Titanium IV fluoride

Titanium IV) fluoride, TiF4. White solid (T1CI4 plus anhydrous HF). Forms [TiFJ- ion. 

Calcium fluoride has also been used in metathetical reactions. Usually, heat is required to promote reactions of this type. Booth and Dutton4 passed vapors of a volatile halide [phosphorus(V) oxychloride] over a bed of heated calcium fluoride to produce the chlorofluoride and fluoride derivatives. Sodium fluoride, potassium fluoride, titanium (IV) fluoride, and zinc fluoride have been used in similar metathetical fluorination reactions. 

The combination of titanium(IV) fluoride with antimony(lll) fluoride was found to open the epoxide ring regioselectively to yield the more-substituted fluoride, but only one example with a moderate yield was given. In another case, it was reported that regioselective epoxide cleavage could be best achieved with bis(isopropoxy)titanium difluoride. 

Aromatic ketones only reaet at temperatures higher than 150 C in the presence of a Lewis acid such as titanium(IV) fluoride. 

Other Lewis acids, such as boron trifluoride-diethyl ether complex, titanium(IV) fluoride, and triethyloxonium tetrafluoroborate, were far less effective. a, -Unsaturated esters and nitriles cannot be cyclopropanated in this manner. 

In the case of the hydrosilylation of C=N bonds, extremely high levels of enantioselectivity were dramatically realized by use of the (tetrahydroinde-nyl)titanium(IV) fluoride T4 (Fig. 12) by Buchwald in 1996 [55]. The in situ catalyst uniquely derived by mixing the titanocene fluoride T4 (1.0-0.02 mol %) with phenylsilane PhSiHj (1.5 eq referred to ketone) as hydrogen atom donor reduces the imines 13-17 (Fig. 13) to the amines A3-A7 in 80-96% yields (Table 3). An alternative activation method for the titanocene by addition of methanol and pyrrolidine was also described. In this case, the imine from acetophenone and methylamine, 13, was converted at room temperature to 35 °C to give the corresponding secondary amine in 94-95% yield with 97-99% ees (S). Moreover, alkylimines were also reduced in 92-99% ees. 

On the other hand titanium(IV) fluoride and silicon(IV) fluoride are nearly insoluble in anhydrous hydrogen fluoride. In the presence of hydrocarbons, tita-nium(IV) fluoride is made to react and to function as a catalyst in hydrocarbon... 

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