Periodic Reporting for period 1 - DUO (Atomically Dispersed Heterobimetallic Catalysts for Cooperative C-H Bonds Activation)
Berichtszeitraum: 2022-11-01 bis 2025-04-30
The central objective of the DUO project is to develop novel, well-defined and highly dispersed heterobimetallic supported catalysts using a molecular approach. Its chemical foundation is to take advantage of both (1) metal-metal cooperative effects and (2) the advantages of site isolation at the surface of a solid support, with the aim of obtaining unprecedented highly reactive active sites. This strategy is designed to enable new bond activation pathways to tackle challenging catalytic transformations.
The project specifically targets early/late pair-site catalysts, ideally suited to promote heterolytic cleavage of strong C-H bonds. This unusual reactivity will be applied in two catalytic areas: (i) the isotopic labeling of organic substrates, such as active pharmaceutical ingredients, and (ii) the valorization of light alkanes under non-oxidative conditions. These catalytic objectives are not only scientifically demanding from a fundamental point of view, but also have significant industrial potential. To achieve these goals, an interdisciplinary approach is proposed, combining innovative molecular chemistry with advances in surface science and heterogeneous catalysis.
The project specifically targets early/late pair-site catalysts, ideally suited to promote heterolytic cleavage of strong C-H bonds. This unusual reactivity will be applied in two catalytic areas: (i) the isotopic labeling of organic substrates, such as active pharmaceutical ingredients, and (ii) the valorization of light alkanes under non-oxidative conditions. These catalytic objectives are not only scientifically demanding from a fundamental point of view, but also have significant industrial potential. To achieve these goals, an interdisciplinary approach is proposed, combining innovative molecular chemistry with advances in surface science and heterogeneous catalysis.
We have successfully developed innovative synthetic methodologies to prepare a library of available early/late heterobimetallic complexes, encompassing a diverse range of metals with over 25 metal-metal combinations achieved to date. These heterobimetallic complexes are specifically designed to serve as precursors for covalent grafting onto solid supports (typically mesoporous silica) using a Surface OrganoMetallic Chemistry (SOMC) approach. This method yields a family of heterobimetallic heterogeneous catalysts featuring atomically dispersed metal sites, with well defined low-coordinate structures not achievable in solution and featuring unique reactivity. The reactivity of these supported catalysts is then explored in Hydrogen Isotope Exchange (HIE) reactions with substrates of increasing difficulty.
We have for instance prepared hafnium-iridium surface species immobilized on silica, HfIr/SiO2. Unlike the monometallic analogous materials Hf/SiO2 and Ir/SiO2, which promote n-pentane deuterogenolysis through C−C bond scission, we have demonstrated that under the same experimental conditions (1 bar D2, 250 °C, 3 h, 0.5 mol %), the heterobimetallic catalyst HfIr/SiO2 is highly efficient and selective for the perdeuteration of alkanes with D2, exemplified on n-pentane, without substantial deuterogenolysis (<2 % at 95 % conversion). Furthermore this HfIr/SiO2 catalyst is robust and can be re-used several times without evidence of decomposition. This represents substantial advance in catalytic H/D isotope exchange (HIE) reactions of C(sp3)−H bonds enabling the late-stage labeling of organic molecules with ²H or ³H isotopes while preserving their carbon skeleton. This original selectivity is attributed to the original structure and reluctance to sintering of the HfIr surface sites. While Ir aggregates or nanoparticles promote deuterogenolysis, the well-defined dual-atom molecular species does not. Therefore, our catalyst synthesis methodology, which ensures highly dispersed and stable bimetallic sites, is crucial to achieving this result.