SYNTHESES AND CRYSTAL-STRUCTURES OF TL5SE2CL AND TL5SE2BR

The compounds Tn5Se2Cl and Tl5Se2Br have been synthesized from stoichi ometric amounts of thallium, selenium and thallous halide. Both crysta llize with the In5Bi3 StruCture which is a subfamily of the Cr5B3 type : Tl5Se2Br crystallizes in space group I4/mcm (a = 859.4(2) pm, c = 12 78.8(4) pm, Z = 4, R = 0.047), Tl5Se2Cl as a lower symmetric distorted variant in P4/ncc (a = 856.5(1) pm, c = 1274.1(2) pm, Z = 4, R = 0.06 9). Around one central thallium atom slightly distorted octahedra of t wo halogen and four selenium atoms occur. These octahedra are covered by cubes of thallium atoms. The octahedra are interconnected via commo n vertices and the cubes via common edges to give the three-dimensiona l structure.