CRYSTAL CHEMISTRY OF LEAD OXIDE CHLORIDES. II. CRYSTAL STRUCTURE OF PB7O4(OH)4CL2

Abstract

The crystal structure of Pb7O4(OH)(4)Cl-2 (monoclinic, C112(i), a=5.791(2), b=12.998(4), c=19.330(6) Angstrom, gamma=90.089(3)degrees, V=1455.1(8) Angstrom(3)) 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 s(2) 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)Pb-2 dimers. The (OH)Pb-2 dimers link the [O2Pb3] chains into a three-dimensional framework with channels parallel to [100] that are occupied by Cl- anions.