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

Malin, A.V.; Ivlev, S.I.; Ostvald, R.V.; Kraus, F.

doi:10.1107/S2414314620001145

inorganic compounds

IUCrDATA

ISSN: 2414-3146

Volume 5| Part 1| January 2020| x200114

https://doi.org/10.1107/S2414314620001145

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

Artem V. Malin,^a Sergei I. Ivlev,^b Roman V. Ostvald ^a and Florian Kraus ^b ^*

^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 ). 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.

Keywords: crystal structure; caesium; tetrafluoridobromate(III); redetermination.

CCDC reference: 1980292

Structure description

The first report of unit-cell parameters of CsBrF₄ from powder X-ray diffraction data was given by Popov et al. (1987 ). 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 ], and consequently CsBrF₄ is not isotypic with KBrF₄ on basis of the data provided by Popov et al. (1987). 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). We have shown that CsBrF₄ is isotypic with CsAuF₄ (Schmidt & Müller, 2004 ) 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). 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) 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 ), 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). 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
M_r	288.82
Crystal system, space group	Orthorhombic, Immm
Temperature (K)	100
a, b, c (Å)	5.5075 (3), 6.7890 (3), 12.2572 (6)
V (Å³)	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 )
T_min, T_max	0.330, 0.558
No. of measured, independent and observed [I > 2σ(I)] reflections	8570, 669, 622
R_int	0.029
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	1.20, −0.88
Computer programs: APEX3 and SAINT (Bruker, 2018 ), SHELXL (Sheldrick, 2015 ), DIAMOND (Brandenburg, 2019 ) and publCIF (Westrip, 2010 ); coordinates taken from previous refinement.

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.

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. Coordinates and atom labelling were taken from the previous refinement from PXRD data (Ivlev et al., 2013).

Structural data

CCDC reference: 1980292

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314620001145/wm4121sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314620001145/wm4121Isup2.hkl

checkCIF report

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

CsBrF₄	D_x = 4.186 Mg m⁻³
M_r = 288.82	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Immm	Cell parameters from 2913 reflections
a = 5.5075 (3) Å	θ = 3.3–36.8°
b = 6.7890 (3) Å	µ = 16.75 mm⁻¹
c = 12.2572 (6) Å	T = 100 K
V = 458.30 (4) Å³	Block, colorless
Z = 4	0.11 × 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 tube	R_int = 0.029
ω and φ scans	θ_max = 36.4°, θ_min = 3.3°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −9→9
T_min = 0.330, T_max = 0.558	k = −11→11
8570 measured reflections	l = −20→20
669 independent reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	w = 1/[σ²(F_o²) + (0.0065P)² + 0.5686P] where P = (F_o² + 2F_c²)/3
R[F² > 2σ(F²)] = 0.012	(Δ/σ)_max = 0.001
wR(F²) = 0.022	Δρ_max = 1.20 e Å⁻³
S = 1.12	Δρ_min = −0.88 e Å⁻³
669 reflections	Extinction correction: SHELXL-2018/3 (Sheldrick 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
26 parameters	Extinction 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

	x	y	z	U_iso*/U_eq
Cs1	0.500000	0.500000	0.71714 (2)	0.01008 (4)
Br1	0.500000	0.000000	0.500000	0.00720 (6)
Br2	0.500000	0.000000	0.000000	0.00760 (6)
F1	0.500000	0.000000	0.34482 (12)	0.0155 (3)
F2	0.500000	0.19339 (16)	0.11100 (9)	0.0169 (2)
F3	0.500000	0.2777 (2)	0.500000	0.0141 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cs1	0.01130 (6)	0.01075 (6)	0.00821 (7)	0.000	0.000	0.000
Br1	0.00756 (12)	0.00827 (11)	0.00578 (13)	0.000	0.000	0.000
Br2	0.00816 (12)	0.00841 (11)	0.00624 (13)	0.000	0.000	0.000
F1	0.0179 (7)	0.0216 (7)	0.0069 (6)	0.000	0.000	0.000
F2	0.0201 (5)	0.0160 (4)	0.0146 (5)	0.000	0.000	−0.0073 (4)
F3	0.0164 (6)	0.0087 (6)	0.0172 (7)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Cs1—F2ⁱ	2.9615 (11)	Cs1—F1^vii	3.4784 (4)
Cs1—F2ⁱⁱ	2.9615 (11)	Cs1—F1ⁱ	3.4784 (4)
Cs1—F3ⁱ	3.0597 (7)	Br1—F3	1.8852 (13)
Cs1—F3	3.0597 (7)	Br1—F3^vii	1.8853 (13)
Cs1—F1ⁱⁱⁱ	3.1674 (8)	Br1—F1^vii	1.9020 (15)
Cs1—F1^iv	3.1674 (8)	Br1—F1	1.9020 (15)
Cs1—F2^v	3.3166 (7)	Br2—F2^viii	1.8907 (10)
Cs1—F2ⁱⁱⁱ	3.3166 (7)	Br2—F2^ix	1.8907 (10)
Cs1—F2^iv	3.3166 (7)	Br2—F2^x	1.8907 (10)
Cs1—F2^vi	3.3166 (7)	Br2—F2	1.8907 (10)

F2ⁱ—Cs1—F2ⁱⁱ	89.32 (4)	F1^iv—Cs1—F1ⁱ	96.194 (16)
F2ⁱ—Cs1—F3ⁱ	105.79 (3)	F2^v—Cs1—F1ⁱ	107.50 (2)
F2ⁱⁱ—Cs1—F3ⁱ	164.90 (3)	F2ⁱⁱⁱ—Cs1—F1ⁱ	61.838 (19)
F2ⁱ—Cs1—F3	164.90 (3)	F2^iv—Cs1—F1ⁱ	61.838 (19)
F2ⁱⁱ—Cs1—F3	105.79 (3)	F2^vi—Cs1—F1ⁱ	107.50 (2)
F3ⁱ—Cs1—F3	59.11 (4)	F1^vii—Cs1—F1ⁱ	154.77 (5)
F2ⁱ—Cs1—F1ⁱⁱⁱ	69.423 (18)	F3—Br1—F3^vii	180.0
F2ⁱⁱ—Cs1—F1ⁱⁱⁱ	69.423 (18)	F3—Br1—F1^vii	90.0
F3ⁱ—Cs1—F1ⁱⁱⁱ	115.46 (2)	F3^vii—Br1—F1^vii	90.0
F3—Cs1—F1ⁱⁱⁱ	115.46 (2)	F3—Br1—F1	90.0
F2ⁱ—Cs1—F1^iv	69.423 (18)	F3^vii—Br1—F1	90.0
F2ⁱⁱ—Cs1—F1^iv	69.423 (18)	F1^vii—Br1—F1	180.0
F3ⁱ—Cs1—F1^iv	115.46 (2)	F2^viii—Br2—F2^ix	87.96 (7)
F3—Cs1—F1^iv	115.46 (2)	F2^viii—Br2—F2^x	92.04 (7)
F1ⁱⁱⁱ—Cs1—F1^iv	120.78 (5)	F2^ix—Br2—F2^x	180.00 (6)
F2ⁱ—Cs1—F2^v	123.869 (16)	F2^viii—Br2—F2	180.0
F2ⁱⁱ—Cs1—F2^v	90.05 (2)	F2^ix—Br2—F2	92.04 (7)
F3ⁱ—Cs1—F2^v	81.61 (2)	F2^x—Br2—F2	87.96 (7)
F3—Cs1—F2^v	57.553 (17)	F2^viii—Br2—Cs1^xi	120.01 (2)
F1ⁱⁱⁱ—Cs1—F2^v	156.305 (19)	F2^ix—Br2—Cs1^xi	120.005 (19)
F1^iv—Cs1—F2^v	58.13 (3)	F2^x—Br2—Cs1^xi	59.995 (19)
F2ⁱ—Cs1—F2ⁱⁱⁱ	90.05 (2)	F2—Br2—Cs1^xi	59.99 (2)
F2ⁱⁱ—Cs1—F2ⁱⁱⁱ	123.868 (16)	F2^viii—Br2—Cs1^xii	59.99 (2)
F3ⁱ—Cs1—F2ⁱⁱⁱ	57.553 (17)	F2^ix—Br2—Cs1^xii	59.995 (19)
F3—Cs1—F2ⁱⁱⁱ	81.61 (2)	F2^x—Br2—Cs1^xii	120.005 (19)
F1ⁱⁱⁱ—Cs1—F2ⁱⁱⁱ	58.13 (3)	F2—Br2—Cs1^xii	120.01 (2)
F1^iv—Cs1—F2ⁱⁱⁱ	156.305 (19)	Cs1^xi—Br2—Cs1^xii	180.0
F2^v—Cs1—F2ⁱⁱⁱ	133.81 (3)	F2^viii—Br2—Cs1^xiii	120.01 (2)
F2ⁱ—Cs1—F2^iv	90.05 (2)	F2^ix—Br2—Cs1^xiii	120.005 (19)
F2ⁱⁱ—Cs1—F2^iv	123.868 (17)	F2^x—Br2—Cs1^xiii	59.995 (19)
F3ⁱ—Cs1—F2^iv	57.553 (17)	F2—Br2—Cs1^xiii	59.99 (2)
F3—Cs1—F2^iv	81.61 (2)	Cs1^xi—Br2—Cs1^xiii	91.951 (5)
F1ⁱⁱⁱ—Cs1—F2^iv	156.305 (19)	Cs1^xii—Br2—Cs1^xiii	88.049 (5)
F1^iv—Cs1—F2^iv	58.13 (3)	F2^viii—Br2—Cs1^xiv	59.99 (2)
F2^v—Cs1—F2^iv	46.64 (4)	F2^ix—Br2—Cs1^xiv	59.995 (19)
F2ⁱⁱⁱ—Cs1—F2^iv	112.26 (3)	F2^x—Br2—Cs1^xiv	120.005 (19)
F2ⁱ—Cs1—F2^vi	123.868 (17)	F2—Br2—Cs1^xiv	120.01 (2)
F2ⁱⁱ—Cs1—F2^vi	90.05 (2)	Cs1^xi—Br2—Cs1^xiv	88.049 (5)
F3ⁱ—Cs1—F2^vi	81.61 (2)	Cs1^xii—Br2—Cs1^xiv	91.951 (5)
F3—Cs1—F2^vi	57.553 (17)	Cs1^xiii—Br2—Cs1^xiv	180.0
F1ⁱⁱⁱ—Cs1—F2^vi	58.13 (3)	Br1—F1—Cs1^xiii	119.61 (2)
F1^iv—Cs1—F2^vi	156.305 (19)	Br1—F1—Cs1^xi	119.61 (2)
F2^v—Cs1—F2^vi	112.26 (3)	Cs1^xiii—F1—Cs1^xi	120.78 (5)
F2ⁱⁱⁱ—Cs1—F2^vi	46.64 (4)	Br1—F1—Cs1^vii	102.61 (2)
F2^iv—Cs1—F2^vi	133.81 (3)	Cs1^xiii—F1—Cs1^vii	83.807 (16)
F2ⁱ—Cs1—F1^vii	147.27 (3)	Cs1^xi—F1—Cs1^vii	83.807 (16)
F2ⁱⁱ—Cs1—F1^vii	57.95 (3)	Br1—F1—Cs1ⁱ	102.61 (2)
F3ⁱ—Cs1—F1^vii	106.94 (3)	Cs1^xiii—F1—Cs1ⁱ	83.807 (16)
F3—Cs1—F1^vii	47.83 (3)	Cs1^xi—F1—Cs1ⁱ	83.807 (16)
F1ⁱⁱⁱ—Cs1—F1^vii	96.194 (16)	Cs1^vii—F1—Cs1ⁱ	154.78 (5)
F1^iv—Cs1—F1^vii	96.194 (16)	Br2—F2—Cs1ⁱ	179.32 (6)
F2^v—Cs1—F1^vii	61.838 (19)	Br2—F2—Cs1^xiii	90.42 (3)
F2ⁱⁱⁱ—Cs1—F1^vii	107.50 (2)	Cs1ⁱ—F2—Cs1^xiii	89.95 (2)
F2^iv—Cs1—F1^vii	107.50 (2)	Br2—F2—Cs1^xi	90.42 (3)
F2^vi—Cs1—F1^vii	61.838 (19)	Cs1ⁱ—F2—Cs1^xi	89.95 (2)
F2ⁱ—Cs1—F1ⁱ	57.95 (3)	Cs1^xiii—F2—Cs1^xi	112.26 (3)
F2ⁱⁱ—Cs1—F1ⁱ	147.27 (3)	Br1—F3—Cs1ⁱ	119.56 (2)
F3ⁱ—Cs1—F1ⁱ	47.83 (3)	Br1—F3—Cs1	119.56 (2)
F3—Cs1—F1ⁱ	106.94 (3)	Cs1ⁱ—F3—Cs1	120.89 (4)
F1ⁱⁱⁱ—Cs1—F1ⁱ	96.194 (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) x−1/2, 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, y−1/2, z−1/2; (xii) −x+1/2, −y+1/2, −z+1/2; (xiii) x−1/2, y−1/2, z−1/2; (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.

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