Arsenic homocycles

Arsenic homocycles have been incorporated in various polycylic structures that are represented by the following structures ... 

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. 

Sulfur or selenium homocycles containing one (or more) exocyclic halogen substituent are prepared by the oxidation of the element with arsenic or... 

This in fact would correspond to a reduction of arsenic yielding the intermediate compound with an As—As bond. As this homocyclic species is even less stable towards oxygen, it readily takes up O2 to generate (MeAsO) (arsonousacid anhydride, also called arsoxane or arsenoxomethyl) which finally, in the presence of moisture, gives MeAsO(OH)2 (arsonic acid) (equations 7 and 8) . 

General names for systems of rings or chains are composed of the name of the substituent and the element. For example, the name methylarsenic refers to all the systems of the type (MeAs) . The progress in the field of organoarsenic or organoanti-mony " mono-and polycycles has been summarized several times in excellent reviews. In this survey stress is laid on recent developments mainly in the field of cyclostibanes, and an attempt is made to compare analogous homocycles of arsenic and antimony. 

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