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

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ISSN: 2414-3146

Redetermination of the crystal structure of caesium tetra­fluorido­bromate(III) from single-crystal X-ray diffraction data

aNational Research Tomsk Polytechnic University, 30 Lenina avenue, 634050 Tomsk, Russian Federation, and bFachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
*Correspondence e-mail: f.kraus@uni-marburg.de

Edited by M. Weil, Vienna University of Technology, Austria (Received 17 December 2019; accepted 28 January 2020; online 31 January 2020)

Caesium tetra­fluorido­bromate(III), CsBrF4, was crystallized in form of small blocks by melting and recrystallization. The crystal structure of CsBrF4 was redetermined from single-crystal X-ray diffraction data. In comparison with a previous study based on powder X-ray diffraction data [Ivlev et al. (2013[Ivlev, S., Woidy, P., Sobolev, V., Gerin, I., Ostvald, R. & Kraus, F. (2013). Z. Anorg. Allg. Chem. 639, 2846-2850.]). Z. Anorg. Allg. Chem. 639, 2846–2850], bond lengths and angles were determined with higher precision, and all atoms were refined with anisotropic displacement parameters. It was confirmed that the structure of CsBrF4 contains two square-planar [BrF4] anions each with point group symmetry mmm, and a caesium cation (site symmetry mm2) that is coordinated by twelve fluorine atoms, forming an anti­cubocta­hedron. CsBrF4 is isotypic with CsAuF4.

3D view (loading...)
[Scheme 3D1]

Structure description

The first report of unit-cell parameters of CsBrF4 from powder X-ray diffraction data was given by Popov et al. (1987[Popov, A. I., Kiselev, Y. M., Sukhoverkhov, V. F., Chumaevskii, N. A., Krasnyanskaya, O. A. & Sadikova, A. T. (1987). Russ. J. Inorg. Chem. 32, 619-622.]). They indexed the powder pattern using a primitive tetra­gonal unit cell with lattice parameters of a = 9.828 (3), c = 7.166 (5) Å, V = 692.2 (3) Å3 (temperature not given). These lattice parameters are quite different compared to those of other known alkali metal tetra­fluorido­bromates(III) that crystallize in the KBrF4 structure type [KBrF4, I4/mcm (No. 140), a = 6.174 (2), c = 11.103 (2) Å, V = 423 Å3; Siegel, 1956[Siegel, S. (1956). Acta Cryst. 9, 493-495.]], and consequently CsBrF4 is not isotypic with KBrF4 on basis of the data provided by Popov et al. (1987[Popov, A. I., Kiselev, Y. M., Sukhoverkhov, V. F., Chumaevskii, N. A., Krasnyanskaya, O. A. & Sadikova, A. T. (1987). Russ. J. Inorg. Chem. 32, 619-622.]). However, neither the crystal structure nor other crystallographic details of CsBrF4 were given at that time.

Recently, we have determined the crystal structure of CsBrF4 from powder X-ray diffraction (PXRD) data where we could only refine the F atoms isotropically (Ivlev et al., 2013[Ivlev, S., Woidy, P., Sobolev, V., Gerin, I., Ostvald, R. & Kraus, F. (2013). Z. Anorg. Allg. Chem. 639, 2846-2850.]). We have shown that CsBrF4 is isotypic with CsAuF4 (Schmidt & Müller, 2004[Schmidt, R. & Müller, B. G. (2004). Z. Anorg. Allg. Chem. 630, 2393-2397.]) and crystallizes in the space group Immm (No. 71) with lattice parameters a = 5.6413 (8), b = 6.8312 (9), c = 12.2687 (17) Å, V = 472.79 (11) Å3, Z = 4 at 293 K. These lattice parameters are not related to the unit cell reported by Popov et al. (1987[Popov, A. I., Kiselev, Y. M., Sukhoverkhov, V. F., Chumaevskii, N. A., Krasnyanskaya, O. A. & Sadikova, A. T. (1987). Russ. J. Inorg. Chem. 32, 619-622.]). We assume that their powder pattern probably contained impurity lines, e.g. from possible hydrolysis products, which led to erroneous indexing. Here we present the results of a redetermination of the crystal structure of CsBrF4 from single-crystal X-ray diffraction data at 100 K, leading to bond lengths and angles with higher precision, and with all atoms refined with anisotropic displacement parameters.

The unit-cell parameters of CsBrF4 obtained from single-crystal X-ray diffraction data (Table 1[link]) are expectedly smaller than those from the PXRD data at 293 K. The crystal structure contains two different square-planar [BrF4] anions, the planes of which are parallel and rotated by about 45° with respect to each other. The first anion consists of one bromine(III) atom (Br1) on the special 2d (mmm) Wyckoff position and two fluorine atoms F1 and F3 on the special 4j (mm2) and 4g (m2m) Wyckoff positions, respectively. As a result of symmetry restrictions, the F—Br—F angle is exactly 90°. The Br1—F bond lengths are 1.8852 (13) and 1.9020 (15) Å [cf. 1.94 (4) and 1.97 (4) Å from PXRD data]. The second [BrF4] anion contains one bromine(III) atom (Br2) on the special 2b (mmm) Wyckoff position and one fluorine atom (F2) on the special 8l (m..) Wyckoff position. The anion is slightly distorted in-plane, resulting in an almost rectangular structure with F2—Br2—F2 angles of 87.96 (7) and 92.04 (7)° and a Br2—F2 bond length of 1.8907 (10) Å [cf. 87.6 (13) and 92.4 (13)°, 1.96 (3) Å from PXRD data]. In general, the bond lengths and angles of the [BrF4] anions in CsBrF4 are in good correspondence with other known tetra­fluorido­bromates(III) [see Table 2 in Ivlev & Kraus (2018[Ivlev, S. I. & Kraus, F. (2018). IUCrData, 3, x180646.]), and references therein]. The caesium cation occupies the special 4i (mm2) Wyckoff position and is coordinated by twelve fluorine atoms. The resulting coordination polyhedron is an anti­cubocta­hedron (Fig. 1[link]). The Cs⋯F distances are in the range 2.9615 (11) to 3.4784 (4) Å [cf. 3.011 (1) to 3.605 (1) from PXRD data].

Table 1
Experimental details

Crystal data
Chemical formula CsBrF4
Mr 288.82
Crystal system, space group Orthorhombic, Immm
Temperature (K) 100
a, b, c (Å) 5.5075 (3), 6.7890 (3), 12.2572 (6)
V3) 458.30 (4)
Z 4
Radiation type Mo Kα
μ (mm−1) 16.75
Crystal size (mm) 0.11 × 0.09 × 0.06
 
Data collection
Diffractometer Bruker D8 QUEST
Absorption correction Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.330, 0.558
No. of measured, independent and observed [I > 2σ(I)] reflections 8570, 669, 622
Rint 0.029
(sin θ/λ)max−1) 0.835
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.012, 0.022, 1.12
No. of reflections 669
No. of parameters 26
Δρmax, Δρmin (e Å−3) 1.20, −0.88
Computer programs: APEX3 and SAINT (Bruker, 2018[Bruker (2018). APEX3 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXL (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), DIAMOND (Brandenburg, 2019[Brandenburg, K. (2019). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]); coordinates taken from previous refinement.
[Figure 1]
Figure 1
The anti­cubocta­hedron around the caesium cation. Displacement ellipsoids are shown at the 70% probability level. [Symmetry codes: (i) −x + 1, −y + 1, −z + 1; (ii) x, y, −z + 1; (iii) x + [{1\over 2}], y + [{1\over 2}], z + [{1\over 2}]; (iv) x  − [{1\over 2}], y + [{1\over 2}], z + [{1\over 2}]; (v) −x + [{1\over 2}], −y + [{1\over 2}], z + [{1\over 2}]; (vi) −x + [{3\over 2}], −y + [{1\over 2}], z + [{1\over 2}]; (vii) −x + 1, −y, −z + 1.]

The crystal structure of CsBrF4 is shown in Fig. 2[link].

[Figure 2]
Figure 2
The crystal structure of CsBrF4 in a projection along the a axis. Displacement ellipsoids are shown at the 70% probability level.

Synthesis and crystallization

Caesium tetra­fluorido­bromate(III) was synthesized by direct reaction of bromine trifluoride with caesium chloride. The reaction was carried out under Freon-113, which acted as a protective layer against hydrolysis and as a heat absorber. The mixture of CsCl and BrF3 was kept in a closed Teflon vessel. After three days the Freon was removed by vacuum distillation and CsBrF4 was obtained as a solid white residue. The powder was melted at 483 K and cooled down to room temperature. Single crystals of CsBrF4 were obtained as small blocks after crushing the solid lumps.

Refinement

Details of data collection and structure refinement are given in Table 1[link]. Coordinates and atom labelling were taken from the previous refinement from PXRD data (Ivlev et al., 2013[Ivlev, S., Woidy, P., Sobolev, V., Gerin, I., Ostvald, R. & Kraus, F. (2013). Z. Anorg. Allg. Chem. 639, 2846-2850.]).

Structural data


Computing details top

Data collection: APEX3 (Bruker, 2018); cell refinement: SAINT (Bruker, 2018); data reduction: SAINT (Bruker 2018); program(s) used to solve structure: coordinates taken from previous refinement; program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2019); software used to prepare material for publication: publCIF (Westrip, 2010).

Caesium tetrafluoridobromate(III) top
Crystal data top
CsBrF4Dx = 4.186 Mg m3
Mr = 288.82Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, ImmmCell parameters from 2913 reflections
a = 5.5075 (3) Åθ = 3.3–36.8°
b = 6.7890 (3) ŵ = 16.75 mm1
c = 12.2572 (6) ÅT = 100 K
V = 458.30 (4) Å3Block, colorless
Z = 40.11 × 0.09 × 0.06 mm
F(000) = 504
Data collection top
Bruker D8 QUEST
diffractometer
622 reflections with I > 2σ(I)
Radiation source: microfocus X-ray tubeRint = 0.029
ω and φ scansθmax = 36.4°, θmin = 3.3°
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)
h = 99
Tmin = 0.330, Tmax = 0.558k = 1111
8570 measured reflectionsl = 2020
669 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0065P)2 + 0.5686P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.012(Δ/σ)max = 0.001
wR(F2) = 0.022Δρmax = 1.20 e Å3
S = 1.12Δρmin = 0.88 e Å3
669 reflectionsExtinction correction: SHELXL-2018/3 (Sheldrick 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
26 parametersExtinction coefficient: 0.00232 (16)
0 restraints
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cs10.5000000.5000000.71714 (2)0.01008 (4)
Br10.5000000.0000000.5000000.00720 (6)
Br20.5000000.0000000.0000000.00760 (6)
F10.5000000.0000000.34482 (12)0.0155 (3)
F20.5000000.19339 (16)0.11100 (9)0.0169 (2)
F30.5000000.2777 (2)0.5000000.0141 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cs10.01130 (6)0.01075 (6)0.00821 (7)0.0000.0000.000
Br10.00756 (12)0.00827 (11)0.00578 (13)0.0000.0000.000
Br20.00816 (12)0.00841 (11)0.00624 (13)0.0000.0000.000
F10.0179 (7)0.0216 (7)0.0069 (6)0.0000.0000.000
F20.0201 (5)0.0160 (4)0.0146 (5)0.0000.0000.0073 (4)
F30.0164 (6)0.0087 (6)0.0172 (7)0.0000.0000.000
Geometric parameters (Å, º) top
Cs1—F2i2.9615 (11)Cs1—F1vii3.4784 (4)
Cs1—F2ii2.9615 (11)Cs1—F1i3.4784 (4)
Cs1—F3i3.0597 (7)Br1—F31.8852 (13)
Cs1—F33.0597 (7)Br1—F3vii1.8853 (13)
Cs1—F1iii3.1674 (8)Br1—F1vii1.9020 (15)
Cs1—F1iv3.1674 (8)Br1—F11.9020 (15)
Cs1—F2v3.3166 (7)Br2—F2viii1.8907 (10)
Cs1—F2iii3.3166 (7)Br2—F2ix1.8907 (10)
Cs1—F2iv3.3166 (7)Br2—F2x1.8907 (10)
Cs1—F2vi3.3166 (7)Br2—F21.8907 (10)
F2i—Cs1—F2ii89.32 (4)F1iv—Cs1—F1i96.194 (16)
F2i—Cs1—F3i105.79 (3)F2v—Cs1—F1i107.50 (2)
F2ii—Cs1—F3i164.90 (3)F2iii—Cs1—F1i61.838 (19)
F2i—Cs1—F3164.90 (3)F2iv—Cs1—F1i61.838 (19)
F2ii—Cs1—F3105.79 (3)F2vi—Cs1—F1i107.50 (2)
F3i—Cs1—F359.11 (4)F1vii—Cs1—F1i154.77 (5)
F2i—Cs1—F1iii69.423 (18)F3—Br1—F3vii180.0
F2ii—Cs1—F1iii69.423 (18)F3—Br1—F1vii90.0
F3i—Cs1—F1iii115.46 (2)F3vii—Br1—F1vii90.0
F3—Cs1—F1iii115.46 (2)F3—Br1—F190.0
F2i—Cs1—F1iv69.423 (18)F3vii—Br1—F190.0
F2ii—Cs1—F1iv69.423 (18)F1vii—Br1—F1180.0
F3i—Cs1—F1iv115.46 (2)F2viii—Br2—F2ix87.96 (7)
F3—Cs1—F1iv115.46 (2)F2viii—Br2—F2x92.04 (7)
F1iii—Cs1—F1iv120.78 (5)F2ix—Br2—F2x180.00 (6)
F2i—Cs1—F2v123.869 (16)F2viii—Br2—F2180.0
F2ii—Cs1—F2v90.05 (2)F2ix—Br2—F292.04 (7)
F3i—Cs1—F2v81.61 (2)F2x—Br2—F287.96 (7)
F3—Cs1—F2v57.553 (17)F2viii—Br2—Cs1xi120.01 (2)
F1iii—Cs1—F2v156.305 (19)F2ix—Br2—Cs1xi120.005 (19)
F1iv—Cs1—F2v58.13 (3)F2x—Br2—Cs1xi59.995 (19)
F2i—Cs1—F2iii90.05 (2)F2—Br2—Cs1xi59.99 (2)
F2ii—Cs1—F2iii123.868 (16)F2viii—Br2—Cs1xii59.99 (2)
F3i—Cs1—F2iii57.553 (17)F2ix—Br2—Cs1xii59.995 (19)
F3—Cs1—F2iii81.61 (2)F2x—Br2—Cs1xii120.005 (19)
F1iii—Cs1—F2iii58.13 (3)F2—Br2—Cs1xii120.01 (2)
F1iv—Cs1—F2iii156.305 (19)Cs1xi—Br2—Cs1xii180.0
F2v—Cs1—F2iii133.81 (3)F2viii—Br2—Cs1xiii120.01 (2)
F2i—Cs1—F2iv90.05 (2)F2ix—Br2—Cs1xiii120.005 (19)
F2ii—Cs1—F2iv123.868 (17)F2x—Br2—Cs1xiii59.995 (19)
F3i—Cs1—F2iv57.553 (17)F2—Br2—Cs1xiii59.99 (2)
F3—Cs1—F2iv81.61 (2)Cs1xi—Br2—Cs1xiii91.951 (5)
F1iii—Cs1—F2iv156.305 (19)Cs1xii—Br2—Cs1xiii88.049 (5)
F1iv—Cs1—F2iv58.13 (3)F2viii—Br2—Cs1xiv59.99 (2)
F2v—Cs1—F2iv46.64 (4)F2ix—Br2—Cs1xiv59.995 (19)
F2iii—Cs1—F2iv112.26 (3)F2x—Br2—Cs1xiv120.005 (19)
F2i—Cs1—F2vi123.868 (17)F2—Br2—Cs1xiv120.01 (2)
F2ii—Cs1—F2vi90.05 (2)Cs1xi—Br2—Cs1xiv88.049 (5)
F3i—Cs1—F2vi81.61 (2)Cs1xii—Br2—Cs1xiv91.951 (5)
F3—Cs1—F2vi57.553 (17)Cs1xiii—Br2—Cs1xiv180.0
F1iii—Cs1—F2vi58.13 (3)Br1—F1—Cs1xiii119.61 (2)
F1iv—Cs1—F2vi156.305 (19)Br1—F1—Cs1xi119.61 (2)
F2v—Cs1—F2vi112.26 (3)Cs1xiii—F1—Cs1xi120.78 (5)
F2iii—Cs1—F2vi46.64 (4)Br1—F1—Cs1vii102.61 (2)
F2iv—Cs1—F2vi133.81 (3)Cs1xiii—F1—Cs1vii83.807 (16)
F2i—Cs1—F1vii147.27 (3)Cs1xi—F1—Cs1vii83.807 (16)
F2ii—Cs1—F1vii57.95 (3)Br1—F1—Cs1i102.61 (2)
F3i—Cs1—F1vii106.94 (3)Cs1xiii—F1—Cs1i83.807 (16)
F3—Cs1—F1vii47.83 (3)Cs1xi—F1—Cs1i83.807 (16)
F1iii—Cs1—F1vii96.194 (16)Cs1vii—F1—Cs1i154.78 (5)
F1iv—Cs1—F1vii96.194 (16)Br2—F2—Cs1i179.32 (6)
F2v—Cs1—F1vii61.838 (19)Br2—F2—Cs1xiii90.42 (3)
F2iii—Cs1—F1vii107.50 (2)Cs1i—F2—Cs1xiii89.95 (2)
F2iv—Cs1—F1vii107.50 (2)Br2—F2—Cs1xi90.42 (3)
F2vi—Cs1—F1vii61.838 (19)Cs1i—F2—Cs1xi89.95 (2)
F2i—Cs1—F1i57.95 (3)Cs1xiii—F2—Cs1xi112.26 (3)
F2ii—Cs1—F1i147.27 (3)Br1—F3—Cs1i119.56 (2)
F3i—Cs1—F1i47.83 (3)Br1—F3—Cs1119.56 (2)
F3—Cs1—F1i106.94 (3)Cs1i—F3—Cs1120.89 (4)
F1iii—Cs1—F1i96.194 (16)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y, z+1; (iii) x+1/2, y+1/2, z+1/2; (iv) x1/2, y+1/2, z+1/2; (v) x+1/2, y+1/2, z+1/2; (vi) x+3/2, y+1/2, z+1/2; (vii) x+1, y, z+1; (viii) x+1, y, z; (ix) x, y, z; (x) x+1, y, z; (xi) x+1/2, y1/2, z1/2; (xii) x+1/2, y+1/2, z+1/2; (xiii) x1/2, y1/2, z1/2; (xiv) x+3/2, y+1/2, z+1/2.
 

Acknowledgements

We thank the Russian Governmental Program `Nauka' N 4.3967.2017/PCh for support. We thank the Deutsche Forschungsgemeinschaft for generous funding.

References

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