Zur Polymorphie des Cadmiumsulfits, Kristallstrukturen von CdSO 3 -I, CdSO 3 -II und CdSO 3 -III / Polymorphic Cadmium Sulfites, Crystal Structures of CdSO 3 -I, CdSO 3 -II, and CdSO 3 -III

The crystal structures of the anhydrous cadmium sulfites CdSO 3 -I (P2 1 /c, Z=4), CdSO3-II (P2 1 /c, Z=8), and CdSO 3 -III (R3̄̄, Z=18 for the hexagonal cell) have been determined by means of single crystal X-ray diffraction data. The final R for the 1475, 2349, and 2138 observed reflections are 0.040, 0.034, and 0.073. Coordination of Cd is trigonal-prismatic, a hitherto unknown coordination of Cd in salts of oxoacids, in CdSO 3 -I and CdSO 3 -II, and octahedral in CdSO 3 -III. The CdO 6 -polyhedra are arranged in two-dimensional (CdSO 3 -I) and three-dimensional (CdSO 3 -II and CdSO 3 -III) networks. SO 3 2- groups act as monodentate and in CdSO 3 -I and CdSO 3 -II also as bidentate ligands. Cd−O distances range from 224.5(3) to 244.6(3) pm, with an average of 231.5 pm for the trigonal-prismatic and of 231.0 pm for the octahedral coordination. S−O dis-tances range from 152.3(3) to 155.3(3) pm with an average of 153.7 pm, the O−S−O angles from 99.2(2) to 106.7(3)° with an average of 103.2°.