Implementation of the HSAB concept in the chemistry of frustrated Lewis couples

如果路易斯酸和碱被阻止直接相互作用，例如通过大体积取代基，则剩余的未使用的反应势可以与小分子极化、结合或激活。受阻Lewis酸碱对(FLP)这一概念的应用范围从氢的异解裂解，从而用作加氢催化剂，到二氧化碳和其他温室气体的活化。FLP使新的反应和催化过程以及高活性粒子的稳定成为可能。到目前为止使用的大多数FLP系统分别使用硼烷和磷烷作为酸或碱功能。还使用了其他元素[Al、Ga、Zn、P(V)、Si、Sn]的酸。在这个项目中，我们希望在Lewis酸功能中使用锡、铅、锑、铟和铊等重主族元素，根据HSAB的概念，这些元素形成相对软的酸结合部位。一方面，这应该使它们特别与底物中的软结合部位结合，另一方面，它们应该更弱地或可逆地结合硬底物，如二氧化碳。在开发催化系统时，这种结合强度的微调可能是至关重要的，因为产品必须是可拆卸的才能再生。二十多年来，我们一直在深入研究分子内或双核Lewis酸碱化合物，包括那些重元素的化合物。我们已经开发出了活性FLP，如中性硅或锡-磷FLP，(C2F5)3E-CH2-P(CMe3)2(E=Si，Sn)，但也有许多其他FLP系统。对于锡化合物，我们已经证明了一些所需的重原子FLP性质。已对锡和锑进行了相关的前期工作。现在，我们希望继续这项工作，并利用这些发现将研究扩展到铅、铟和铊元素。为此，我们正在开发试剂，使这些具有空间要求和强烈电负性基团的元素的功能引入具有磷烷功能的刚性碳氢化合物骨架。这样，就可以合成具有不同定义的酸碱距离的FLP体系。我们想要系统地了解反应性对几何参数和Lewis酸功能(元素和配体)的依赖关系，以便得出可用于优化反应性的趋势。为此，将在一些底物上测试上述系统的结合、活化活性和催化适宜性(例如，不饱和底物的氢化)，以及通过同时转化氢和二氧化碳进行还原的方法。

If Lewis acids and bases are prevented from directly interacting with each other, e.g. by bulky substituents, an unused reaction potential remains with which small molecules can be polarized, bound or activated. Applications of this concept of Frustrated Lewis Acid/Base Pairs (FLP) range from the heterolytic cleavage of hydrogen and thus their use as hydrogenation catalysts to the activation of carbon dioxide and other greenhouse gases. FLP enable novel reactions and catalytic processes and the stabilization of highly reactive particles. Most FLP systems employed so far use boranes and phosphanes as acid or base functions, respectively. Acids of other elements [Al, Ga, Zn, P(V), Si, Sn] have also been used. In this project, we want to use heavy main group elements such as tin, lead, antimony, indium and thallium in Lewis acid functions, which then form relatively soft acid binding sites according to the HSAB concept. On the one hand, this should make them particularly affine to soft binding sites in substrates, and on the other hand, they should bind hard substrates such as CO2 more weakly or reversibly. The fine-tuning of such binding strengths can be crucial when developing catalytic systems, since the products must be removable for regeneration. For more than two decades, we have been intensively investigating intramolecular or geminal Lewis acid/base compounds, including those of heavy elements. We have developed active FLP such as the neutral silicon or tin-phosphorus FLP, (C2F5)3E-CH2-P(CMe3)2 (E = Si, Sn) but also numerous other FLP systems. For the tin compound we could already prove some of the desired heavy atom FLP properties. Relevant preliminary work has been performed for tin and antimony. Now we want to continue this work and use these findings to extent the research to the elements lead, indium and thallium. For this purpose, we are developing reagents that enable the introduction of functions of these elements with sterically demanding and strongly electronegative groups to rigid hydrocarbon frameworks with phosphane functions. Thus FLP systems with different, defined distances between acid and base functions will be synthesized. We want to systematically understand the dependence of reactivity on the geometric parameters, on the Lewis acid function (element and ligand), in order to derive trends that can be used to optimize reactivities. To this end, the systems mentioned above will be tested on a number of substrates for their activity for binding, activation and their catalytic suitability (e.g. hydrogenation of unsaturated substrates), among other things also by means of a simultaneous conversion of hydrogen and carbon dioxide for its reduction.