Crystal chemistry of lead oxide chlorides. II. Crystal structure of Pb7O4(OH)4Cl2

The crystal structure of Pb 7 O 4 (OH) 4 Cl 2 (monoclinic, C 112 1 , a = 5.791(2), b = 12.998(4), c = 19.330(6) A, γ = 90.089(3)°, V = 1455.1(8) A 3 ) has been solved by direct methods and refined to R 1 = 0.061 using X-ray diffraction data collected from a crystal twinned on (010). There are seven symmetrically independent Pb 2+ cations in the structure. Each has a strongly distorted coordination polyhedron due to stereochemically active s 2 lone electron pairs on the Pb 2+ cations. The structure is based on [O 2 Pb 3 ] double chains extending along [100] formed by edge-sharing (OPb 4 ) oxocentered tetrahedra. Hydroxyl groups form two short (OH)-Pb bonds that result in (OH)Pb 2 dimers. The (OH)Pb 2 dimers link the [O 2 Pb 3 ] chains into a three-dimensional framework with channels parallel to [100] that are occupied by Cl - anions.