Reactions of organoaluminium compounds with electron donors
The application of organoaluminium compounds as components of organometallic or complex systems is connected with a knowledge of their reactions with electron donors. Reactions with nitriles, ketones, esters, ethers, alkyl chlorides, vinyl chloride, and acid chlorides as the electron donors were investigated. The first stage of the reaction of an organoaluminium compound with an electron donor involves formation of the corresponding donor-acceptor complex. A knowledge of the structure of the formed complexes is very important for an elucidation of the reaction course and mechanism. The heat of formation, composition, and molecular weight of the corresponding complexes were determined, and their i.r. and n.m.r. spectra were studied. From these investigations general conclusions were made concerning, the influence of the Lewis acidity of the organoaluminium compound on the structure of its complexes and on their reactivity; the effect of reactant mole ratio (organoaluminium compound to electron donor) on the reaction course, and the influence of the molecular structure of the complex and of dislocation of electrons on the reaction mechanism. Hallwachs and Schafarik' synthesized the first organoaluminium compound 120 years ago. By treating aluminium with ethyl iodide they prepared ethylaluminium sesqui-iodide. However, the chemistry of organoaluminium compounds received little attention until the investigations of Ziegler and his collaborators, in about 1950. The development of the direct synthesis of organoaluminium compounds from aluminium, ethylene. and hydrogen, and elaboration of normal pressure polymerization of ethylene, aroused great interest. Almost simultaneously, numerous research centres over the world undertook research and technological investigations. Organoaluminium compounds proved to be of both theoretical and technological interest because of their ability to form auto and other complexes, their high reactivity, and associated structure and valence theory problems. In spite of the two decades that have passed since Ziegler's discoveries and the intensive studies that have been conducted throughout. the interest in the chemistry of organoaluminium compounds has not declined. This is mainly due to the use of organoaluminium compounds as constituents of complex catalyst systems. 509