Dimethyltitanium

A dimethyltitanium complex bearing phosphinimide Hgands TiMe2[N=P(t-Bu)3]2 reacts with Ss to give the titanium pentasulfido complex TiS5[N=P(t-Bu)3]2 (Scheme 17) [58]. This result is in a sharp contrast to the... 

Bis(Tj-indenyl)dicarbonyltitanium (34) was first reported in 1975 independently by two different research groups using different synthetic routes. Rausch and Alt discovered that the photolysis of a pentane solution of bis(i7-indenyl)dimethyltitanium in a CO atmosphere resulted in the evolution of methane and the formation of 34 in 50% yield (75). 

Dimethyltitanium complex 25, bearing an ethylene and methyl ligands, catalyzed the dimerization of ethylene via a metallacyclopentane intermediate 26 (Eq. 1) [30]. During the dimerization, no insertion of ethylene into the Ti-Me bond was observed due to the perpendicular orientation between methyl and ethylene ligands. This inertness could be attributed to the low oxidation state of 25, i.e. Ti(II). 

Chien JCW, Rausch MD, Llinas GH, Lin Y, Winter HH (1991) Two-state propagation mechanism for propylene polymerization catalyzed by rac-anti-ethylidene(l-r 5-tetramethylcy-clopentadienyl)(l-r 5-indenyl).dimethyltitanium. J Am Chem Soc 113 8569-8570... 

Chien JCW, Llinas GH, Rausch MD, Lin YG, Winter HH, Atwood JL, Bott SG (1992) Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac-anri -ethylidene(l-T 5-tetramethylcyclopentadienyl)(l-r 5-indenyl) dimethyltitanium A two-state propagation. J Polym Sci A 30 2601-2617... 

Trimethylaluminum369 and dimethyltitanium dichloride370 exhaustively methylate ketones to give gem-dimethyl compounds371 (see also 0-90) ... 

Ethylene Polymerization with the System Bis(tj5-cyclopentadienyl)dimethyltitanium(IV), Trimethylaluminum, and... 

Cyano or chloromethyl groups also do not interfere with carbonyl addition. Dimethyltitanium diisopropoxide 6321), easily accessible from 62 84), reacts chemoselectively with 64 to form <55 (95%)82 63 is considerably more reactive than... 

The first system to be studied was 2-methyl-2-tolyl-cyclopentanone 168. In early 1979 we attempted to perform direct geminal dimethylation of this compound using dimethyltitanium dichloride 17114 in hope of obtaining curparene (Sect. F.II). Initial attempts were unsuccessful, since the product turned out to be the Grignard-type adducts 169 and 170 (Equation 57). 

Relative to tertiary alkyl halides, secondary derivatives react considerably slower. At room temperature and long reaction periods ( 24h) cyclohexyl chloride is almost quantitatively methylated with dimethyltitanium dichloride (prepared in situ from dimethylzinc and catalytic amounts of TiQ4)137>, but other cyclic or acyclic halides tend to undergo competing rearrangements prior to C—C bond formation 77). The same applies to 1,2-dihalides such as 1,2-dibromocyclohexane which affords 1,1-dimethylcyclohexane instead of the 1,2-dimethyl derivative137. In complete contrast, activated secondary chlorides behave much like tertiary derivatives, i.e., methylation is fast and position specific at low temperatures. Examples are shown in Equation 86137>. It should be noted that in such cases cuprate chemistry affords less than 40 % of methylation products138). 

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

The 2-(indenyl)-phenoxo ligand exhibits different coordination modes to Ti center. Mono-Gp monoalkoxo dichloro and dimethyltitanium derivatives containing 4,6-di-/-butylphenoxo-indenyl ligands have been synthesized (Scheme 352). Reactions of the corresponding phenols with CpTiCl3 in the presence of pyridine generates the... 

Dicyclopropyl ketone reacted with dimethyltitanium(IV) chloride under inert conditions to give the product of dimethylation, 2,2-dicyclopropylpropane, in 84% yield.A similar reaction took place on reaction of cyclopropyldiphenylsufonium tetrafluoroborate with cyclo-propanecarbaldehyde under basic conditions giving 2-cyclopropylcyclobutanone. ... 

The direct geminal dimethylation of ketones using dimethyltitanium dichloride has provided an extremely simple synthesis of cuparene (120) from the ketone (121).77 This efficient procedure should prove useful in other sesquiterpenoid syntheses in view of the fact that the gem-dimethyl group is a common feature in a number of such compounds. A new sesquiterpene, (—)-herbertene (122), has been... 

Iwasaki, F., Maki, T., Onomura, O., Naka.shima, W Matsumura, Y. JOC65, 996 (2000). Dimethyltitanium dichloride. 

Chien, J. C. W. Elinas, G. H. Rausch, M. D. Lin, Y. G Winter, H. H. Atwood, J. L. Bott, S. G. J. Metallocene catalysts for olefin polymerization catalyzed by rac-[anft -ethylidene(l-r -tetramethylcyclopentadienyl)(l-r -indenyl)]dimethyltitanium A two-state propagation. XXIV. Stereoblock propylene polymerization. J. Polym. ScL, Part A Polym. Chem. 1992, 30, 2601-2617. 

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