Kristallstruktur von Cadmium‐Kupfer‐Hydroxidnitrat, CdCu3 (OH)6 (NO3)2·H2O

Abstract

AbstractThe crystal structure of cadmium copper hydroxide nitrate, CdCu3 (OH)6 (NO3)2 · H2O, has been determined from three dimensional single crystal X‐ray data.One single elementary cell of the compound has to be of triclinic symmetry, but as either the crystal is built up from such triclinic domains grown together regularly at angles of 120 degrees, or the nitrate groups of the whole crystal are distributed statistically over three possible orientations standing at 120 degree angles respectively to each other, the structure can also be described in the hexagonal system: a = 6.522 ± 0.005 Å, c = 7.012 ± 0.006 Å, space group D – P 3 m 1, cell content one formula unit.Mixed layers (00.1) of Cu and Cd atoms are embedded between layers consisting of the OH groups and one oxygen atom per nitrate group. The nitrate groups extend with their trigonal plane nearly perpendicular to the layers (00.1) and connect them by hydrogen bridges between the remaining two oxygen atoms and OH groups of the next layer. The Cd atoms are coordinated octahedrally by six equidistant OH groups, and the Cu atoms have a strongly distorted octahedral (4 + 2) coordination with four OH groups and two nitrate oxygens. Thermogravimetric measurements allowed to distinguish the crystal water molecule from variable amounts of excess water. The hydrogen bonds between OH groups and nitrate oxygen atoms and the deformation of the nitrate groups were confirmed by infrared spectra.