The preparation of sulfur dioxide complexes M(SO2)2(AsFe) (1 a-1 g M = Mn, Fe, Co, Ni, Cu, Zn, Mg) is possible in liquid SO2 (a) by oxidation of the metals with AsF5, (b) by metathesis of metal halides, e.g. NiBro, with AgAsF6, (c) by the reaction of metal fluorides, e.g. ZNF2, with AsF5. The spectroscopic properties of these complexes are discussed and the structure of [Mg(SO2)2(AsF6)2]n (1 g) is reported.