Chan Ka Lok, Lau Pak Fung, Lin Zhenyang
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China.
Chemistry. 2025 May 14;31(27):e202500807. doi: 10.1002/chem.202500807. Epub 2025 Apr 21.
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.
近几十年来，由于电正性铝在配体中作为供体原子的特殊作用，人们对一价铝配合物的兴趣激增。许多以前被认为过于不稳定的一价铝配合物已被分离出来。其中，β-二酮亚胺铝（I）配合物NacNacAl（I）因其独特的反应活性（包括氧化加成和π键活化）而脱颖而出。然而，对涉及NacNacAl（I）的反应的理解尚未完全确立。本研究通过密度泛函理论计算揭示了NacNacAl（I）与五种结构相似的氮杂芳烃反应多样性背后的机制。有趣的是，计算结果表明，这五个反应中的一些可以通过自由基过程进行。对所有结果的整体比较突出了单环和双环氮杂芳烃之间的机理差异。在与NacNacAl（I）反应的初始步骤中，单环氮杂芳烃形成Al（I）-氮杂芳烃加合物，而双环氮杂芳烃生成Al（II）-氮杂芳烃双自由基。这些中间体对于理解它们独特的反应活性至关重要。对于单环氮杂芳烃，其取代基对氮杂芳烃加合物的电子效应导致不同的反应结果，而对于双环氮杂芳烃，双自由基随后的分子间或分子内配位导致不同的产物。本研究为与NacNacAl（I）配合物相关反应提供了更深入的机理见解，从而有助于更全面地理解这些反应。
