The reaction of SF5Br with select 1,2-dihaloethylenes

SF5Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean reaction a 1:1 mixture of SF5CHCHBr and CHBr2CHBr2 is found. The mechanism for this reaction is discussed.