Titanium tetraiodide

Titanium tetraiodide is a chemical compound with the formula TiI₄. It is a dark violet-black solid at room temperature and is one of the most stable iodides of the transition metals. Titanium tetraiodide is used in organic synthesis, primarily as a reagent in the preparation of certain organometallic compounds.

Properties

Titanium tetraiodide is a volatile solid under standard conditions. It sublimes readily, even at room temperature, giving off a violet vapor. It is soluble in nonpolar organic solvents such as benzene and toluene, forming dark solutions. In the presence of moisture, TiI₄ hydrolyzes, releasing hydrogen iodide gas and forming titanium dioxide and iodine, which can be observed as a purple vapor.

Synthesis

Titanium tetraiodide can be synthesized by the direct combination of titanium and iodine at elevated temperatures. The reaction is typically carried out in a sealed tube to prevent the loss of iodine vapor.

\[ \text{Ti} + 2\text{I}_2 \rightarrow \text{TiI}_4 \]

Another method involves the reaction of titanium trichloride (TiCl₃) with hydrogen iodide (HI) in the presence of a reducing agent such as hydrazine.

Applications

In organic synthesis, titanium tetraiodide is used as a Lewis acid catalyst for the cleavage of ethers, the rearrangement of epoxides, and the isomerization of dienes. It is also employed in the preparation of certain organometallic compounds, including Grignard reagents, where it serves to activate the magnesium metal.

Safety

Titanium tetraiodide is considered to be a hazardous material. It is corrosive to the skin, eyes, and mucous membranes. Upon hydrolysis, it releases hydrogen iodide, a toxic and corrosive gas. Appropriate safety precautions, including the use of personal protective equipment and adequate ventilation, are necessary when handling this compound.