Boron-Sulfur and -Selenium Rings

The most common organic derivatives of boron-sulfur rings are based on the three ring systems found in the binary boron sulfides, viz. the five-membered rings (RB)2S3 (9.27) and six-membered rings (RBS)3 (9.28) and, less frequently. 

A fascinating aspect of the chemistry of boron-chalcogen ring systems is the use of four-membered rings containing tin, (Tbt)B(p-E)2SnPh2 E = S, Se  

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