NEW POLYMORPHIC AND PSEUDOSYMMETRICAL COBALT SELENITE MONOHYDRATES, COSEO3-CENTER-DOT-H2O-II AND COSEO3-CENTER-DOT-H2O-III

The crystal structures of two polymorphic, hydrothermally synthesized cobalt selenite monohydrates, CoSeO3 . H2O II (a = 568.1(1) pm, b = 47 6.7(1) pm, c = 1348.0(2) pm, beta = 101.37(1)degrees) and CoSeO3 . H2O III (a=477.2(1)pm, b = 1320.9(3)pm, c=568.6(1)pm, beta = 90.54(1)degr ees), both mP32, P2(1)/n, Z = 4, have been determined by single crysta l X-ray diffraction. Both structures are built up from buckled trans l ayers (2)(infinity)[CoSeO3 . H2O] consisting of strongly distorted CoO 5(H2O) octahedra and trigonal pyramidal SeO32- ions. The structures di ffer with respect to the stacking of the layers, which originates in t heir pseudosymmetry and in the stereochemical requirements of the sele nite lone electron pair. Only intra-layer H bond schemes are built, i. e., the layers are held together by van der Waals interactions.