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

如果刘易斯酸和碱被阻止彼此直接相互作用，例如通过大体积取代基，则保留未使用的反应电势，小分子可以利用该反应电势被极化、结合或活化。阻挫刘易斯酸/碱对（FLP）概念的应用范围从氢的异裂及其作为加氢催化剂的用途到二氧化碳和其他温室气体的活化。FLP能够实现新的反应和催化过程以及高活性颗粒的稳定化。迄今为止使用的大多数FLP系统分别使用硼烷和膦作为酸或碱官能团。还使用了其它元素[Al、Ga、Zn、P（V）、Si、Sn]的酸。在这个项目中，我们希望在刘易斯酸功能中使用重主族元素，如锡、铅、锑、铟和铊，然后根据HSAB概念形成相对软的酸结合位点。一方面，这应该使它们特别亲合于基质中的软结合位点，另一方面，它们应该更弱地或可逆地结合硬基质如CO2。在开发催化体系时，这种结合强度的微调可能是至关重要的，因为产物必须是可移除的以进行再生。二十多年来，我们一直在深入研究分子内或孪位刘易斯酸/碱化合物，包括重元素。我们已经开发了活性FLP，例如中性硅或锡-磷FLP，（C2 F5）3E-CH 2-P（CMe 3）2（E = Si，Sn），以及许多其他FLP系统。对于锡化合物，我们已经可以证明一些所需的重原子FLP性质。已就锡和锑开展了相关的初步工作。现在，我们想继续这项工作，并利用这些发现将研究扩展到元素铅，铟和铊。为此，我们正在开发试剂，使这些元素的功能与空间要求和强电负性基团的刚性烃框架与膦功能的介绍。因此，FLP系统与不同的，确定的距离之间的酸和碱功能将被合成。我们希望系统地了解反应性对几何参数的依赖性，对刘易斯酸功能（元素和配体），以获得可用于优化反应性的趋势。为此，将在许多底物上测试上述系统的结合、活化活性及其催化适用性（例如不饱和底物的氢化），其中还通过氢气和二氧化碳的同时转化以还原氢气和二氧化碳。

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.