New Lead Orthosilicate {Pb4(О(ОН)2)}[SiO4] with a Framework of Anion-Centered Pb Tetrahedra Related to Sodalite

Abstract

Abstract: New lead silicate {Pb4(О(ОН)2)}[SiO4] was synthesized under hydrothermal conditions and structurally characterized, sp. gr. P213, а = 8.9756(13) Å. According to the commonly used classification, the new compound belongs to orthosilicates. In the crystal structure, isolated SiO4 tetrahedra are located between numerous Pb atoms. The structure can be considered as an anion-centered positively charged zeolite-like framework composed of {O3Pb7}8+ clusters, which are linked to each other and include three edge-sharing (OPb4)6+ tetrahedra with one common vertex. The formula of this positively charged antiframework is {O(ОН)2Pb4}4+, and its cavities are occupied by negatively charged [SiO4]4– tetrahedra. This framework is similar to that of sodalite when relating the sites to the centers of gravity of the {O3Pb7}8+ clusters.