Titanium IV Compounds

Titanic Acid. Add a 10% ammonia solution to 10 ml of a solution of titanium tetrachloride in hydrochloric acid with constant stirring up to the complete precipitation of titanic acid. Let the precipitate settle, pour off the solution, and rinse it several times with water by decantation. 

See how titanic acid reacts with 10% solutions of acids and alkalies. Shake a small amount of titanic acid in a test tube with water and boil it. Pour oft the water and again see how the titanic acid reacts with acids and alkalies. How and why did the reactivity of the titanic acid change  

Put a small amount of the titanic acid on the lid of a crucible, dry it in a drying cabinet, and then roast it. What is obtained Write the equation of the reaction. How does the colour of the preparation change when roasted Is the previous colour restored after the substance has been cooled Dry the remaining amount of the titanic acid in the air and hand it in to the laboratory assistant. 

What hydrates are called alpha- and beta-titanic acids, how are they prepared, and what are their properties How, having at hand titanium(IV) oxiue, can you prepare potassium titanate and titanyl sulphate  

Compare the properties of titanium(IV), zirconium(IV), and hafnium(IV) hydroxides. 

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Peroxidic Compounds. When hydrogen peroxide is added to a solution of titanium(IV) compounds, an intense, stable, yellow solution is obtained, which forms the basis of a sensitive method for determining small amounts of titanium. The color probably results from the peroxo complex [Ti(02)(0H)(H20)J, and crystalline salts such as K2[Ti(02)(S0 2] H20 can be isolated from alkaline solutions. The peroxo ligand is bidentate the two oxygen atoms ate equidistant from the titanium (98). 

The six coordinated titanium(IV) compounds, Ti(acac)2(X)2, where X is methoxy, ethoxy, isopropoxy, -butoxy, or chloro, all adopt the cis-configuration. This is beheved to result from the ligand-to-metal TT-electron donation (88,89). 

Titanium-IV compounds with their Lewis acid activity may catalyze an interfering rearrangement of the starting allylic alcohol or the epoxy alcohol formed. In order to avoid such side-reactions, the epoxidation is usually carried out at room temperature or below. 

The hydrolysis should be carried out with access of air so that the black titanium(II) derivatives are oxidized rapidly and completely to colorless titanium(IV) compounds. 

Allyl Ketones from Imidazolides and Allyl Titanium(IV) Compounds... 

Titanium(IV) complexes, 25 97-101 Titanium(IV) compounds six-coordinated, 25 90 Titanium(IV) cyclopentadienyls, 25 110, 111—112t... 

Thus far we have seen that Schiff base ligands tend to promote six-coordination, but an unusual reaction has been found to occur between TiCl2(salen) and borohydride. No reduction at titanium is seen, but rather, addition of BtLr to the imino function of the ligand occurs to give a dimeric seven-coordinate titanium(IV) compound, (24), containing amine-boranes as... 

Breslow (139) discovered a homogeneous system well suited for kinetic analysis. He realized that bis(cyclopentadienyl)titanium(IV) compounds, which are very soluble in aromatic hydrocarbons, could be used instead of titanium tetrachloride as the transition-metal compound together with aluminum alkyls to give Ziegler catalysts. Subsequent research on this and other systems with various alkyl groups has been conducted by Natta et al. (140, 141), Belov el at. (142-144), Patat (145), Patat and Sinn (146) Sinn et al. (119, 147), Shilov and co-workers (148-150), Chien and Hsieh (20), Adema (151), Clauss and Bestian (152), Henrici-Olive and Olive (153), and Reichert and Schoetter (154) and Fink (155). 

Organometallic Titanium(iv) Compounds.—As in earlier volumes only selected aspects of this chemistry are presented. 

See, e.g.. Fix, R. M. Gordon, R. G. and Hoffman, D. M., Synthesis of thin films by atmospheric pressure chemical vapor deposition using amido and imido titanium(IV) compounds as precursors. Chem. Mater. 2 (1990) 235-241. 

The majority of titanium (III) compounds are rather easily oxidized and must be handled in an inert atmosphere. However, the titanium(III) urea derivative is relatively stable and can be kept in dry air for several weeks without suffering any apparent oxidation. In moist air or aqueous solution oxidation is much more rapid. Hexaureatita-nium(III) perchlorate has been prepared by the reduction of titanium (IV) compounds and subsequent reaction of the titanium (III) ion with urea in the presence of sodium perchlorate. The following procedure is a modification of this method. 

When the ligand system consists of chlorine atoms, monoalkyl- and monoaryl-titanium(IV) compounds are readily made from TiCU by a chlorine atom replacement. The parent compound in this series, MeTiCb, is made conveniently from the reaction of TiCU and dimethylzinc without the use of ethereal solvents, the preparation being carried out in n-pentane or dichloromethane. Other methylating species can be used, such as MeMgBr, MeLi and MeAlCh. When MeLi is used in diethyl ether, an equilibrium takes place between different complexation states of Ti in the resulting MeTiCU with the solvent (equation 8). Transmetallation from organotin compounds like (15 equation 9) has also been utilized to make trichlorotitanium compounds. ... 

Homogeneous catalysts for the ethylene polymerization based on bis(cyclopenta-dienyl)titanium(IV) compounds [4], tetrabenzyltitanium [14], tetraallylzirconium and hafnium are formed with diethylaluminum chloride, dimethylaluminum chloride or triethylaluminum as co-catalysts. Their activities are poor (less than 200 kg PE/mol catalyst per h), so no industrial application resulted. 

This chapter attempts to summarize the literature on this class of complexes from the publication of COMC (1995) to 2004 or early 2005. Synthesis, structure, and chemical properties of organometallic titanium(iv) compounds, which contain different types of Ti-C bonds supported by additional ligands, will be covered. We attempt to highlight the major developments from 1993 and tentatively to reveal new trends in this field over the next few years. 

Most of the homogeneous Ziegler-type catalysts have been preferentially investigated in order to understand the elementary steps of the polymerization, which is simplified in soluble systems. Bis(cyclopentadienyl)titanium(IV) compounds, which are soluble in aromatic hydrocarbons could be used together with aluminum alkyls to give Ziegler-catalysts. As to the kinetics of polymerization and to side reactions of the catalyst components, this system is probably the best understood. It has not been used in a technical process because of the low activity and short life of systems that contain chloride (see Table 1). 

Other Titanium(iv) Compounds. The anhydrous nitrate is a very interesting volatile compound (m.p. 58°), made by the action of N2Os on hydrated TiIV nitrate.15 It is very reactive toward organic substances, often causing inflammation or explosion it probably reacts by releasing the very reactive N03 radical. The structure shown in Fig. 25-A-2, is a special case of the dodecahedral structure as explained on page 29. 

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