CRYSTAL-STRUCTURE AND THERMAL-PROPERTIES OF COBALT HYDROGENSELENITE DIHYDRATE, CO(HSEO3)(2)CENTER-DOT-2H(2)O

Co(HSeO3)(2).2H(2)O crystallizes in a monoclinic space group P2(1)/n with cell dimensions a=7.117(1), b=6.872(1) and c=8.018(2) Angstrom, and beta=113.17(2)degrees, Z=2. R- and wR-values are 6.50 and 8.95, respectively, for 790 observed reflections. The cobalt ion coordination is slightly distorted octahedral with water molecules at the apexes at a distance of 2.110(4) Angstrom. The basal plane is formed by four hydrogenselenite oxygen atoms with the distances of 2.061(4) and 2.130(5) Angstrom. Each oxygen belongs to a different hydrogenselenite ion which bridges two cobalt ions, forming a two-dimensional layer-like structure. The Se-O distances within the hydrogenselenite ion are 1.660(5) and 1.662(4) Angstrom, and 1.759(5) Angstrom for the Se-OH distance. The protonated oxygen atom participates in hydrogen bonding, joining the adjacent layers with an O-O distance of 2.707(6) Angstrom. Thermal decomposition proceeds via three intermediate phases to CoO, which is the end product. The IR spectrum was also recorded and interpreted.