The Interhalogen Cations [Br₂ F₅ ]⁺ and [Br₃ F₈ ]

Area of Science:

• Inorganic Chemistry
• Halogen Chemistry
• Materials Science

Background:

• Polyhalogen cations are of interest due to their unique bonding characteristics.
• Bridging fluorine atoms in polyhalogen species are rare and present synthetic challenges.

Purpose of the Study:

• To synthesize and characterize novel polyhalogen cations incorporating μ-bridging fluorine atoms.
• To elucidate the structural and electronic properties of [Br2F5]+ and [Br3F8]+ cations.

Main Methods:

• Synthesis of polyhalogen cations as hexafluoridometalate(V) ([SbF6]-) salts.
• Spectroscopic characterization using Raman and fluorine-19 Nuclear Magnetic Resonance (19F NMR).
• Structural determination via single-crystal X-ray diffraction.
• Computational analysis using quantum chemical calculations.

Main Results:

• Successful synthesis and characterization of [Br2F5]+ and [Br3F8]+ cations.
• The [Br2F5]+ cation exhibits a symmetric [F2Br-μ-F-BrF2]+ structure.
• The [Br3F8]+ cation displays asymmetric μ-F bridges.
• Quantum chemical calculations and population analyses indicate that the bridging fluorine atoms bear the most negative partial charge.

Conclusions:

• The study reports the first synthesis of polyhalogen cations featuring μ-bridging fluorine atoms.
• The characterized cations ([Br2F5]+ and [Br3F8]+) represent new examples of stable fluoronium ions.
• Bridging fluorine atoms play a crucial role in the electronic structure and stability of these novel polyhalogen species.