Titanium halide

Table 6. and for Catalytic Systems Based on Titanium Halides... 

Polystyrene produced by free-radical polymerisation techniques is part syndio-tactic and part atactic in structure and therefore amorphous. In 1955 Natta and his co-workers reported the preparation of substantially isotactic polystyrene using aluminium alkyl-titanium halide catalyst complexes. Similar systems were also patented by Ziegler at about the same time. The use of n-butyl-lithium as a catalyst has been described. Whereas at room temperature atactic polymers are produced, polymerisation at -30°C leads to isotactic polymer, with a narrow molecular weight distribution. 

Titan-gehalt, m. titanium content. -halogen, n, titanium halide. 

Attempts to synthesize transition metal alkyl compounds have been continuous since 1952 when Herman and Nelson (1) reported the preparation of the compound C H6>Ti(OPri)3 in which the phenyl group was sigma bonded to the metal. This led to the synthesis by Piper and Wilkinson (2) of (jr-Cpd)2 Ti (CH3)2 in 1956 and a large number of compounds of titanium with a wide variety of ligands such as ir-Cpd, CO, pyridine, halogen, etc., all of which were inactive for polymerization. An important development was the synthesis of methyl titanium halides by Beerman and Bestian (3) and Ti(CH3)4 by Berthold and Groh (4). These compounds show weak activity for ethylene polymerization but are unstable at temperatures above — 70°C. At these temperatures polymerizations are difficult and irreproduceable and consequently the polymerization behavior of these compounds has been studied very little. In 1963 Wilke (5) described a new class of transition metal alkyl compounds—x-allyl complexes,... 

The way in which aluminum alkyls and titanium halides combine together to form propagating centers have been discussed in depth for the last 15 years without any one mechanism taking precedence over another (6). The simplest explanation is that aluminum alkyl alkylates the transition metal in the crystal lattice to give a transition metal alkyl center. Polymerization takes place by... 

A process related to ionic polymerisation where the catalyst system complexes of aluminium alkyls and titanium halides governs the way in which a monomer and a growing chain approach each other. 

Titanium disulfide, 25 57, 58 Titanium disulfide electrodes sloping discharge curve, 3 414 Titanium esters, 25 1 Titanium fluorides, 25 47-49 Titanium halides, 25 47-55 Titanium hydride, 13 626 Titanium hydrides, 25 5 Titanium-hydrogen system, 25 3-5 phase diagram for, 25 5 Titanium iodides, 25 54-55 Titanium/isopropoxy/nitrilotriethoxy ratio, 25 93... 

Aluminium alkyls act as the electron acceptor and the electron donor is titanium halides and the combination, therefore, readily forms coordination complexes. 

Titanium(IV) chloride is used as the catalyst in a Knoevenagel reaction between various 2,2-disubstituted 3-hydroxypropanals and malonic acid or its esters. The products are substituted dihydropyran-2-ones (536) (79LA751). The reaction, which occurs cleanly and in good yield, utilizes an excess of the titanium halide and is thought to involve a cyclic complex which undergoes an ester exchange to a lactone complex (Scheme 198). 

Fig. 3 shows the catalysts in relative qualitative position in the chart of ionicities. The alkylaluminum halides and titanium halides are placed according to their electrophilic or cationic polymerization strength. The exact quantitative positions relative to Bawn s and Ledwith s representation of ionic freedom have not been established. 

Chemicals. Polymerization Catalysts are used in the production of polymers, such as linear and low-density polyethylene (LLDPE). An example of these catalysts are Ziegler Natta catalysts, which are combinations of titanium halides with aluminium and magnesium alkyls. 

Low pressure polymerization via ionic catalysts, using Ziegler catalysts (aluminum alkyls and titanium halides). 

Titanium can be etched in fluorine-, chlorine-, or bromine-containing gases, because all the titanium halides are volatile. Chlorides and bromides have been studied to a great extent, because they result in high selectivity over silicon-containing films and do not promote staining on gold (158,160). 

Aminocyclopropanations, via Ti(IV) complexes, 4, 655 Amino-diamido ligands, in Ti(IV) dialkyl complexes, 4, 349 Aminodiolates, with Zr(IV), 4, 805 /3-Aminoenonate, liquid crystals, 12, 259 Aminoethyl side chains, on bis-Cp titanium halides, 4, 524 Amino glycal reagents, via rhodium(II)-catalyzed... 

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

Bis(cyclopentadienyl)titanium(II) dicarbonyl complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium(II) dinitrogen complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium halides ligand metathesis reactions, 4, 537 olefin polymerization, 4, 538 organic reactions, 4, 540 properties, 4, 530 reductions, 4, 532 synthesis, 4, 510... 

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