Redetermination of the crystal structure of ThI4

Single crystals of ThI4, thorium(IV) tetra­iodide, were grown from thorium dioxide and aluminium triiodide. In comparison with the structure model reported previously for this compound [Zalkin et al. (1964). Inorg. Chem. 3, 639–644], we have determined the lattice parameters and fractional coordinates to a much higher precision, also leading to a better reliability factor (R = 0.029 versus 0.09). The coordination number of the ThIV atom is eight. Its coordination polyhedron has the shape of an irregular square anti­prism. The I atoms each bridge two ThIV atoms, resulting in the formation of infinite layers parallel to (-101) that can be described with the Niggli formula 2∞[ThI6/2I2/2].