gerSchmitz, Alexander JonasLeitner, WalterKlankermayer, JürgenEntwicklung von Pincer Metall-NHC-Komplexen für die indirekte CO$_{2}$-Hydrierung zu Methanol am Beispiel von Harnstoffderivateninfo:eu-repo/classification/ddc/540carbon dioxidehomogeneous catalysishydrogenationnobel and earth-abundant transition metalsorganometallic chemistryureaThe present thesis describes the development of homogeneous metal-NHC catalysts with a pincer ligand framework for the indirect hydrogenation of CO2-derivatives to methanol. For the investigation of this reductive transformation, a particular focus is put on the hydrogenation of urea derivatives. The use of CO2 as a renewable C1-building block is central to establishing a greener chemical industry. Of particular importance is the hydrogenation of CO2 to methanol, which is as a key chemical linking many future chemical value chains. The various strategies and challenges associated with the hydrogenation of CO2 are presented in Chapter 1. In addition, an overview is given of the key structural features and the current state of research on the CO2 hydrogenation using ruthenium as the metal centre, which has attracted much attention due to its outstanding performance. In this context, Chapter 2 describes the motivation for the development and investigation of metal-NHC complexes for indirect CO2 hydrogenation via urea derivatives. The design and the synthesis of a novel Ru(II)-NHC complex based on a pincer ligand is described in Chapter 3. In the following Chapter 4, the newly established catalyst was successfully applied to the hydrogenation of urea derivatives. After optimising the reaction conditions, various aromatic and aliphatic urea derivatives are tested in the catalytic hydrogenation. Subsequently, mechanistic studies are carried out to elucidate the reactive intermediates and the elementary steps in the catalytic cycle. In particular, a Ru(II)-ureate complex is formed and identified as the catalytic resting state. In addition, an unusual ruthenium dimer is crystallographically characterised, providing important insights into the catalytic behaviour of the catalyst. These mechanistic investigations allow the proposal of a catalytic cycle based on a stepwise hydrogenation of urea via the MLC pathway. The development of catalytic systems based on earth-abundant 3d metals is of particular importance in creating a more sustainable chemistry. Following the diagonal relationship in the periodic table, the synthesis of a Mn(I) analogue of the developed pincer NHC-Ru(II) complex is reported in Chapter 5. Moreover, the synthetic route and structure determination of two structurally related NHC-Mn(I) complexes are presented. DFT calculations are performed to verify the formation of diastereomers in the synthesis of the CPhNP-Mn(I) complex. Finally, the catalytic performance of the NHC-Mn(I) complexes is investigated in the hydrogenation of diphenylurea, showing promising stability and activity for the CNP-type catalyst system.Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen (2024). doi:10.18154/RWTH-2025-00369 = Dissertation, RWTH Aachen University, 2024info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionRWTH Aachen University2024info:eu-repo/semantics/openAccessDEhttps://publications.rwth-aachen.de/record/1000454https://publications.rwth-aachen.de/search?p=id:%22RWTH-2025-00369%22StudentsStudent Financial Aid ProvidersTeachersResearchersinfo:eu-repo/semantics/altIdentifier/doi/10.18154/RWTH-2025-00369