One-, Two- and Multi-Electron Transformations from Titanium(IV): Controlling Reductive Elimination for Small Molecule Valorization

• Applicant: Professorin Dr. Gabriele Hierlmeier
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570277833

The development of new strategies in organometallic chemistry depends critically on a deep understanding of the elementary steps that govern catalytic processes. Among these, reductive elimination from titanium(IV) remains strikingly underexplored, both mechanistically and synthetically. This is largely due to the inherent instability of titanium in low oxidation states, which has limited studies on reductive elimination pathways, particularly those proceeding via concerted mechanisms, which remain virtually unknown. This project aims to fill this gap by developing fundamental insights and practical methods to control reductive elimination reactions from pincer-supported Ti(IV) complexes, ultimately enabling the transformation of simple, abundant molecules into value-added products. The key strategy of this proposal centers on exploring how external stimuli such as light, heat, oxidants, or coordinating ligands, facilitate one- or two-electron reductive elimination processes. By dissecting these stimuli-responsive transformations, the project will establish a set of rules on concerted versus radical elimination pathways and will uncover general principles that can be applied across different catalytic systems. In parallel, novel routes towards Ti(II) and Ti(III) synthons will be developed, unlocking new strategies in small molecule activation. Building on early successes in visible-light-induced ligand-to-metal-charge-transfer (LMCT) catalysis, the conversion of simple hydrocarbons such as alkynes, alkenes and alkanes into structurally more complex products will be studied. Specifically, the mechanism of a recently discovered method for catalytic cyclodimerization of internal alkynes will be investigated and optimized based on mechanistic insights. Additionally, LMCT-catalysis for alkane functionalization using visible light titanium catalysis will be explored. Further investigations will focus on the development of titanium-catalyzed cross-coupling using two complementary concepts. First, a ±1-electron redox cycle leveraging recently established homolytic substitution reactivity will be leveraged. Second, a dual catalytic system merging photocatalysis with oxidatively induced reductive elimination at Ti(IV) will be exploited for cross couplings. Lastly, multi-electron strategies starting from Ti(IV) will be developed by combining ‘masked’ Ti(II) complexes and metal-ligand cooperativity. These investigations will be complemented by atom- and group-transfer reactions for the valorization of activated fragments. Overall, the project builds on strong preliminary results from the group and will introduce novel mechanistic insights on the very challenging and central bond-forming step in titanium chemistry, i.e. reductive elimination. These insights will be leveraged for both homogeneous catalysis and small molecule activation, ultimately leading to novel approaches for the conversion of abundant small molecules into value-added products.

• DFG Programme: Emmy Noether Independent Junior Research Groups
• International Connection: United Kingdom
• Major Instrumentation: Glovebox
• Instrumentation Group: 4670 Handschuhkästen, Schutzgasanlagen
• Cooperation Partner: Dr. Daniel J. Scott