ON A LEAD COPPER TELLURATE PBCU3TEO7 CONT AINING CU2+ IN DISTORTED SQUARE PYRAMIDAL AND TETRAHEDRAL OXYGEN COORDINATION

PbCu3TeO7 has been prepared from the element oxides by solid state rea ction in air. Single crystal X-ray work led to orthorhombic symmetry, space group D-2h(16)-Pnma, a = 10.488(1), b = 6.353(2), c = 8.813(2) A ngstrom, Z = 4. Cu(1)O-5 square pyramids and TeO6 octahedra are member s of the anionic part of the crystal structure, Cu(2) atoms show tetra hedral coordination by oxygen. The Cu(2)(2+) and the Pb2+ cations are incorporated into a [Cu(1)(2)TeO7] network. PbCu3TeO7 can thus be view ed as a lead copper oxocuprate(II) tellurate. Calculations of the Coul omb terms of lattice energy reveal two possible positions for the lone pair of electrons at Pb2+.