Dithiadiphosphetane 2,4-disulfides are a class of four-membered ring compounds which contain a P2S2 ring, many of these compounds are able to act as sources of the dithiophosphine ylides. The most well known example of this class of compound is Lawesson's reagent. But many other examples of this class of compound have been made, many inorganic chemists are now using Fc2P2S4 as a starting material in reactions investigating the general chemistry of the 1,3,2,4-dithiadiphosphetane 2,4-disulfides, one reaction for this is that the Fc2P2S4 compound and all its derivatives are red which make column chromatography of the products more easy.