Alkyl titanium compound

RjAl, R = alkyl) titanium compounds aluminum = 1.9 4.2, weight ratio) ... 

The type of cleavage of the alkyl titanium bond is certainly dependent upon the titanium valence state. Tetravalent compounds will tend to cleave homolytically, but heterolytic cleavage will become more favorable at the lower valence states because of higher bond polarity (290). Ethylene polymerization takes place more readily on alkyl vanadium compounds than on alkyl titanium compounds and yields higher molecular weight linear polymer (340). This is attributable to the fact that... 

Conventionally, HAS are blended with PO during processing. 2-(Diethy-lamino)-4,6-bis[butyl(l,2,2,6,6-pentamethyl-4-piperidyl) amino]-l,3,5-triazine may be fed with an olefin directly into the low pressure polymerization process catalyzed with a modified MgCl2 supported Ziegler-Natta catalyst [142]. The catalytic activity was not impaired [143], Tetramethylpiperidine was reported to be a useful component in MgC -supported Ziegler-Natta catalysts as well. Very high stereospecificity of the synthesised PO was achieved. A complex of HAS with the alkyl aluminium activator was envisaged without interaction with the catalytically active alkyl titanium compound [144],... 

A model olefin polymerization catalyst previously characterized as [(C5H5)2TiAlEt2]2 has been studied by X-ray diffraction, H n.m.r., and mass spectral techniques. The compound contains (l- -CjHj) and/i(l- dimeric titanium-aluminium hydride structure (3) has been suggested. Alkyl exchange between a polymeric alkyl-titanium compound and alkylaluminium compound, present in excess, is... 

When the alkylation step was recognized as essential, various alkyl-titanium compounds were employed as modified Ziegler-Natta catalysts. It is reasonably postulated that ethylene coordinates to the titanium at positions cis to the R ligand. This cis ligand orientation effect on the metal ion is essential to polymerization. 

Ziegler-Natta catalysts-—there are many different formulations—are organometallic transition-metal complexes prepared by treatment of an alkyl-aluminum with a titanium compound. Triethylaluminum and titanium tetrachloride form a typical preparation. 

Natta A process for polymerizing propylene and other higher olefins, catalyzed by crystalline titanium trichloride and an alkyl aluminum compound such as triethyl aluminum. The polymer can exhibit various types of stereoregularity, depending on the catalyst and the conditions. Invented in 1954 by G. Natta at the Istituto de Chimica Industrial del Politecnico di Milano, Italy, and commercialized in 1957. Now used widely, worldwide. See also Ziegler, Ziegler-Natta. 

Among titanium-based precursors, monocyclopentadienyl compounds of the type CpTiCl3 or Cp TiCl3 activated by MAO or B(C6F5)3 showed the best performance, although several substituted mono-Cp or indenyl derivative and Cp-free compounds as Ti(CH2Ph)4 and Ti(OR)4 (R = alkyl, aryl) are quite active as well. In short, practically any soluble titanium compound can be used as precatalyst.154-158... 

The patent literature contains several references to the use of sulfoxide complexes, usually generated in situ, as catalyst precursors in oligomerization and polymerization reactions. Thus, a system based upon bis(acrylonitrile)nickel(0> with added Me2SO or EtgSO is an effective cyclotrimerization catalyst for the conversion of butadiene to cyclo-1,5,-9-dodecatriene (44). A similar system based on titanium has also been reported (407). Nickel(II) sulfoxide complexes, again generated in situ, have been patented as catalyst precursors for the dimerization of pro-pene (151) and the higher olefins (152) in the presence of added alkyl aluminum compounds. 

Several organo-titanium compounds with the oxidation states IV, III, II, 0,-1 have been prepared. A starting point was the discovery by Ziegler et al. (1955), Ziegler (1963) and Natta et al. (1955) and Natta (1963) of the catalytic properties of TiClj-Al-alkyl mixtures in hydrocarbons in reactions such as the ethylene and propylene polymerization. 

Careful preliminary tests were necessary to demonstrate the suitability of these methods for the present study. In particular, it was necessary to verify that the radioactivity detectable in the polymer may not be caused by contamination or other processes different from the ones taken into consideration. It was then found that it is possible to remove throughly from the polymer the last traces of unreacted ethylaluminum or of its soluble complexes with titanium compounds by washing with anhydrous hydrocarbon. No alkylation of the preformed polymer caused by triethylalu-minum or its derivatives has been observed (4 ). 

The amount of amorphous polymer, which is generally produced in small percentage (9-16%) contemporaneously with the non-atactic polymer, is independent of reaction time (see Table II). It is on the contrary closely connected with the nature of the catalytic system employed and changes, for instance, when the triethylaluminum is substituted by other metal alkyls (beryllium alkyls, propylaluminum, isobutylaluminum, etc.) 5,28). It also depends on the purity of the a-titanium trichloride, in particular increasing in the presence of other crystalline modifications of titanium trichloride [i.e. -TiCU (27)] and of titanium compounds obtained by reduction of titanium tetrachloride at low temperature with aluminum alkyls. 

A series of alkyl- and aryl-substituted titanium compounds of type 1 have been prepared3 they exhibit the same reactivity for carbonyl compounds, but vary in stability although all are more stable than the lithium counterparts. 

Fuel additives - [AMNES-CYCLOALIPHATIC AMINES] (Vol 2) - [SULFONIC ACIDS] (Vol 23) -arsenic compds as [ARSENIC COMPOUNDS] (Vol 3) -boron compds as [BORON COMPOUNDS - BORIC ACID ESTERS] (Vol 4) -coordination compounds as [COORDINATION COMPOUNDS] (Vol 7) -ethers m [ETHERS] (Vol 9) -magnesium alkyls as [MAGNESIUM COMPOUNDS] (Vol 15) -polyamines as [DIAMINES AND HIGHER AMINES ALIPHATIC] (Vol 8) -htanates as [TITANIUM COMPOUNDS - ORGANIC] (Vol 24) -use of copper compounds [COPPER COMPOUNDS] (Vol 7)... 

Note that only ca 1% of the titanium atoms introduced with TiCl3 into the system give rise to the formation of surface active sites (since most of the titanium atoms remain inside the solid TiCl3 particles) [40], However, such active sites exhibit rather low stereospecificity in propylene polymerisation. The activity and stereospecificity of catalysts based on the / -TiCl3 modification also depend on the type of alkyl aluminium compound used as the activator. The application of triethylaluminium leads to a catalyst of much higher activity but of much lower stereospecificity, and on account of this diethylaluminium chloride is used for the polymerisation of propylene and other a-olefins, while triethylaluminium (and also triisobutylaluminium) is used for ethylene polymerisation [28],... 

Table II is a summary of results obtained with soluble bis(cyclopenta-dienyl)titanium compounds as catalysts (52-56). The activity for polymerization increases in each run after a short induction period. After reaching a maximum, a continuous decrease in activity is observed as a consequence of rapid aging processes, such as alkyl exchange, hydrogen transfer, and reduction of the titanium. The average activity is 7-200 kg of PE...

Sinn and Patat (59) drew attention to the electron-deficient character of those main group alkyls that afford complexes with the titanium compound. Fink et al. (51) showed by 13C NMR spectroscopy with 13C-enriched ethylene at low temperatures (when no alkyl exchange was observed) that, in the more highly halogenated systems, insertion of the ethylene takes place into a titanium-carbon bond of a titanium-aluminum complex. 

Burger et al. have shown that the presence of amino ligands at the metal enhances the thermal stability of primary, secondary and tertiary alkyl as well as allyl and vinyl titanium compounds dramatically 39). For example, n-propyltitanium tris(di-ethylamide) 16 can be isolated in pure form by sublimation at 60 °C/10-3 torr (68 %)39b>. 

The oxidative alkylation of titanium compounds (Cp TiX Cp" = r] -C5MQs, X = Me, OMe, Cl, N=CH-f-Bu) by dimethylzinc and dimethylcadmium has been reported to afford diamagnetic see Diamagnetism) compounds of general formula Cp2TiMe(X) and metallic zinc and cadmium, respectively. ... 

G g = 1,99 — Ti3+ compounds with titanium-alkyl < titanium-hydride bonds... 

Elastomeric copolymers are made by either solution or suspension process using a vanadium based catalyst along with alkyl aluminum compound as cocatalyst. In the suspension process propylene is used as a diluent, whereas in the solution process hexane is used as diluent. Superior catalysts based on supported titanium compounds have further improved the suspension process in recent years. In the conventional suspension process, ethylene, propylene and catalysts are fed continuously to a stirred reactor at 20 °C and 12 kg cm total pressure. Diethylzinc is used to control molecular weight. 

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