Synthesis and structure of the layered thorium telluride CsTh₂Te₆

The compound CsTh₂Te₆ has been synthesized at 800 °C by the reaction of Th with a CS₂te₃/Te melt as a reactive flux. The compound crystallizes in the space group D_2h¹⁷-Cmcm of the orthorhombic system with two formula units in a cell of dimensions a = 4.367(2) Å, b = 25.119(10) Å, c = 6.140(3) Å, and V = 673.5(5) ų at T = 113 K. The structure of CsTh₂Te₆ has been determined from single-crystal X-ray data. The structure comprises infinite, two-dimensional double layers of ThTe₈-bicapped trigonal prisms. The structural motif of the trigonal prisms resembles that found in UTe₂. Cs⁺ cations, disordered equally over two crystallographically equivalent sites, separate the layers and are coordinated by eight Te atoms at the corners of a rectangular parallelepiped. Short Te - Te distances of 3.052(3) and 3.088(3) Å form linear, infinite, one-dimensional chains within the layers. Simple formalisms describe neither the Te - Te bonding in the chain nor the oxidation state of Th. The compound shows weak semiconducting behavior along the Th/Te layers perpendicular to the Te - Te chain.