Activation of small molecules by P–N(imido)–P pincer complexes of transition metals

小分子的催化活化以及元素氢键的活化和断裂是化学中的一个重要挑战。为此特别提出了有机金属学原理和配位化学原理。该项目的重点是开发具有新型螯合钳形配体的过渡金属络合物，这些络合物通常赋予相应的络合物动力学和热稳定性。通过引入能够接受、存储和捐赠质子或氢原子到需要它们的位置的官能团，可以实现高效的金属配体合作，从而在元素-H活化中实现钳形络合物的高反应活性。为了结合高效的金属配位配合和强施主的反式稳定作用，我们开发了P-C(卡宾)-P络合物。然而，这些配合物在催化中的应用受到镁尺度合成和失活过程的限制。该项目提出了一种新的方法，通过结合磷给体和亚胺多官能团来规避这些限制。通过开发N-CH(~Pr2)2配体体系，将实现配体与过渡金属中心之间的亚胺键的应用。螯合主链结构的改变将允许精确地调整N-和P-功能的给体性质。在这个项目中，这些调整良好的配体系统将协调到早期和晚期过渡金属中心。P-N(亚胺)-P配体的合成概念允许多种取代模式和合成途径。通过N-H活化法合成这类P-N(亚胺)-P络合物的方法估计为合成提供了适宜的条件。除了P-N(亚胺)-P过渡金属络合物的合成外，这些络合物的表征也是本项目的重点。因此，将采用红外光谱、核磁共振和电子顺磁共振光谱方法，以及质谱学和X射线衍射法。通过P-N(亚胺)-P过渡金属络合物的光谱和结构表征所获得的见解将被反应性研究所补充。因此，P-N(亚胺)-P过渡金属络合物与CO的反应提供了以CO为反式排列指示配体的M=N键性质的详细研究。P-N(亚胺)-P络合物的应用是该项目的另一个中心方面。首先，将通过与胺、末端炔烃和二氢的反应来考察P-N(亚胺)-P络合物的键活化能力。这些研究将在以后用于开发P-N(亚胺)-P络合物的催化应用。

The catalytic activation of small molecules in combination with the activation and cleavage of element–H bonds is one important challenge in chemistry. Principles of organometallics and coordination chemistry are therefor particularly claimed. In focus of this project is the development of transition metal complexes with novel chelating pincer ligands that generally confer kinetic and thermal stability to the corresponding complexes. A productive metal ligand cooperation and therefor a high reactivity of pincer complexes in element–H activations can be achieved by the incorporation of functionalities that are capable of accepting, storing and donating protons or hydrogen atoms to the position where they are needed. To combine a productive metal ligand cooperation with the trans-labilizing effect of strong donors, P–C(carbene)–P complexes were developed. However, the application of these complexes in catalysis is limited by mg-scale synthesis as well as deactivation processes. This project presents a novel approach to circumvent these limitations by the combination of phosphorous donors and an imido functionality. The application of an imido bond between the ligand and the transition metal center will be achieved by the development of a :N–CH(~PR2)2 ligand system. The changed structure of the chelating backbone will allow an accurate adjustment of the donor properties of the N- and P-functions. These well adjusted ligand systems will be coordinated to early as well as late transition metal centers in this project. The synthetic concept for P–N(imido)–P ligands allows versatile substitution patterns and synthetic pathways. The synthetic approach to such P–N(imido)–P complexes by N–H activation is estimated to allow moderate conditions for the synthesis. In addition to the synthesis of P–N(imido)–P transition metal complexes the characterization of those complexes is in focus of this project. Therefore IR, NMR and EPR spectroscopic methods as well as mass spectrometry and X-ray diffraction will be applied. The insights gained by the spectroscopic and structural characterization of P–N(imido)–P transition metal complexes will be supplemented by reactivity studies. Therefor reactions of P–N(imido)–P transition metal complexes with CO provide a detailed investigation of the nature of the M=N bond by using the CO as trans-arranged indicator ligand. The application of P–N(imido)–P complexes is another central aspect of this project. At first the capability of P–N(imido)–P complexes for bond activations will be investigated by test reactions with amines, terminal alkynes and dihydrogen. These investigations will be used later on for the development of a catalytic application of P–N(imido)–P complexes.