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 us ing single-crystal X-ray diffraction data up to sin theta/lambda = 0.7 Angstrom(-1) [monoclinic, space group C2/c, a = 15.646(3) Angstrom, b = 9.947(2) Angstrom, c = 14.984(3) Angstrom, beta = 110.65(1)degrees, Z = 32; R(w) = 0.038 for 2938 unique reflections with F-o > 3 sigma(F -o)]. The structure of CoSeO3-II is built up from complex infinity(2) [CO3(SeO3)(4)] sheets parallel to (100), which are composed of, in par t, strongly distorted CoO6 octahedra and pyramidal SeO3 groups. These closely packed sheets are further linked by a less distorted type of C oO6 octahedra. Individual Co-O and Se-O bond lengths within the four c rystallographically different CoO6 and SeO3 polyhedra in CoSeO3-II ran ge from 2.018 to 2.344 Angstrom and from 1,662 to 1.771 Angstrom, resp ectively. The structure of CoSeO3-II is closely related to that of Co- 3(SeO3)(3) . H2O. (C) 1995 Academic Press, Inc.