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 chemist ...
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 betwee ...
TiI
4. 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 ...
for the purification of titanium.
Physical properties
TiI
4 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, TiI
4 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 TiCl
4 (m.p. -24 °C) and TiI
4 (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 TiI
4 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 o ...
and HI.
::TiCl4 + 4 HI → TiI4 + 4 HCl
3) Oxide-iodide exchange from aluminium iodide
Aluminium iodide is a chemical compound containing aluminium and iodine. Invariably, the name refers to a compound of the composition , formed by the reaction of aluminium and iodine or the action of on metal. The hexahydrate is obtained f ...
.
::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
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{{DEFAULTSORT:Titanium Tetraiodide
Titanium(IV) compounds
Iodides
Titanium halides