The Lewis superacid Al[N(C6F5)2]3 and its higher homolog Ga[N(C6F5)2]3 – structural features, theoretical investigation and reactions of a metal amide with higher fluoride ion affinity than SbF5†

IF 7.6 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY Chemical Science Pub Date : 2017-10-23 DOI:10.1039/C7SC03988C

J. F. Kögel, D. A. Sorokin, A. Khvorost, M. Scott, K. Harms, D. Himmel, I. Krossing and J. Sundermeyer

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引用次数: 23

Abstract

Herein we present the synthesis of the two Lewis acids Al[N(C₆F₅)₂]₃ (ALTA) and Ga[N(C₆F₅)₂]₃ (GATA) via salt elimination reactions. The metal complexes were characterized by NMR-spectroscopic methods and X-ray diffraction analysis revealing the stabilization of the highly Lewis acidic metal centers by secondary metal–fluorine contacts. The Lewis acidic properties of Al[N(C₆F₅)₂]₃ and Ga[N(C₆F₅)₂]₃ are demonstrated by reactions with Lewis bases resulting in the formation of metallates accompanied by crucial structural changes. The two metallates [Cs(Tol)₃]⁺[FAl(N(C₆F₅)₂)₃]⁻ and [AsPh₄]⁺[ClGa(N(C₆F₅)₂)₃]⁻ contain interesting weakly coordinating anions. The reaction of Al[N(C₆F₅)₂]₃ with trityl fluoride yielded [CPh₃]⁺[FAl(N(C₆F₅)₂)₃]⁻ which could find application in the activation of metallocene polymerization catalysts. The qualitative Lewis acidity of Al[N(C₆F₅)₂]₃ and Ga[N(C₆F₅)₂]₃ was investigated by means of competition experiments for chloride ions in solution. DFT calculations yielded fluoride ion affinities in the gas phase (FIA) of 555 kJ mol⁻¹ for Al[N(C₆F₅)₂]₃ and 472 kJ mol⁻¹ for Ga[N(C₆F₅)₂]₃. Thus, Al[N(C₆F₅)₂]₃ can be considered a Lewis superacid with a fluoride affinity higher than SbF₅ (493 kJ mol⁻¹) whereas the FIA of the corresponding gallium complex is slightly below the threshold to Lewis superacidity.

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路易斯超强酸Al[N（C6F5）2]3及其高级同系物Ga[N（C6 F5）2]3-具有比SbF5更高的氟离子亲和力的金属酰胺的结构特征、理论研究和反应†

本文介绍了通过盐消除反应合成两种路易斯酸Al[N（C6F5）2]3（ALTA）和Ga[N（C6 F5）2]3（GATA）。通过NMR光谱方法和X射线衍射分析对金属配合物进行了表征，揭示了高路易斯酸性金属中心通过仲金属-氟接触的稳定性。Al[N（C6F5）2]3和Ga[N（C6F5）2]3的路易斯酸性质通过与路易斯碱的反应来证明，该反应导致金属化物的形成并伴随着关键的结构变化。两种金属化物[Cs（Tol）3]+[FAl（N（C6F5）2）3]−和[AsPh4]+[ClGa（N（C6 F5）2。Al[N（C6F5）2]3与氟化三苯酯的反应生成[CPh3]+[FAl（N（C6F52）3]−，可用于茂金属聚合催化剂的活化。通过溶液中氯离子的竞争实验，研究了Al[N（C6F5）2]3和Ga[N（C6 F5）2]3。DFT计算得出，对于Al[N（C6F5）2]3，气相（FIA）中的氟离子亲和力为555 kJ mol−1，对于Ga[N（C6 F5）2]3。因此，Al[N（C6F5）2]3可以被认为是一种路易斯超强酸，其氟化物亲和力高于SbF5（493 kJ mol−1），而相应镓络合物的FIA略低于路易斯超强酸的阈值。

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来源期刊

Chemical Science CHEMISTRY, MULTIDISCIPLINARY-

CiteScore

14.40

自引率

4.80%

发文量

1352

审稿时长

2.1 months

期刊介绍： Chemical Science is a journal that encompasses various disciplines within the chemical sciences. Its scope includes publishing ground-breaking research with significant implications for its respective field, as well as appealing to a wider audience in related areas. To be considered for publication, articles must showcase innovative and original advances in their field of study and be presented in a manner that is understandable to scientists from diverse backgrounds. However, the journal generally does not publish highly specialized research.