Thiosulfoxide

A thiosulfoxide or thiothionyl compound is a chemical compound containing a sulfur to sulfur double bond, with the formula, where R and R' represent any group amines' of the type are another group of stable compounds containing a S=S bond. The first such compound was prepared in 1974 reaction of the nitroso compound N'',N-dimethyl-p-nitrosoaniline with tetraphosphorus decasulfide. Heating to 200 °C extrudes sulfur in this compound and forms the corresponding azo compound. Disulfur monoxide S=S=O is stable at 20 °C for several days.
Occasionally thiosulfates are depicted as having a S=S unit but the sulfur-sulfur bond in it is in fact a single bond.