Crystal Structure of a New Modification of CoSeO3

The crystal structure of a hydrothermally synthesized new modification of CoSeO3 (CoSeO3-II) was determined by direct and Fourier methods using single-crystal X-ray diffraction data up to sin θ/λ = 0.7 Å-1 [monoclinic, space group C2/c, a = 15.646(3) Å, b = 9.947(2) Å, c = 14.984(3) Å, β = 110.65(1)°, Z = 32; Rw = 0.038 for 2948 unique reflections with Fo > 3 σ (Fo)]. The structure of CoSeO3-II is built up from complex 2∞ [Co3(SeO3)4] sheets parallel to (100), which are composed of, in part, strongly distorted CoO6 octahedra and pyramidal SeO3 groups. These closely packed sheets are further linked by a less distorted type of CoO6 octahedra. Individual Co-O and Se-O bond lengths within the four crystallographically different CuO6 and SeO3 polyhedra in CoSeO3-II range from 2.018 to 2.344 Å and from 1.662 to 1.771 Å, respectively. The structure of CoSeO3-11 is closely related to that of Co3(SeO3)3 · H2O.