Structure of copper(II) hydroxide, Cu(OH)2

Cu(OH)2, mineral name spertiniite, Mr=97.578, orthorhombic, Cmc21, a=2.9471 (5), b=10.593 (1), c=5.2564 (7) A, V=164.1 (1) A3, Z=4, Dx=3.4949 Mg m-3, λ(Mo Kα)=0.71073 A, μ=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 could be confirmed. An analysis of the thermal displacement parameters of the O atoms, however, shows that the correct space group is non-centrosymmetric, Cmc21. 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) A within the equatorial plane of the square pyramid, the apical distance is 2.356 (5) A and the Cu atom is displaced by 0.134 A from the equatorial plane. Assuming octahedral coordination the next vertex distance is 2.915 (5) A 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) A and the angle around H(1) is 167 (2)deg. (orig.)