Research

Motivation

Our research aims at a detailed understanding of chemical processes at the molecular level. We believe that the thus gained mechanistic insight is not only of interest in its own right, but in the long term will provide the best way for reagent and catalyst optimization as well as the development of new synthetic methods and materials

Methods

Much of our work involves organic/organometallic synthesis to prepare samples of interest, which we then analyze by various analytical methods, such as NMR spectroscopy, UV/vis spectroscopy, and electrical conductivity measurements. As a particularly useful tool to probe ionic intermediates, we employ electrospray ionization (ESI) mass spectrometry. With our optimized protocols, we can even detect highly sensitive and elusive species. To improve our experiments further, we also seek a better understanding of the ESI process. In this regard, we study the relative ESI activities of different analytes. Additionally, we investigate the effective internal energy of analyte ions by means of thermometer ions. Moreover, to study the reactivity of mass-selected ionic intermediates in the gas phase, we conduct collision-induced dissociation and ion-molecule reaction experiments by the use of a home-built substrate-inlet system. Thus, we achieve ultimate control over the probed systems and can assess how single bound solvent molecules, different ligands, and different aggregation states affect the reactivity at the molecular level. In addition, ion-mobility measurements and spectroscopic studies (with collaboration partners) help us to obtain structural information. For a detailed interpretation of the experimental results, we also use theoretical methods (quantum-chemical and statistical rate-theory calculations).

Methods

Fields of Interest

Current activities in the field of organometallics center on Grignard reagents, organocuprates, organozinc, and organoindium compounds. We probe the aggregation and association equilibria of these reagents in solution and determine their reactivity by kinetic measurements in solution and in the gas phase. We also analyze transition-metal mediated reactions, such as cross-coupling, C-H activation processes, hydrogenation and polymerizations, and have been able to identify key intermediates. Research Intermediates I We are particularly interested in the reactivity of organometallic species and catalytic intermediates. Gas-phase experiments on mass-selected ions permit us to probe single elementary steps in unprecedented detail. Here, we focus on reductive elimination, transmetallation, oxidative addition, protodemetalation and β-hydrogen elimination reactions. reductive elimination

ESI is commonly referred to as soft ionization method and is supposed to transfer labile species into the gas phase without extensive fragmentation. Therefore, we also use ESI mass spectrometry to probe the association of biomolecules. Biomolecule

For designing improved electrolytes, the actual molecular constituents of these materials must be known. We apply a combination of ESI mass spectrometry and electrical conductivity measurements to analyze the ions present in solutions of new aluminate-based electrolytes. electrolytes

Research Projects

Currently, we focus on six projects in our group. For further details, see the following descriptions of research projects.