Titanium butoxide

Titanium butoxide is a metal alkoxide with the formula Ti(OBu)4 (Bu = –CH2CH2CH2CH3). It is a colorless odorless liquid although aged samples can appear yellowish. Owing to hydrolysis, samples have a weak alcohol-like odor. It is soluble in many organic solvents. Decomposition in water is not hazardous, and therefore titanium butoxide is often used as a liquid source of titanium dioxide, which allows deposition of TiO2 coatings of various shapes and sizes down to the nanoscale.

Titanium butoxide is often used to prepare titanium oxide materials and catalysts.

Structure and synthesis
Like most titanium alkoxides (exception: titanium isopropoxide), Ti(OBu)4 is not a monomer but exists as a cluster (see titanium ethoxide). Nonetheless it is often depicted as a simple monomer.

It is produced by treating titanium tetrachloride with butanol:
 * TiCl4 + 4 HOBu →  Ti(OBu)4  +  4 HCl

The reaction requires base to proceed to completion.

Reactions
Like other titanium alkoxides, titanium butoxide exchanges alkoxide groups:
 * Ti(OBu)4 + HOR   →    Ti(OBu)3(OR)  +  HOBu
 * Ti(OBu)3(OR) + HOR   →    Ti(OBu)2(OR)2  +  HOBu

etc. For this reason, titanium butoxide is not compatible with alcohol solvents.

Analogous to the alkoxide exchange, titanium butoxide hydrolyzes readily. The reaction details are complex, but the overall process can be summarized with this balanced equation.
 * Ti(OBu)4 + 2 H2O   →    TiO2  +  4 HOBu

Diverse oxo-alkoxo intermediates have been trapped and characterized. Pyrolysis also affords the dioxide:
 * Ti(OBu)4 →    TiO2  +  2 Bu2O

Titanium butoxide reacts with alkylcyclosiloxanes. With ocatamethylcyclotetrasiloxane it produces dibutoxydimethylsilane, 1,5-dibutoxyhexamethyltrisiloxane, 1,7-dibutoxyoctamethyltetrasiloxane, 1,3-dibutoxytetramethyldisiloxane and polymers. With hexamethylcyclotrisiloxane it also produces dibutoxydimethylsilane.



Safety
LD50 is 3122 mg/kg (rat, oral) and 180 mg/kg (mouse, intravenal).

Titanium butoxide is a corrosive, flammable liquid which reacts violently with oxidizing materials. It is incompatible with sulfuric and nitric acids, inorganic hydroxides and peroxides, bases, amines, amides, isocyanates and boranes. It is irritating to skin and eyes, and causes nausea and vomiting if swallowed. LD50 is 3122 mg/kg (rat, oral) and 180 mg/kg (mouse, intravenal); flash point is 77 °C. When heated it emits irritating fumes, which form explosive mixtures with air at concentrations above 2 vol%.