Titanium(IV) fluoride is the inorganic compound with the formula TiF4. 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, TiF4 is a strong Lewis acid.
Preparation and structure The traditional method involves treatment of titanium tetrachloride with excess hydrogen fluoride: TiCl4 + 4 HF → TiF4 + 4 HCl Purification is by sublimation, which involves reversible cracking of the polymeric structure.Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200. X-ray crystallography reveals that the Ti centres are octahedral, but conjoined in an unusual columnar structure.
Reactions
TiF4 forms adducts with many ligands. One example is the complex cis-TiF4(CH3CN)2, which is formed by treatment with acetonitrile. It is also used as a reagent in the preparation of organofluorine compounds. With fluoride, the cluster [Ti4F18]2- forms. It has an adamantane-like Ti4F6 core.
Related to its Lewis acidity, TiF4 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.
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