Titanium tetraiodide is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

TiI₄. It is a black volatile solid, first reported by Rudolph Weber in 1863. It is an intermediate in the

van Arkel–de Boer process The van Arkel–de Boer process, also known as the iodide process or crystal-bar process, was the first industrial process for the commercial production of pure ductile titanium, zirconium and some other metals. It was developed by Anton Eduard v ...

for the purification of titanium.

Physical properties

TiI₄ is a rare molecular binary metal iodide, consisting of isolated molecules of tetrahedral Ti(IV) centers. The Ti-I distances are 261 pm. Reflecting its molecular character, TiI₄ can be distilled without decomposition at one atmosphere; this property is the basis of its use in the van Arkel–de Boer process. 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 (m.p. -23 °C) and CI₄ (m.p. 168 °C), reflecting the stronger intermolecular van der Waals bonding in the iodides. Two polymorphs of TiI₄ exist, one of which is highly soluble in organic solvents. In the less soluble cubic form, the Ti-I distances are 261 pm.

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 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 ...

and HI. ::TiCl₄ + 4 HI → TiI₄ + 4 HCl 3) Oxide-iodide exchange from aluminium iodide. ::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. TiI₄ exhibits extensive reactivity toward alkenes and alkynes resulting in organoiodine derivatives. It also effects

pinacol coupling A pinacol coupling reaction is an organic reaction in which a carbon–carbon bond is formed between the carbonyl groups of an aldehyde or a ketone in presence of an electron donor in a free radical process. The reaction product is a vicinal diol. ...

s and other C-C bond-forming reactions.

References

__notoc__ {{DEFAULTSORT:Titanium Tetraiodide Titanium(IV) compounds Iodides Titanium halides