Millet Clement R P, Willcox Dominic R, Nichol Gary S, Anstöter Cate S, Ingleson Michael J
EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom.
Angew Chem Int Ed Engl. 2025 Feb 10;64(7):e202419094. doi: 10.1002/anie.202419094. Epub 2024 Nov 26.
Oxoboranes (R-BO) are transient species that rapidly trimerise to form boroxines. To date, the only method used to stabilise oxoboranes is to add a Lewis base, but this forms a three-coordinate at boron oxoborane that has a different bonding/reactivity profile. Herein we report a base-free, two-coordinate oxoborane that is isolated as a Lewis adduct with AlCl. This species, MesBO-AlCl (Mes=2,4,6-Bu-CH), has a νΒΟ stretching frequency of 1843 cm, indicating a strong BO bond. Computational analysis indicates this is due to a highly polarised BO bonding interaction combined with modest BO multiple bond character. While the polarisation of the BO bond on AlCl coordination enhances the Lewis acidity at boron it also reduces the basicity at oxygen and the latter is key to accessing a base-free oxoborane. Finally, this oxoborane reacts with PhN in a unique way to form an unprecedented boron heterocycle.
氧硼烷（R-BO）是会迅速三聚形成硼氧六环的瞬态物种。迄今为止，用于稳定氧硼烷的唯一方法是添加路易斯碱，但这会形成一种在硼上具有三配位的氧硼烷，其具有不同的键合/反应活性特征。在此，我们报道了一种无碱的二配位氧硼烷，它作为与AlCl的路易斯加合物被分离出来。这种物种，MesBO-AlCl（Mes = 2,4,6-Bu-CH），具有1843 cm的νΒΟ伸缩频率，表明存在强的B-O键。计算分析表明，这是由于高度极化的B-O键合相互作用以及适度的B-O多重键特征所致。虽然在AlCl配位时B-O键的极化增强了硼的路易斯酸性，但它也降低了氧的碱性，而后者是获得无碱氧硼烷的关键。最后，这种氧硼烷与PhN以独特的方式反应形成了一种前所未有的硼杂环。
