Titanium(IV) fluoride is the inorganic compound with the formula TiF<sub>4</sub>. It is a white hygroscopic solid. In contrast to the other tetrahalides of titanium, it adopts a polymeric structure. In common with the other tetrahalides, TiF<sub>4</sub> is a strong Lewis acid.
The traditional method involves treatment of titanium tetrachloride with excess hydrogen fluoride:
Purification is by sublimation, which involves reversible cracking of the polymeric structure. X-ray crystallography reveals that the Ti centres are octahedral, but conjoined in an unusual columnar structure.
TiF<sub>4</sub> forms adducts with many ligands. One example is the complex cis-TiF<sub>4</sub>(CH<sub>3</sub>CN)<sub>2</sub>, which is formed by treatment with acetonitrile. It is also used as a reagent in the preparation of organofluorine compounds. With fluoride, the cluster [Ti<sub>4</sub>F<sub>18</sub>]<sup>2-</sup> forms. It has an adamantane-like Ti<sub>4</sub>F<sub>6</sub> core.
Related to its Lewis acidity, TiF<sub>4</sub> forms a variety of hexafluorides also called hexafluorotitanates. Hexafluorotitanic acid has been used commercially to clean metal surfaces. These salts are stable at pH<4 in the presence of hydrogen fluoride, otherwise they hydrolyze to give oxides.