STRUCTURE OF HEXAAQUACOBALT(II) PERBROMATE

The structure of [Co(H2O)6](BrO4)2 consists of stacks of water-oxygen octahedra, alternate ones of which contain a central Co(II) ion, each surrounded by six stacks of perbromate ions. The water O atoms form a virtually regular octahedron about Co, while the perbromate geometry is nearly regular tetrahedral. The structure is compared with those of [Hg(H2O)6]-(ClO4)2, [Cd(H2O)6](ClO4)2 and [Ni(H2O)6](BrO4)2. Although the structures of the perchlorates cited above are broadly similar to that of the title salt, and although all three structures have been assigned in space group P3m1BAR, the perchlorates and the title salt are not isostructural. Location and isotropic refinement of the single type of H atom permitted detailed analysis of the hydrogen bonding. From the point of view of the water molecules, the hydrogen bonding is remarkably similar, even in quantitative detail, to that of the water molecules in [Co(H2O)6]-(BrO3)2.