Triethyl aluminium

As indicated by the title, these processes are largely due to the work of Ziegler and coworkers. The type of polymerisation involved is sometimes referred to as co-ordination polymerisation since the mechanism involves a catalyst-monomer co-ordination complex or some other directing force that controls the way in which the monomer approaches the growing chain. The co-ordination catalysts are generally formed by the interaction of the alkyls of Groups I-III metals with halides and other derivatives of transition metals in Groups IV-VIII of the Periodic Table. In a typical process the catalyst is prepared from titanium tetrachloride and aluminium triethyl or some related material. 

Triethyl aluminium Triethyl aluminium ethereate Trimethyl aluminium... 

Titanium tetrachloride and aluminium triethyl form a hydrocarbon soluble complex at low temperatures which decomposes at —30°C to give the trichloride as a major product [32]. Complexes containing tetravalent titanium stabilized by adsorption on titanium trichloride apparently persist in catalysts prepared at Al/Ti ratios below 1.0 [33], but at higher ratios there are some Ti(II) sites present in the catalyst [34]. Analysis shows that at Al/Ti ratios above 1.0 the solid precipitate contains divalent titanium or even lower valency states of the metal [35]. Reduction of TiCl4 with AlEt2 Cl is less rapid and extensive than with AlEts and even at high Al/Ti ratios [36] reduction does not proceed much below the trivalent state. Aluminium alkyl dihalides are still less reactive and reduction to TiClj is slow and incomplete except at high Al/Ti ratios or elevated temperatures [37]. 

Fig. 9. Propene polymerization by aluminium triethyl and vanadium halides [30], (a) VCl3/AlEt3 AlEt3 = 0.019 mole 1 , Al/V = 3 propene pressure, 1 atm temp., 60°C. (b) VCls/AlEtjCl AlEtjCl = 0.064 mole Al/V = 4 [M] = 1.785 mole 72-heptane solvent.

Aluminium triethyl may he prepared in a similar manner to the methyl compound. Aluminium triethyi is a liquid, B.pt. 194° C. when distilled in hydrogen it does not solidify at —18° C. It is decomposed with explosive violence by water with iodine it yields ethyl iodide and iodine derivatives. At 234° C. the vapour density is 4 5 (theory 8 9), the refractive index ha ing the value hb 1-480 at 6-5° C. 

Aluminium triethyl-etherate, 4AlEt3, BEtgO, may be obtained in several ways, namely ... 

It is manufactured by heating ethylene to 200 C at a pressure of 1500 atmospheres in the presence of a trace of oxygen -which acts as a catalyst. When aluminium triethyl and titanium tetrachloride are used as the catalysts the polymerization can be carried out at lower, or even at atmospheric, pressure. Polyethylene can be melt-spun into fibres, but they have not yet found significant textile application because of their wax-like handle, the complete absence of affinity for dyes, and the low softening point at 90 C and the melting point at 110° to 120°C. Monofilaments are made for electrical use on account of the excellent insulating property of the substance. 

Another way of polymerising ethene is by using titanium tetrachloride and aluminium triethyl, but this is not a homolytic mechanism. 

The mechanism of trimerisation of butadiene by a mixed cobalt(ii) chloride-aluminium triethyl catalyst has been inferred from the natures of the three products characterised. The determination of the enthalpy of dimerisation of aluminium triethyl provides a useful piece of thermochemical data for quantitative discussion of the role and energetics of aluminium triethyl in this type of reaction. Polymerisation of isoprene in the presence of Fe(acac)3-aluminium triethyl-pyridine derivatives mixtures has a negative apparent activation enthalpy, which can be attributed to the instability of the catalytic complex at elevated temperatures. Bis-cyclo-octatetraeneiron(o) is an effective oligomerisation catalyst. The composition of products accessible only by hydrogen migration indicates an oxidative addition-reductive elimination mechanism rather than insertion. 

Mixtures containing nickel chloride, aluminium triethyl, and l,2-bis(di-phenylphosphino)ethane (dpe) or l,2-bis(diphenyIphosphino)propane (dpp) catalyse the reaction of ethylene and butadiene to give 1,4,9-decatriene vv hen the ratio of dpe or dpp to nickel is less than 1. However, when more phosphine is present [dpe Ni > 1 or dpp Ni = 1-5], 1,4-hexadiene is produced. At higher ratios, dpe Ni 3, there is little reaction. Such marked discrimination is unusual even the replacement of these chelating phosphines by triphenylphosphine leads to greatly reduced selectivity. ... 

Addition of ethylene to butadiene is catalysed by cobalt(ii) chloride-bidentate diphosphine-aluminium triethyl mixtures [c/. similar nickel(ii) case above]. Addition of butadiene or of 1,1-dimethylallene to nor-bornadiene is catalysed by iron(o) complexes, for instance the cyclo-octene complex. ... 

In a stirring flask rendered inert with argon are place 5 ml of Silicone Oil AV 1000 (Goldschmidt, Essen) and 31 ml of 100% aluminium triethyl (control of activity by hydrolysis followed by measurement of the resulting gas volume recommended). Then are added 41 ml of distilled titanium tetrabutylate drop-wise to this solution over a period of 1 hour while the temperature is maintained at 40 2°C. The gaseous products of the reaction, which are largely dissolved in the catalyst mixture, are subsequently removed by evacuating at room temperature for 2 hours. For some of the experiments, the catalyst solution thus prepared is heated at a particular temperature (60-150°C) for a defined period (0.2-2.0 hours). The solution is then evacuated at 0.1 mbar/20°C for 1 hour. 

To a 250-ml three-neck flask rendered inert with argon are added 80 ml of absolute toluene and 30 ml of aluminium triethyl. Then 19.4 ml of absolute -butanol are added drop-wise over a period of 50 minutes at room temperature, and the solution heated for an hour at boiling temperature and fractionated under vacuum. After a small number of first runnings, the main... 

Catalyst 16636-101-3 was produced by adding 7.7 ml of aluminium triethyl drop-wise over a period of 1 hour under argon to 16636-101-2, raising the aluminium-titanium ration to 4 1. Degassing for an hour at 0.1 mbar/20°C again followed and half of the product was used to make Catalyst 16636-101-4. 

For the preparation of Catalyst 16636-101-4, 16636-101-3 was heated under argon at 120°C (reaction temperature). The black catalyst mass produces white fumes, pointing to reaction of the excess aluminium triethyl. After continuing to anneal for 2 hours, the reaction mixture was cooled to room temperature and degassed at 0.1 mbar as described above. 

Sodium-catalyzed polybutadienes contain a preponderance of 1,2-structures but since there are also significant quantities of other microstructures the products are not stereoregular. Since the discovery of the Ziegler-Natta catalyst systems both syndiotactic and isotactic 1,2-polybutadienes have been prepared. The syndiotactic polymers are obtained by the use of aluminium triethyl and halogen-free compounds of vanadium, molybdenum and cobalt, particularly the acetyl acetonates. 

Commercial aluminium plating processes, based on aluminium triethyl at 80-100° C are currently in operation on a production scale (up to 2200 dm electrolyte volume), e.g. the Sigal process (Hegin Galvano-Aluminium bv). 

Alkylene sulfide rubber Aluminium triethyl Alumina trihydrate Antimony trioxide... 

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