An Experimental Acidity Scale for Intramolecularly Stabilized Silyl Lewis Acids
An Experimental Acidity Scale for Intramolecularly Stabilized Silyl Lewis Acids
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DOI：
10.1002/chem.201903241
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发表时间：
2019-11-27
影响因子：
4.3
通讯作者：
Mueller, Thomas
中科院分区：
文献类型：
--
作者：
Kuenzler, Sandra;Rathjen, Saskia;Mueller, Thomas
提出了一种新的基于核磁共振的刘易斯酸度标度，并演示了其在硅基刘易斯酸家族中的应用。对氟苯腈（FBN）与硅基阳离子（通过与远端硫原基或卤素供体相互作用而在内部稳定）的反应产生与硅原子在三角双锥体配位环境中的硅化腈离子。这些腈离子的F-19核磁共振化学位移和(1)J（CF）偶联常数随稳定基团给体能力的变化而变化。光谱参数是衡量路易斯酸酸度的合适探针。这些新探针可以区分非常相似的路易斯酸，这是传统的核磁共振测试无法做到的，比如成熟的Gutmann-Beckett方法。
A new NMR-based Lewis acidity scale is suggested and its application is demonstrated for a family of silyl Lewis acids. The reaction of p-fluorobenzonitrile (FBN) with silyl cations that are internally stabilized by interaction with a remote chalcogenyl or halogen donor yields silylated nitrilium ions with the silicon atom in a trigonal bipyramidal coordination environment. The F-19 NMR chemical shifts and the (1)J(CF) coupling constants of these nitrilium ions vary in a predictable manner with the donor capability of the stabilizing group. The spectroscopic parameters are suitable probes for scaling the acidity of Lewis acids. These new probes allow for the discrimination between very similar Lewis acids, which is not possible with conventional NMR tests, such as the well-established Gutmann-Beckett method.