Selenium homocycles cations

Similar, but less stable, selenium homocycles, as well as mixed sulfur-selenium related heterocycles formed by heteroatom replacement, are also well docnmented. Cationic chalcogen homocycles are also known and have been reviewed. ... 

Spectrophotometric and potentiometric studies of the reduction of SeCl4 by elemental selenium in eutectic NaCl-AlCl3 melts at 150°C indicate that Se can exist in up to five different oxidation states, which have been interpreted in terms of the dications Se 2+, with n = 2, 4, 8, 12, or 16, but the exact nature and the structures of these species are unknown, and no pure compounds have been isolated from these mixtures (84, 85). Oxidation of (C2F5)2Se2 by either SbF5 or 02(Sb2Fn) results in a wine-red cation of composition (SeC2Fs)2 "+, where n is probably equal to 2. A homocyclic structure has been discussed for this species (86). 

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