Insertion and b-hydrogen transfer at Aluminium

Insertion and elimination of C=X bonds are two fundamental steps of organometallic chemistry. In aluminium chemistry, these reaction steps are important in olefin oligomerization and possibly polymerization, as well as in the reaction of carbonyl compounds with aluminium alkyls. The general importance of a third fundamental step, direct beta-hydrogen transfer from an aluminium-bound group to a substrate, has not been recognized as widely, despite the fact that it is the key step in the reduction of ketones by alcohols (Meerwein-Pondorf-Verley reduction) and by aluminium alkyls bearing beta-hydrogens. In this review we will combine experimental and theoretical results to illustrate how the delicate balance between these three reaction types determines much of the chemistry of organoaluminium compounds. Such an understanding may create new opportunities for ligand design.