Methyl fluoride-antimony pentafluoride complex

The alkylating ability of methyl and ethyl fluoride-antimony pentafluoride complexes has been investigated by Olah et al.,143,144 who showed the extraordinary reactivity of these systems. Self-condensation was observed as well as alkane alkylation. When CH3F-SbF5 was reacted with excess of CH3F at 0°C, at first only an exchanging complex was observed in the H NMR spectrum. After 0.5 h, the starting material was converted into the ferf-butyl cation 4 (Scheme 5.19). 

Sulphur-Oxygeii-Halogen Compounds.—Chemical analysis of a relatively stable complex of methyl fluoride-antimony pentafluoride, prepared from solution in SO2, showed it to contain bonded SO2. A reinvestigation of the solution of the MeF-SbFs system in SO2 and in SO2CIF revealed that both SO2 and SO2CIF may be O-methylated, giving stable non-exchanging ions (5) and (6). 

Lewis Acid Complexes. Sulfolane complexes with Lewis acids, such as boron trifluoride or phosphoms pentafluoride (17). For example, at room temperature, sulfolane and boron trifluoride combine in a 1 1 mole ratio with the evolution of heat to give a white, hygroscopic soHd which melts at 37°C. The reaction of sulfolane with methyl fluoride and antimony pentafluoride inhquid sulfur dioxide gives crystalline tetrahydro-l-methoxythiophenium-l-oxidehexafluoroantimonate, the first example of an alkoxysulfoxonium salt (18). 

When methyl fluoride was absorbed into neat antimony pentafluoride at room temperature a low field band at —12-5 p.p.m. appears. The relative intensity of this species compared with the covalently polarized methyl fluoride complex is, however, small and it could originate from impurities in the system. 

Ene reactions. The antimony pentafluoride—methyl fluoride complex in SO2 undergoes the ene reaction with vinyl halides (1) at -65 to give unsaturated methyl sulfinates (2), isolated after addition of methanol. Yields... 

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