Probing the Extremes of Covalency in M–Al bonds : Lithium and Zinc Aluminyl Compounds

Abstract

Synthetic routes to lithium, magnesium and zinc aluminyl complexes are reported, allowing for the first structural character-ization of a lithium-aluminium bond. Structural and quantum chemical studies are consistent with the presence of a highly polar Li–Al interaction, characterized by a low bond order and relatively little charge transfer from Al to Li. Comparison with the magnesium and zinc systems reveals changes to both the M–Al bond and the (NON)Al fragment consistent with greater covalent character, with the latter complex being shown to react with CO 2 via a pathway that implies that the zinc centre acts as the nucleophilic partner.