl hydrogen bonds and by O—H···O hydrogen bonds. As already mentioned by Palm & MacGillavry (1963), the Na⁺ ions are octahedrally coordinated by two Cl^- ions, two water O atoms and two carbonyl O atoms (Tables 1 and 3). The Cl^- ions are twofold coordinated by two Na⁺ ions in a nonlinear manner. If hydrogen bonds to Cl (Tables 2 and 4) are included, an irregular sevenfold coordination results.

Within one organic layer, the orientation of the planar urea molecules alternates in the 〈110〉 directions by a form of local 4 operation, i.e. one molecule is transformed into the vicinal one (approximately) by mirroring at, for example, (x, y, 3/4) and a subsequent rotation by 90° about a [001] axis roughly located at (0, 1/2, z) or (1/2, 0, z). When going from one organic layer to the vicinal one in the [001] direction, there is a similar relation between two vicinal urea molecules. Here, the mirror plane is, for example, (x, y, 1/2) and the rotation axis is defined by the (approximately) coinciding axes of the two carbonyl groups [close to (0, 0, z) or (1/2, 1/2, z)].

The 117 K Pn2₁m structure of (I) (Fig. 1b) differs from the room-temperature I2 structure exclusively by the fact that this latter operation (and only this one) is replaced by a real mirror m, i.e. the rotation by 90° about the [001] axis drops out. This means that in the transition from room temperature to 117 K the inorganic layers and one of the two organic layers remain essentially the same, while in the second organic layer all urea molecules perform a synchronized 90° flip about a [001] axis defined (approximately) by their respective carbonyl groups. While a superposition of the projections of the two structures parallel [100] hardly shows any positional differences, small, but significant, differences can be seen in the second organic layers when viewed parallel to the [010] direction (Fig. 4).

The coordination polyhedra of Na and of two of the four Cl atoms remain unaltered by the transition. For the other two Cl atoms, the absolute configuration of the coordination polyhedron (including H atoms) changes; furthermore, two of the H atoms (H11 and H21) are `donated' to a given Cl atom by two different urea molecules after the transition as compared with the situation before the transition (which obviously is reversible, see the Experimental section).

Thus, hydrogen bonds are broken and reformed. There is, on the other hand, no group–subgroup relation between the two space groups I2 (room temperature) and Pn2₁m (117 K), the multiplicity of the general position being 4 in both cases. Instead, the relationship between the two structures is reflected in the fact that both space groups are maximal non-isomorphic subgroups to Im2m. As the different components of the structure do not change significantly during the transition and as even the interactions between these different parts seem to be unaffected in principle (at least when seen from an energetical point of view), we could find no obvious reason for the transition to occur.

Another question is how easily alkali halides, purely organic molecules and water form crystalline structures as a `joint venture' as in (I). As an answer to this, a search in the 2008 release of the Cambridge Structural Database (CSD; Allen, 2002) yielded some 50 structures fulfilling this condition. However, we found only nine structures [including (I)] with a 1:1:1 composition (Table 5). In most of these, the alkali ion is `captured' (i.e. multiply coordinated) by a cyclic part of the organic molecule. Only two structures [CSD refcodes CMHTRB (Fodor et al., 1971 or 1973??) and KESGUL (Fan et al., 2007)] do not show this feature and are as such comparable to (I). In contrast to the latter, in KESGUL the inorganic part consists of isolated NaI `molecules' and isolated water molecules. Details of the CMHTRB structure are not available. Finally, it should be noted that thiourea (CH₄N₂S) forms structures with CsX (X = F and Cl) and water, but the compositions are 1:4:2 and 1:4:1 in these cases (Boeyens 1968a,b).

Related literature

For related literature, see: Fan et al. (2007); Georg-Kerschensteiner-Gymnasium (2008); Palm & MacGillavry (1963).

S2. Experimental

Urea (40.0 g, 0.666 mol), NaCl (15.5 g, 0.265 mol) and H₂O (40 ml) were stirred at 303 K by a magnetic stirrer until a clear solution had formed. After slow evaporation of the water at 285 K (in a refrigerator), large crystal plates formed. The experiment was repeated. The separated solution was cooled to room temperature. A seed crystal cut from one of the crystal plates obtained in the previous experiment was added and the solution was put into the refrigerator. Large crystal plates formed comparatively rapidly in the solution. The solution was removed and the plates were dried with paper. Two small roughly isometric fragments were cut from the large crystal plates and measured in sealed capillaries. The first fragment was measured first at 117 K and then at room temperature. The second fragment was measured first at room temperature and then at 117 K.

S3. Refinement

After solution and/or refinement, the two room-temperature (and the two low-temperature) structures turned out to be essentially the same (Figs. 5 and 6). The two structures yielding the best reliability factors (the room-temperature structure of crystal 1 and the low-temperature structure of crystal 2) are referred to in the tables and figures. All H atoms were located in difference maps, but free refinement did not lead to positions of sufficient quality. Therefore, in both structures, the H atoms bonded to N atoms were treated as riding atoms, with N—H distances of 0.88 Å and with U_iso(H) values of 1.2U_eq(N). Restraints were applied to the water molecules [specify values of restraints]. The correct absolute configuration for the ambient-temperature structure, and the correct orientation of the low-temperature structure with respect to the polar-axis direction, were established by means of the Flack ( 1983) parameters, although these have no chemical significance.

Computing details

For both compounds, data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SCHAKAL99 (Keller, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The room-temperature I2 (a) and low-temperature Pn21m (b) structures of (I) (view parallel to [100]). All x values of corresponding atoms differ by approximately 0.25 (before and after the transition, see Fig. 4). The two structures differ significantly only in the shaded range (location of one-half of the amide groups). In (b), atom Na2 is positioned exactly behind Na1.
	Fig. 2. A ball-and-stick model and a space-filling model of the room-temperature structure of (I) superimposed, as seen parallel to [010]. In the space-filling model, the atoms of the inorganic layers have been shaded grey.
	Fig. 3. An inorganic layer of (I), as seen parallel to [101], with O3 atoms and O—H···O hydrogen bonds added.
	Fig. 4. : A superimposition of the room-temperature structure (red solid lines) and the low temperature structure (blue dashed lines) of (I) as seen parallel to [0–10]. After aligning both a vectors vertically, prior to superimposition the room temperature structure has been rotated by 0.076° counterclockwise to account for the difference of 0.152° between the monoclinic angle and 90°. The point of coincidence in the center is marked by "*".
	Fig. 5. : The molecular structure of (I) at room temperature. Displacement ellipsoids are shown at the ??% probability level.
	Fig. 6. : The molecular structure of (I) at 115 K. Displacement ellipsoids are shown at the ??% probability level.

(I_293K) Rock salt–urea–water (1/1/1) (NaCl.CH₄N₂O.H₂O)

Crystal data

NaCl·CH4N2O·H2O	F(000) = 280
Mr = 136.52	Dx = 1.539 Mg m^−3
Monoclinic, I2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: I 2y	Cell parameters from 5993 reflections
a = 6.4845 (2) Å	θ = 3.1–35.2°
b = 5.2362 (2) Å	µ = 0.62 mm^−1
c = 17.3497 (5) Å	T = 293 K
β = 90.152 (2)°	Distorted cube, colourless
V = 589.09 (3) Å^3	0.4 × 0.4 × 0.4 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	1728 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.057
Graphite monochromator	θmax = 30.3°, θmin = 2.4°
phi and ω scans	h = −9→9
7728 measured reflections	k = −7→7
1752 independent reflections	l = −24→24

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.085	w = 1/[σ^2(Fo^2) + (0.0443P)^2 + 0.0989P] where P = (Fo^2 + 2Fc^2)/3
S = 1.25	(Δ/σ)max = 0.006
1752 reflections	Δρmax = 0.36 e Å^−3
71 parameters	Δρmin = −0.31 e Å^−3
5 restraints	Absolute structure: Flack (1983), 783 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (7)

Special details

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.

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 (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.50588 (6)	0.41569 (9)	0.61655 (2)	0.03345 (12)
Na1	0.24084 (9)	0.19015 (15)	0.49905 (4)	0.02959 (16)
O1	0.5000	−0.1216 (3)	0.5000	0.0336 (4)
H1	0.482 (4)	−0.215 (5)	0.5372 (9)	0.050*
O2	0.0000	0.5314 (3)	0.5000	0.0334 (4)
H2	0.005 (4)	0.629 (5)	0.5372 (9)	0.050*
O3	0.4972 (2)	0.4896 (3)	0.91172 (7)	0.0336 (3)
N1	0.3855 (3)	0.6191 (5)	0.79495 (11)	0.0564 (6)
H11	0.3002	0.7254	0.8152	0.068*
H12	0.3937	0.6057	0.7457	0.068*
N2	0.6330 (3)	0.3147 (5)	0.80417 (11)	0.0561 (6)
H21	0.7129	0.2178	0.8309	0.067*
H22	0.6357	0.3080	0.7547	0.067*
C1	0.5041 (2)	0.4763 (3)	0.83970 (9)	0.0291 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0389 (2)	0.0384 (2)	0.02304 (17)	−0.00727 (17)	0.00164 (13)	−0.00221 (16)
Na1	0.0232 (3)	0.0338 (3)	0.0318 (3)	0.0006 (2)	0.0000 (2)	0.0007 (3)
O1	0.0398 (8)	0.0244 (9)	0.0365 (9)	0.000	−0.0020 (7)	0.000
O2	0.0418 (9)	0.0247 (8)	0.0339 (9)	0.000	0.0026 (7)	0.000
O3	0.0371 (6)	0.0431 (7)	0.0206 (5)	0.0038 (5)	−0.0004 (4)	−0.0025 (4)
N1	0.0666 (11)	0.0731 (14)	0.0294 (8)	0.0388 (11)	−0.0009 (8)	−0.0016 (8)
N2	0.0612 (11)	0.0750 (14)	0.0320 (9)	0.0392 (10)	0.0006 (8)	−0.0049 (8)
C1	0.0316 (7)	0.0336 (9)	0.0220 (7)	0.0034 (6)	−0.0003 (5)	−0.0009 (5)

Geometric parameters (Å, º)

Cl1—Na1^i	2.8516 (8)	Na1—O3^iv	2.4281 (15)
Cl1—Na1	2.9130 (8)	O3—C1	1.252 (2)
Na1—Na1^ii	3.1237 (12)	N1—C1	1.323 (2)
Na1—Na1^i	3.3612 (12)	N2—C1	1.341 (2)
Na1—O1	2.3430 (13)	O1—H1	0.819 (15)
Na1—O2	2.3732 (15)	O2—H2	0.825 (16)
Na1—O3^iii	2.4251 (15)
Cl1^i—Na1—Cl1	89.11 (2)	O2—Na1—Cl1	94.41 (3)
Na1^i—Cl1—Na1	71.32 (2)	O3^iii—Na1—Cl1	174.21 (4)
O1—Na1—O2	175.26 (5)	O3^iv—Na1—Cl1	95.97 (4)
O1—Na1—O3^iii	99.71 (5)	Na1—O1—Na1^i	91.66 (7)
O2—Na1—O3^iii	84.43 (4)	Na1^ii—O2—Na1	82.31 (6)
O1—Na1—O3^iv	98.70 (5)	C1—O3—Na1^v	128.51 (12)
O2—Na1—O3^iv	84.36 (4)	C1—O3—Na1^vi	133.19 (12)
O3^iii—Na1—O3^iv	78.28 (6)	Na1^v—O3—Na1^vi	80.12 (5)
O1—Na1—Cl1^i	83.05 (3)	O3—C1—N1	122.16 (16)
O2—Na1—Cl1^i	94.21 (3)	O3—C1—N2	121.16 (16)
O3^iii—Na1—Cl1^i	96.63 (4)	N1—C1—N2	116.68 (17)
O3^iv—Na1—Cl1^i	174.81 (4)	H1—O1—H1^i	106 (3)
O1—Na1—Cl1	81.70 (3)	H2—O2—H2^ii	103 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H12···Cl1	0.86	2.56	3.3671 (19)	157
N1—H11···Cl1^vi	0.86	2.52	3.3512 (19)	163
N2—H22···Cl1	0.86	2.60	3.397 (2)	155
N2—H21···Cl1^vii	0.86	2.58	3.4242 (19)	168
O1—H1···Cl1^viii	0.82 (2)	2.38 (2)	3.1559 (14)	159 (2)
O2—H2···O3^vi	0.83 (2)	2.08 (2)	2.846 (2)	154 (2)

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

(I_117K) Rock salt–urea–water (1/1/1) (NaCl.CH₄N₂O.H₂O)

Crystal data

NaCl·CH4N2O·H2O	F(000) = 280
Mr = 136.52	Dx = 1.574 Mg m^−3
Orthorhombic, Pn21m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P -2 -2bc	Cell parameters from 4386 reflections
a = 6.4374 (2) Å	θ = 2.4–34.9°
b = 5.1744 (2) Å	µ = 0.63 mm^−1
c = 17.2998 (5) Å	T = 117 K
V = 576.25 (3) Å^3	Distorted cube, colourless
Z = 4	0.3 × 0.3 × 0.3 mm

Data collection

Bruker SMART CCD area-detector diffractometer	2022 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.079
Graphite monochromator	θmax = 35.6°, θmin = 2.4°
phi and ω scans	h = −10→10
15591 measured reflections	k = −8→8
2688 independent reflections	l = −27→28

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.086	w = 1/[σ^2(Fo^2) + (0.0424P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.95	(Δ/σ)max = 0.002
2688 reflections	Δρmax = 0.66 e Å^−3
76 parameters	Δρmin = −0.36 e Å^−3
5 restraints	Absolute structure: Flack (1983), 1109 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.02 (6)

Special details

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.

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 (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.26051 (4)	0.41551 (8)	0.616725 (17)	0.01411 (8)
Na1	0.51476 (11)	0.19051 (16)	0.5000	0.01254 (17)
Na2	−0.00615 (11)	0.19552 (16)	0.5000	0.01291 (17)
O1	0.25054 (19)	−0.1198 (3)	0.5000	0.0148 (3)
H1	0.236 (2)	−0.215 (4)	0.5380 (8)	0.030*
O2	−0.2449 (2)	0.5368 (3)	0.5000	0.0142 (3)
H2	−0.234 (2)	0.631 (4)	0.5389 (8)	0.028*
O3	0.24513 (15)	0.4920 (2)	0.91144 (6)	0.0143 (2)
N1	0.1363 (2)	0.6310 (4)	0.79429 (7)	0.0261 (3)
H11	0.0490	0.7409	0.8155	0.031*
H12	0.1454	0.6201	0.7436	0.031*
N2	0.3852 (2)	0.3192 (4)	0.80336 (7)	0.0265 (3)
H21	0.4666	0.2178	0.8307	0.032*
H22	0.3897	0.3141	0.7525	0.032*
C1	0.2549 (2)	0.4807 (3)	0.83891 (8)	0.0131 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.01587 (13)	0.01720 (14)	0.00927 (11)	−0.0034 (2)	0.00045 (11)	−0.00067 (13)
Na1	0.0095 (3)	0.0144 (4)	0.0136 (4)	−0.0007 (3)	0.000	0.000
Na2	0.0102 (3)	0.0155 (4)	0.0130 (4)	−0.0004 (3)	0.000	0.000
O1	0.0162 (6)	0.0129 (8)	0.0152 (6)	−0.0008 (7)	0.000	0.000
O2	0.0170 (7)	0.0122 (7)	0.0133 (6)	−0.0004 (6)	0.000	0.000
O3	0.0165 (4)	0.0187 (5)	0.0076 (4)	0.0013 (4)	0.0006 (4)	−0.0008 (4)
N1	0.0280 (7)	0.0370 (8)	0.0134 (6)	0.0173 (7)	−0.0002 (5)	0.0000 (6)
N2	0.0283 (7)	0.0371 (8)	0.0141 (6)	0.0160 (6)	−0.0009 (5)	−0.0023 (6)
C1	0.0131 (6)	0.0159 (6)	0.0102 (5)	−0.0012 (5)	0.0000 (5)	0.0007 (5)

Geometric parameters (Å, º)

Cl1—Na1	2.8481 (7)	Na2—O2	2.3411 (17)
Cl1—Na2	2.8845 (7)	Na2—O3^iii	2.4131 (12)
Na1—Na2^i	3.0842 (11)	O3—C1	1.2577 (17)
Na1—Na2	3.3534 (11)	N1—C1	1.336 (2)
Na1—O1	2.3392 (16)	N2—C1	1.334 (2)
Na1—O2^i	2.3674 (17)	O1—H1	0.827 (15)
Na1—O3^ii	2.4066 (12)	O2—H2	0.833 (15)
Na2—O1	2.3223 (16)
Cl1^iv—Na1—Cl1	90.31 (3)	O3^iii—Na2—O3^vi	78.83 (6)
Cl1—Na2—Cl1^iv	88.86 (3)	O1—Na2—Cl1	81.59 (3)
Na1—Cl1—Na2	71.60 (2)	O2—Na2—Cl1	95.34 (3)
O1—Na1—O2^i	174.16 (6)	O3^iii—Na2—Cl1	174.94 (4)
O1—Na1—O3^ii	100.02 (4)	O3^vi—Na2—Cl1	96.15 (3)
O2^i—Na1—O3^ii	84.45 (4)	Na2—O1—Na1	92.01 (6)
O3^ii—Na1—O3^v	79.08 (6)	Na2—O2—Na1^vii	81.84 (6)
O1—Na1—Cl1^iv	82.11 (3)	C1—O3—Na1^viii	128.53 (10)
O2^i—Na1—Cl1^iv	93.79 (3)	C1—O3—Na2^ix	133.28 (10)
O3^ii—Na1—Cl1^iv	174.23 (3)	Na1^viii—O3—Na2^ix	79.57 (4)
O3^v—Na1—Cl1^iv	95.29 (3)	O3—C1—N2	121.36 (14)
O2^i—Na1—Cl1	93.79 (3)	O3—C1—N1	121.40 (14)
O1—Na2—O2	175.67 (6)	N2—C1—N1	117.24 (13)
O1—Na2—O3^iii	98.45 (5)	H1—O1—H1^iv	105 (3)
O2—Na2—O3^iii	84.88 (4)	H2—O2—H2^iv	108 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H12···Cl1	0.88	2.55	3.3643 (14)	155
N1—H11···Cl1^ix	0.88	2.48	3.3260 (14)	161
N2—H22···Cl1	0.88	2.55	3.3641 (13)	155
N2—H21···Cl1^ii	0.88	2.52	3.3877 (15)	168
O1—H1···Cl1^x	0.83 (2)	2.35 (2)	3.1405 (12)	160 (2)
O2—H2···O3^ix	0.83 (2)	2.06 (2)	2.8097 (18)	150 (2)

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