Thiepane
Thiepane is the organosulfur compound with the formula 6S. Thiepanes are seven-membered ring heterocycles that contains sulfide. The parent thiepane has seldom been studied.
A variety of derivatives are known. Hexathiathiepane is CH2S6. A naturally occurring derivative is lenthionine, 1,4-2S5.
Thiepane itself may be a product of spontaneous coal fires in post-mining waste heaps.