Recent developments in low‐valent aluminum chemistry

The past decade has seen some remarkable advances in the development of low‐coordinate and/or oxidation state aluminum chemistry. With efforts striving to find more economical and environmentally benign methods for bond activations and catalysis, aluminum presents itself as an ideal candidate owing to its low cost and high natural abundance. Concerning low‐valent aluminum chemistry, these complexes have been shown to act like transition‐metal mimics with Al(I) species undergoing facile oxidative addition with a series of strong σ bonds. This represents the first step in a redox‐active catalytic cycle, with the challenge still remaining to undergo reductive elimination from the stable Al(III) species. In this regard, efforts have focused on reversible bond activations as well as the development of alternate methodologies to enhance the reactive aluminum center. The ambiphilic nature of Al(I) chemistry has largely been dictated by the vacant p‐orbital and as such its electrophilicity. Recent advances have made it possible to amplify the nucleophilic character of Al(I), and as such the first examples highlighting aluminum's nucleophilic behavior have been reported. In addition, isolation of the first neutral aluminum multiple bond has also aided our understanding of the bonding properties of aluminum while also allowing for further advances in bond activations and catalysis. These recent advances in the chemistry of low‐valent aluminum are discussed in the following sections, along with the fundamental concepts that have aided the development of this field.