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Extra resources for Houben-Weyl Methoden der organischen Chemie vol.E8b Hetarenes III, Part 2

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134 Ε. J. Arlman and P. Cossee, / . Catalysis, 3 (1964) 80, 89, 99. 398 TITANIUM: R. J. H. CLARK arrangement in which the monomer molecule is inserted between the existing chain and the transition metal atom X—Μ— K—U— A + C2H4 X —— Μ— ΜI I— — — X—Μ M- A A CH2 / R \ -CH2 ^ X The latter still has a vacant position for further attachment of an olefin molecule. It is believed that the rearrangement of the alkyl group is the rate-determining step and that the alkyl aluminium is not essential for the propagation step.

The aluminium-containing compound mentioned above, which covers the faces parallel to [001], does not appear to be catalytically active; these faces are estimated to constitute 9 5 % of the total surface of a-TiC^. On the other hand, certain Ti-Al bimetallic complexes (such as those synthesized by Natta and coworkers) d o function as catalysts in solution. Indeed, it seems beyond doubt that both Arlman-Cossee centres (see below) and bimetalhc centres do in general act as catalyst centres. Extensive work by Boor and coworkers^^^ has further defined the nature and distribution of stereospecific and non-stereospecific polymerization sites in the TÍCI3 lattice.

Sinn, Angew. Chem. 70 (1958) 496; Naturwissenschaften, 45 (1958) 312. 134 Ε. J. Arlman and P. Cossee, / . Catalysis, 3 (1964) 80, 89, 99. 398 TITANIUM: R. J. H. CLARK arrangement in which the monomer molecule is inserted between the existing chain and the transition metal atom X—Μ— K—U— A + C2H4 X —— Μ— ΜI I— — — X—Μ M- A A CH2 / R \ -CH2 ^ X The latter still has a vacant position for further attachment of an olefin molecule. It is believed that the rearrangement of the alkyl group is the rate-determining step and that the alkyl aluminium is not essential for the propagation step.

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