Abstract:

The preparation and characterization of new molecular covalent compounds with a xenon-carbon bond is described within the framework of this thesis. Pentafluorophenylxenon(II) fluoride and 2,4,6-trifluorophenylxenon(II) fluoride are prepared by metathesis of arylxenon(II)salts and tetramethylammonium fluoride in dichloromethane at -78 °C. These asymmetric hypervalent molecules possess a weak and elongated xenon-fluorine bond when compared to xenon difluoride. The high polarity of the Xe-F bond enables the fluorine abstraction even with weak Lewis acids. The fluorine-ligand in arylxenon(II) fluorides can easily substituted, e.g. during the reaction with diarylcadmium the corresponding diarylxenon(II) compounds are formed. Using that approach bis(pentafluorophenyl)xenon(II), bis(2,4,6-trifluorophenyl)xenon(II) and the asymmetric compound (pentafluorophenyl)2,4,6-trifluorophenylxenon(II) are prepared and characterized by multinuclear NMR spectroscopy. Further the preparation of bis(pentafluorophenyl)xenon(II) starting from pentafluorophenylxenon(II) fluoride or xenon difluoride and pentafluorophenylsilanes with different Lewis acidities is investigated. This procedure was also extended to perfluoroalkenyl or perfluoroalkyl ligands. Pentafluorophenylxenon(II) chloride and 2,4,6-trifluorophenylxeon(II) chloride are prepared by conversion of the corresponding Arylxenon(II) fluorides with trimethylsilyl chloride while Pentafluorophenylxenon(II) cyanide is generated using trimethylsilyl cyanide as a substrate. The reactions with trimethylesilyl thiocyanide and -bromide did not yield pentafluorphenylxenon(II) thiocyanide or bromide respectively. The NMR spectra of the new arylxenon(II) compounds are discussed as well as compared with NMR data from existing arylxenon(II) compounds. The interpretation is supported by ab initio calculations on RHF level.