The structure of [Co(NH3)(5)CO3]NO3. H2O is determined ab initio from conve
ntional X-ray powder diffractometry by the direct methods. The cell is mono
clinic, space group P2(t), Z = 2, a = 7.6733(4) Angstrom, b = 9.6398(5) Ang
strom, c = 7.0852(3) Angstrom and beta = 106.195(3)degrees. Refinements by
the Rietveld method, lead to R-B = 0.053, R-p = 0.100, and R-WP = 0.119. Hy
drogen atoms could not be located. Nevertheless a bonding scheme can be pro
posed for the water molecule linking the isolated [NO3] group to the carbon
atopentamine octahedron through the [CO3] group.