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Crystals of sodium zinc diiron(III) triphosphate, NaZnFe2(PO4)3, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The compound features a new structural type built up from ZnO6 octahedra, FeO6 octahedra and FeO4 tetrahedra, linked together via the corners and edges of PO4 tetrahedra to form a three-dimensional framework, with tunnels running along [100]. Within these tunnels, Na+ cations occupy a highly distorted cubic site.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010201541X/iz1022sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S010827010201541X/iz1022Isup2.hkl
Contains datablock I

Comment top

The investigation of iron phosphates during the past two decades has led to the synthesis and characterization of numerous compounds with a variety of network structures. Most of these compounds belong to the binary A3PO4—FePO4 system, where A is a monovalent cation. By contrast, the bibliographic data reveal only a small number of ternary iron phosphates of the A3PO4M3(PO4)2-FePO4 system, where A and M are a monovalent and a divalent cation, respectively, namely, Na3Ca18Fe(PO4)14 (Strunkova et al., 1997), Na2Fe3(PO4)3 (Yakubovich et al., 1977), NaFe3(PO4)3 (Corbin et al., 1986), Na7Fe4(PO4)6 (Lii, 1996), NaFe3.67(PO4)3 (Korzenski et al., 1998), KBaFe2(PO4)3 (Battle et al., 1986) and Cu1.35Fe3(PO4)3 (Warner et al., 1993).

As part of our study of the crystal chemistry of ternary iron monophosphates belonging to the Na3PO4M3(PO4)2-FePO4 system, we report here the synthesis and structural characterization of NaZnFe2(PO4)3. This compound features a new type of structure (Fig. 1), comprising FeO6, FeO4 and ZnO6 polyhedra connected together via the corners and edges of three crystallographically distinct PO4 tetrahedra. The resulting complex three-dimensional framework contains tunnels running along the [100] direction, in which the Na+ cations reside.

The oxygen environment around the Zn atoms in NaZnFe2(PO4)3 approximates a highly distorted octahedron, as indicated by the Zn—O bond lengths and O—Zn—O bond angles (Table 1 Do you wish to publish any angles?). The ZnO6 octahedron shares two corners, atoms O11 and O14, with two P1O4 tetrahedra, one edge, O23—O24, with one P2O4 tetrahedron, and the remaining two corners, atoms O31 and O34, with two P3O4 tetrahedra.

The Fe1 atoms also exhibit a distorted octahedral environment. The Fe1O6 octahedron shares one edge, O13—O14, with one P1O4 tetrahedron, and three corners, atoms O21, O23 and O24, with three P2O4 tetrahedra. The sixth vertex, atom O34, is shared with the P3O4 group.

The Fe2 atoms exhibit an unusual tetrahedral environment. The corresponding bond distances are close to those observed in FePO4 (Calvo, 1975). The Fe2O4 tetrahedron shares the corners O12 and O22 with P1O4 and P2O4 tetrahedra, respectively, and the other two corners, atoms O32 and O33, with two P3O4 groups.

The Na+ cations are located within tunnels running along [100]. Their environment (Fig. 2) was determined assuming Na—O distances of less than 3.0 Å. They then have an irregular eight-coordinate site, with Na—O bond distances similar to those frequently observed for Na atoms with coordination number 8.

Experimental top

Crystals of NaZnFe2(PO4)3 were prepared from a stoichiometric mixture of Fe(NO3)3·9H2O, ZnO, NaH2PO4 and (NH4)2HPO4. The mixture was initially heated for 12 h at 873 K to evacuate the decomposition products (H2O, NH3, etc.), then melted for 1 h at 1253 K and finally cooled down to room temperature at the rate of 10 K h-1. Elemental analysis on crystal samples using an MEB Please define indicated the presence of Zn, Fe, P and Na in the atomic ratio 1:2:3:1.

Refinement top

The Zn and Fe atoms were located by direct methods, and the remaining atoms were found by successive difference Fourier maps.

Computing details top

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare, 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The structure of NaZnFe2(PO4)3, viewed along the a direction. The ZnO6 and PO4 polyhedra are illustrated by lined and crossed patterns, respectively. The remaining polyhedra are Fe1O6 and Fe2O4. The Na+ cations are represented by solid circles.
[Figure 2] Fig. 2. The coordination environment of the Na+ cations. Displacement ellipsoids are drawn at the 50% probability level.
Sodium zinc diiron(III) triphosphate top
Crystal data top
NaZnFe2(PO4)3F(000) = 936
Mr = 484.97Dx = 3.415 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 25 reflections
a = 5.124 (1) Åθ = 10–15°
b = 12.213 (5) ŵ = 6.18 mm1
c = 15.072 (9) ÅT = 293 K
V = 943.2 (7) Å3Parallelepiped, brown
Z = 40.22 × 0.10 × 0.06 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1184 reflections with I > 2σi(I)
Radiation source: fine-focus sealed tubeRint = 0.020
Graphite monochromatorθmax = 27.0°, θmin = 2.2°
ω/2θ scansh = 06
Absorption correction: ψ scan
(North et al., 1968)
k = 015
Tmin = 0.529, Tmax = 0.690l = 119
1314 measured reflections2 standard reflections every 120 min
1293 independent reflections intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0392P)2 + 0.4314P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.029(Δ/σ)max = 0.006
wR(F2) = 0.078Δρmax = 0.64 e Å3
S = 1.24Δρmin = 1.05 e Å3
1293 reflectionsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=3DkFc[1+0.001xFc2λ3/sin(2θ)]-1/4
173 parametersExtinction coefficient: 0.0038 (8)
0 restraintsAbsolute structure: Flack (1983) with 70 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.02 (3)
Crystal data top
NaZnFe2(PO4)3V = 943.2 (7) Å3
Mr = 484.97Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 5.124 (1) ŵ = 6.18 mm1
b = 12.213 (5) ÅT = 293 K
c = 15.072 (9) Å0.22 × 0.10 × 0.06 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1184 reflections with I > 2σi(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.020
Tmin = 0.529, Tmax = 0.6902 standard reflections every 120 min
1314 measured reflections intensity decay: none
1293 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0290 restraints
wR(F2) = 0.078Δρmax = 0.64 e Å3
S = 1.24Δρmin = 1.05 e Å3
1293 reflectionsAbsolute structure: Flack (1983) with 70 Friedel pairs
173 parametersAbsolute structure parameter: 0.02 (3)
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
Zn0.06981 (16)0.29213 (7)0.74255 (6)0.0133 (2)
Fe10.49416 (18)0.71170 (7)0.63627 (6)0.0070 (2)
Fe20.2579 (2)0.08015 (7)0.50767 (6)0.0092 (2)
Na0.5429 (7)0.9796 (2)0.7110 (2)0.0214 (7)
P10.0151 (4)0.54300 (13)0.65861 (11)0.0075 (3)
O110.0420 (11)0.4470 (4)0.7200 (3)0.0152 (11)
O120.0233 (12)0.5088 (4)0.5609 (3)0.0183 (11)
O130.2989 (9)0.5830 (4)0.6726 (3)0.0114 (10)
O140.1754 (9)0.6382 (4)0.6799 (3)0.0112 (10)
P20.0162 (4)0.86363 (13)0.57751 (11)0.0072 (3)
O210.0078 (10)0.8096 (4)0.4874 (3)0.0150 (10)
O220.0432 (10)0.9871 (4)0.5716 (3)0.0152 (11)
O230.2801 (9)0.8501 (4)0.6256 (3)0.0102 (10)
O240.1845 (9)0.8099 (4)0.6423 (3)0.0103 (10)
P30.4055 (4)0.23909 (13)0.63258 (11)0.0082 (4)
O310.1171 (10)0.2191 (4)0.6504 (3)0.0157 (11)
O320.5368 (10)0.1316 (4)0.6024 (3)0.0139 (11)
O330.4459 (11)0.3255 (4)0.5590 (3)0.0196 (11)
O340.5425 (10)0.2787 (4)0.7192 (3)0.0166 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn0.0117 (4)0.0142 (4)0.0139 (4)0.0003 (3)0.0006 (3)0.0005 (3)
Fe10.0053 (4)0.0070 (4)0.0087 (4)0.0002 (4)0.0004 (4)0.0007 (3)
Fe20.0102 (5)0.0090 (4)0.0084 (4)0.0017 (4)0.0001 (4)0.0013 (4)
Na0.0205 (17)0.0193 (13)0.0245 (15)0.0002 (14)0.0051 (15)0.0035 (12)
P10.0066 (7)0.0074 (7)0.0086 (8)0.0006 (7)0.0009 (7)0.0008 (6)
O110.016 (3)0.009 (2)0.021 (2)0.003 (2)0.000 (2)0.0022 (19)
O120.022 (3)0.026 (3)0.007 (2)0.004 (2)0.005 (2)0.002 (2)
O130.007 (2)0.011 (2)0.016 (2)0.001 (2)0.003 (2)0.002 (2)
O140.008 (2)0.008 (2)0.017 (2)0.0028 (19)0.003 (2)0.0009 (19)
P20.0072 (8)0.0073 (7)0.0070 (7)0.0007 (7)0.0007 (7)0.0005 (6)
O210.013 (2)0.021 (2)0.011 (2)0.001 (2)0.000 (2)0.002 (2)
O220.016 (3)0.008 (2)0.022 (3)0.005 (2)0.009 (2)0.0000 (19)
O230.009 (2)0.008 (2)0.014 (2)0.002 (2)0.002 (2)0.0014 (19)
O240.010 (2)0.013 (2)0.008 (2)0.0029 (19)0.0013 (19)0.0007 (19)
P30.0075 (8)0.0092 (7)0.0080 (7)0.0010 (7)0.0011 (7)0.0007 (6)
O310.011 (2)0.020 (2)0.016 (2)0.001 (2)0.001 (2)0.006 (2)
O320.015 (3)0.015 (2)0.012 (2)0.005 (2)0.004 (2)0.0024 (18)
O330.021 (3)0.015 (2)0.023 (3)0.003 (2)0.001 (3)0.011 (2)
O340.012 (2)0.020 (2)0.018 (2)0.006 (2)0.005 (2)0.003 (2)
Geometric parameters (Å, º) top
Zn—O311.908 (5)Na—O32viii2.476 (6)
Zn—O112.006 (5)Na—O13iv2.497 (6)
Zn—O34i2.024 (5)Na—O24ix2.705 (6)
Zn—O24ii2.181 (5)Na—O34vii2.705 (6)
Zn—O14ii2.279 (5)Na—O14vii2.922 (6)
Zn—O23ii2.369 (5)Na—O22ix2.987 (6)
Fe1—O21iii1.882 (5)P1—O111.521 (5)
Fe1—O131.942 (5)P1—O121.544 (5)
Fe1—O241.991 (5)P1—O131.549 (5)
Fe1—O14i2.026 (5)P1—O141.552 (5)
Fe1—O23i2.054 (5)P2—O211.511 (5)
Fe1—O34iv2.340 (5)P2—O221.541 (5)
Fe2—O22v1.852 (5)P2—O231.543 (5)
Fe2—O33vi1.851 (5)P2—O241.563 (5)
Fe2—O12vi1.872 (5)P3—O311.522 (5)
Fe2—O32i1.881 (5)P3—O321.544 (5)
Na—O11vii2.401 (7)P3—O331.545 (5)
Na—O232.444 (6)P3—O341.559 (5)
O31—Zn—O11100.0 (2)O32viii—Na—O13iv94.52 (19)
O31—Zn—O34i109.1 (2)O11vii—Na—O24ix65.25 (17)
O11—Zn—O34i109.1 (2)O23—Na—O24ix65.63 (16)
O31—Zn—O24ii109.0 (2)O32viii—Na—O24ix109.13 (19)
O11—Zn—O24ii82.5 (2)O13iv—Na—O24ix156.21 (19)
O34i—Zn—O24ii137.1 (2)O11vii—Na—O34vii79.91 (18)
O31—Zn—O14ii96.1 (2)O23—Na—O34vii61.90 (17)
O11—Zn—O14ii158.9 (2)O32viii—Na—O34vii159.3 (2)
O34i—Zn—O14ii77.84 (19)O13iv—Na—O34vii96.03 (18)
O24ii—Zn—O14ii79.40 (18)O24ix—Na—O34vii62.46 (16)
O31—Zn—O23ii168.10 (19)O11vii—Na—O14vii55.13 (15)
O11—Zn—O23ii89.45 (19)O23—Na—O14vii176.0 (2)
O34i—Zn—O23ii73.97 (19)O32viii—Na—O14vii83.18 (18)
O24ii—Zn—O23ii64.82 (17)O13iv—Na—O14vii61.09 (16)
O14ii—Zn—O23ii73.03 (17)O24ix—Na—O14vii117.90 (19)
O21iii—Fe1—O1399.5 (2)O34vii—Na—O14vii117.54 (17)
O21iii—Fe1—O2497.2 (2)O11vii—Na—O22ix71.37 (18)
O13—Fe1—O2493.7 (2)O23—Na—O22ix92.32 (18)
O21iii—Fe1—O14i105.3 (2)O32viii—Na—O22ix61.35 (17)
O13—Fe1—O14i88.88 (19)O13iv—Na—O22ix146.51 (19)
O24—Fe1—O14i156.6 (2)O24ix—Na—O22ix52.23 (14)
O21iii—Fe1—O23i92.2 (2)O34vii—Na—O22ix114.60 (18)
O13—Fe1—O23i168.0 (2)O14vii—Na—O22ix91.41 (16)
O24—Fe1—O23i87.52 (19)O11—P1—O12110.3 (3)
O14i—Fe1—O23i85.38 (19)O11—P1—O13109.9 (3)
O21iii—Fe1—O34iv166.1 (2)O12—P1—O13109.6 (3)
O13—Fe1—O34iv94.29 (19)O11—P1—O14109.3 (3)
O24—Fe1—O34iv80.26 (18)O12—P1—O14108.6 (3)
O14i—Fe1—O34iv76.38 (18)O13—P1—O14109.0 (3)
O23i—Fe1—O34iv74.09 (19)O21—P2—O22111.7 (3)
O22v—Fe2—O33vi109.2 (3)O21—P2—O23113.6 (3)
O22v—Fe2—O12vi106.7 (2)O22—P2—O23107.8 (3)
O33vi—Fe2—O12vi113.5 (2)O21—P2—O24111.1 (3)
O22v—Fe2—O32i98.2 (2)O22—P2—O24108.4 (3)
O33vi—Fe2—O32i121.3 (2)O23—P2—O24103.8 (3)
O12vi—Fe2—O32i106.1 (2)O31—P3—O32109.8 (3)
O11vii—Na—O23127.5 (2)O31—P3—O33111.5 (3)
O11vii—Na—O32viii114.9 (2)O32—P3—O33108.1 (3)
O23—Na—O32viii97.5 (2)O31—P3—O34109.8 (3)
O11vii—Na—O13iv102.9 (2)O32—P3—O34108.3 (3)
O23—Na—O13iv114.9 (2)O33—P3—O34109.2 (3)
Symmetry codes: (i) x+1, y, z; (ii) x, y1/2, z+3/2; (iii) x+1/2, y+3/2, z+1; (iv) x, y+1/2, z+3/2; (v) x, y1, z; (vi) x+1/2, y+1/2, z+1; (vii) x1, y+1/2, z+3/2; (viii) x, y+1, z; (ix) x1, y, z.

Experimental details

Crystal data
Chemical formulaNaZnFe2(PO4)3
Mr484.97
Crystal system, space groupOrthorhombic, P212121
Temperature (K)293
a, b, c (Å)5.124 (1), 12.213 (5), 15.072 (9)
V3)943.2 (7)
Z4
Radiation typeMo Kα
µ (mm1)6.18
Crystal size (mm)0.22 × 0.10 × 0.06
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.529, 0.690
No. of measured, independent and
observed [I > 2σi(I)] reflections
1314, 1293, 1184
Rint0.020
(sin θ/λ)max1)0.638
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.029, 0.078, 1.24
No. of reflections1293
No. of parameters173
Δρmax, Δρmin (e Å3)0.64, 1.05
Absolute structureFlack (1983) with 70 Friedel pairs
Absolute structure parameter0.02 (3)

Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SIR92 (Altomare, 1993), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 1998), SHELXL97.

Selected geometric parameters (Å, º) top
Zn—O311.908 (5)Na—O32viii2.476 (6)
Zn—O112.006 (5)Na—O13iv2.497 (6)
Zn—O34i2.024 (5)Na—O24ix2.705 (6)
Zn—O24ii2.181 (5)Na—O34vii2.705 (6)
Zn—O14ii2.279 (5)Na—O14vii2.922 (6)
Zn—O23ii2.369 (5)Na—O22ix2.987 (6)
Fe1—O21iii1.882 (5)P1—O111.521 (5)
Fe1—O131.942 (5)P1—O121.544 (5)
Fe1—O241.991 (5)P1—O131.549 (5)
Fe1—O14i2.026 (5)P1—O141.552 (5)
Fe1—O23i2.054 (5)P2—O211.511 (5)
Fe1—O34iv2.340 (5)P2—O221.541 (5)
Fe2—O22v1.852 (5)P2—O231.543 (5)
Fe2—O33vi1.851 (5)P2—O241.563 (5)
Fe2—O12vi1.872 (5)P3—O311.522 (5)
Fe2—O32i1.881 (5)P3—O321.544 (5)
Na—O11vii2.401 (7)P3—O331.545 (5)
Na—O232.444 (6)P3—O341.559 (5)
O31—Zn—O11100.0 (2)O34i—Zn—O14ii77.84 (19)
O31—Zn—O34i109.1 (2)O24ii—Zn—O14ii79.40 (18)
O11—Zn—O34i109.1 (2)O31—Zn—O23ii168.10 (19)
O31—Zn—O24ii109.0 (2)O11—Zn—O23ii89.45 (19)
O11—Zn—O24ii82.5 (2)O34i—Zn—O23ii73.97 (19)
O34i—Zn—O24ii137.1 (2)O24ii—Zn—O23ii64.82 (17)
O31—Zn—O14ii96.1 (2)O14ii—Zn—O23ii73.03 (17)
O11—Zn—O14ii158.9 (2)
Symmetry codes: (i) x+1, y, z; (ii) x, y1/2, z+3/2; (iii) x+1/2, y+3/2, z+1; (iv) x, y+1/2, z+3/2; (v) x, y1, z; (vi) x+1/2, y+1/2, z+1; (vii) x1, y+1/2, z+3/2; (viii) x, y+1, z; (ix) x1, y, z.
 

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