The large steric profile of the N-heterocyclic boryloxy ligand, –OB(NDippCH)₂, and its ability to stabilize the metal-centered HOMO, are exploited in the synthesis of the first example of a “naked” acyclic aluminyl complex, [K(2.2.2-crypt)][Al{OB(NDippCH)₂}₂]. This system, which is formed by substitution at Al^I (rather than reduction of Al^III), represents the first O-ligated aluminyl compound and is shown to be capable of hitherto unprecedented reversible single-site [4 + 1] cycloaddition of benzene. This chemistry and the unusual regioselectivity of the related cycloaddition of anthracene are shown to be highly dependent on the availability (or otherwise) of the K⁺ countercation.

中文翻译：

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“裸”无环铝基化合物对芳烃的可逆 [4 + 1] 环加成

N-杂环硼酰氧基配体 –OB(NDippCH) ₂的大空间分布及其稳定金属中心 HOMO 的能力，被用于合成第一个“裸”无环铝基配合物的例子，[K (2.2.2-隐窝)][Al{OB(NDippCH) ₂ } ₂ ]。该系统是通过 Al ^I处的取代（而不是 Al ^III的还原）形成的，代表了第一个 O-配位的铝基化合物，并且被证明能够进行迄今为止前所未有的可逆单点 [4 + 1] 苯环加成。这种化学反应和相关的蒽环加成的不寻常的区域选择性高度依赖于 K ⁺抗衡阳离子的可用性（或其他）。