Aluminum complexes mixed halides

Evans et al. sequentially reacted the Nd carboxylate precursor Nd[C>2CC (CH3)2CH2CH3]3 % first with DEAC and then with TIBA. By this reaction catalytically active systems are obtained which polymerize IP. In the first reaction step in which Nd carboxylate is reacted with DEAC mixed ligand complexes are formed which contain neodymium and aluminum as well as halide and ethyl groups. Upon crystallization NdC -based compounds are obtained in which solvent is coordinated. These compounds exhibit a more complex... 

In spite of the impression that may have been gained from the earlier part of this chapter, reactions involving the use of aluminum halides, and especially aluminum chloride, constitute the majority of Friedel-Crafts acylation reactions. The interaction of the three components, i.e. the acyl halide, the aromatic substrate and the aluminum halide, results in the formation of hydrogen halide and a complex of the aromatic ketone with aluminum halide from which the ketone is literated after hydrolysis. There are a number of sequences in which the three components can be mixed. 

The prior formation of the reactive species, for example by mixing an acyl halide with aluminum halide, which is then allowed to react with the aromatic substrate, is known as the Perrier procedure. It is normally carried out in a solvent, such as carbon disulfide or dichloromethane, that allows the 1 1 complex to be separated from excess aluminum halide. The main advantage of this method is the solubility of the addition complex in the solvent, but it is frequently observed that the complex of the acylation product and catalyst is insoluble in carbon disulfide and may be separated from soluble by-products. The prior formation of acylium salts mentioned earlier " ° 2 and their use in the preparation of aromatic ketones can be regarded as a modification of the Perrier procedure. 

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