in sulfur dioxide exclusion of air and moisture; 1. method: NMR-tube; SO2 and SbF5 alternate condensed to CsPHF5 at 77 K; melted off; shake at 205 K; 2.method: react. in two leg vessel; 1.method: CsSbF6 pptd.; NMR-spectroscopy; 2.method: pptn. separated; solvent removed; Raman-spectroscopy of residue;