Aluminium complexation

To the cold acid chloride add 175 ml. of pure carbon disulphide, cool in ice, add 30 g, of powdered anhydrous aluminium chloride in one lot, and immediately attach a reflux condenser. When the evolution of hydrogen chloride ceases (about 5 minutes), slowly warm the mixture to the boiling point on a water bath. Reflux for 10 minutes with frequent shaking the reaction is then complete. Cool the reaction mixture to 0°, and decompose the aluminium complex by the cautious addition, with shaking, of 100 g. of crushed ice. Then add 25 ml. of concentrated hydrochloric acid, transfer to a 2 htre round-bottomed flask and steam distil, preferably in the apparatus, depicted in Fig. II, 41, 3 since the a-tetralone is only moderately volatile in steam. The carbon disulphide passes over first, then there is a definite break in the distillation, after whieh the a-tetralone distils completely in about 2 htres of distillate. 

Akitt, J. W., Greenwood, N. N. Lester, G. D. (1971). Nuclear magnetic resonance and Raman studies of aluminium complexes formed in aqueous solutions of aluminium salts containing phosphoric acid and fluoride ions. Journal of the Chemical Society, A, 2450-7. 

Trimethyldialuminium trichloride (Aluminium chloride-trimethyl-aluminium complex)... 

Once in the serum, aluminium can be transported bound to transferrin, and also to albumin and low-molecular ligands such as citrate. However, the transferrrin-aluminium complex will be able to enter cells via the transferrin-transferrin-receptor pathway (see Chapter 8). Within the acidic environment of the endosome, we assume that aluminium would be released from transferrin, but how it exits from this compartment remains unknown. Once in the cytosol of the cell, aluminium is unlikely to be readily incorporated into the iron storage protein ferritin, since this requires redox cycling between Fe2+ and Fe3+ (see Chapter 19). Studies of the subcellular distribution of aluminium in various cell lines and animal models have shown that the majority accumulates in the mitochondria, where it can interfere with calcium homeostasis. Once in the circulation, there seems little doubt that aluminium can cross the blood-brain barrier. 

In a similar vein, tris-aluminium complexes have been reported in which related 2-methyl- and 2-phenyl-substituted azaindoles use their two N-centres to bridge two Group 13 metal centres. In either case the oxide itself adopts a trigonal planar geometry (angles sum to 360.0° and 359.7°, respectively) with... 

Fig. 12. Dimeric tetra(aluminium) complex 2-[Et2Al0C(0)]-C6H40AlEt2 2 [193]...

A hither facet of research has involved the structural characterisation of aluminium complexes which incorporate polydentate salen-type ligands. These have been noted in both neutral and monocationic (ion-separated) contexts (the latter requiring that the metal centre be stabilised by an external Lewis base) [35]. While such charged systems are invariably mononuclear the same is only usually true of their neutral analogues by virtue of the sterically demanding bis(aryloxide), chelating ligand. In the context of these latter complexes, dimerisation has been noted [251] while, more recently, the employment of flexible alkyl chains between two salen-coordinated aluminium ions has enabled the observation of dinuclear compounds [160, 161]. 

Chiral aluminium complexes have been used as catalysts for inverse electron-demand 1,3-dipolar cycloadditions of alkenes with nitrones, and the first contribution to this field was pubhshed in 1999 (344). The chiral AlMe-BEMOL (BINOL = 2,2 -bis(diphenylphosphino)-l,l -binaphthyl) complexes 235 were excellent catalysts for the reaction between nitrone 225a and vinyl ethers 232 (Scheme 12.68). The diastereo- and enantioselectivities are highly dependent on the chiral ligand. An exo/endo ratio of 73 27 was observed, and the exo-product was... 

The enantioselective inverse electron-demand 1,3-dipolar cycloadditions of nitrones with alkenes described so far are catalyzed by metal complexes that favor a monodentate coordination of the nitrone, such as boron and aluminium complexes. However, the glyoxylate-derived nitrone 256 favors abidentate coordination to the catalyst, and this nitrone is an interesting substrate, since the products that are obtained from the reaction with alkenes are masked ot-amino acids (Scheme 12.81). 

An understanding of the chemical behaviour of the element can aid in the choice of appropriate techniques and methods, the application of which would not disrupt the interaction of the element with associated constituents. For example, in the study of aluminium some relevant information may include its amphoteric nature, its ability to form predominantly ionic complexes, its tendency to form hydroxides, and the stability of aluminium complexes formed with biological ligands. It is clear that in order to maintain the ionic interactions the pH, ionic strength and, of lesser importance, the ionic composition of the medium used for sample preparation should be similar to that found in vivo. In addition, highly charged surfaces should not come into contact with the sample. 

Aluminium complexes of chelating amido ligands are perhaps the most common type of monomeric four-coordinate aluminium amide. A full listing of such complexes will not be provided and selected examples will suffice to illustrate synthetic approaches and... 

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