Pyridine N-sulphides. Some simple N-arylthiopyridinium salts and a possible source of arylsulphenium ions

NN′-Dipyridinium disulphide dichloride (1) and 1-(4-nitrophenylthio)pyridinium chloride (5) and its 4-NMe2 derivative (2) have been synthesized and their structures established unambiguously; they undergo nucleophilic attack at sulphur rather than in the pyridine ring and the tetrafluoroborate from (5) serves as a possible source of 4-nitrophenylsulphenium ion which can attack anisole readily to give (7).