New polymorphic and pseudosymmetrical cobalt selenite monohydrates, CoSe03 · H2O II and CoSeO3 · H2O III

Abstract The crystal structures of two polymorphic, hydrothermally synthesized cobalt selenite monohydrates, CoSeO 3 · H 2 O II ( a = 568.1(1) pm, b = 476.7(1) pm, c = 1348.0(2) pm, μ = 101.37(1)°) and CoSeO 3 · H 2 O III ( a = 477.2(1) pm, b = 1320.9(3) pm, c = 568.6(1) pm, β = 90.54(1)°), both mP 32, P 2 1 / n , Z = 4, have been determined by single crystal X-ray diffraction. Both structures are built up from buckled trans layers 2 ∞ [CoSeO 3 · H 2 O] consisting of strongly distorted CoO 5 (H 2 O) octahedra and trigonal pyramidal SeO 3 2− ions. The structures differ with respect to the stacking of the layers, which originates in their pseudosymmetry and in the stereochemical requirements of the selenite lone electron pair. Only intra-layer H bond schemes are built, i.e., the layers are held together by van der Waals interactions.