Trialkylaluminium

Ley and Middleton synthesized ketone-functionalized lactam complexes 260 (Scheme 2.64) by sonication of vinylaziridines 259 with Fe2(CO)9 in benzene. These complexes were easily converted into the corresponding (3-lactams 261 by stereoselective addition of nucleophiles such as NaBH4 or trialkylaluminium to the carbonyl group followed by decomplexation with Me3NO [96]. 

Cu(i(-catalyzed kinetic resolutions of racemic, cyclic 1,3-diene monoepoxides through the use of dialkylzinc [123] or trialkylaluminium reagents [124] have re-... 

Trialkylaluminiums Hexacarbonyl molybdenum Copper (II) sulphide Trimethylphosphine... 

Figure 15. Formation of Ptig clusters stabilized by trialkylaluminium.

See METAL DERIVATIVES OF ORGANOFLUORINE COMPOUNDS See entry TRIALKYLALUMINIUMS See Other ALKYLMETALS... 

See metal derivatives of organofluorine compounds See other alkylmetals, trialkylaluminiums... 

The higher thermal stability of dialkylaluminium hydrides over the corresponding trialkylaluminiums is particularly marked in this case with 2 branched alkyl groups [ ] Used industrially as a powerful reducant, it is supplied as a solution in hydrocarbon solvents. The undiluted material ignites in air unless diluted to below 25%... 

A catalyst of aluminium and other metal alkyls in combination with metallic halides, e.g., the catalyst obtained by the interaction of a trialkylaluminium with titanium tetrachloride. Such catalysts, discovered by Karl Ziegler, are used in making stereospecific polymers. 

Although substitution of a hydrogen atom or an alkoxy group for one alkyl group in a trialkylaluminium tends to increase stability and reduce reactivity and the tendency to ignition, these compounds are still of high potential hazard, the hydrides being used industrially as powerful reducants. 

This main class of alkylaluminium derivatives is divided for structural convenience into the 3 groups TRIALKYLALUMINIUMS ALKYLALUMINIUM ALKOXIDES and hydrides and ALKYLALUMINIUM halides. 

Three main structural sub-groups can be recognised alkylaluminium dihalides, dialkylaluminium halides, and trialkyldialuminium trihalides (equimolar complexes of a trialkylaluminium and an aluminium trihalide). While this is generally a very reactive group of compounds, similar in reactivity to trialkylaluminium compounds, increase in size of the alkyl groups present and in the degree of halogen substitution tends to reduce pyrophoricity. 

The reaction of 1-alkoxypolyfiuoroalkyl sulfonates with lithium tetraalkyl alumin ates yields stereospecifically alkylated products with a high degree of inversion. However, the reaction with trialkylaluminium reagents is considerably less stereospecific. 

Sen reported that (C6F5)2AlR (2) (generated in situ) is an ethene polymerization catalyst (precursor) [13]. Moreover, the system also catalyzes copolymerization of ethene and propene. This latter fact, in particular, is remarkable, since a j5-branched alkyl (formed after propene insertion) should undergo very easy jS-elimination and hydrogen transfer to ethene, as discussed above. Thus, for this system to work the intrinsic chain transfer barriers of (QF5)2AlR should be much higher than those of trialkylaluminium. 

Scheme 3. Reactions of ketones and aldehydes with trialkylaluminium...

Poly(R)-4-methyl-l-hexen und Poly(R)(S)-4-methyl-l-hexen bestatigt (77). Die verwendeten Katalysatoren — es handelte sich um Mischungen aus Trialkylaluminium und Titan-(III)- bzw.Titan-(IV)-chlorid — muBten also neben ihrer Fahigkeit, stereospezifisch zu polymerisieren, auch die Eigenschaft besitzen, den einen Oder anderen Antipoden selektiv in die Molekulkette einzubauen. 

Throughout Section 6 molar ratios are given on the basis of the formula R 3A1, even though the trialkylaluminium may actually be present entirely, or largely, as the dimeric species R4A12. 

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