REPOSITORY > RESULTS

Abstract

This thesis describes the chemistry of persistent N-heterocyclic carbene (NHC), namely, 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (LDipp) and its fluoride salt 1,3-bis(2,6-diisopropylphenyl)imidazolium fluoride, [(LDipp)H][F], with different metalloid fluoride substrates. It consists of three parts summarizing the results published in three scientific papers. The focus of the research was the reactivity of group 14 and 15 metalloid fluorides, namely, SiF4, GeF4 and SbF3, with [(LDipp)H][F] and (LDipp).
In the first part we take a look at how NHCs react with antimony(III) fluoride, the problems that arose from this system and how we solved and explained all the unexpected phenomena of the reaction system. We managed to explain the reaction mechanism and behaviour of this system in the solution and in the solid state together with the characterization of the synthesized products with spectroscopic and chemical analyses.
During the research work, we found a need for a suitable fluoride donor that would be based on a persistent LDipp NHC. By reacting LDipp NHC with various HF sources, we managed to obtain pure, anhydrous imidazolium fluoride [(LDipp)H][F] that served us as a good reagent. The path that led us to the isolation of the imidazolium fluoride also produced analogous imidazolium poly(hydrogen fluoride) salts that were all characterized with spectroscopic and chemical analyses.
In the last part we explored the reactivity of imidazolium fluoride with SiF4 and GeF4 compounds and managed to obtain discrete trigonal bipyramidal SiF5− and GeF5− anions, respectively. Trigonal bipyramidal geometry is relatively rare compared to the octahedral geometry of anions. Additionally, we report the first 19F NMR spectra of GeF5− and GeF62− anions in organic solvents, namely acetonitrile. We conclude the thesis with a rich discussion on stability of trigonal bipyramidal vs. octahedral species along with explained disorder in the crystals structure that arises from either anion rotation or Berry pseudorotation mechanisms of the prepared anions.