Dissecting the Diverse Reactivity of β-Diketiminate Aluminum(I) Compound towards Azaarenes: Insight From DFT Calculations

Interest in aluminum(I) complexes has surged in recent decades due to the unusual role of electropositive aluminum as donor atoms in ligands. Numerous Al(I) complexes, which were previously considered too unstable, have been isolated. Among these, β-diketiminate aluminum(I) complex, NacNacAl(I), stands out for its unique reactivities including oxidative addition and π-bond activation. However, the understanding of reactions involving NacNacAl(I) has not yet been fully established. This study unveils the mechanisms behind the diverse reactivity of NacNacAl(I) with five structurally similar azaarenes through DFT calculations. Interestingly, computational results indicate that some of the five reactions can proceed via radical processes. A holistic comparison of all results highlights the mechanistic differences between monocyclic and bicyclic azaarenes. In the initial step with NacNacAl(I), monocyclic azaarenes form Al(I)-azaarene adducts, whereas bicyclic azaarenes generate Al(II)-azaarene biradicals. These intermediates are critical for understanding their distinctive reactivity. For monocyclic azaarenes, electronic effects of their substituents on the azaarene adducts result in varying reaction outcomes, while for bicyclic azaarenes, subsequent intermolecular or intramolecular coordination of biradicals leads to different products. This study provides deeper mechanistic insights into reactions associated with NacNacAl(I) complexes, thereby contributing to a more comprehensive understanding of these reactions.