Transition metal chemistry of low valent group 13 organyls

The coordination of low-valent group 13 organyls E^IR [E = Al, Ga, In; R = Cp*, C(SiMe₃)₃] to transition metals has attracted increasing interest over the past decade. Complexes and cluster compounds of these new ligands with a number of transition metals have been isolated and characterised. The E^IR moiety is formally isolobal with CO and PR₃ (R = alkyl, Cp*) or carbenes (R = chelating group) with varying σ-donor and π-acceptor properties depending on the organic group R as well as the group 13 metal E. In this review, different ways of forming M-E bonds such as substitution reactions of labile ligands or insertion of E^IR into transition metal halide bonds are described. Furthermore, the reactivity of homoleptic complexes M_a(E^IR) _b, is discussed, outlining the use of these new complex types in bond activation reactions.