Related Experiment Video
Updated: Jun 28, 2025

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor SiFA for Positron Emission Tomography
Published on: January 11, 2020
Fluoride-Ion Donor Properties of AsF5
Felix O'Donnell1, Stacey D Wetmore1, Michael Gerken1
1Canadian Centre for Research in Advanced Fluorine Technologies and Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge T1K 3M4, Canada.
Abstract:
Arsenic pentafluoride undergoes ligand-induced autoionization in the presence of 1,10-phenanthroline (phen) in a SO2ClF solution to form the donor-stabilized [AsF4(phen)][AsF6] salt. Reacting [AsF4(phen)][AsF6] with the strong Lewis acid SbF5·SO2 yields the mixed arsenic-antimony salt [AsF4(phen)][Sb2F11]. These salts are the first examples of crystallographically characterized donor-stabilized [AsF4]+ cations. The analogous reaction of AsF5 and 2,2'-bipyridine (bipy) does not result in autoionization but leads to the formation of the neutral 2:1 adduct (AsF5)2·bipy. The gas-phase and solution fluoride-ion affinities of [AsF4]+ and [SbF4]+ were calculated, revealing them to be incredibly strong Lewis acids. Density functional theory calculations and natural bond orbital analysis show that significant electron-pair donation from phen to the As center in [AsF4(phen)]+ occurs and quenches the extreme electrophilicity of the [AsF4]+ cation.
Related Concept Videos
Electron Affinity
Atomic Fluorescence Spectroscopy
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Halogens
Lewis Structures of Molecular Compounds and Polyatomic Ions
Molecular Shape and Polarity

