Bimetallic Al–M complexes derived from low-valent aluminium sources (M = s-/p-block metal)

Bimetallic complexes containing direct metal-metal bonds occupy an important position in many aspects of coordination chemistry and catalysis. The reactivity of these compounds often differs from that shown by their monometallic analogues as the two metal centres complement each other in a synergistic manner. Aluminium is a p-block metal whose compounds can exhibit Lewis amphoteric properties based largely on its oxidation state, where Al(III) is considered as a Lewis acid and Al(I) can behave as a Lewis base. As such, bimetallic compounds containing Al-M bonds offer a wealth of opportunity for the development of new chemistry and reactivity. The recent development of aluminyl anions as a class of compound in which the Al(I) centre displays nucleophilic properties has facilitated access to a range of bimetallic Al-M species. These compounds complement an existing family of Al-M complexes derived from neutral Al(I) sources and the chemistry of these compounds is undergoing a resurgence of interest. This review brings together recent developments in the field of bimetallic Al-M compounds, where M = s-/p-block metal. It focusses on compounds derived from low-valent Al(I) sources and describes the synthesis, structure and reactivity of these compounds.