in dichloromethane byproducts: 2-bromo-2,3-dihydro-1,2-thiaarsole; (Ar or N2); dropwise addn. of soln. of thiastannole to soln. of AsBr3 in CH2Cl2; removal of volatiles in vacuo; as waxy mixt. (1:1) of products which was difficult to separate;