Titanium tetrachloride

Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide () and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula () to the word. is a dense, colourless distillable liquid, although crude samples may be yellow or even red-brown. It is one of the rare transition metal halides that is a liquid at room temperature, being another example. This property reflects the fact that molecules of weakly self-associate. Most metal chlorides are polymers, wherein the chloride atoms bridge between the metals. Its melting point is similar to that of . has a "closed" electronic shell, with the same number of electrons as the noble gas argon. The tetrahedral structure for is consistent with its description as a d0 metal center () surrounded by four identical ligands. This configuration leads to highly symmetrical structures, hence the tetrahedral shape of the molecule. adopts similar structures to and ; the three compounds share many similarities. and react to give mixed halides , where x = 0, 1, 2, 3, 4. Magnetic resonance measurements also indicate that halide exchange is also rapid between and . is soluble in toluene and chlorocarbons. Certain arenes form complexes of the type . reacts exothermically with donor solvents such as THF to give hexacoordinated adducts. Bulkier ligands (L) give pentacoordinated adducts . is produced by the chloride process, which involves the reduction of titanium oxide ores, typically ilmenite (), with carbon under flowing chlorine at 900 °C. Impurities are removed by distillation. The coproduction of is undesirable, which has motivated the development of alternative technologies. Instead of directly using ilmenite, "rutile slag" is used.