Alkylaluminum chloride

The metal catalyzed production of polyolefins such as high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polypropylene (PP) has grown into an enormous industry. Heterogeneous transition metal catalysts are used for the vast majority of PE and all of the PP production. These catalysts fall generally within two broad classes. Most commercial PP is isotactic and is produced with a catalyst based on a combination of titanium chloride and alkylaluminum chlorides. HDPE and LLDPE are produced with either a titanium catalyst or one based on chromium supported on silica. Most commercial titanium-based PE catalysts are supported on MgCl2. 

Twenty years later Reichert [9] and Breslow [10] discovered that the addition of small amounts of water to the alkylaluminum chloride co-catalysts resulted in a one to two orders of magnitude increase in ethylene polymerization activity. In the 1980s the first reports appeared concerning the homogeneous stereospecilic polymerisation, but they received relatively little attention because in the same period the first highly active, supported,... 

Karapinka, Smith, Carrick (79) studied the use of methyltitanium trichloride as a catalyst for polyethylene. Alone it was inactive for the polymerization of polyethylene. It required the predecomposition to titanium trichloride at 120° or the addition of titanium trichloride to produce an active catalyst. Vanadium tetrachloride also produced an active catalyst. Aluminum bromide failed to activate the catalyst, whereas trialkylaluminum which reacts to produce alkylaluminum chlorides was effective. 

Tracer studies have been used in an attempt to determine the nature of the ends of the chain but these were as unsatisfactory as for propylene. Feldman and Perry (83) used triterated methanol to react the polyethylene from a titanium tetrachloridetrialkylaluminum catalyst. They found a continual increase in the number of polymeric chain ends which react with the tritium. This agrees with the results of Roha and Beears (84) who showed the very rapid exchange of alkyls which took place when ethylene was grown on a Ziegler catalyst in the presence of excess alkylaluminum chloride. In these experiments only an extremely small... 

The T1(I) salt of the isolated [commo-3,3 -Al(3,l,2-AlC2B9H11)2] ion was reported most recently (23). This compound was synthesized from the reaction of Tl2B9C2Hn with a variety of alkylaluminum chlorides or trial-kylaluminum compounds as outlined in Eq. (3). This commo complex has... 

F. W. Billmeyer. The free-radical polymerization of methyl methacrylate, acrylonitrile, and other polymer monomers can be accelerated by adding Lewis acids, like zinc chloride or alkylaluminum chloride. The polar monomer forms a complex with the Lewis acid and becomes more electron accepting. In the presence of a nonpolar olefin or conjugated diene, the complexed polar monomer transfers its charge and copolymerizes readily, as described by N. G. Gaylord and A. Takahashi. 

The solid studies have also shown that all trialkylaluminum compounds are more or less equivalent as cocatalysts. Thus with a good solid, such as the 0.9 i-Bu3Al solid, trialkyls—as far apart as the trimethyl- and trioctyl-aluminum—are essentially equivalent. This indicates that the poorer activity of unseparated catalysts prepared from the lower alkyls (trimethyl-, triethyl-aluminum) must be directly related to the resulting reaction products with TiCl4, i.e., the reduced and/or alkylated Ti species (expected to be found in the solid phase) and the alkylaluminum chlorides (unless strongly adsorbed, expected to be found in the liquid phase). 

The dimerization reaction catalyzed by a nickel compound and an alkylaluminum chloride derivative was first described in a patent in 1955 [4], In 1966 Wilke et al. [5] gave crucial impetus to this reaction starting from a well-defined cationic / -allylnickel complex (Structure 1). 

Under standard conditions the tetrakis(allyl)neodymium complex, like the tris(allyl)neodymium complex, shows only moderate catalytic activity with a high trans selectivity, but in combination with appropriate Lewis acids such as alkylaluminum chlorides or methylalumoxane the activity can be increased considerably and the selectivity changes mainly to cis. Extremely active catalysts of very high cis selectivity are obtained with the chloro(allyl)neodymium compounds in combination with methylalumoxane in heptane. For more details see [39, 49, 106]. 

The studies of MeAlCh-induced cyclization of unsaturated ketones indicate the advantage of alkylaluminum chloride over AlCI in Lewis acid catalyzed reactions, since these reagents are capable of acting as proton scavengers as well as Lewis acids [33]. The reaction is interpreted as a MeAlCL-promoted cyclization of the y,b-unsaturated ketone followed by the sequential hydride and methyl shift as illustrated below. 

Organoaluminum halides, obtained as above, can also be converted into tri-alkylaluminums by reduction with alkali metals and, conversely, alkylaluminum chlorides can be obtained from trialkylaluminums and aluminum chloride.236... 

Since the discovery of the Tebbe reagent, related systems have been developed that offer advantages in cases where alkylaluminum chloride-free conditions are necessary [27]. One example is the Petasis reagent, Cp2TiMe2, synthesized... 

Despite all the advantages of this process, one main limitation is the continuous catalyst carry-over by the products, with the need to deactivate it and dispose of wastes. One way to optimize catalyst consumption and waste disposal is to operate the reaction in a biphasic system. The first difliculty was to choose a good solvent. N,N-Dialkylimidazolium chloroaluminate ionic liquids proved to be the best candidates. They are liquid at the reaction temperature, butenes are reasonably soluble in them (Table 5.4-3), and they are poorly miscible with the products (Table 5.4-2, case (a)). The chloroaluminate eSiciently dissolves and stabilizes the nickel catalyst in the ionic medium without the addition of special ligand. The ionic liquid plays the role of both catalyst solvent and co-catalyst. Its Lewis acidity can be adjusted to get the best performance. The catalytically active nickel complex is generated directly in the ionic liquid by reaction of a commercialized tiickel(II) salt, as used in the Dimersol process, with an alkylaluminum chloride derivative. 

In a similar way, isobutene is very quickly polymerized in acidic chloroaluminates to high molecular weight polyisobutene. The addition of alkylaluminum chloride does not stop the reaction [39]. 

Typical soluble catalysts for copolymerization of ethylene and propylene are formed from mixtures of vanadium salts with alkylaluminum chlorides, e.g., VCI4 with either AIR2CI or AIRCI2 where R = alkyl group (Ver Strate, 1986). A possible hexacoordinated metal structure for the resulting active catalyst is shown below. 

Unsaturated fatty compounds are of interest as renewable raw materials (1). These compounds can be functionalized at the C,C-double bond by electrophilic addition reactions to give new oleochemicals with potentially new and interesting properties. The alkylaluminum chloride-induced Friedel-Crafts acylation of unsaturated fatty compounds (Fig. 1), such as oleic acid [la], 10-undecenoic acid [2a], petroselinic acid [3a], and erucic acid [4a], and the respective esters and alcohols yield the corresponding P,y-unsaturated ketones (2,3). 

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