Titanium, trichloride, 1:1.5 complex with

S. Fuji, Ethylene Polymerization with the Catalysts of One- and Two-Component Systems Based on Titanium Trichloride Complex, in Ref. 9, p. 135. 

The reagent can also be used for intramolecular reductive coupling (equation I) but for this reaction a reagent obtained by reduction of cyclopentadienyl-titanium trichloride (Alfa) with lithium aluminum hydride is also effective (equation II). A Ti(II) complex of known structure (1) was also shown to be effective for pinacolic coupling. It is more effective than titanocene. ... 

In the vertical mode [88], constructing a trisubstituted furan (102) was considered a suitable starting point. Subsequent cyclo-addition reaction with the allene derivative 103 gave the Diels-Alder adduct which with lithiumaluminiumhydride-titanium trichloride complex and triethyl amine opened up to form the penta substituted benzene derivative 104. This was converted into 86a in five steps as depicted in Scheme 21. 

The Lewis acid mediated addition of allylic tin reagents to nitroalkenes has been reported. The condensation reaction of tributyl[(Z)-2-butenyl]tin(IV) with (E)-(2-nitroethenyl)benzene or (L)-l-nitropropene catalyzed by titanium(IV) chloride proceeded with modest anti diastereoselectivity. Poorer diastereoselection resulted when diethyl ether aluminum trichloride complex was employed as the Lewis acid 18. 

However, more recent reinvestigations have shown the process to be more complex, its outcome (formation of side products), for example, being dependent on the reaction temperature [102]. A cleaner hydrocarbon 249 is obtained in 43% yield as the sole product when bis(l-bromocyclopropyl) ketone is treated with titanium trichloride and zinc-copper couple [103]. 

Titanium forms three series of salts in which the element is respectively tetra-, tri-, and mono-valent. Thus, titanium and chlorine form titanium tetrachloride, TiCl4, titanium trichloride, TiCl3, and titanium monochloride, TiCl. The two last are unstable and readily pass into the higher chloride. Titanium tetrachloride shows a marked resemblance to tin tetrachloride it unites easily with hydrochloric acid in solution, with formation of the complex acid, ehloro-titanic acid, [TiCl6]tI2, and forms many crystalline products with other chlorides. It also unites with ammonia, forming ammines. 

In addition to reaction of metal alkyl with the lateral edges of the titanium trichloride crystal, reaction also occurs at the main faces although this does not initiate polymerization. A study of the stoichiometry and mechanism of the TiCl3 /AlMe3 reaction indicates that a complex of the structure TiCl3—TiCl2 AlMej is formed on the 001 face, in which the titanium and chlorine atoms maintain their original positions in... 

Titanium tetrachloride and aluminium triethyl form a hydrocarbon soluble complex at low temperatures which decomposes at —30°C to give the trichloride as a major product [32]. Complexes containing tetravalent titanium stabilized by adsorption on titanium trichloride apparently persist in catalysts prepared at Al/Ti ratios below 1.0 [33], but at higher ratios there are some Ti(II) sites present in the catalyst [34]. Analysis shows that at Al/Ti ratios above 1.0 the solid precipitate contains divalent titanium or even lower valency states of the metal [35]. Reduction of TiCl4 with AlEt2 Cl is less rapid and extensive than with AlEts and even at high Al/Ti ratios [36] reduction does not proceed much below the trivalent state. Aluminium alkyl dihalides are still less reactive and reduction to TiClj is slow and incomplete except at high Al/Ti ratios or elevated temperatures [37]. 

These Ziegler-Natta catalysts are complexes of transition metal halides with organometallic compounds typically, triethylaluminum-titanium trichloride. 

In catalytic processes with enzymes such as D-oxynitrilase and (R) xynitrilase (mandelonitrilase) or synthetic peptides such as cyclo[(5)-phenylalanyl-(5)-histidyl], or in reaction with TMS-CN pro-mot by chiral titanium(IV) reagents or with lanthanide trichlorides, hydrogen cyanide adds to numerous aldehydes to form optically active cyanohydrins. The optically active Lewis acids (8) can also be used as a catalyst. Cyanation of chiral cyclic acetals with TMS-CN in the presence of titanium(IV) chloride gives cyanohydrin ethers, which on hydrolysis lead to optically active cyanohydrins. An optically active cyanohyrMn can also be prepared from racemic RR C(OH)CN by complexation with bru-... 

Chlorotitanium(III) phthalocyanine is formed by the reaction of titanium trichloride with dilithium phthalocyanine in boiling quinoline in the absence of air. This d1 complex has a magnetic moment of 1.79 B.M. (see Section VI,D) 341). It is stable to air oxidation in the solid state but is oxidized in solution. The oxidation product is oxytitanium(IV) phthalocyanine (titanyl phthalocyanine). This latter diamagnetic complex may also be prepared by the reaction of titanium tetrachloride dipyridinate and phthalonitrile at 270°C followed by sublimation at 400°C/10 6 mm 213). Titanium tetrachloride reacts with phthalonitrile to yield, after recrystallization from sulfuric acid, dihydroxytitanium(IV) phthalocyanine 820). 

Neutral compounds such as boron trifluoride and aluminum trichloride form Lewis acid-base complexes by accepting an electron pair from the donor molecule. The same functional groups that act as electron pair donors to metal cations can form complexes with boron trifluoride, aluminum trichloride, titanium tetrachloride, and related compounds. In this case the complex is formed between two neutral species, it too is neutral, but there is a formal positive charge on the donor atom and a formal negative charge on the acceptor atom. 

Fig. 4.2. Surface lattice structure of titanium trichloride showing (a) active site titanium ion with a ligand vacancy, and (b) a propylene molecule complexed to the titanium ion of the active site. The black sphere represent the growing polymeric chain (54). Copyright 1962 by The Chemical Society.

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