I want to send a special thank-you to Professor Dean Tantillo of UC Davis (http://blueline.ucdavis.edu). In response to my call for molecules that are really odd, yet exciting, Dean brought up thiosulfoxides. Wow – these things are bizarre, aren’t they? Sulfur is like a box of chocolates, if you know what I mean… Take a look at the reference Dean sent me. Apparently, there has been a long-standing controversy with regard to which one of the two structures shown is actually the more stable one. The Schleyer paper below claims that the linear form is more stable. These are the outskirts of reality, they are here to show that there is little better than to be a chemist as nature has had very little reason to conceive such unusual structures. We’ll need to wait till Dean sheds some new light on this process.
the corresponding S-methylated salt of dimethylthiosulfoxide is actually quite common, and behaves as a mild electrophile delivering MeS(+) group. It is made from MeSSMe and Me3O(+)BF4(-) and it can be used as a replacement for NCS for oxidative cleavage of dithioacetals. Aldrich even sells it.
That is totally correct, and these are even preferable (sometimes) to trialkylsulfoniums. However, it is the rearrangement and concomitant fluorine migration that sets S2F2 apart. It is an strange molecule.