Titanium complexes halides

Nugent, W. A. (1998) Desymmetrization of meso-epoxides with halides A new catalytic reaction based on mechanistic insight, J. Am. Chem. Soc., 120 7139-7140. Bruns, S. Haufe, G. (1999) Catalytic asymmetric ring opening of epoxides to chlorohydrins with mild chloride donors and enantiopure titanium complexes.. 

Ziegler-Natta catalysts are primarily complexes of a transition metal halide and an organometallic compound whose structure is not completely understood for all cases. Let us use as an example TiCU and R3AI. The mechanism of the polymerization catalysis is somewhat understood. This is shown in Fig. 14.6. The titanium salt and the organometallic compound react to give a pentacoordinated titanium complex with a sixth empty site of... 

Investigations of the diars complexes of the titanium(IV) halides resulted in the first... 

For general properties of the halides and oxyhalides of titanium, reference to the work by Clark is recommended.14 The chemistry of the complex halides will be treated here. 

Hydrolysis, redox, metathetical, and halide abstraction reactions are covered here. Some of these reactions lead to specific complexes with Ti-O, Ti-N, and Ti-C bonds which are described in subsequent sections. Comments on the applications of the mono-Cp trihalo titanium complexes as olefin polymerization pre-catalysts have been mentioned in Section 4.05.3.1.1 and some recent advances in this field are also considered here. (See Chapter 4.09 of this work.)... 

Thus, it is clear why water cannot be used as a solvent Most titanium esters or halides are too reactive and would react with the water solvent rather than the silica surface. One procedure that permits titanation from an aqueous solution is to use a water-soluble titanium complex that resists hydrolysis until after silica dehydration temperatures are reached, when only silanol groups remain. Titanate complexes of triethanolamine [569], acetylacetonate [570], lactate [569], or even peroxide [571] can be used in this way to perform aqueous titanation. 

Titanium, tetrakis(trimethysilyl)oxy-, 334 Titanium complexes alloy hydrides, 353 amino adds, 342 antimony, 345 arsenic, 345 bromides, 357 chlorides, 355, 356 fluorides, 354 Group IV derivatives, 352 halides, 354 electron spectra, 358 hexamethylphosphoramide, 335 iodides, 357... 

An IR study of the complexes fonned from TiCl4 and dialkyl H-phosphonates indicates that at low temperatures, a a-donor complex through the phosphoryl oxygen atom is formed [415], Similar to the analogous complexes of tin halides, these titanium complexes are thermally unstable and easily undergo dealkylation with cleavage of alkyl halides even at low temperatures. 

An unoccupied coordination site and titanium alkyl bond in the titanium complex are fundamental requirements for its catalytic activity in olefin oligomerization. The titanium-alkyl bond is formed in the reaction of a titanium compound with alkyl or alkylchloroaluminum compounds when, for example, halide atoms or alkoxy groups of titanium compounds are replaced by alkyl groups of aluminum derivatives. There are many proposals concerning the structure of the Ziegler-Natta catalyst active centers. These are presented in structural formulas (16)-(21) [291. 

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