The electrophilic phosphonium cation (EPC) salt [(3,5-(CF₃)₂C₆H₃)₃PF][B(C₆F₅)₄] (2) is prepared via oxidation of the precursor phosphine with XeF₂ and subsequent abstraction of fluoride with [Et₃Si(tol)][B(C₆F₅)₄]. The Lewis acidity of 2 is evaluated by experimental and computational methods and by preliminary catalysis testing. Exchange reactions of 2 and [(C₆F₅)₃PF][B(C₆F₅)₄] with their respective difluorophosphoranes are studied by 2D ¹⁹F–¹⁹F NOESY/EXSY and selective 1D ¹⁹F NMR exchange spectroscopy (SEXSY) experiments affording comparative rates of fluoride exchange. Collectively, although these data show that 2 is less Lewis acidic than [(C₆F₅)₃PF][B(C₆F₅)₄], the improved access to the P center of 2 provides a kinetic acceleration for fluoride exchange and catalysis where the transition states are more sterically demanding.

中文翻译：

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探索空间对亲电phospho阳离子的影响：[[3,5-（CF ₃）₂ C ₆ H ₃）₃ PF] ⁺和[（C ₆ F ₅）₃ PF] ⁺ †的比较

亲电子phospho阳离子（EPC）盐[（3,5-（CF ₃）₂ C ₆ H ₃）₃ PF] [B（C ₆ F ₅）₄ ]（2）是通过用XeF氧化前体膦而制得的₂和随后用[Et ₃ Si（tol）] [B（C ₆ F ₅）₄ ]提取氟化物。的路易斯酸性2是通过实验和计算方法，并通过初步催化测试评价。的交换反应2和[（C ₆ ˚F ₅）通过2D ¹⁹ F- ¹⁹ F NOESY / EXSY和选择性1D ¹⁹ F NMR交换光谱法（SEXSY）实验研究了₃ PF] [B（C ₆ F ₅）₄ ]和它们各自的二氟磷烷。总体而言，尽管这些数据表明2的路易斯酸性比[（C ₆ F ₅）₃ PF] [B（C ₆ F ₅）₄ ]弱，但改善了对2的P中心的访问。 在过渡态对空间的要求更高的情况下，为氟化物交换和催化提供了动力学加速。