Alkynyl aluminium compounds: bonding modes and structures

Alkynyl aluminium compounds and the method of hydroalumination of multiple bonds are very useful tools in the hands of a synthetic chemist. The different reactions of alkynyl aluminium compounds as well as hydroalumination have resulted in versatile applications in organic synthesis, thereby various functionalities can be selectively transformed under mild reaction conditions. However, the bonding situation of alkynyl aluminium compounds and the structures of the intermediates formed by hydroalumination of different alkyne systems were only understood within limits. From the point of view of coordination chemistry the features of bonding and the structures of aluminium complexes in addition to their utilities in preparative chemistry are of significant interest. In this perspective, the chemistry of alkynyl aluminium and hydroalumination is traced back to its origin and is accentuated with respect to bonding and structures. A few recent results in alkynyl aluminium chemistry and the successful structural determination of the intermediates of hydroalumination gives insight into the unique properties of alkynyl aluminium compounds and opens a route to a new class of aluminium clusters.