Bond activation reactions by means of metal ligand cooperation in carbene complexes

元素和元素氢键的活化是许多过渡金属催化转化的一个基本过程。通常，这些过程通过氧化加成步骤直接发生在金属中心。然而，在过去的几年里，涉及金属和配体作为活性位点的机制在键断裂和生成步骤中已经成为键激活化学的另一种工具。新型配体体系的发展已经导致将这种金属配体的协同性纳入化学计量和催化转化，从而为均相催化的未来过程开辟了新的可能性。这种配合配体的公认例子是酰亚胺、氨基或羰基功能化配体。相比之下，碳配体在这一化学领域的探索要少得多，它们的应用仅限于少数例子。本研究计划的目标是克服碳化合物化学的这一不足，建立碳化合物配合物用于协同键激活反应和催化。为此，本文将讨论配合碳配体配合物的系统设计、它们在键激活反应中的应用以及对M=C相互作用的电子需求的理解。因此，将针对两种不同类型的卡宾体系：i)甲脒衍生的卡宾配合物以及ii)基于PCD钳形配体的配合物。配体中取代基的变化将影响金属碳相互作用的电子学，从而允许通过M=C键上的加成来控制E-E -和E-H键的激活反应。系统的实验和计算研究将提供对所设计系统的分子和电子结构之间的关系及其作为合作配体的适用性的深刻理解。从而实现不同E-E -和E-H键的可逆活化过程以及它们向有机底物的转移。这将是催化转化最终发展的基础。在这里，我们还将重点关注用于生产和储存二氢的无受体脱氢反应。

The activation of element element and element hydrogen bonds is a fundamental process in many transition metal catalyzed transformations. Typically, these processes directly occur at the metal center via an oxidative addition step. In the last years however, mechanisms involving both the metal as well as the ligand as active sites in the bond breaking and making steps have become an alternative tool in bond activation chemistry. The development of novel ligand systems has led to the incorporation of this metal ligand cooperativity into stoichiometric as well as catalytic transformations, thus opening new possibilities for future processes in homogenous catalysis. Well-established examples for such cooperating ligands are imido, amido or carbonyl-functionalized ligands. In contrast, carbene ligands are by far less explored in this chemistry and their application limited to only few examples. Goal of the present research proposal is to overcome this lack in carbene chemistry and to establish carbene complexes in cooperative bond activation reactions and catalysis. To this end, the systematic design of complexes with cooperating carbene ligands, their application in bond activation reactions as well as an understanding of the electronic demands on the M=C interaction will be addressed. Thereby two different types of carbene systems will be targeted: i) methandiide-derived carbene complexes as well as ii) complexes based on PCD pincer ligands. Variation of the substituents in the ligands will influence the electronics of the metal carbon interaction and thus allow for controlled E–E- and E–H bond activation reactions via addition across the M=C bond. Systematic experimental as well as computational studies will provide a profound understanding of the relations between the molecular and electronic structures of the designed systems and their applicability as cooperating ligands. Thus, reversible activation processes of different E–E- und E–H bonds as well as their transfer to organic substrates will be realized. This will be basis for the final development of catalytic transformations. Here, we will also focus on acceptor-less dehydrogenation reactions for the production and storage of dihydrogen.