Abstract
The crystal structure of spangolite, Cu6Al(SO4)(OH)12Cl·3H2O, trigonal, a = 8.254(4) Å, c = 14.354(8) Å, V = 846.8(8) Å3, space group = P31c, has been solved by direct methods and refined to an R index of 6.5% using MoKα X-ray data. There are two distinct Cu positions, and each Cu2+ cation is coordinated by six anions in [4 + 2]-distorted octahedral arrangements typical of the Jahn-Teller-type distortion characteristic of divalent [6]Cu. There is one distinct S position coordinated by a very regular tetrahedral arrangement of O anions, and one distinct Al position coordinated by a fairly regular octahedral arrangement of O anions. The Cl anion is only bonded to the Cu2+ cations.
The structure consists of an edge-sharing sheet of Cuϕ6 and Alϕ6 octahedra, decorated on one side by SO4 tetrahedra. The Cuϕ6 octahedra are associated together in edge-sharing trimers lying on threefold rotation axes; the sulfate tetrahedron links to the central anion on one side of this trimer. These clusters link outward by sharing edges with Alϕ6 octahedra that lie on adjacent threefold axes, producing a continuous Mϕ2, sheet. These sheets then link along the c-axis by H-bonding between OH and H2O anions of one sheet and sulfate O atoms of the adiacent sheet.
