Structures of the BrF(4)(+) and IF(4)(+) cations

Area of Science:

• Inorganic chemistry
• Solid-state chemistry
• Crystallography

Background:

• Previous structural studies of BrF(4)(+) and IF(4)(+) showed significant discrepancies between calculated and observed data.
• These discrepancies prompted a re-evaluation of the crystal structures to ensure accuracy.

Purpose of the Study:

• To redetermine the crystal structures of BrF(4)(+)Sb(2)F(11)(-) and IF(4)(+)SbF(6)(-).
• To compare the redetermined structures with theoretical calculations and previous experimental data.
• To investigate the influence of interionic fluorine bridges on the observed geometries.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the crystal structures.
• The crystal structures were refined using crystallographic software.
• Comparison of experimental data with results from computational chemistry methods.

Main Results:

• The crystal structure of BrF(4)(+)Sb(2)F(11)(-) was determined in the monoclinic space group P2(1)/c.
• The crystal structure of IF(4)(+)SbF(6)(-) was determined in the orthorhombic space group Ibca.
• Redetermined geometries show excellent agreement with theoretical calculations, resolving previous discrepancies attributed to experimental errors.
• Interionic fluorine bridges were observed to cause preferential compression of specific bond angles in both ions, with the effect varying based on the counterion.

Conclusions:

• The geometries of the free BrF(4)(+) and IF(4)(+) ions are accurately represented by theoretical calculations.
• Previous structural data for these ions were affected by experimental errors and, in one case, an incorrect space group determination.
• Interionic interactions, specifically fluorine bridges, play a significant role in distorting the observed geometries in the solid state.