STRUCTURE OF COPPER(II) HYDROXIDE, CU(OH)2

Cu(OH)2, mineral name spertiniite, M(r) = 97.578, orthorhombic, Cmc2(1), a = 2.9471 (5), b = 10.593 (1), c = 5.2564 (7) angstrom, V = 164.1 (1) angstrom-3, Z = 4, D(x) = 3.949 Mg m-3, lambda-(Mo K-alpha) = 0.71073 angstrom, mu = 124.62 cm-1, F(000) = 188, T = 295 K, R is 0.042 for 417 unique observed reflections. The general features of the structure determined in the centrosymmetric space group Cmcm from X-ray powder data [Jaggi & Oswald (1961). Acta Cryst. 14, 1041-1045] could be confirmed. An analysis of the thermal displacement parameters of the O atoms, however, shows that the correct space group is non-centrosymmetric, Cmc2(1). Therefore, the resulting Cu-O coordination polyhedron is square pyramidal or strongly (4 + 1 + 1) distorted octahedral, but not (4 + 2) octahedral. In addition, the H-atom positions could be localized from difference Fourier syntheses. Cu-O distances are 1.948 (3) and 1.972 (3) angstrom within the equatorial plane of the square pyramid, the apical distance is 2.356 (5) angstrom and the Cu atom is displaced by 0.134 angstrom from the equatorial plane. Assuming octahedral coordination the next vertex distance is 2.915 (5) angstrom resulting in a (4 + 1 + 1) configuration. Chains of octahedra are formed by sharing equatorial edges along [100]. These chains build up corrugated layers perpendicular to the b axis by sharing edges of apical and equatorial OH- ions. The layers are connected via hydrogen bonds of the type O(1)-H(1)...O(1i) with distances O(1)...O(1i) = 2.904 (4), H(1)...O(1i) = 1.92 (2) angstrom and the angle around H(1) is 167 (2)-degrees.