Investigation of iron-catalyzed cross-coupling reactions
Cross-coupling reactions are counted among the most important reactions in homogeneous catalysis since they show a high tolerance towards functional groups and use ecologically and economically harmless iron as catalytic material. Despite this importance the reaction mechanism, especially the catalytically active species, its structure and oxidation state are widely unknown. Using a combination of preparative inorganic chemistry and synchrotron spectroscopy first insights into this complex reaction could be achieved. Depending on the used coupling reagent, especially of the organic residue, species with an oxidation state between 0 and +I are formed. In all cases iron nanoparticles are generated, which strongly vary in size and coordinating ligands.
Preparation of mono- and bimetallic nanoparticles using organometallic reduction and mechanistic investigation of the formation process
Generation of nanoparticles during Fe-catalyzed cross coupling reactions simulates the opportunity to synthesize nanoparticles through reduction of a precursor by a metal organic compound. Shape, type and number of stabilizing groups and the degree of mixture when two precursors are used, are subject of recent studies using a variety of spectroscopic methods (XAS, XES, Raman, UV/Vis, EPR, NMR, Mößbauer). The mechanism of nanoparticle formation and the identification of short-lived intermediates are also subject of recent studies using time-resolved X-ray absorption spectroscopy in combination with UV/Vis spectroscopy.
Application of non-noble metal nanoparticles as precursors for a targeted synthesis of model catalysts for CO oxidation
The nanoparticles mentioned above possess a coordination shell composed of the metal of the reduction compound. With appropriate selection of the reduction reagent the metal of the shell can be identical to the metal of the support material. Through impregnation catalysts were obtained, which show promising performances in CO oxidation. The catalytic activity is investigated at the moment regarding metal composition, support material and reduction compound. Furthermore detailed studies to elucidate the reaction mechanism using XAS and XES in combination with IR- and UV/Vis-spectroscopy and GC/MS are performed.
Development and mechanistic investigation of catalytical water splitting reactions
Currently, new bimetallic complexes are developed, which should enable a targeted improvement of photocatalytical water reduction by directed electron transfer from photoactive center to the catalytically active center using conducting linker in so-called dyads. In these complexes both the type of coordinating ligands and the dimension of the conducting ligand are varied. Therefore these complexes represent a challenge regarding their synthesis and the investigation of their mode of operation. For mechanistical studies the development of new X-ray-methods is essential, since they allow the pursuit of electronic and structural changes on differing time scales up to pico second range. The figure shows a setup for the investigation of photocatalytical water reduction at the synchrotron.