Heats of formation, ΔHf⊖(298 K), for TiI4(335.9), SnI2(143.9), SnI4(215.3), and CuI (68.2 kJ mol–1) have been determined from heats of solution in 0.1 mol dm–3 FeCl3 and 3 mol dm–3 HCl. The value for SnI2 has been confirmed from heats of solution of SnI2 and iodine in ethyl acetate.
Caesiumheptaiodo-dititanate(III), CsTi2I7, is obtained from CsI, Ti and TiI4 at 250 °C in a sealed tantalum ampoule as dark red single crystals. The crystal structure (trigonal, R-3, a = 1706.6(3), c = 2088.3(5) pm, Z = 12, R1 = 0.0619) contains [TiI4] tetrahedra sharing common vertices (with Ti—I—Ti angles of 180°) to isolated ditetrahedra [Ti2I7]—. It may also be described as a cubic closest packing