Tetrazolium salts

Tetrazolium salts, as the name indicates, are quartenary. Substitution is possible on positions 2, 3, and 5 of the ring as is shown in type formula (I). When these substituent groups are bifunctional ditetrazolium salts of types (II), (III), and (IV) result. Compounds bridged at both R\u27 and R\u27\u27 at the same time are theoretical possible, but no such cases have been reported, probably on account of the practical limitations of synthesis. The anion, which is indicated by X, may be halide, sulfate, acetate, picrate, succinate, thiocyanate, or practically any atom or group capable of existing as a negative ion