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.