Methyltitanium trichloride

The report of Bestian Clauss that methyltitanium trichloride will undergo a slow growth reaction with ethylene in polar inert solvents at low temperatures (6) is considerably important because of its relation to the Ziegler polymerization reaction. 

How does the anionic alkyl of the original trialkylaluminum or of the dialkylaiuminum chloride, which has sufficient anionic character to undergo anionic hydride exchange or CH3OT reaction, form a catalyst which becomes cationic under certain polymerization conditions No studies of this have been reported. One possibility is an internal oxidation-reduction reaction that converts an anionic alkyltitanium trichloride to a cationic alkyltitanium trichloride (Equation 10). Basic and electrophilic catalyst components would determine the relative contributions of the anionic and cationic forms. This type of equilibrium or resonance structures could also explain the color in transition metal compounds such as methyltitanium trichloride (73). 

Karapinka, Smith, Carrick (79) studied the use of methyltitanium trichloride as a catalyst for polyethylene. Alone it was inactive for the polymerization of polyethylene. It required the predecomposition to titanium trichloride at 120° or the addition of titanium trichloride to produce an active catalyst. Vanadium tetrachloride also produced an active catalyst. Aluminum bromide failed to activate the catalyst, whereas trialkylaluminum which reacts to produce alkylaluminum chlorides was effective. 

The unique nature of the alkyl attached to titanium in a polyethylene catalyst has been indicated by Gray (80). Methyltitanium trichloride has an infrared spectrum which is unique and different from the bridged or unbridged methyl of methylaluminum chlorides. Although methyltitanium trichloride is not an effective catalyst to polymerize ethylene, this unique character is an indication of a difference which is developed further in the effective polyethylene catalysts. 

The electronic configuration of titanium is [Ar] 3d24s2, which means that Ti(IV) compounds are d° species with free coordination sites 1-27,28). H-NMR and 13C-NMR data are known and have been occasionally discussed in terms of bond polarity 19), but such interpretations are obviously of limited value. The electronic structure of methyltitanium trichloride 17 and other reagents have been considered qualitatively 52) and quantitatively S3 56> using molecular orbital procedures. It is problematical to compare these calculations in a quantitative way with those that have been carried out for methyllithium 57> since different methods, basis sets and assumptions are involved, but the extreme polar nature of the C—Li bond does not appear to apply to the C—Ti analog. Several MO calculations of the w-interaction between ethylene and methyltitanium trichloride 17 (models for Ziegler-Natta polymerization) clearly emphasize the role of vacant coordination sites at titanium 58). 

As already shown in Section B.I, certain organotitanium reagents readily form isolable, octahedral 1 2 adducts with such donor molecules as THF, glyme, thio-ethers, amines and diamines1,19) (Equation 47). In case of methyltitanium trichloride 17, structural data show the methyl group to occupy the equatorial position 96). In order to test whether such molecules undergo stereoselective addition to aldehydes (Equation 47), we reacted 134, 135 and 136 (prepared from TMEDA, glyme and THF, respectively) with 2-phenylpropanal 12491. The 125 126 ratios of 80 20, 82 18 und 85 15 show that the Cram product is preferred in all cases... 

Methyltitanium trichloride, CH3TiCl3 Dimethyltitanium dichloride, (CH3),TiCl2. These alkyltitanium compounds are prepared from (CHi),Zn and TiCl4. 

Methyl sesamol, 353, 354 3-Methylsulfonyl-2,5-dihydrofurane, 270 Methylthiotrimethylsilane, 113 Methyltitanium trichloride, 270-271 (S)-(—)-Methyl p-toluenesulfinate, 405 l-Methyl-2-trimethylsiloxy-l, 3-butadiene, 271-272... 

Titanium tetrachloride I methyllithiumitriphenylphosphine Chemoselective syntheses with methyltitanium trichloride Tert. methylcarbinols from ketones with in 5iVii-protection of aldehyde groups as titanium(IV) 1-phosphonioalkoxide complexes... 

Alkyltitanium halides are prepared using a variety of alkylating agents. Methyltitanium trichloride may be prepared from methyl aluminium compounds. 

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