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Redetermination of the crystal structure of K[BrF4] from single-crystal X-ray diffraction data

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aFachbereich 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 12 April 2018; accepted 26 April 2018; online 1 May 2018)

Single crystals of K[BrF4], potassium tetra­fluorido­bromate(III), were grown from a solution of KHF2 in bromine trifluoride. The current report is the first refinement of the crystal structure of K[BrF4] using single-crystal X-ray diffraction data. In comparison with previous refinements from powder data, the fractional coordinates of the F atom were determined with higher precision, and anisotropic displacement parameters were refined for all atoms. The structure contains square-planar [BrF4] anions. The coordination polyhedron of the potassium cation is a square anti­prism.

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

Structure description

The first attempt to elucidate the crystal structure of K[BrF4] was carried out by Siegel using powder X-ray diffraction data (Siegel, 1956[Siegel, S. (1956). Acta Cryst. 9, 493-495.]). He could index the powder pattern in a tetra­gonal cell, space group I4/mcm, with a = 6.162 (2), c = 11.081 (2) Å, and the [BrF4] anion having a tetra­hedral configuration. Subsequently, the diffraction data of Siegel were re­inter­preted by Sly & Marsh (1957[Sly, W. G. & Marsh, R. E. (1957). Acta Cryst. 10, 378-379.]). They kept the unit cell but assigned different positions to the atoms within the same group type, yielding a more reasonable square-planar [BrF4] anion. This shape of the anion was later confirmed by Edwards and Jones using powder neutron diffraction data [a = 6.17 (1), c = 11.10 (1) Å; Edwards & Jones, 1969[Edwards, A. J. & Jones, G. R. (1969). J. Chem. Soc. A, pp. 1936-1938.]]. Similar cell parameters were reported later by Chrétien and Bouy using powder X-ray diffraction data (a = 6.162, c = 11.081 Å, no s.u. given; Chrétien & Bouy, 1958[Chrétien, A. & Bouy, P. (1958). C. R. Hebd. Seances Acad. Sci. 246, 2493-2495.]) and by Popov et al. [powder X-ray diffraction data, a = 6.192 (5), c = 11.108 (7) Å; 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.]]. Although this was not reported anywhere, we assume that all measurements were performed at room temperature. Here we report our results of the crystal structure determination of K[BrF4] using single-crystal X-ray diffraction data at 100 K.

The lattice parameters obtained from our diffraction data (Table 1[link]) are in good correspondence with previously published values. The K+ cation resides on Wyckoff position 4a (site symmetry 422). The centre of the [BrF4] anion is located on Wyckoff position 4d (m.mm), with the F atoms occupying Wyckoff position 16l (..m). The Br—F bond length amounts to 1.8924 (9) Å. This value is typical for the [BrF4] anion and is observed in other known tetra­fluorido­bromates that were investigated earlier by us (Table 2[link]). The F—Br—F angles are 90.02 (3) and 89.98 (5)°, respectively, and are right angles within the 3σ criterion. The nearest K—F distance is 2.7112 (6) Å. The resulting coordination sphere of the potassium cation by fluorine atoms is a square anti­prism. The crystal structure of K[BrF4] and its unit cell is shown in Fig. 1[link].

Table 1
Experimental details

Crystal data
Chemical formula K[BrF4]
Mr 195.01
Crystal system, space group Tetragonal, I4/mcm
Temperature (K) 100
a, c (Å) 6.0999 (6), 11.0509 (14)
V3) 411.19 (10)
Z 4
Radiation type Mo Kα
μ (mm−1) 10.95
Crystal size (mm) 0.23 × 0.15 × 0.13
 
Data collection
Diffractometer STOE IPDS 2T
Absorption correction Numerical (X-RED32 and X-SHAPE; Stoe & Cie, 2017[Stoe & Cie (2017). X-AREA, X-RED32 and X-SHAPE. Stoe & Cie GmbH, Darmstadt, Germany.])
Tmin, Tmax 0.157, 0.272
No. of measured, independent and observed [I > 2σ(I)] reflections 2822, 214, 198
Rint 0.050
(sin θ/λ)max−1) 0.742
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.015, 0.032, 1.24
No. of reflections 214
No. of parameters 13
Δρmax, Δρmin (e Å−3) 0.60, −0.73
Computer programs: WinXpose in X-AREA (Stoe & Cie, 2016[Stoe & Cie (2016). X-AREA WinXpose. Stoe & Cie GmbH, Darmstadt, Germany.]), Recipe in X-AREA (Stoe & Cie, 2015[Stoe & Cie (2015). X-AREA Recipe. Stoe & Cie GmbH, Darmstadt, Germany.]), Integrate in X-AREA (Stoe & Cie, 2018[Stoe & Cie (2018). X-AREA Integrate. Stoe & Cie GmbH, Darmstadt, Germany.]), SHELXT2014 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2016 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), DIAMOND (Brandenburg, 2018[Brandenburg, K. (2018). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Table 2
Inter­atomic distances (Å) in known M tetra­fluorido­bromates(III) (M = Na, K, Rb, Cs, Ba)

Compound Br—F M—F
K[BrF4] (at 100 K; this work) 1.8924 (9) 2.7112 (6)
Na[BrF4] (at 100 K; Ivlev et al., 2016[Ivlev, S. I., Ostvald, R. V. & Kraus, F. (2016). Monatsh. Chem. 147, 1661-1668.]) 1.899 (1) 2.4674 (4)
Rb[BrF4] (at RT; Ivlev et al., 2015[Ivlev, S., Karttunen, A. J., Ostvald, R. & Kraus, F. (2015). Z. Anorg. Allg. Chem. 641, 2593-2598.]) 1.932 (8) 2.851 (7)
Cs[BrF4] (at RT; Ivlev et al., 2013[Ivlev, S., Woidy, P., Sobolev, V., Gerin, I., Ostvald, R. & Kraus, F. (2013). Z. Anorg. Allg. Chem. 639, 2846-2850.]) 1.94 (7) − 1.97 (4) 2.89 (3) − 3.490 (8)
Ba[BrF4]2 (at RT; Ivlev et al., 2014[Ivlev, S., Sobolev, V., Hoelzel, M., Karttunen, A. J., Müller, T., Gerin, I., Ostvald, R. & Kraus, F. (2014). Eur. J. Inorg. Chem. pp. 6261-6267.]) 1.801 (4)–1.935 (2) 2.696 (3)–3.376 (3)
[Figure 1]
Figure 1
The crystal structure of K[BrF4] in a projection along the a axis. Displacement ellipsoids are shown at the 70% probability level.

Synthesis and crystallization

Potassium tetra­fluorido­bromate(III) was synthesized using potassium hydrogen fluoride KHF2 (0.20 g, 2.6 mmol, 1 eq.) and an excess of liquid bromine trifluoride (1 ml, 2.8 g, 20.4 mmol, 8.0 eq.). The reaction was carried out in an FEP vessel (perfluorinated ethyl­ene propyl­ene copolymer) at 393 K. After complete dissolution of KHF2, the resulting solution was allowed to cool down to room temperature. Within two hours, large colourless crystals were observed, which were picked directly out of liquid BrF3.

Refinement

Details of data collection and structure refinement are given in Table 1.

Structural data


Computing details top

Data collection: WinXpose in X-AREA (Stoe & Cie, 2016); cell refinement: Recipe in X-AREA (Stoe & Cie, 2015); data reduction: Integrate in X-AREA (Stoe & Cie, 2018); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 2018); software used to prepare material for publication: publCIF (Westrip, 2010).

Potassium tetrafluoridobromate(III) top
Crystal data top
K+·BrF4Melting point: 533 K
Mr = 195.01Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4/mcmCell parameters from 3833 reflections
a = 6.0999 (6) Åθ = 3.7–32.1°
c = 11.0509 (14) ŵ = 10.95 mm1
V = 411.19 (10) Å3T = 100 K
Z = 4Block, colorless
F(000) = 3600.23 × 0.15 × 0.13 mm
Dx = 3.150 Mg m3
Data collection top
STOE IPDS 2T
diffractometer
214 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus198 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.050
Detector resolution: 6.67 pixels mm-1θmax = 31.8°, θmin = 3.7°
rotation method, ω scansh = 99
Absorption correction: numerical
(X-RED32 and X-SHAPE; Stoe & Cie, 2017)
k = 89
Tmin = 0.157, Tmax = 0.272l = 1616
2822 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0152P)2 + 0.2331P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.015(Δ/σ)max < 0.001
wR(F2) = 0.032Δρmax = 0.60 e Å3
S = 1.24Δρmin = 0.73 e Å3
214 reflectionsExtinction correction: SHELXL2016 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
13 parametersExtinction coefficient: 0.0087 (11)
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
Br10.5000000.0000000.5000000.00790 (12)
K10.5000000.5000000.2500000.01054 (16)
F10.65508 (11)0.15508 (11)0.37889 (7)0.0138 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.00811 (14)0.00811 (14)0.00749 (15)0.00046 (10)0.0000.000
K10.0108 (2)0.0108 (2)0.0101 (3)0.0000.0000.000
F10.0146 (3)0.0146 (3)0.0122 (4)0.0008 (4)0.0030 (2)0.0030 (2)
Geometric parameters (Å, º) top
Br1—F11.8923 (9)K1—F1viii2.7112 (6)
Br1—F1i1.8924 (9)K1—F1ix2.7112 (6)
Br1—F1ii1.8924 (9)K1—F1x2.7112 (6)
Br1—F1iii1.8924 (9)K1—F12.7112 (6)
K1—F1iv2.7112 (6)K1—K1xi4.3133 (6)
K1—F1v2.7112 (6)K1—K1xii4.3133 (6)
K1—F1vi2.7112 (6)K1—K1xiii4.3133 (6)
K1—F1vii2.7112 (6)K1—K1x4.3133 (6)
F1—Br1—F1i90.02 (5)F1viii—K1—K1xi142.700 (14)
F1—Br1—F1ii89.98 (5)F1ix—K1—K1xi37.300 (14)
F1i—Br1—F1ii180.0F1x—K1—K1xi72.421 (19)
F1—Br1—F1iii180.0F1—K1—K1xi107.579 (19)
F1i—Br1—F1iii89.98 (5)F1iv—K1—K1xii37.300 (14)
F1ii—Br1—F1iii90.02 (5)F1v—K1—K1xii142.700 (14)
F1iv—K1—F1v144.84 (4)F1vi—K1—K1xii107.579 (19)
F1iv—K1—F1vi139.16 (4)F1vii—K1—K1xii72.421 (19)
F1v—K1—F1vi73.977 (14)F1viii—K1—K1xii37.300 (14)
F1iv—K1—F1vii73.977 (14)F1ix—K1—K1xii142.700 (14)
F1v—K1—F1vii139.16 (3)F1x—K1—K1xii107.579 (19)
F1vi—K1—F1vii74.60 (3)F1—K1—K1xii72.421 (19)
F1iv—K1—F1viii74.60 (3)K1xi—K1—K1xii180.0
F1v—K1—F1viii116.61 (3)F1iv—K1—K1xiii107.579 (19)
F1vi—K1—F1viii73.977 (15)F1v—K1—K1xiii107.579 (19)
F1vii—K1—F1viii78.20 (4)F1vi—K1—K1xiii37.300 (14)
F1iv—K1—F1ix116.61 (3)F1vii—K1—K1xiii37.300 (14)
F1v—K1—F1ix74.60 (3)F1viii—K1—K1xiii72.421 (19)
F1vi—K1—F1ix78.20 (4)F1ix—K1—K1xiii72.421 (19)
F1vii—K1—F1ix73.977 (15)F1x—K1—K1xiii142.700 (14)
F1viii—K1—F1ix144.84 (4)F1—K1—K1xiii142.699 (15)
F1iv—K1—F1x73.977 (14)K1xi—K1—K1xiii90.0
F1v—K1—F1x78.20 (4)K1xii—K1—K1xiii90.0
F1vi—K1—F1x144.84 (4)F1iv—K1—K1x72.421 (19)
F1vii—K1—F1x116.61 (3)F1v—K1—K1x72.421 (19)
F1viii—K1—F1x139.16 (3)F1vi—K1—K1x142.700 (14)
F1ix—K1—F1x73.977 (15)F1vii—K1—K1x142.700 (14)
F1iv—K1—F178.20 (4)F1viii—K1—K1x107.579 (19)
F1v—K1—F173.978 (14)F1ix—K1—K1x107.579 (19)
F1vi—K1—F1116.61 (3)F1x—K1—K1x37.300 (14)
F1vii—K1—F1144.84 (4)F1—K1—K1x37.301 (14)
F1viii—K1—F173.977 (14)K1xi—K1—K1x90.0
F1ix—K1—F1139.16 (4)K1xii—K1—K1x90.0
F1x—K1—F174.60 (3)K1xiii—K1—K1x180.0
F1iv—K1—K1xi142.700 (14)Br1—F1—K1x125.809 (18)
F1v—K1—K1xi37.300 (14)Br1—F1—K1125.809 (18)
F1vi—K1—K1xi72.421 (19)K1x—F1—K1105.40 (3)
F1vii—K1—K1xi107.579 (19)
Symmetry codes: (i) x, y, z+1; (ii) x+1, y, z; (iii) x+1, y, z+1; (iv) y+1/2, x1/2, z+1/2; (v) y+1, x, z; (vi) x+1, y+1, z; (vii) x1/2, y+1/2, z+1/2; (viii) y, x+1, z; (ix) y+1/2, x+3/2, z+1/2; (x) x+3/2, y+1/2, z+1/2; (xi) x+3/2, y+3/2, z+1/2; (xii) x+1/2, y+1/2, z+1/2; (xiii) x+1/2, y+3/2, z+1/2.
Interatomic distances (Å) in known M tetrafluoridobromates(III) (M = Na, K, Rb, Cs, Ba) top
CompoundBr—FM—F
K[BrF4] (at 100 K; this work)1.8924 (9)2.7112 (6)
Na[BrF4] (at 100 K; Ivlev et al., 2016)1.899 (1)2.4674 (4)
Rb[BrF4] (at RT; Ivlev et al., 2015)1.932 (8)2.851 (7)
Cs[BrF4] (at RT; Ivlev et al., 2013)1.94 (7) - 1.97 (4)2.89 (3) - 3.490 (8)
Ba[BrF4]2 (at RT; Ivlev et al., 2014)1.801 (4) - 1.935 (2)2.696 (3) - 3.376 (3)
 

Acknowledgements

We are grateful to Dr Harms (Marburg) for X-ray measurement time.

Funding information

We thank the DFG for very generous funding.

References

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