Röther Alexander, Farmer James C, Portwich Flavio L, Görls Helmar, Kretschmer Robert
Institute of Inorganic and Analytical Chemistry (IAAC), Friedrich Schiller University Jena, Humboldtstraße 8, 07743, Jena, Germany.
Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743, Jena, Germany.
Chemistry. 2023 Nov 21;29(65):e202302544. doi: 10.1002/chem.202302544. Epub 2023 Oct 6.
The dinuclear bis(N-heterocyclic carbene) borane adduct 2 rapidly reacts with tritylium salts at room temperature but the outcome is strongly impacted by the respective counter-ion. Using tritylium tetrakis(perfluoro-tert-butoxy)aluminate affords - depending on the solvent - either the bis(boronium) ion 4 or the hydride-bridged dication 5. In case of tritylium hexafluorophosphate, however, H/F exchange occurs between boron and phosphorus yielding the dinuclear BF adduct 3 along with phosphorus dihydride trifluoride. H/F exchange also takes place when using the mononuclear N-heterocyclic carbene BH adduct 6 and hence provides a facile route to PH F , which is usually synthesized in more complex reaction sequences regularly involving toxic hydrogen fluoride. DFT calculations shed light on the H/F exchange between the borenium ion and the [PF ] counter-ion and the computed mechanism features only small barriers in line with the experimental observations.
双核双（N-杂环卡宾）硼烷加合物2在室温下能迅速与三苯甲基盐反应，但反应结果受相应抗衡离子的强烈影响。使用四（全氟叔丁氧基）铝酸三苯甲基盐，根据溶剂的不同，可得到双（硼鎓）离子4或氢化物桥连的双阳离子5。然而，使用六氟磷酸三苯甲基盐时，硼和磷之间会发生H/F交换，生成双核BF加合物3以及二氢化磷三氟化物。使用单核N-杂环卡宾BH加合物6时也会发生H/F交换，从而为合成PHF提供了一条简便途径，PHF通常是通过更复杂的反应序列合成的，这些反应序列通常涉及有毒的氟化氢。密度泛函理论计算揭示了硼鎓离子与[PF]抗衡离子之间的H/F交换，计算出的机理仅具有较小的势垒，这与实验观察结果一致。
