inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Redetermination of Fe2[BP3O12]

aDepartment of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, Henan 454000, People's Republic of China
*Correspondence e-mail: lifeifei@hpu.edu.cn

(Received 8 July 2010; accepted 27 July 2010; online 4 August 2010)

Explorations of phases in the quaternary FeIII–BIII–PV–O system prepared by the high temperature solution growth (HTSG) method led to single-crystal growth of anhydrous diiron(III) borotriphosphate, Fe2[BP3O12]. This phase has been synthesized previously as a microcrystalline material and its structure refined in space group P3 from powder X-ray diffraction data using the Rietveld method [Chen et al. (2004[Chen, H. H., Ge, M. H., Yang, X. X., Mi, J. X. & Zhao, J. T. (2004). J. Inorg. Mater. 19, 429-432.]). J. Inorg. Mater. 19, 429-432]. In the current single-crystal study, it was shown that the correct space group is P63/m. The three-dimensional structure of the title compound is built up from FeO6 octa­hedra (3.. symmetry), trigonal–planar BO3 groups ([\overline{6}] symmetry) and PO4 tetra­hedra (m.. symmetry). Two FeO6 octa­hedra form Fe2O9 dimers via face-sharing, while the anionic BO3 and PO4 groups are connected via corner-sharing to build up the [BP3O12]6− anion. Both units are inter­connected via corner-sharing.

Related literature

Reviews on the crystal chemistry of borophosphates were given by Kniep et al. (1998[Kniep, R., Engelhardt, H. & Hauf, C. (1998). Chem. Mater. 10, 2930-2934.]) and Ewald et al. (2007[Ewald, B., Huang, Y. X. & Kniep, R. (2007). Z. Anorg. Allg. Chem. 633, 1517-1540.]). For the previous powder study of Fe2[BP3O12], see: Chen et al. (2004[Chen, H. H., Ge, M. H., Yang, X. X., Mi, J. X. & Zhao, J. T. (2004). J. Inorg. Mater. 19, 429-432.]). For the structure of a related borophosphate, see: Zhao et al. (2009[Zhao, D., Cheng, W. D., Zhang, H., Huang, S. P., Xie, Z., Zhang, W. L. & Yang, S. L. (2009). Inorg. Chem. 48, 6623-6629.]). Meisel et al. (2004[Meisel, M., Päch, M., Wilde, L. & Wulff-Molder, D. (2004). Z. Anorg. Allg. Chem. 630, 983-985.]) have reported the structure of V2[BP3O12] and Mi et al. (2000[Mi, J. X., Zhao, J. T., Mao, S. Y., Huang, Y. X., Engelhardt, H. & Kniep, R. (2000). Z. Kristallogr. New Cryst. Struct. 215, 201-202.]) that of Cr2[BP3O12].

Experimental

Crystal data
  • Fe2[BP3O12]

  • Mr = 407.42

  • Hexagonal, P 63 /m

  • a = 8.0347 (8) Å

  • c = 7.4163 (13) Å

  • V = 414.63 (9) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 4.15 mm−1

  • T = 293 K

  • 0.15 × 0.05 × 0.05 mm

Data collection
  • Rigaku Mercury70 CCD diffractometer

  • Absorption correction: multi-scan (ABSCOR; Higashi, 1995[Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan.]) Tmin = 0.575, Tmax = 0.819

  • 3247 measured reflections

  • 345 independent reflections

  • 338 reflections with I > 2σ(I)

  • Rint = 0.042

Refinement
  • R[F2 > 2σ(F2)] = 0.035

  • wR(F2) = 0.072

  • S = 1.07

  • 345 reflections

  • 33 parameters

  • Δρmax = 0.58 e Å−3

  • Δρmin = −0.78 e Å−3

Table 1
Selected bond lengths (Å)

Fe1—O3i 1.929 (2)
Fe1—O2 2.103 (2)
P1—O3 1.507 (3)
P1—O2 1.538 (3)
P1—O1 1.586 (3)
O1—B1 1.357 (3)
Symmetry code: (i) -x+2, -y+1, -z+1.

Data collection: CrystalClear (Rigaku, 2004[Rigaku (2004). CrystalClear. Rigaku Corporation, Tokyo, Japan.]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 2004[Brandenburg, K. (2004). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]).

Supporting information


Comment top

The systematic development of borophosphates has led to a broad spectrum of new borophosphate compounds with quite different anionic partial structures, such as oligomeric units, chains, ribbons, layers, and three-dimensional frameworks. (Kniep et al., 1998; Ewald et al., 2007; Zhao et al., 2009).

Most of the borophosphate compounds were synthesized under hydrothermal conditions; hence, their structures usually incorporate water molecules, hydroxy groups or organic templates. There are considerably less anhydrous borophosphate compounds known, which might have better chemical and thermal stability than the hydrous or templated phases to ensure the feasibility of industrial applications. Herein, we report the redetermined structure of the anhydrous diiron(III) borotriphosphate, Fe2[BP3O12].

The basic building units of the three-dimensional structure of the title compound are FeO6 octahedra (3.. symmetry), trigonal-planar BO3 groups (6 symmetry) and PO4 tetrahedra (m.. symmetry) (Fig. 1). Two neighboring FeO6 octahedra are connected via their faces to form Fe2O9 dimers. Trigonal-planar BO3 units and PO4 tetrahedra are isolated. Each BO3 triangle connects three PO4 tetrahedra via corner-sharing O atoms and each PO4 connects three Fe2O9 groups and one BO3 group also via corner sharing. As shown in Fig. 2, the aforementioned groups are interconnected to form the three-dimensional framework of the title compound. Chen et al. (2004) have previously refined the structure of Fe2[BP3O12] in space group P3 using the Rietveld method. The analogous chromium compound Cr2[BP3O12] (Mi et al., 2000) is isotypic to this structure model. The differences between the previous and the current model are discussed in the Refinement Section. The three-dimensional frameworks of Cr2[BP3O12] (space group P3) and our model of Fe2[BP3O12] (space group P63/m) are very similar, and the differences mainly lie in the distortion of the MO6 octahedra (M = Cr, Fe). The asymmetric unit of Cr2[BP3O12] consists of four Cr atoms, and the Cr–O bond distances range from 1.88 (2) to 2.07 (2) Å, while there is only one Fe site in the asymmetric unit of Fe2[BP3O12] with Fe–O bond distances ranging from 1.929 (2) to 2.103 (2) Å. Based on the current findings, a space group change from P3 to P63/m seems to be most likely for the Cr compound but has to be evidenced experimentally. Meisel et al. (2004) have reported the analogous vanadium(III) compound V2[BP3O12] in space group P63/m, but with a tripled unit cell (a of the V compound 31/2 × a of the Fe and Cr compounds). However, a comparison of the three structures shows very similar frameworks.

Related literature top

Reviews on the crystal chemistry of borophosphates were given by Kniep et al. (1998) and Ewald et al. (2007). For the previous powder study of Fe2[BP3O12], see: Chen et al. (2004). For the structure of a related borophosphate, see: Zhao et al. (2009). Meisel et al. (2004) have reported the structure of V2[BP3O12] and Mi et al. (2000) that of Cr2[BP3O12].

Experimental top

Single crystals of Fe2[BP3O12] have been prepared by the high temperature solution growth (HTSG) method in air. A powder mixture of Fe2O3, B2O3 and NaPO3 at the molar ratio of Fe: B: Na: P = 1:5:10:10 was first ground in an agate mortar and then transferred to a platinum crucible. The sample was gradually heated in air at 1173 K for 24 h. In this stage, the reagents were completely melted. After that, the intermediate product was slowly cooled to 673 K at the rate of 2 K h-1 and then quenched to room temperature. The obtained crystals were light-red and of prismatic shape. The dimensions of the used sample were typical for the grown crystals in this batch.

Refinement top

Chen et al. (2004) have refined the structure of Fe2[BP3O12] using the Rietved method from powder X-ray data and determined the space group to be P3, in analogy with the chromium compound Cr2[BP3012] (Mi et al., 2000). However, in our study we determined the structure from single-crystal X-ray diffraction data in the centrosymmetric space group P63/m. In the progress of the space group determination using XPREP (Sheldrick, 2008), the mean |E*E-1| statistics gave a value of 0.948 revealing that the structure is centrosymmetric; the CFOM (combined figure-of-merit) value for each space group determination were P3 (16.06), P3 (7.16), P63 (7.56), P63/m (1.75). So we selected the latter space group to solve the structure. The final refinement converged with satisfactory results (R1(gt) = 0.0348). Furthermore, the final refined model was checked with the ADDSYM algorithm using the program PLATON (Spek, 2009), and no higher symmetry was found. Hence, our final structure model is considered to be reasonable and corrects the previous model by Chen et al. (2004).

The highest peak in the difference electron density map is located at a distance of 1.41 Å from the Fe1 site while the deepest hole is at a distance of 0.83 Å from the same site.

Structure description top

The systematic development of borophosphates has led to a broad spectrum of new borophosphate compounds with quite different anionic partial structures, such as oligomeric units, chains, ribbons, layers, and three-dimensional frameworks. (Kniep et al., 1998; Ewald et al., 2007; Zhao et al., 2009).

Most of the borophosphate compounds were synthesized under hydrothermal conditions; hence, their structures usually incorporate water molecules, hydroxy groups or organic templates. There are considerably less anhydrous borophosphate compounds known, which might have better chemical and thermal stability than the hydrous or templated phases to ensure the feasibility of industrial applications. Herein, we report the redetermined structure of the anhydrous diiron(III) borotriphosphate, Fe2[BP3O12].

The basic building units of the three-dimensional structure of the title compound are FeO6 octahedra (3.. symmetry), trigonal-planar BO3 groups (6 symmetry) and PO4 tetrahedra (m.. symmetry) (Fig. 1). Two neighboring FeO6 octahedra are connected via their faces to form Fe2O9 dimers. Trigonal-planar BO3 units and PO4 tetrahedra are isolated. Each BO3 triangle connects three PO4 tetrahedra via corner-sharing O atoms and each PO4 connects three Fe2O9 groups and one BO3 group also via corner sharing. As shown in Fig. 2, the aforementioned groups are interconnected to form the three-dimensional framework of the title compound. Chen et al. (2004) have previously refined the structure of Fe2[BP3O12] in space group P3 using the Rietveld method. The analogous chromium compound Cr2[BP3O12] (Mi et al., 2000) is isotypic to this structure model. The differences between the previous and the current model are discussed in the Refinement Section. The three-dimensional frameworks of Cr2[BP3O12] (space group P3) and our model of Fe2[BP3O12] (space group P63/m) are very similar, and the differences mainly lie in the distortion of the MO6 octahedra (M = Cr, Fe). The asymmetric unit of Cr2[BP3O12] consists of four Cr atoms, and the Cr–O bond distances range from 1.88 (2) to 2.07 (2) Å, while there is only one Fe site in the asymmetric unit of Fe2[BP3O12] with Fe–O bond distances ranging from 1.929 (2) to 2.103 (2) Å. Based on the current findings, a space group change from P3 to P63/m seems to be most likely for the Cr compound but has to be evidenced experimentally. Meisel et al. (2004) have reported the analogous vanadium(III) compound V2[BP3O12] in space group P63/m, but with a tripled unit cell (a of the V compound 31/2 × a of the Fe and Cr compounds). However, a comparison of the three structures shows very similar frameworks.

Reviews on the crystal chemistry of borophosphates were given by Kniep et al. (1998) and Ewald et al. (2007). For the previous powder study of Fe2[BP3O12], see: Chen et al. (2004). For the structure of a related borophosphate, see: Zhao et al. (2009). Meisel et al. (2004) have reported the structure of V2[BP3O12] and Mi et al. (2000) that of Cr2[BP3O12].

Computing details top

Data collection: CrystalClear (Rigaku, 2004); cell refinement: CrystalClear (Rigaku, 2004); data reduction: CrystalClear (Rigaku, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. Section of the structure of Fe2[BP3012] with the atom labelling scheme. The displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 2 - x, 1 - y, 1 - z; (ii) x-y, -1 + x, 1 - z; (iii) y, 1 - x + y, 1 - z; (iv) 1 - x + y, 1 - x, 0.5 - z; (v) 1 - y, x-y, z; (vi) x, y, 0.5 - z; (vii) 2 - y, 1 + x-y, z; (viii) 1 - x + y, 2 - x, 0.5 - z.]
[Figure 2] Fig. 2. View of the crystal structure of Fe2[BP3012] in a projection along [001].
diiron(III) borotriphosphate top
Crystal data top
Fe2[BP3O12]Dx = 3.263 Mg m3
Mr = 407.42Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63/mCell parameters from 1049 reflections
Hall symbol: -P 6cθ = 4.0–27.4°
a = 8.0347 (8) ŵ = 4.15 mm1
c = 7.4163 (13) ÅT = 293 K
V = 414.63 (9) Å3Prism, light-red
Z = 20.15 × 0.05 × 0.05 mm
F(000) = 396
Data collection top
Rigaku Mercury70 CCD
diffractometer
345 independent reflections
Radiation source: fine-focus sealed tube338 reflections with I > 2σ(I)
Graphite Monochromator monochromatorRint = 0.042
Detector resolution: 14.6306 pixels mm-1θmax = 27.4°, θmin = 2.9°
ω scansh = 1010
Absorption correction: multi-scan
(ABSCOR; Higashi, 1995)
k = 1010
Tmin = 0.575, Tmax = 0.819l = 96
3247 measured reflections
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.035Secondary atom site location: difference Fourier map
wR(F2) = 0.072 w = 1/[σ2(Fo2) + (0.0168P)2 + 3.P]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max < 0.001
345 reflectionsΔρmax = 0.58 e Å3
33 parametersΔρmin = 0.78 e Å3
Crystal data top
Fe2[BP3O12]Z = 2
Mr = 407.42Mo Kα radiation
Hexagonal, P63/mµ = 4.15 mm1
a = 8.0347 (8) ÅT = 293 K
c = 7.4163 (13) Å0.15 × 0.05 × 0.05 mm
V = 414.63 (9) Å3
Data collection top
Rigaku Mercury70 CCD
diffractometer
345 independent reflections
Absorption correction: multi-scan
(ABSCOR; Higashi, 1995)
338 reflections with I > 2σ(I)
Tmin = 0.575, Tmax = 0.819Rint = 0.042
3247 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.03533 parameters
wR(F2) = 0.0720 restraints
S = 1.07Δρmax = 0.58 e Å3
345 reflectionsΔρmin = 0.78 e Å3
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
Fe10.66670.33330.45190 (12)0.0072 (3)
P11.04513 (17)0.68473 (17)0.25000.0064 (3)
O20.8735 (5)0.4782 (5)0.25000.0080 (7)
O10.9428 (5)0.8099 (5)0.25000.0097 (8)
B11.00001.00000.25000.0101 (19)
O31.1626 (3)0.7289 (3)0.4200 (4)0.0115 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Fe10.0076 (3)0.0076 (3)0.0063 (5)0.00381 (15)0.0000.000
P10.0055 (6)0.0057 (6)0.0077 (7)0.0025 (5)0.0000.000
O20.0067 (15)0.0059 (16)0.0099 (19)0.0021 (13)0.0000.000
O10.0060 (16)0.0056 (16)0.017 (2)0.0022 (13)0.0000.000
B10.008 (2)0.008 (2)0.014 (5)0.0040 (12)0.0000.000
O30.0116 (12)0.0115 (12)0.0127 (15)0.0066 (10)0.0045 (11)0.0019 (10)
Geometric parameters (Å, º) top
Fe1—O3i1.929 (2)P1—O21.538 (3)
Fe1—O3ii1.929 (2)P1—O11.586 (3)
Fe1—O3iii1.929 (2)O2—Fe1iv2.103 (2)
Fe1—O2iv2.103 (2)O1—B11.357 (3)
Fe1—O22.103 (2)B1—O1vii1.357 (3)
Fe1—O2v2.103 (2)B1—O1viii1.357 (3)
P1—O31.507 (3)O3—Fe1i1.929 (2)
P1—O3vi1.507 (3)
O3i—Fe1—O3ii97.83 (11)O3—P1—O3vi113.6 (2)
O3i—Fe1—O3iii97.83 (11)O3—P1—O2111.85 (12)
O3ii—Fe1—O3iii97.83 (11)O3vi—P1—O2111.85 (12)
O3i—Fe1—O2iv93.65 (11)O3—P1—O1108.24 (12)
O3ii—Fe1—O2iv91.53 (11)O3vi—P1—O1108.24 (12)
O3iii—Fe1—O2iv164.04 (11)O2—P1—O1102.37 (18)
O3i—Fe1—O291.53 (11)P1—O2—Fe1129.13 (10)
O3ii—Fe1—O2164.04 (11)P1—O2—Fe1iv129.14 (10)
O3iii—Fe1—O293.65 (11)Fe1—O2—Fe1iv90.78 (13)
O2iv—Fe1—O274.92 (10)B1—O1—P1136.3 (3)
O3i—Fe1—O2v164.04 (11)O1vii—B1—O1viii120.000 (1)
O3ii—Fe1—O2v93.65 (11)O1vii—B1—O1120.000 (1)
O3iii—Fe1—O2v91.53 (11)O1viii—B1—O1120.000 (1)
O2iv—Fe1—O2v74.92 (10)P1—O3—Fe1i142.54 (17)
O2—Fe1—O2v74.92 (10)
Symmetry codes: (i) x+2, y+1, z+1; (ii) xy, x1, z+1; (iii) y, x+y+1, z+1; (iv) x+y+1, x+1, z+1/2; (v) y+1, xy, z; (vi) x, y, z+1/2; (vii) y+2, xy+1, z; (viii) x+y+1, x+2, z+1/2.

Experimental details

Crystal data
Chemical formulaFe2[BP3O12]
Mr407.42
Crystal system, space groupHexagonal, P63/m
Temperature (K)293
a, c (Å)8.0347 (8), 7.4163 (13)
V3)414.63 (9)
Z2
Radiation typeMo Kα
µ (mm1)4.15
Crystal size (mm)0.15 × 0.05 × 0.05
Data collection
DiffractometerRigaku Mercury70 CCD
diffractometer
Absorption correctionMulti-scan
(ABSCOR; Higashi, 1995)
Tmin, Tmax0.575, 0.819
No. of measured, independent and
observed [I > 2σ(I)] reflections
3247, 345, 338
Rint0.042
(sin θ/λ)max1)0.648
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.072, 1.07
No. of reflections345
No. of parameters33
Δρmax, Δρmin (e Å3)0.58, 0.78

Computer programs: CrystalClear (Rigaku, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2004), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Selected bond lengths (Å) top
Fe1—O3i1.929 (2)P1—O21.538 (3)
Fe1—O22.103 (2)P1—O11.586 (3)
P1—O31.507 (3)O1—B11.357 (3)
Symmetry code: (i) x+2, y+1, z+1.
 

Acknowledgements

The authors acknowledge the Doctoral Foundation of Henan Polytechnic University (B648174).

References

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