Crystal structures of transition-metal halides TiCl4, alpha-TiCl3, WCl4, and TiI2

The crystal structures of halides TiCl4, alpha-TiCl3 (low-temperature modif ication), WCl4, and TiI2 are determined. The crystals of TiCl4 are built of tetrahedral molecules with Ti-Cl distances of 2.156-2.172 Angstrom. The ph ase transition in the three-layered modification alpha-TiCl3 below 220 K is accompanied by the distortion of the symmetry to triclinic and formation o f the Ti ... Ti pairs spaced by 3.33 Angstrom. The structure of WCl4 contai ns linear chains of WCl6 octahedra that share opposite edges with the dista nces of 2.69 Angstrom in the W-W pairs. In the layered structure of TiI2, t he titanium atoms occupy the octahedral cavities in the two-layer packing o f iodine atoms with a Ti-I distance of 2.903 Angstrom.