No abstract

The recently prepared novel naked fluoride reagent 1,3-bis(2,6-diisopropylphenyl)imidazolium fluoride ([(L)H][F]), treated with an excess of MF (M = Si, Ge), results in isolation of [(L)H][MF] products with the elusive trigonal bipyramidal MF anions. Specific steric characteristics of the [(L)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 GeF anion was characterized by X-ray single-crystal diffraction for the first time. We report the missing F NMR entries for the discrete GeF and GeF anions in acetonitrile. All the products were also characterized by Raman spectroscopy and elemental analysis and supported by quantum-mechanical calculations.

The reactivity of antimony trifluoride, SbF, in non-polar aprotic solvents has been unexplored due to its negligible solubility. The reaction of the [SbF(tmen)] complex (2) with the N-heterocyclic carbene, 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene, (L), probably leads to the formation of a neutral [(L)SbF] intermediate (3) in non-polar solvents. Mild heat treatment of the reaction mixture unexpectedly activates the SbF molecules to undergo the auto-ionization reaction. In this process, one of the (L) ligands undergoes rearrangement into the mesoionic carbene (MIC) and further coordinates to the cation to form [(L)SbF][SbF], product (4). Studies have confirmed that N,N,N',N'-tetramethylethane-1,2-diamine (tmen) present in the solution is not involved in the conversion mechanism and serves solely as an auxiliary ligand to increase the solubility of SbF. The compound (4) shows a rare pnictogen(iii) halide auto-ionization process with the first mesoionic NHC rearrangement on any metal/metalloid fluoride compound and the first reported reaction system where a N-heterocyclic carbene ligand facilitates the auto-ionization process on a fluorido substrate.