Chemistry of open-shell metal complexes: Tuning spin density distributions between P-ligands and metals

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Due to the scarcity in knowledge about metal coordination chemistry of open-shell P-ligands, this project will endeavor to achieve new fundamental insights. We want to explore oxidative SET reactions of two classes of redox-active anionic P-ligands, categorized according to the formal charge location, i.e., at phosphorus or an alpha-neighbouring heteroatom such as O or N. The ligand-centered reactions shall generate triplet radicals that possess different electron spin density distributions; the latter is addressed by the two main research lines A and B of this project. Additionally, N-O bond homolysis will be established as viable route in part B. The different reaction opportunities of such radicals shall be disclosed by varying the substitution pattern of the anionic complex precursors as well as by the nature of the employed oxidative SET reagents: organic oxidants may provide clean trapping opportunities, whereas inorganic oxidants may open entirely new pathways. The role of the metal complex fragment in the bonding of such radicals will be comparatively studied for related group 6-10 metal complexes in order to study and modulate the influence of the metal electron configuration on the spin density distribution. Intermediates will be investigated by cyclic voltammetry (collaboration with R. Boeré), EPR, NMR or IR spectroscopy at low temperatures, and theoretical support will deepen insights into the bonding (collaboration with A. Frontera and Z.-W. Qu). The long-term goal of this proposed research project is to identify fundamental aspects of interest for metal P-ligand cooperativity in redox reactions, but also help preparing for applications in radical catalysis.