Titanium tetraiodide is an inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 TiI₄. It is a rare molecular binary metal iodide, consisting of isolated molecules of tetrahedral Ti(IV) centers. Reflecting its molecular character, TiI₄ can be distilled without decomposition at one atmosphere; this property is the basis of the Van Arkel process for the purification of titanium. The difference in melting point between TiCl₄ (m.p. -24 °C) and TiI₄ (m.p. 150 °C) is comparable to the difference between the melting points of CCl₄

Carbon tetrachloride

Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...

 (m.p. -23 °C) and CI₄

Carbon tetraiodide

Carbon tetraiodide is CI4, a tetrahalomethane. Being bright red, it is a relatively rare example of a highly colored methane derivative. It is only 2% by weight carbon, although other methane derivatives are known with still less carbon....

 (m.p. 168 °C), reflecting the stronger intermolecular van der Waals bonding in the iodides.

Production

Three methods are well known:
1) From the elements, typically using a tube furnace at 425 °C:

Ti + 2 I₂ → TiI₄

This reaction can be reversed to produce highly pure films of Ti metal.

2) Exchange reaction from titanium tetrachloride

Titanium tetrachloride

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is an unusual example of a metal halide that is highly volatile...

 and HI.

TiCl₄ + 4 HI → TiI₄ + 4 HCl

3) Oxide-iodide exchange from aluminium iodide

Aluminium iodide

Aluminium iodide is any chemical compound containing only aluminium and iodine. Invariably, the name refers to a compound of the composition AlI3, formed by the reaction of aluminium and iodine or the action of HI on Al metal. The hexahydrate is obtained from a reaction between metallic aluminum...

.

3 TiO₂ + 4 AlI₃ → 3 TiI₄ + 2 Al₂O₃

Reactions

Like TiCl₄ and TiBr₄, TiI₄ forms adducts with Lewis bases, and it can also be reduced. When the reduction is conducted in the presence of Ti metal, one obtains polymeric Ti(III) and Ti(II) derivatives such as CsTi₂I₇ and the chain CsTiI₃, respectively. As a solution in CH₂Cl₂, TiI₄ exhibits some reactivity toward alkenes and alkynes resulting in organoiodine derivatives.