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

The crystal structure of Pb₇O₄(OH)₄Cl₂ (monoclinic, C112₁, a = 5.791(2), b = 12.998(4), c = 19.330(6) Å, γ = 90.089(3)°, V = 1455.1(8) ų) has been solved by direct methods and refined to R1 = 0.061 using X-ray diffraction data collected from a crystal twinned on (010). There are seven symmetrically independent Pb²⁺ cations in the structure. Each has a strongly distorted coordination polyhedron due to stereochemically active s² lone electron pairs on the Pb²⁺ cations. The structure is based on [O₂Pb₃] double chains extending along [100] formed by edge-sharing (OPb₄) oxocentered tetrahedra. Hydroxyl groups form two short (OH)-Pb bonds that result in (OH)Pb₂ dimers. The (OH)Pb₂ dimers link the [O₂Pb₃] chains into a three-dimensional framework with channels parallel to [100] that are occupied by Cl^- anions.