Kurumada Satoshi, Takamori Shuhei, Yamashita Makoto
Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Nagoya, Japan.
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Tokyo, Japan.
Nat Chem. 2020 Jan;12(1):36-39. doi: 10.1038/s41557-019-0365-z. Epub 2019 Nov 25.
Aluminium anions with an unoccupied orbital are generally considered as highly difficult synthetic targets, as aluminium is the most electropositive element in the p block. Stabilizing effects from two nitrogen substituents and/or the coordination of a Lewis base were recently used to synthesize the first examples of anionic nucleophilic aluminium species. Here we show the synthesis and properties of a potassium salt of a non-stabilized dialkylaluminium anion that exhibits very strong basicity, which reflects the electropositive character of aluminium. An X-ray diffraction analysis revealed a monomeric structure and the shortest Al-K distance hitherto reported. The ultraviolet visible spectrum in combination with density functional theory calculations suggests an electronic structure characterized by a lone pair of electrons and an unoccupied p orbital on the aluminium centre. This species readily deprotonates benzene to form the corresponding (hydrido)(phenyl)aluminate. Reactions with other electrophiles corroborate the nucleophilicity of the aluminium centre.
具有未占据轨道的铝阴离子通常被认为是极难合成的目标，因为铝是p区中电正性最强的元素。最近，利用两个氮取代基的稳定作用和/或路易斯碱的配位作用，合成了首例阴离子亲核铝物种。在此，我们展示了一种不稳定的二烷基铝阴离子钾盐的合成及其性质，该钾盐表现出很强的碱性，这反映了铝的电正性特征。X射线衍射分析揭示了一种单体结构以及迄今报道的最短的铝-钾距离。紫外可见光谱结合密度泛函理论计算表明，其电子结构的特征是铝中心有一对孤对电子和一个未占据的p轨道。该物种很容易使苯去质子化，形成相应的（氢）（苯基）铝酸盐。与其他亲电试剂的反应证实了铝中心的亲核性。
