A new crystal modification of diammonium hydrogen phosphate, (NH4)2(HPO4)

Kunz, P.C.; Wetzel, C.; Spingler, B.

doi:10.1107/S1600536810009839

inorganic compounds

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ISSN: 2056-9890

Volume 66| Part 4| April 2010| Pages i26-i27

doi:10.1107/S1600536810009839

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A new crystal modification of diammonium hydrogen phosphate, (NH₄)₂(HPO₄)

Peter C. Kunz,^a ^* Corinna Wetzel ^a and Bernhard Spingler ^b

^aHeirich-Heine-Universität Düsseldorf, Institut für Anorganische Chemie und Strukturchemie I, Universitätsstrasse 1, D-40225 Düsseldorf, Germany, and ^bAnorganisch-Chemisches Institut, Universität Zürich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
^*Correspondence e-mail: peter.kunz@uni-duesseldorf.de

(Received 8 February 2010; accepted 16 March 2010; online 20 March 2010)

The addition of hexafluoridophosphate salts (ammonium, silver, thallium or potassium) is usually used to precipitate complex cations from aqueous solutions. It has long been known that PF₆⁻ is sensitive towards hydrolysis under acidic conditions [Gebala & Jones (1969 ). J. Inorg. Nucl. Chem. 31, 771–776; Plakhotnyk et al. (2005 ). J. Fluorine Chem. 126, 27–31]. During the course of our investigation into coinage metal complexes of diphosphine ligands, we used ammonium hexafluoridophosphate in order to crystallize [Ag(diphosphine)₂]PF₆ complexes. From these solutions we always obtained needle-like crystals which turned out to be the title compound, 2NH₄⁺·HPO₄²⁻. It was received as the hydrolysis product of NH₄PF₆. The crystals are a new modification of diammonium hydrogen phosphate. In contrast to the previously published polymorph [Khan et al. (1972 ). Acta Cryst. B28, 2065–2069], Z′ of the title compound is 2. In the new modification of the title compound, there are eight molecules of (NH₄)₂(HPO₄) in the unit cell. The structure consists of PO₃OH and NH₄ tetrahedra, held together by O—H⋯O and N—H⋯O hydrogen bonds.

Related literature

For the study of another crystal modification of the title compound, see: Khan et al. (1972). For the hydrolysis of hexafluoridophosphates, see: Akbayeva et al. (2006 ); Deifel et al. (2008 ); Fernandez-Galan et al. (1994 ); Gebala & Jones (1969); Nikitenko et al. (2007 ); Plakhotnyk et al. (2005).

Experimental

Crystal data

2NH₄⁺·HPO₄²⁻
M_r = 132.06
Monoclinic, P 2₁ /c
a = 11.2868 (3) Å
b = 15.3466 (4) Å
c = 6.41894 (19) Å
β = 90.795 (3)°
V = 1111.74 (5) Å³
Z = 8
Mo Kα radiation
μ = 0.42 mm⁻¹
T = 183 K
0.44 × 0.17 × 0.11 mm

Data collection

Oxford Xcalibur Ruby CCD diffractometer
Absorption correction: multi-scan CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction, Yarnton, England.]$ ) T_min = 0.891, T_max = 0.955
22537 measured reflections
5384 independent reflections
4400 reflections with I > 2σ(I)
R_int = 0.033

Refinement

R[F² > 2σ(F²)] = 0.048
wR(F²) = 0.158
S = 1.21
5384 reflections
181 parameters
16 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.82 e Å⁻³
Δρ_min = −0.69 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O7ⁱ	0.78 (4)	1.80 (4)	2.570 (2)	168 (4)
O5—H5⋯O8ⁱⁱ	0.85 (4)	1.79 (4)	2.632 (2)	170 (4)
N11—H11A⋯O4ⁱⁱⁱ	0.86 (2)	1.89 (2)	2.747 (2)	175 (4)
N11—H11B⋯O8ⁱ	0.86 (2)	2.10 (2)	2.951 (2)	171 (3)
N11—H11C⋯O3^iv	0.88 (2)	1.99 (2)	2.852 (3)	169 (3)
N11—H11D⋯O4ⁱ	0.88 (2)	2.01 (2)	2.870 (2)	167 (3)
N12—H12A⋯O6^v	0.87 (2)	1.91 (2)	2.755 (2)	165 (3)
N12—H12B⋯O5^vi	0.88 (2)	2.16 (2)	3.008 (3)	161 (3)
N12—H12C⋯O6ⁱ	0.87 (2)	1.99 (2)	2.827 (2)	161 (3)
N12—H12D⋯O2	0.88 (2)	1.88 (2)	2.754 (2)	175 (3)
N13—H13A⋯O3	0.86 (2)	1.92 (2)	2.773 (2)	172 (3)
N13—H13B⋯O2^vii	0.86 (2)	1.96 (2)	2.822 (2)	175 (3)
N13—H13C⋯O6^v	0.89 (2)	1.95 (2)	2.830 (2)	168 (3)
N13—H13D⋯O2ⁱⁱ	0.86 (2)	1.96 (2)	2.820 (2)	176 (3)
N14—H14A⋯O7	0.87 (2)	1.90 (2)	2.771 (2)	174 (3)
N14—H14B⋯O8^vii	0.86 (2)	2.01 (2)	2.859 (2)	171 (3)
N14—H14C⋯O3^iv	0.86 (2)	1.92 (2)	2.784 (2)	178 (3)
N14—H14D⋯O4	0.89 (2)	1.89 (2)	2.771 (2)	171 (3)
Symmetry codes: (i) -x, -y+1, -z+1; (ii) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iii) $[-x, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) -x, -y+1, -z+2; (v) x+1, y, z+1; (vi) x+1, y, z; (vii) x, y, z+1.

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction, Yarnton, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablock global. DOI: 10.1107/S1600536810009839/br2137sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810009839/br2137Isup2.hkl

checkCIF report

Comment top

The addition of hexafluorophosphate salts (ammonium, silver, thallium or potassium) is usually used to precipitate complex cations from aqueous solutions. It is long known, that PF₆^- is sensitive towards hydrolysis under acidic conditions (Gebala and Jones 1969; Plakhotnyk, Ernst et al. 2005). In organic solvents the spatial hydrolysis to intermediate species as HF, POF₃ and PO₂F₂^- is observed (Fernandez-Galan, Manzano et al. 1994; Akbayeva, Vaira et al. 2006; Nikitenko, Berthon et al. 2007) and under hydrothermal conditions this reaction is used for the formation of phosphate materials (Deifel, Holman et al. 2008).

During the course of our investigation into coinage metal complexes of diphosphine ligands we used ammonium hexafluorophosphate in order to crystallise [Ag(diphosphine)₂]PF₆ complexes. From these solutions we always obtained needle-like crystals which turned out to be the title compound (NH₄)₂(HPO₄) as the product of hydrolysis of NH₄PF₆.

A modification of diammonium hydrogen phosphate is known with the cell parameters a = 11.043 (6), b = 6.700 (3), c = 8.031 (4), β = 113.42 (3)° and Z = 4.(Khan, Roux et al. 1972) In the new modification of the title compound reported here, there are eight molecules of (NH₄)₂(HPO₄) in the unit cell. The structure consists of PO₄ and NH₄ tetrahedra, held together by O—H···O and N—H···O hydrogen bonds. These hydrogen bonds are more or less linear (169 ° < <(DHA) < 178 °). Of the four P-O bonds in both PO₄ tetrahedra, one is longer than the remaining three, typical of a O₃P(OH) group. The two different HPO₄^- molecules (P1O₄ and P2O₄) are hydrogen bonded to ten and seven ammonium ions, respectively. In hydrogen phosphate P2, one NH₄⁺ molecule is bound to O5 and O7, two to O8 and three to O6. In the other hydrogen phosphate, the three non-protonated O-atoms O2, O3 and O4 are bound to three NH₄⁺ molecules each, whereas the protonated O1 is only bound to one NH₄⁺ molecule. In the hydrogen phosphate P1 the hydroxyl group O1H1 forms a hydrogen bridge to O7 (d = 1.80 (4) Å) and in the hydrogen phosphate P2 the hydroxyl group O5H5 forms a hydrogen bridge to O8 (d = 1.79 (4) Å). The N—O distances around the four-coordinated ammonium ions N13 and N14 are within the range of 2.77 < d < 2.86 Å; The N···O distances around N12 fall within this range with the exception of N12···O5 which is significantly longer (d_N12O5 = 3.007 Å). A very different picture is found around N11. Here, five neighbouring O-atoms are found, three of which are in a shorter distance (2. 74 < d < 2.87 Å) and two in a longer distance (d_N11O5 = 2.951 Å and d_N1101 = 3.048 Å). The fifth N···O contact may be a result of dynamic or static disorder of the ammonium ion or that each N atom in addition to three normal N—H···O bonds also formed one bifurcated bond. This is in contrast to the other modification, in which each ammonium ion has five N···O contacts smaller than 3.4 Å. Since Khan and Roux (Khan, Roux et al. 1972) only reported that they used "a commercially supplied crystalline sample", we cannot compare the crystallization conditions that lead to the two different crystal forms.

Related literature top

For the study of another crystal modification of the title compound, see: Khan et al. (1972). For the hydrolysis of hexafluorophosphates, see: Akbayeva et al. (2006); Deifel et al. (2008); Fernandez-Galan et al. (1994); Gebala & Jones (1969); Nikitenko et al. (2007); Plakhotnyk et al. (2005).

Experimental top

A suitable crystal was covered with oil (Infineum V8512, formerly known as Paratone N), mounted on top of a glass fibre and immediately transferred to the diffractometer. The final model was checked for higher symmetry with help of the program PLATON (Spek, 2009).

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

Fig. 1. H-bonded network in the solid-state of the title compound. Displacement ellipsoids are drawn at a 50 % level, H-atoms are represented as capped sticks.

diammonium hydrogen phosphate top

Crystal data top

2NH₄⁺·HPO₄²⁻	F(000) = 560
M_r = 132.06	D_x = 1.578 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 2ybc	Cell parameters from 11185 reflections
a = 11.2868 (3) Å	θ = 2.7–37.6°
b = 15.3466 (4) Å	µ = 0.42 mm⁻¹
c = 6.41894 (19) Å	T = 183 K
β = 90.795 (3)°	Needle, colourless
V = 1111.74 (5) Å³	0.44 × 0.17 × 0.11 mm
Z = 8

Data collection top

Oxford Xcalibur Ruby CCD diffractometer	5384 independent reflections
Radiation source: Enhance (Mo) X-ray Source	4400 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.033
Detector resolution: 10.4498 pixels mm^-1	θ_max = 36.3°, θ_min = 2.7°
ω oscillation scan	h = −18→18
Absorption correction: multi-scan CrysAlis PRO (Oxford Diffraction, 2009)	k = −25→25
T_min = 0.891, T_max = 0.955	l = −9→10
22537 measured reflections

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.158	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	w = 1/[σ²(F_o²) + (0.0508P)² + 1.9491P] where P = (F_o² + 2F_c²)/3
5384 reflections	(Δ/σ)_max < 0.001
181 parameters	Δρ_max = 0.82 e Å⁻³
16 restraints	Δρ_min = −0.69 e Å⁻³

Crystal data top

2NH₄⁺·HPO₄²⁻	V = 1111.74 (5) Å³
M_r = 132.06	Z = 8
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.2868 (3) Å	µ = 0.42 mm⁻¹
b = 15.3466 (4) Å	T = 183 K
c = 6.41894 (19) Å	0.44 × 0.17 × 0.11 mm
β = 90.795 (3)°

Data collection top

Oxford Xcalibur Ruby CCD diffractometer	5384 independent reflections
Absorption correction: multi-scan CrysAlis PRO (Oxford Diffraction, 2009)	4400 reflections with I > 2σ(I)
T_min = 0.891, T_max = 0.955	R_int = 0.033
22537 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.048	16 restraints
wR(F²) = 0.158	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	Δρ_max = 0.82 e Å⁻³
5384 reflections	Δρ_min = −0.69 e Å⁻³
181 parameters

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.

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
O1	0.12341 (16)	0.48227 (11)	0.6812 (3)	0.0260 (4)
H1	0.181 (4)	0.502 (3)	0.635 (6)	0.039*
O2	0.25104 (13)	0.34866 (10)	0.7264 (2)	0.0180 (3)
O3	0.13920 (15)	0.40992 (11)	1.0319 (2)	0.0198 (3)
O4	0.02645 (13)	0.34042 (10)	0.7334 (3)	0.0190 (3)
O5	−0.41866 (14)	0.29289 (11)	0.4731 (3)	0.0209 (3)
H5	−0.368 (3)	0.259 (3)	0.529 (6)	0.031*
O6	−0.47633 (13)	0.40326 (10)	0.2142 (2)	0.0174 (3)
O7	−0.30247 (15)	0.43252 (11)	0.4549 (2)	0.0209 (3)
O8	−0.28270 (13)	0.32102 (10)	0.1683 (2)	0.0182 (3)
P1	0.13662 (4)	0.39195 (3)	0.79806 (7)	0.01228 (10)
P2	−0.36645 (4)	0.36515 (3)	0.32105 (7)	0.01211 (10)
N11	0.03108 (16)	0.66864 (12)	0.7030 (3)	0.0185 (3)
H11A	0.009 (3)	0.7219 (13)	0.720 (5)	0.028*
H11B	0.1058 (17)	0.667 (2)	0.730 (5)	0.028*
H11C	−0.017 (3)	0.638 (2)	0.780 (5)	0.028*
H11D	0.018 (3)	0.658 (2)	0.570 (3)	0.028*
N12	0.47645 (17)	0.41255 (13)	0.7925 (3)	0.0188 (3)
H12A	0.500 (3)	0.402 (2)	0.920 (3)	0.028*
H12B	0.523 (3)	0.382 (2)	0.711 (5)	0.028*
H12C	0.479 (3)	0.4675 (13)	0.760 (5)	0.028*
H12D	0.4031 (19)	0.395 (2)	0.770 (5)	0.028*
N13	0.29995 (16)	0.32905 (12)	1.2991 (3)	0.0182 (3)
H13A	0.252 (3)	0.351 (2)	1.207 (4)	0.027*
H13B	0.285 (3)	0.339 (2)	1.428 (3)	0.027*
H13C	0.3748 (18)	0.345 (2)	1.278 (5)	0.027*
H13D	0.288 (3)	0.2742 (12)	1.282 (5)	0.027*
N14	−0.18493 (17)	0.42049 (12)	0.8356 (3)	0.0178 (3)
H14A	−0.227 (3)	0.425 (2)	0.720 (4)	0.027*
H14B	−0.221 (3)	0.394 (2)	0.933 (4)	0.027*
H14C	−0.169 (3)	0.4726 (14)	0.877 (5)	0.027*
H14D	−0.1132 (19)	0.398 (2)	0.814 (5)	0.027*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0185 (7)	0.0193 (7)	0.0403 (10)	0.0021 (6)	0.0007 (6)	0.0145 (7)
O2	0.0140 (6)	0.0182 (6)	0.0220 (7)	0.0022 (5)	0.0025 (5)	−0.0015 (5)
O3	0.0225 (7)	0.0215 (7)	0.0153 (6)	0.0000 (5)	−0.0005 (5)	−0.0035 (5)
O4	0.0142 (6)	0.0179 (6)	0.0249 (7)	−0.0037 (5)	−0.0022 (5)	−0.0034 (5)
O5	0.0183 (6)	0.0207 (7)	0.0237 (7)	0.0025 (5)	0.0055 (5)	0.0099 (5)
O6	0.0145 (6)	0.0189 (6)	0.0188 (6)	0.0015 (5)	−0.0032 (5)	0.0032 (5)
O7	0.0221 (7)	0.0242 (7)	0.0165 (6)	−0.0048 (6)	−0.0035 (5)	−0.0031 (5)
O8	0.0150 (6)	0.0206 (7)	0.0192 (6)	−0.0010 (5)	0.0046 (5)	−0.0033 (5)
P1	0.01141 (19)	0.01162 (19)	0.01380 (19)	−0.00003 (14)	−0.00053 (14)	−0.00007 (14)
P2	0.01113 (18)	0.0140 (2)	0.01122 (18)	−0.00061 (14)	0.00038 (13)	0.00073 (14)
N11	0.0167 (7)	0.0184 (7)	0.0205 (8)	0.0015 (6)	−0.0007 (6)	−0.0001 (6)
N12	0.0170 (7)	0.0226 (8)	0.0169 (7)	0.0013 (6)	−0.0008 (6)	−0.0018 (6)
N13	0.0160 (7)	0.0199 (7)	0.0187 (7)	−0.0015 (6)	−0.0001 (5)	0.0002 (6)
N14	0.0178 (7)	0.0197 (7)	0.0159 (7)	−0.0006 (6)	0.0001 (5)	−0.0016 (6)

Geometric parameters (Å, º) top

O1—P1	1.5821 (17)	N11—H11D	0.877 (18)
O1—H1	0.78 (4)	N12—H12A	0.869 (18)
O2—P1	1.5287 (15)	N12—H12B	0.878 (18)
O3—P1	1.5257 (16)	N12—H12C	0.868 (18)
O4—P1	1.5262 (15)	N12—H12D	0.879 (18)
O5—P2	1.5955 (16)	N13—H13A	0.863 (18)
O5—H5	0.85 (4)	N13—H13B	0.862 (18)
O6—P2	1.5254 (15)	N13—H13C	0.892 (18)
O7—P2	1.5201 (16)	N13—H13D	0.859 (18)
O8—P2	1.5295 (15)	N14—H14A	0.874 (18)
N11—H11A	0.862 (18)	N14—H14B	0.856 (18)
N11—H11B	0.859 (18)	N14—H14C	0.861 (18)
N11—H11C	0.876 (18)	N14—H14D	0.890 (18)

P1—O1—H1	116 (3)	H11C—N11—H11D	110 (3)
P2—O5—H5	115 (3)	H12A—N12—H12B	107 (3)
O3—P1—O4	111.44 (9)	H12A—N12—H12C	113 (3)
O3—P1—O2	111.70 (9)	H12B—N12—H12C	111 (3)
O4—P1—O2	112.43 (9)	H12A—N12—H12D	112 (3)
O3—P1—O1	107.95 (10)	H12B—N12—H12D	108 (3)
O4—P1—O1	104.71 (10)	H12C—N12—H12D	106 (3)
O2—P1—O1	108.21 (9)	H13A—N13—H13B	118 (3)
O7—P2—O6	111.73 (9)	H13A—N13—H13C	112 (3)
O7—P2—O8	111.74 (9)	H13B—N13—H13C	107 (3)
O6—P2—O8	112.79 (9)	H13A—N13—H13D	101 (3)
O7—P2—O5	107.68 (9)	H13B—N13—H13D	105 (3)
O6—P2—O5	103.69 (9)	H13C—N13—H13D	113 (3)
O8—P2—O5	108.73 (9)	H14A—N14—H14B	114 (3)
H11A—N11—H11B	107 (3)	H14A—N14—H14C	107 (3)
H11A—N11—H11C	105 (3)	H14B—N14—H14C	109 (3)
H11B—N11—H11C	119 (3)	H14A—N14—H14D	112 (3)
H11A—N11—H11D	105 (3)	H14B—N14—H14D	112 (3)
H11B—N11—H11D	110 (3)	H14C—N14—H14D	102 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O7ⁱ	0.78 (4)	1.80 (4)	2.570 (2)	168 (4)
O5—H5···O8ⁱⁱ	0.85 (4)	1.79 (4)	2.632 (2)	170 (4)
N11—H11A···O4ⁱⁱⁱ	0.86 (2)	1.89 (2)	2.747 (2)	175 (4)
N11—H11B···O8ⁱ	0.86 (2)	2.10 (2)	2.951 (2)	171 (3)
N11—H11C···O3^iv	0.88 (2)	1.99 (2)	2.852 (3)	169 (3)
N11—H11D···O4ⁱ	0.88 (2)	2.01 (2)	2.870 (2)	167 (3)
N12—H12A···O6^v	0.87 (2)	1.91 (2)	2.755 (2)	165 (3)
N12—H12B···O5^vi	0.88 (2)	2.16 (2)	3.008 (3)	161 (3)
N12—H12C···O6ⁱ	0.87 (2)	1.99 (2)	2.827 (2)	161 (3)
N12—H12D···O2	0.88 (2)	1.88 (2)	2.754 (2)	175 (3)
N13—H13A···O3	0.86 (2)	1.92 (2)	2.773 (2)	172 (3)
N13—H13B···O2^vii	0.86 (2)	1.96 (2)	2.822 (2)	175 (3)
N13—H13C···O6^v	0.89 (2)	1.95 (2)	2.830 (2)	168 (3)
N13—H13D···O2ⁱⁱ	0.86 (2)	1.96 (2)	2.820 (2)	176 (3)
N14—H14A···O7	0.87 (2)	1.90 (2)	2.771 (2)	174 (3)
N14—H14B···O8^vii	0.86 (2)	2.01 (2)	2.859 (2)	171 (3)
N14—H14C···O3^iv	0.86 (2)	1.92 (2)	2.784 (2)	178 (3)
N14—H14D···O4	0.89 (2)	1.89 (2)	2.771 (2)	171 (3)

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

Experimental details

Crystal data
Chemical formula	2NH₄⁺·HPO₄²⁻
M_r	132.06
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	183
a, b, c (Å)	11.2868 (3), 15.3466 (4), 6.41894 (19)
β (°)	90.795 (3)
V (Å³)	1111.74 (5)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.42
Crystal size (mm)	0.44 × 0.17 × 0.11

Data collection
Diffractometer	Oxford Xcalibur Ruby CCD diffractometer
Absorption correction	Multi-scan CrysAlis PRO (Oxford Diffraction, 2009)
T_min, T_max	0.891, 0.955
No. of measured, independent and observed [I > 2σ(I)] reflections	22537, 5384, 4400
R_int	0.033
(sin θ/λ)_max (Å⁻¹)	0.833

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.158, 1.21
No. of reflections	5384
No. of parameters	181
No. of restraints	16
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.82, −0.69

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SIR97 (Altomare et al., 1999), ORTEP-3 (Farrugia, 1997), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O7ⁱ	0.78 (4)	1.80 (4)	2.570 (2)	168 (4)
O5—H5···O8ⁱⁱ	0.85 (4)	1.79 (4)	2.632 (2)	170 (4)
N11—H11A···O4ⁱⁱⁱ	0.862 (18)	1.888 (18)	2.747 (2)	175 (4)
N11—H11B···O8ⁱ	0.859 (18)	2.100 (19)	2.951 (2)	171 (3)
N11—H11C···O3^iv	0.876 (18)	1.988 (19)	2.852 (3)	169 (3)
N11—H11D···O4ⁱ	0.877 (18)	2.008 (19)	2.870 (2)	167 (3)
N12—H12A···O6^v	0.869 (18)	1.91 (2)	2.755 (2)	165 (3)
N12—H12B···O5^vi	0.878 (18)	2.16 (2)	3.008 (3)	161 (3)
N12—H12C···O6ⁱ	0.868 (18)	1.99 (2)	2.827 (2)	161 (3)
N12—H12D···O2	0.879 (18)	1.877 (18)	2.754 (2)	175 (3)
N13—H13A···O3	0.863 (18)	1.915 (19)	2.773 (2)	172 (3)
N13—H13B···O2^vii	0.862 (18)	1.962 (18)	2.822 (2)	175 (3)
N13—H13C···O6^v	0.892 (18)	1.952 (19)	2.830 (2)	168 (3)
N13—H13D···O2ⁱⁱ	0.859 (18)	1.963 (18)	2.820 (2)	176 (3)
N14—H14A···O7	0.874 (18)	1.900 (18)	2.771 (2)	174 (3)
N14—H14B···O8^vii	0.856 (18)	2.010 (19)	2.859 (2)	171 (3)
N14—H14C···O3^iv	0.861 (18)	1.924 (18)	2.784 (2)	178 (3)
N14—H14D···O4	0.890 (18)	1.889 (19)	2.771 (2)	171 (3)

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

Acknowledgements

BS thanks the University of Zürich for financial support.

References

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