Redetermination of the crystal structure of caesium tetra-fluorido-bromate(III) from single-crystal X-ray diffraction data.

Artem V Malin,Florian Kraus,Roman V Ostvald,Sergei I Ivlev

doi:10.1107/s2414314620001145

Abstract

Caesium tetra-fluorido-bromate(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 anti-cubocta-hedron. CsBrF4 is isotypic with CsAuF4.

Highlights

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
It was confirmed that the structure of CsBrF4 contains two squareplanar [BrF4]À anions each with point group symmetry mmm, and a caesium cation that is coordinated by twelve fluorine atoms, forming an anticuboctahedron

Summary

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) A , V = 692.2 (3) A 3 (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) A , V = 423 A 3; Siegel, 1956], and CsBrF4 is not isotypic with KBrF4 on basis of the data provided by Popov et al (1987). We have shown that CsBrF4 is isotypic with CsAuF4 (Schmidt & Muller, 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) A , V = 472.79 (11) A 3, Z = 4 at 293 K These lattice parameters are not related to the unit cell reported by Popov et al (1987). CsBrF4 288.82 Orthorhombic, Immm 100 5.5075 (3), 6.7890 (3), 12.2572 (6) 458.30 (4) 4 Mo K 16.75 0.11 Â 0.09 Â 0.06

Data collection Diffractometer Absorption correction

No of reflections

Synthesis and crystallization

Crystal data

Data collection

Special details