Mixed chalcogen dications

Similar chemistiy has been described for the vicinal -dications of selenium, tellurium, and mixed chalcogen systems, both for the preparation and reactions of these vicinal -dications.91... 

Although diselenonium-, ditelluronium- and mixed sulfonium-selenonium dications can exhibit either oxidative or electrophilic properties in reactions with nucleophiles, substitution at the onium chalcogen atom is more typical.96 Owing to the increased stability of heavier dichalcogenium-dications, they react only with highly activated substrates such as aniline and tV,A-dimethylaniline, while no reaction is observed with phenol and diphenylamine.113 Reactions of ditelluronium dications with activated aromatics are also not known (Scheme 44).114... 

Dealkylation is the main direction in the decomposition of mixed dications 124-126. Stability of these dications strongly depends on the nature of the chalcogen and substituents.119 In general, the order of stability is consistent with the difference in electronegativities and changes as follows Te > > Se > S (Scheme 46).95 119... 

---