Discrete GeF₅^- Anion Structurally Characterized with a Readily Synthesized Imidazolium Based Naked Fluoride Reagent

The recently prepared novel naked fluoride reagent 1,3-bis(2,6-diisopropylphenyl)imidazolium fluoride ([(L^Dipp)H][F]), treated with an excess of MF₄ (M = Si, Ge), results in isolation of [(L^Dipp)H][MF₅] products with the elusive trigonal bipyramidal MF₅^- anions. Specific steric characteristics of the [(L^Dipp)H]⁺ cation readily support isolation of monomeric and discrete trigonal bipyramidal fluorido anions of silicon and germanium. Based on combination of experimental results and DFT calculations, we demonstrate that the role of bulky cation is not solely due to steric hindering but also due to electrostatic effects, which are important in the design of such uncommon species. The discrete GeF₅^- anion was characterized by X-ray single-crystal diffraction for the first time. We report the missing ¹⁹F NMR entries for the discrete GeF₅^- and GeF₆^2- anions in acetonitrile. All the products were also characterized by Raman spectroscopy and elemental analysis and supported by quantum-mechanical calculations.