Chalcogen homocycles

OXIDISED CHALCOGEN HOMOCYCLES 12.2.1 With Exocyclic Oxygen Substituents... 

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. ... 

The effect shown in Fig. 9 is a result of the bond-bond interaction which is a characteristic feature for chains and rings of two-valent chalcogen atoms. It can also be recognized from the relatively large bond interaction force constants fir of such compounds. The stretching force constants /r(SS) of polysulfur compounds depend on the SS bond distances as shown in Fig. 10. The data used in this figure include several excited electronic states of the S2 molecule as well as the disulfide anion and a number of sulfur homocycles [77]. 

There are two types of compounds known that contain 10 chalcogen atoms a neutral Si0 homocycle and several isostructural bicyclic Se102+ salts. 

Relatively little is known of the chemistry of antimony rings compared to arsenic rings. The reactions of arsenic homocycles have been reviewed several times " . They include cleavage of the As—As bonds with halogens and insertion of chalcogens or unsaturated hydrocarbons and reductive cleavage with potassium metal. Representative examples are given in equations 15-18. 

---