The present invention relates to oxonium salts having [(Ro)3O]+ cations and sulfonium salts having [(Ro)3S]+ cations, where Ro denotes straight-chain or branched alkyl groups having 1-8 C atoms or phenyl which is unsubstituted or substituted by Ro, ORo, N(Ro)2, CN or halogen, and anions selected from the group of [PFx(CyF2y+1−xHz)6−x]− anions, where 2≦x≦5, 1≦y≦8 and 0≦z≦2y+1, or anions selected from the group of [BFn(CN)4−n]− anions, where n=0, 1, 2 or 3, or anions selected from the group of [(Rf1SO2)2N]− anions or anions selected from the group of [BFWRf24−w]− anions, to processes for the preparation thereof, and to the use thereof, in particular for the preparation of ionic liquids.