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The title compound, (NH4)ZnPO4–HEX, is built up from a three-dimensional network of ZnO4 and PO4 tetrahedra [dav(Zn—O) = 1.9400 (7) Å and dav(P—O) = 1.5396 (7) Å], fused together via Zn—O—P links [θav = 133.47 (4)°]. An undisordered linear Zn—O—P bond occurs (all three atoms lie on a threefold axis). Extra-framework NH4+ cations, which interact with the [ZnPO4] framework by hydrogen bonds, complete the crystal structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101002992/gd1138sup1.cif
Contains datablocks ltbill, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101002992/gd1138Isup2.hkl
Contains datablock I

Comment top

MZnPO4 phases (M = univalent cation) built up from a three-dimensional framework of vertex-sharing ZnO4 and PO4 tetrahedra are of interest for their physical properties (Blum et al., 1986), their phase transition behaviour (Kahlenberg, 1998; Hammond, Barbier & Gallardo, 1998), and their structural relationship to polymorphs of silica and aluminosilicate zeolites (Harrison, 2000). Here, we describe the low-temperature (10 K) structure of the hexagonal form (Averbuch-Pouchot & Durif, 1968) of ammonium zinc phosphate, NH4ZnPO4. We have named this phase NH4ZnPO4—HEX in order to distinguish it from monoclinic NH4ZnPO4—ABW (Bu et al., 1997).

There are 12 framework (2 Zn, 2 P, 8 O) and eight extra-framework (2 N, 6 H) atoms in this structure. The geometrical parameters for the ZnO4 and PO4 tetrahedra [dav(Zn—O) = 1.9400 (7) Å; dav(P—O) = 1.5396 (7) Å]. are typical (Bu et al., 1997). The linkage of these moieties by Zn—O—P bonds results in a strictly alternating array of Zn and P tetrahedral nodes with an average Zn—O—P bond angle of 133.47 (4)° excluding the linear Zn2—O6—P2 bond.

The framework structure of NH4ZnPO4—HEX is built up from infinite sheets of tetrahedral six rings arrayed normal to [0001] (Figure 2). Topologically, this linkage pattern of Zn and P atoms via O atom bridges may be described as layers of simple 63 hexagonal nets (Hyde & O'Keeffe, 1996). The fourth Zn—O or P—O vertex points approximately either up (U) or down (D) with respect to the the [0001] direction. Using the up/down classification (Liebau, 1985), two types of six ring may be identified as UDUDUD and UUUDDD. In this structure, there are three UUUDDD rings for every UDUDUD ring in any [0001] sheet.

The extra-framework ammonium cations occupy the [0001] channels and interact with the [ZnPO4]- framework by N—H···O hydrogen bonds (Table 2). N1 occupies the UUUDDD channels and makes four N—H···O hydrogen bonds to framework oxygen species. N2 occupies the UDUDUD channels, and makes three equivalent H bonds, as N2—H22···O1. The N2—H21 moiety which occupies the threefold axis does not participate in any H bonds: all these bonds point the same way in this polar crystal structure. Framework atoms O1—O5 act as H bond acceptors, with only O6 not involved in these guest-framework interactions.

NH4ZnPO4—HEX is isostructural with NH4CoPO4 (Feng et al., 1997) and α-AgZnPO4 (Hammond et al., 1998). As noted recently (Hammond et al., 1998; Harrison, 2000) the NH4ZnPO4—HEX structure is not isostructural with hexagonal nepheline types such as β-(Na3/4K1/4)AlGeO4 (Hammond & Barbier, 1998) which have the same space group and similar lattice parameters to NH4ZnPO4—HEX. The nepheline types contain just one topologically distinct six-ring (type UDUDUD), as adopted by the tridymite form of SiO2.

A notable feature of the NH4ZnPO4—HEX structure is the symmetry constrained, linear Zn2—O6—P2 bond. At 10 K, there is negligible anisotropy in the thermal motion of O6, which has a ratio of longest-to-shortest ellipsoid axes, U3/U1, of 3.11, compared to an average of 2.53 for the other five O atoms. Conversely, in α-AgZnPO4 (Hammond et al., 1998), the equivalent linear Zn—O—P bond is disordered over three equivalent positions about the threefold axis [resulting Zn—O—P bond angle = 165.8 (4)°]. It was suggested that Ag—O bonding may play a role in promoting this situation, whereas for NH4ZnPO4—HEX, the linear Zn—O6—P bond is the only one not involved in interactions with the ammonium cation.

Related literature top

For related literature, see: Averbuch-Pouchot & Durif (1968); Blum et al. (1986); Bu et al. (1997); Feng et al. (1997); Hammond & Barbier (1998); Hammond, Barbier & Gallardo (1998); Harrison (2000); Hyde & O'Keeffe (1996); Kahlenberg (1998); Liebau (1985).

Experimental top

A mixture of N2H4 (2.35 g, 73 mmol), zinc acetate (2.20 g, 10 mmol), 85% H3PO4 (4.6 g, 40 mmol) and water (9.08 g, 500 mmol) was placed in a plastic bottle (initial pH = 6.5) and heated to 343 K for 14 d. Numerous bicapped,hexagonal rods (maximum size 1 mm) of the title compound were recovered by vacuum filtration and drying in air. Elemental analysis (Found: N 7.85, 2.22%; calculated 7.86%, H 2.24%) was consistent with the crystal structure.

Refinement top

All H atoms were located from diffence maps and their atomic coordinates and isotropic thermal factors were freely refined.

Computing details top

Data collection: local routines; cell refinement: local routines; data reduction: local routines; program(s) used to solve structure: SHELXS86 (Sheldrick, 1986); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Shape Software Inc., 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Fragment of the NH4ZnPO4—HEX structure (50% displacement ellipsoids). [Symmetry codes (i) 1 - x + y, 1 - x, z; (ii) 1 - y, x - y, z; (iii) 1 + x - y, x, -1/2 + z; (iv) y, 1 - x + y, -1/2 + z; (v) -x + y, -x, z; (vi) -y, x - y, z.]
[Figure 2] Fig. 2. Polyhedral view down [0001] of NH4ZnPO4—HEX with selected tetrahedra labelled to show a UDUDUD six ring centred at x = 0, y = 1 and a UUUDDD six ring at x = 0.4, y = 1. The N1 ammonium cations occupy the UUUDDD channels; the N2 ammonium cations occupy the UDUDUD channels.
(I) top
Crystal data top
(NH4)·(ZnPO4)Dx = 2.745 Mg m3
Mr = 178.38Melting point: decomposes before melting K
Hexagonal, P63Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 6cCell parameters from 20 reflections
a = 10.702 (2) Åθ = 13.3–13.7°
c = 8.703 (2) ŵ = 5.95 mm1
V = 863.2 (3) Å3T = 10 K
Z = 8Hexagonal prism, colourless
F(000) = 7040.20 × 0.20 × 0.20 mm
Data collection top
Huber
diffractometer
3026 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.026
Graphite monochromatorθmax = 37.6°, θmin = 3.2°
θ/2θ scansh = 018
Absorption correction: analytical
(ABSORB; Hall et al., 1995)
k = 1815
Tmin = 0.824, Tmax = 0.952l = 1414
9471 measured reflections3 standard reflections every 97 reflections
3049 independent reflections intensity decay: none
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.013 w = 1/[σ2(Fo2) + (0.013P)2 + 0.062P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.031(Δ/σ)max = 0.003
S = 1.15Δρmax = 0.38 e Å3
3049 reflectionsΔρmin = 0.58 e Å3
109 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.0329 (5)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.000 (5)
Crystal data top
(NH4)·(ZnPO4)Z = 8
Mr = 178.38Mo Kα radiation
Hexagonal, P63µ = 5.95 mm1
a = 10.702 (2) ÅT = 10 K
c = 8.703 (2) Å0.20 × 0.20 × 0.20 mm
V = 863.2 (3) Å3
Data collection top
Huber
diffractometer
3026 reflections with I > 2σ(I)
Absorption correction: analytical
(ABSORB; Hall et al., 1995)
Rint = 0.026
Tmin = 0.824, Tmax = 0.9523 standard reflections every 97 reflections
9471 measured reflections intensity decay: none
3049 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.013H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.031Δρmax = 0.38 e Å3
S = 1.15Δρmin = 0.58 e Å3
3049 reflectionsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
109 parametersAbsolute structure parameter: 0.000 (5)
1 restraint
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
xyzUiso*/Ueq
N10.05046 (8)0.53438 (8)0.75371 (10)0.00646 (10)
N20.00000.00000.74956 (16)0.00664 (18)
Zn10.822249 (9)0.674521 (9)0.951768 (11)0.00320 (2)
Zn20.66670.33330.57517 (2)0.00317 (3)
P10.81947 (2)0.67342 (2)0.57189 (3)0.00309 (4)
P20.66670.33330.96623 (5)0.00338 (6)
O11.02517 (7)0.81712 (7)0.97324 (7)0.00520 (10)
O20.77303 (7)0.68119 (7)0.73743 (7)0.00543 (9)
O30.69860 (7)0.72409 (7)1.07217 (8)0.00558 (9)
O40.77175 (7)0.48534 (7)1.03021 (8)0.00556 (9)
O50.71408 (7)0.52403 (7)0.50269 (8)0.00567 (9)
O60.66670.33330.79295 (13)0.00863 (19)
H110.084 (3)0.574 (2)0.838 (3)0.018 (5)*
H120.110 (3)0.528 (2)0.697 (3)0.019 (5)*
H130.0144 (18)0.4453 (18)0.769 (2)0.004 (3)*
H140.011 (2)0.578 (2)0.702 (3)0.017 (5)*
H210.00000.00000.642 (4)0.022 (9)*
H220.082 (2)0.026 (2)0.789 (2)0.020 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0068 (2)0.0064 (2)0.0065 (3)0.0035 (2)0.0003 (2)0.0004 (2)
N20.0065 (3)0.0065 (3)0.0069 (4)0.00325 (13)0.0000.000
Zn10.00284 (4)0.00291 (4)0.00376 (4)0.00136 (3)0.00003 (3)0.00007 (3)
Zn20.00291 (4)0.00291 (4)0.00367 (6)0.00146 (2)0.0000.000
P10.00267 (7)0.00279 (8)0.00370 (9)0.00129 (6)0.00002 (6)0.00023 (6)
P20.00327 (8)0.00327 (8)0.00359 (15)0.00164 (4)0.0000.000
O10.0039 (2)0.0052 (2)0.0065 (2)0.00225 (18)0.00124 (16)0.00025 (17)
O20.0054 (2)0.0070 (2)0.0037 (2)0.00299 (19)0.00018 (17)0.00011 (16)
O30.0064 (2)0.0043 (2)0.0073 (2)0.00359 (18)0.0020 (2)0.00118 (19)
O40.0051 (2)0.0030 (2)0.0079 (2)0.00144 (19)0.00142 (18)0.00023 (18)
O50.0063 (2)0.0036 (2)0.0060 (2)0.00169 (19)0.00147 (19)0.00037 (18)
O60.0111 (3)0.0111 (3)0.0036 (4)0.00556 (14)0.0000.000
Geometric parameters (Å, º) top
N1—H110.83 (2)Zn2—O5i1.9455 (7)
N1—H120.84 (2)Zn2—O5ii1.9455 (7)
N1—H130.865 (17)Zn2—O51.9455 (7)
N1—H140.89 (2)P1—O21.5398 (7)
N2—H210.93 (4)P1—O3iii1.5423 (7)
N2—H220.85 (2)P1—O1iv1.5423 (7)
Zn1—O41.9399 (7)P1—O51.5451 (7)
Zn1—O11.9406 (8)P2—O61.5081 (13)
Zn1—O21.9494 (7)P2—O4i1.5465 (7)
Zn1—O31.9577 (7)P2—O41.5465 (7)
Zn2—O61.8953 (12)P2—O4ii1.5465 (7)
H11—N1—H12114 (2)O2—P1—O3iii109.70 (4)
H11—N1—H13109 (2)O2—P1—O1iv109.75 (4)
H12—N1—H13103.1 (18)O3iii—P1—O1iv108.40 (4)
H11—N1—H14112.1 (19)O2—P1—O5109.40 (4)
H12—N1—H14109 (2)O3iii—P1—O5110.27 (4)
H13—N1—H14109.1 (18)O1iv—P1—O5109.30 (4)
H21—N2—H22113.6 (13)O6—P2—O4i111.10 (3)
O4—Zn1—O1113.90 (3)O6—P2—O4111.10 (3)
O4—Zn1—O2115.82 (3)O4i—P2—O4107.79 (3)
O1—Zn1—O2106.26 (3)O6—P2—O4ii111.10 (3)
O4—Zn1—O3102.77 (3)O4i—P2—O4ii107.79 (3)
O1—Zn1—O3112.18 (3)O4—P2—O4ii107.79 (3)
O2—Zn1—O3105.70 (3)P1v—O1—Zn1131.77 (4)
O6—Zn2—O5i108.92 (2)P1—O2—Zn1142.46 (4)
O6—Zn2—O5ii108.92 (2)P1vi—O3—Zn1133.60 (4)
O5i—Zn2—O5ii110.02 (2)P2—O4—Zn1130.37 (4)
O6—Zn2—O5108.92 (2)P1—O5—Zn2129.17 (4)
O5i—Zn2—O5110.02 (2)P2—O6—Zn2180.0
O5ii—Zn2—O5110.02 (2)
Symmetry codes: (i) x+y+1, x+1, z; (ii) y+1, xy, z; (iii) xy+1, x, z1/2; (iv) y, x+y+1, z1/2; (v) xy+1, x, z+1/2; (vi) y, x+y+1, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H11···O5vii0.83 (3)1.97 (2)2.7843 (13)165 (2)
N1—H12···O4viii0.84 (3)1.98 (3)2.8018 (14)169 (3)
N1—H13···O2ix0.864 (17)2.070 (17)2.8553 (12)150.7 (19)
N1—H14···O3x0.89 (2)1.90 (2)2.7702 (14)166 (2)
N2—H22···O1ix0.85 (2)2.10 (2)2.8670 (15)150.3 (17)
Symmetry codes: (vii) xy, x, z+1/2; (viii) x+1, y+1, z1/2; (ix) x+y, x+1, z; (x) xy, x, z1/2.

Experimental details

Crystal data
Chemical formula(NH4)·(ZnPO4)
Mr178.38
Crystal system, space groupHexagonal, P63
Temperature (K)10
a, c (Å)10.702 (2), 8.703 (2)
V3)863.2 (3)
Z8
Radiation typeMo Kα
µ (mm1)5.95
Crystal size (mm)0.20 × 0.20 × 0.20
Data collection
DiffractometerHuber
diffractometer
Absorption correctionAnalytical
(ABSORB; Hall et al., 1995)
Tmin, Tmax0.824, 0.952
No. of measured, independent and
observed [I > 2σ(I)] reflections
9471, 3049, 3026
Rint0.026
(sin θ/λ)max1)0.857
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.013, 0.031, 1.15
No. of reflections3049
No. of parameters109
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.38, 0.58
Absolute structureFlack H D (1983), Acta Cryst. A39, 876-881
Absolute structure parameter0.000 (5)

Computer programs: local routines, SHELXS86 (Sheldrick, 1986), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997) and ATOMS (Shape Software Inc., 1999), SHELXL97.

Selected geometric parameters (Å, º) top
Zn1—O41.9399 (7)P1—O21.5398 (7)
Zn1—O11.9406 (8)P1—O3iii1.5423 (7)
Zn1—O21.9494 (7)P1—O1iv1.5423 (7)
Zn1—O31.9577 (7)P1—O51.5451 (7)
Zn2—O61.8953 (12)P2—O61.5081 (13)
Zn2—O5i1.9455 (7)P2—O4i1.5465 (7)
Zn2—O5ii1.9455 (7)P2—O41.5465 (7)
Zn2—O51.9455 (7)P2—O4ii1.5465 (7)
P1v—O1—Zn1131.77 (4)P2—O4—Zn1130.37 (4)
P1—O2—Zn1142.46 (4)P1—O5—Zn2129.17 (4)
P1vi—O3—Zn1133.60 (4)P2—O6—Zn2180.0
Symmetry codes: (i) x+y+1, x+1, z; (ii) y+1, xy, z; (iii) xy+1, x, z1/2; (iv) y, x+y+1, z1/2; (v) xy+1, x, z+1/2; (vi) y, x+y+1, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H11···O5vii0.83 (3)1.97 (2)2.7843 (13)165 (2)
N1—H12···O4viii0.84 (3)1.98 (3)2.8018 (14)169 (3)
N1—H13···O2ix0.864 (17)2.070 (17)2.8553 (12)150.7 (19)
N1—H14···O3x0.89 (2)1.90 (2)2.7702 (14)166 (2)
N2—H22···O1ix0.85 (2)2.10 (2)2.8670 (15)150.3 (17)
Symmetry codes: (vii) xy, x, z+1/2; (viii) x+1, y+1, z1/2; (ix) x+y, x+1, z; (x) xy, x, z1/2.
 

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