Erdmann Philipp, Greb Lutz
Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Department of Chemistry and Biochemistry-Inorganic Chemistry, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany.
Angew Chem Int Ed Engl. 2022 Jan 21;61(4):e202114550. doi: 10.1002/anie.202114550. Epub 2021 Dec 8.
IUPAC defines Lewis acidity as the thermodynamic tendency for Lewis pair formation. This strength property was recently specified as global Lewis acidity (gLA), and is gauged for example by the fluoride ion affinity. Experimentally, Lewis acidity is usually evaluated by the effect on a bound molecule, such as the induced P NMR shift of triethylphosphine oxide in the Gutmann-Beckett (GB) method. This type of scaling was called effective Lewis acidity (eLA). Unfortunately, gLA and eLA often correlate poorly, but a reason for this is unknown. Hence, the strength and the effect of a Lewis acid are two distinct properties, but they are often granted interchangeably. The present work analyzes thermodynamic, NMR specific, and London dispersion effects on GB numbers for 130 Lewis acids by theory and experiment. The deformation energy of a Lewis acid is identified as the prime cause for the critical deviation between gLA and eLA but its correction allows a unification for the first time.
国际纯粹与应用化学联合会（IUPAC）将路易斯酸度定义为形成路易斯对的热力学倾向。这种强度性质最近被指定为全局路易斯酸度（gLA），例如通过氟离子亲和力来衡量。在实验中，路易斯酸度通常通过对结合分子的影响来评估，比如在古特曼 - 贝克特（GB）方法中三乙膦氧化物的诱导磷核磁共振位移。这种标度类型被称为有效路易斯酸度（eLA）。不幸的是，gLA和eLA常常相关性很差，但其中的原因尚不清楚。因此，路易斯酸的强度和效应是两个不同的性质，但它们常常被互换使用。本工作通过理论和实验分析了130种路易斯酸的热力学、核磁共振特异性和伦敦色散效应，这些效应与GB数值有关。路易斯酸的变形能被确定为gLA和eLA之间关键偏差的主要原因，但对其进行校正首次实现了两者的统一。
