Redox-Active Ligand-Mediated Radical Reactivity in the Coordination Sphere of Noble Metals

• Applicant: Professor Dr. Jarl Ivar van der Vlugt
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 515359302

Typically, metals dictate the activation and (catalytic) transformation of substrates, with supporting ligands merely tuning the reactivity of the metal center. Stoichiometric and catalytic conversions involving transient radicals have attracted much attention in the last decade. Mononuclear closed-shell metal complexes, common for the second and third row of the late d-block elements, are very well-suited to bind a wide variety of substrates. However, these metals are are not normally disposed to accommodate single-electron chemistry. Ligand-centered reactivity can alleviate this dichotomy. Redox-active ligands are organic frameworks that can undergo reversible shuttling between at least two well-defined redox-states. Notably, only a relatively small number of complexes featuring a redox-active ligand (radical) in the first coordination sphere of a group 9-11 metal are reported to date. Secondly, ligand-centered redox-activity to tune or induce reactivity and bond activation processes has been sparcely utilized to date. This DFG-project will address this knowledge gap by exploring the chemical space for single electron transfer between a redox-active ligand and a substrate in the coordination sphere of the late transition metals rhodium, palladium and gold. A library of well-defined mononuclear complexes will be synthesized and characterized and their coordination and redox chemistry examined. Building on preliminary data, the potential for ligand-to-substrate single-electron transfer (LtS SET) to induce radical-type chemistry with these closed-shell metal ions will be interrogated. Although the redox-chemistry is anticipated to be primarily ligand-centered, the intricate subtleties of the coordination chemistry and substrate pre-activation via binding to the specific metal ion being an integral aspect of the chemistry, are expected to affect and impact reactivity. Several questions concerning the potential and scope of this methodology for selective substrate activation and reactivity will be addressed in this proposal. These center around strategies to enable radical-type reactivity for chemoselective radical-type carbon-nitrogen bond formation via C(sp3)-H functionalization or hydrocarbon π-system activation. As such, these ligand-centered reactivity manifolds offer opportunities that go beyond the well-known organometallic chemistry of “redox-inert” metals and their current-day concepts to forge chemical bonds in a stochiometric or catalytic manner.

• DFG Programme: Research Grants