Titanium IV Iodide

Submitted by R. NEIL LOWRY and ROBERT C. FAY Checked by B. L. CHAMBERLANDf 

Titanium (IV) iodide may be prepared by a variety of methods. High-temperature methods include reaction of titanium metal with iodine vapor,titanium carbide with iodine, titanium(IV) oxide with aluminum (III) iodide, and titanium(IV) chloride with a mixture of hydrogen and iodine. At lower temperatures, titanium (IV) iodide has been obtained by the combination of titanium and iodine in refluxing carbon tetrachloride and in hot benzene or carbon disulfide a titanium-aluminum alloy may be used in place of titanium metal. It has been reported that iodine combines directly with titanium at room temperature if the metal is prepared by sodium reduction of titanium(IV) chloride and is heated to a high temperature before iodine is 

When all the iodine has sublimed out of tube C (10 to 12 hours), nitrogen is admitted into the system, and the apparatus is allowed to cool to room temperature. Tube C is removed, and the glass-wool plugs and unreacted titanium (0.23 g.) are removed with a hooked copper wire while purging with nitrogen. Caution. Care should be exercised in removing the unreacted titanium from the tube the titanium may be pyrophoric. Then tube C is cleaned, dried, and reattached to tube B. Tube B is removed from attachment to A and, while holding tube B 

For purification of the product, tubes A and B are cleaned, dried, and reassembled with a dry glass-wool insert in B. Tube C, containing the initially formed product, is attached to tube B as shown in Fig. 2. The system is evacuated and this time left open to the vacuum. The two furnaces are separated by ca. 1.5 cm. Furnace I is heated to 80° and furnace II to 130 to 140°. Sublimation is allowed to continue until all the titanium(IV) iodide has left tube C (12 to 16 hours). The purified product crystallizes in tube B at the separation of the two furnaces. The major impurity, iodine, crystallizes in tube A and in the liquid-nitrogen trap. A fluffy tan residue of negligible weight (0.04 to 0.06 g.) remains in tube C. If desired, further purification can be accomplished by moving tube B farther into furnace II, which results in a second sublimation of the product. 

After removing tube B from attachment A, the product is scraped, as before, into the flask. Tube B is removed, the flask is stoppered, and the stopcock closed. It is best to release any excess pressure in the flask before storage. The yield of tita-nium(IV) iodide is 25.0 g. (93% based on the titanium which reacted, 84% based on the total weight of titanium used). Anal. Calcd. for Til4 Ti, 8.62 I, 91.38. Found Ti, 8.61 I, 91.28. 

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There are many colorimetric methods used for trace analysis of peroxides using reagents such as ferrous ion, leuco base of methylene blue, yy -diphenylcarbohydrazide, titanium(IV), iodide ion, and Ai,A7-dimethyl- -phenylenediamine. The latter two are the most commonly used reagents... 

Reaction of titanium metal with a 3% excess of iodine in refluxing carbon tetrachloride (24 hours) gave titanium (IV) iodide in only 30 to 50% yield. 

Titanium (IV) iodide is a lustrous, dark reddish-brown, crystalline solid. It melts at 150°6 and boils at atmospheric pressure without decomposition at 377.2°.3 Its vapor pressure in the range 160 to 370° is given by the relationship ... 

Titanium(IV) iodide is extremely hygroscopic. It dissolves in water with decomposition, and it fumes in air owing to hydrolysis. It forms 2 1 adducts with ammonia,7 pyridine,33 and ethyl acetate.34 With excess ammonia it undergoes ammo-nolysis to give ammonobasic titanium(IV) iodides.7 Analogous aminolysis reactions occur when titanium(IV) iodide is treated with an excess of primary or secondary amine.36 Titanium(IV) iodide is sparingly soluble in petroleum ether, moderately soluble in benzene, and even more soluble in chlorinated hydrocarbons and carbon disulfide. At elevated temperatures it... 

Titanium(iv) iodide" " or a combination of a titanium(iv) salt and an iodide source promotes pinacol coupling reactions of aromatic aldehydes. The combination of the reagents is considered to generate titanium(m) species along with U. 

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