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Acta Crystallogr Sect E Struct Rep Online. 2010 April 1; 66(Pt 4): i26–i27.
Published online 2010 March 20. doi:  10.1107/S1600536810009839
PMCID: PMC2984071

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

Abstract

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 [triangle]). J. Inorg. Nucl. Chem. 31, 771–776; Plakhotnyk et al. (2005 [triangle]). 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 +·HPO4 2−. 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 [triangle]). 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 [triangle]). For the hydrolysis of hexa­fluorido­phosphates, see: Akbayeva et al. (2006 [triangle]); Deifel et al. (2008 [triangle]); Fernandez-Galan et al. (1994 [triangle]); Gebala & Jones (1969 [triangle]); Nikitenko et al. (2007 [triangle]); Plakhotnyk et al. (2005 [triangle]).

Experimental

Crystal data

  • 2NH4 +·HPO4 2−
  • M r = 132.06
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-00i26-efi1.jpg
  • 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 [triangle]) 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[F 2 > 2σ(F 2)] = 0.048
  • wR(F 2) = 0.158
  • S = 1.21
  • 5384 reflections
  • 181 parameters
  • 16 restraints
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.82 e Å−3
  • Δρmin = −0.69 e Å−3

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

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

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

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

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

BS thanks the University of Zürich for financial support.

supplementary crystallographic information

Comment

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 (dN12O5 = 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 (dN11O5 = 2.951 Å and dN1101 = 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.

Experimental

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).

Refinement

All hydrogen atoms were located by difference Fourier synthesis and refined with fixed individual displacement parameters [U(H) = 1.5Ueq(O)] at an O-H distance of 0.87 Å.

Figures

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.

Crystal data

2NH4+·HPO42F(000) = 560
Mr = 132.06Dx = 1.578 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 2ybcCell parameters from 11185 reflections
a = 11.2868 (3) Åθ = 2.7–37.6°
b = 15.3466 (4) ŵ = 0.42 mm1
c = 6.41894 (19) ÅT = 183 K
β = 90.795 (3)°Needle, colourless
V = 1111.74 (5) Å30.44 × 0.17 × 0.11 mm
Z = 8

Data collection

Oxford Xcalibur Ruby CCD diffractometer5384 independent reflections
Radiation source: Enhance (Mo) X-ray Source4400 reflections with I > 2σ(I)
graphiteRint = 0.033
Detector resolution: 10.4498 pixels mm-1θmax = 36.3°, θmin = 2.7°
ω oscillation scanh = −18→18
Absorption correction: multi-scan CrysAlis PRO (Oxford Diffraction, 2009)k = −25→25
Tmin = 0.891, Tmax = 0.955l = −9→10
22537 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.048Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.158H atoms treated by a mixture of independent and constrained refinement
S = 1.21w = 1/[σ2(Fo2) + (0.0508P)2 + 1.9491P] where P = (Fo2 + 2Fc2)/3
5384 reflections(Δ/σ)max < 0.001
181 parametersΔρmax = 0.82 e Å3
16 restraintsΔρmin = −0.68 e Å3

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 (Å2)

xyzUiso*/Ueq
O10.12341 (16)0.48227 (11)0.6812 (3)0.0260 (4)
H10.181 (4)0.502 (3)0.635 (6)0.039*
O20.25104 (13)0.34866 (10)0.7264 (2)0.0180 (3)
O30.13920 (15)0.40992 (11)1.0319 (2)0.0198 (3)
O40.02645 (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)
P10.13662 (4)0.39195 (3)0.79806 (7)0.01228 (10)
P2−0.36645 (4)0.36515 (3)0.32105 (7)0.01211 (10)
N110.03108 (16)0.66864 (12)0.7030 (3)0.0185 (3)
H11A0.009 (3)0.7219 (13)0.720 (5)0.028*
H11B0.1058 (17)0.667 (2)0.730 (5)0.028*
H11C−0.017 (3)0.638 (2)0.780 (5)0.028*
H11D0.018 (3)0.658 (2)0.570 (3)0.028*
N120.47645 (17)0.41255 (13)0.7925 (3)0.0188 (3)
H12A0.500 (3)0.402 (2)0.920 (3)0.028*
H12B0.523 (3)0.382 (2)0.711 (5)0.028*
H12C0.479 (3)0.4675 (13)0.760 (5)0.028*
H12D0.4031 (19)0.395 (2)0.770 (5)0.028*
N130.29995 (16)0.32905 (12)1.2991 (3)0.0182 (3)
H13A0.252 (3)0.351 (2)1.207 (4)0.027*
H13B0.285 (3)0.339 (2)1.428 (3)0.027*
H13C0.3748 (18)0.345 (2)1.278 (5)0.027*
H13D0.288 (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)

U11U22U33U12U13U23
O10.0185 (7)0.0193 (7)0.0403 (10)0.0021 (6)0.0007 (6)0.0145 (7)
O20.0140 (6)0.0182 (6)0.0220 (7)0.0022 (5)0.0025 (5)−0.0015 (5)
O30.0225 (7)0.0215 (7)0.0153 (6)0.0000 (5)−0.0005 (5)−0.0035 (5)
O40.0142 (6)0.0179 (6)0.0249 (7)−0.0037 (5)−0.0022 (5)−0.0034 (5)
O50.0183 (6)0.0207 (7)0.0237 (7)0.0025 (5)0.0055 (5)0.0099 (5)
O60.0145 (6)0.0189 (6)0.0188 (6)0.0015 (5)−0.0032 (5)0.0032 (5)
O70.0221 (7)0.0242 (7)0.0165 (6)−0.0048 (6)−0.0035 (5)−0.0031 (5)
O80.0150 (6)0.0206 (7)0.0192 (6)−0.0010 (5)0.0046 (5)−0.0033 (5)
P10.01141 (19)0.01162 (19)0.01380 (19)−0.00003 (14)−0.00053 (14)−0.00007 (14)
P20.01113 (18)0.0140 (2)0.01122 (18)−0.00061 (14)0.00038 (13)0.00073 (14)
N110.0167 (7)0.0184 (7)0.0205 (8)0.0015 (6)−0.0007 (6)−0.0001 (6)
N120.0170 (7)0.0226 (8)0.0169 (7)0.0013 (6)−0.0008 (6)−0.0018 (6)
N130.0160 (7)0.0199 (7)0.0187 (7)−0.0015 (6)−0.0001 (5)0.0002 (6)
N140.0178 (7)0.0197 (7)0.0159 (7)−0.0006 (6)0.0001 (5)−0.0016 (6)

Geometric parameters (Å, °)

O1—P11.5821 (17)N11—H11D0.877 (18)
O1—H10.78 (4)N12—H12A0.869 (18)
O2—P11.5287 (15)N12—H12B0.878 (18)
O3—P11.5257 (16)N12—H12C0.868 (18)
O4—P11.5262 (15)N12—H12D0.879 (18)
O5—P21.5955 (16)N13—H13A0.863 (18)
O5—H50.85 (4)N13—H13B0.862 (18)
O6—P21.5254 (15)N13—H13C0.892 (18)
O7—P21.5201 (16)N13—H13D0.859 (18)
O8—P21.5295 (15)N14—H14A0.874 (18)
N11—H11A0.862 (18)N14—H14B0.856 (18)
N11—H11B0.859 (18)N14—H14C0.861 (18)
N11—H11C0.876 (18)N14—H14D0.890 (18)
P1—O1—H1116 (3)H11C—N11—H11D110 (3)
P2—O5—H5115 (3)H12A—N12—H12B107 (3)
O3—P1—O4111.44 (9)H12A—N12—H12C113 (3)
O3—P1—O2111.70 (9)H12B—N12—H12C111 (3)
O4—P1—O2112.43 (9)H12A—N12—H12D112 (3)
O3—P1—O1107.95 (10)H12B—N12—H12D108 (3)
O4—P1—O1104.71 (10)H12C—N12—H12D106 (3)
O2—P1—O1108.21 (9)H13A—N13—H13B118 (3)
O7—P2—O6111.73 (9)H13A—N13—H13C112 (3)
O7—P2—O8111.74 (9)H13B—N13—H13C107 (3)
O6—P2—O8112.79 (9)H13A—N13—H13D101 (3)
O7—P2—O5107.68 (9)H13B—N13—H13D105 (3)
O6—P2—O5103.69 (9)H13C—N13—H13D113 (3)
O8—P2—O5108.73 (9)H14A—N14—H14B114 (3)
H11A—N11—H11B107 (3)H14A—N14—H14C107 (3)
H11A—N11—H11C105 (3)H14B—N14—H14C109 (3)
H11B—N11—H11C119 (3)H14A—N14—H14D112 (3)
H11A—N11—H11D105 (3)H14B—N14—H14D112 (3)
H11B—N11—H11D110 (3)H14C—N14—H14D102 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O1—H1···O7i0.78 (4)1.80 (4)2.570 (2)168 (4)
O5—H5···O8ii0.85 (4)1.79 (4)2.632 (2)170 (4)
N11—H11A···O4iii0.86 (2)1.89 (2)2.747 (2)175 (4)
N11—H11B···O8i0.86 (2)2.10 (2)2.951 (2)171 (3)
N11—H11C···O3iv0.88 (2)1.99 (2)2.852 (3)169 (3)
N11—H11D···O4i0.88 (2)2.01 (2)2.870 (2)167 (3)
N12—H12A···O6v0.87 (2)1.91 (2)2.755 (2)165 (3)
N12—H12B···O5vi0.88 (2)2.16 (2)3.008 (3)161 (3)
N12—H12C···O6i0.87 (2)1.99 (2)2.827 (2)161 (3)
N12—H12D···O20.88 (2)1.88 (2)2.754 (2)175 (3)
N13—H13A···O30.86 (2)1.92 (2)2.773 (2)172 (3)
N13—H13B···O2vii0.86 (2)1.96 (2)2.822 (2)175 (3)
N13—H13C···O6v0.89 (2)1.95 (2)2.830 (2)168 (3)
N13—H13D···O2ii0.86 (2)1.96 (2)2.820 (2)176 (3)
N14—H14A···O70.87 (2)1.90 (2)2.771 (2)174 (3)
N14—H14B···O8vii0.86 (2)2.01 (2)2.859 (2)171 (3)
N14—H14C···O3iv0.86 (2)1.92 (2)2.784 (2)178 (3)
N14—H14D···O40.89 (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.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2137).

References

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