PbMSeO6 (M = Mo and W): New quaternary mixed metal selenites with asymmetric cationic coordination environments

Abstract

Two new isostructural mixed metal selenites, PbMSeO6 (M = Mo6+ or W6+), that are only composed of second-order Jahn-Teller (SOJT) distortive cations have been synthesized by standard solid-state reaction techniques using PbO, SeO2, and MoO3 (or WO3) as reagents. The structures of the reported materials were determined by single-crystal and powder X-ray diffraction. The materials show a three-dimensional framework structure consisting of chains of corner-shared MO6 octahedra connected by SeO3 and PbO8 polyhedra. All of the constituent cations (M6+, Se4+, and Pb2+) are in distorted environments attributable to second-order Jahn-Teller (SOJT) effects. While the Mo6+ cations undergo a C-2-type intraoctahedral distortion toward an edge, the Se4+ and Pb2+ cations are in asymmetric coordination environments attributable to their lone pairs. The SeO3 polyhedra strongly influence the direction of the Mo6+ intraoctahedral distortion. Infrared spectroscopy, thermogravimetric analysis, the magnitudes of out-of-center distortions, and dipole moment calculations are also presented. Crystal data: PbMoSeO6, triclinic, space group P-1 (No. 2), with a = 6.8944(6) angstrom, b = 7.2219(6) angstrom, c = 10.8294(9) angstrom, alpha = 99.751 (2)degrees, beta = 99.996(2)degrees, gamma = 90.041(2)degrees, V = 523.09(8) angstrom(3), and Z = 2; PbWSeO6, triclinic, space group P-1 (No. 2), with a = 6.8689(2) angstrom, b = 7.2398(2) angstrom, c = 10.9037(3) angstrom, alpha = 99.699(4)degrees, beta = 100.348(3)degrees, gamma = 90.139(4)degrees, V = 525.50(3) angstrom(3), and Z = 2.