Heterogenization of a Molecular Ni Catalyst within a Porous Macroligand for the Direct C-H Arylation of Heteroarenes

International audienceDirect C–H functionalization catalyzed by a robust and recyclable heterogeneous catalyst is highly desirable for sustainable fine chemical synthesis. Bipyridine units covalently incorporated into the backbone of a porous organic polymer were used as a porous macroligand for the heterogenization of a molecular nickel catalyst. A controlled nickel loading within the porous macroligand is achieved, and the nickel coordination to the bipyridine (bpy) sites is assessed at the molecular level using IR and solid-state NMR spectroscopy. The heterogenized Ni-bpy catalyst was successfully applied to the direct and fully selective C2 arylation of benzothiophenes, thiophene, and selenophene, as well as for the arylation of free NH-indole. Recyclability of the catalyst was achieved by employing hydride activators to reach a cumulative turnover number of more than 300 after seven cycles of catalysis, which corresponds to a total productivity of 12 g of 2-phenylbenzothiophene, chosen as model target biaryl, per gram of catalyst

Unravelling the molecular structure and confinement of an or-ganometallic catalyst heterogenized within amorphous porous polymers

The catalytic activity of multifunctional microporous materials is directly linked to the spatial arrangement of their struc-tural building blocks. Despite great achievements in the design and use of isolated catalytic sites within such materials, the precise determination of their atomic-level structure and their local environment still remains a fundamental chal-lenge, especially when they are hosted in non-crystalline solids. Here, we show that by combining NMR measurements with pair distribution function (PDF) analysis and computational chemistry, a very accurate picture of the organometallic Cp*Rh catalytic sites inside the cavity of porous organic polymers can be determined. Two microporous supports based on bipyridine and biphenyl motifs functionalized with NH2 or NO2 groups were considered. Making use of differential PDF, Dynamic Nuclear Polarization (DNP) enhanced solid-state NMR spectroscopy on 15N labelled–NH2 and –NO2 materi-als, and 129Xe NMR, the detailed structure of the heterogenized organometallic complex and its confinement within the amorphous porous organic polymers is revealed with a precision of 0.1 Å, fully matched by the computed models. While the same well-defined molecular structure is observed for the organometallic catalyst independently of the functionalisa-tion of the porous organic polymer, subtle changes are detected in the average ligand-pore wall distance and interactions in the two materials

Unravelling the Molecular Structure and Confining Environment of an Organometallic Catalyst Heterogenized within Amorphous Porous Polymers.

The catalytic activity of multifunctional, microporous materials is directly linked to the spatial arrangement of their structural building blocks. Despite great achievements in the design and incorporation of isolated catalytically active metal complexes within such materials, a detailed understanding of their atomic-level structure and the local environment of the active species remains a fundamental challenge, especially when these latter are hosted in non-crystalline organic polymers. Here, we show that by combining computational chemistry with pair distribution function analysis, 129 Xe NMR, and Dynamic Nuclear Polarization enhanced NMR spectroscopy, a very accurate description of the molecular structure and confining surroundings of a catalytically active Rh-based organometallic complex incorporated inside the cavity of amorphous bipyridine-based porous polymers is obtained. Small, but significant, differences in the structural properties of the polymers are highlighted depending on their backbone motifs

Unravelling the Molecular Structure and Confining Environment of an Organometallic Catalyst Heterogenized within Amorphous Porous Polymers

The catalytic activity of multifunctional, microporous materials is directly linked to the spatial arrangement of their structural building blocks. Despite great achievements in the design and incorporation of isolated catalytically active metal complexes within such materials, a detailed understanding of their atomic‐level structure and the local environment of the active species remains a fundamental challenge, especially when these latter are hosted in non‐crystalline organic polymers. Here, we show that by combining computational chemistry with pair distribution function analysis, 129Xe NMR and Dynamic Nuclear Polarization enhanced NMR spectroscopy, a very accurate description of the molecular structure and confining surroundings of a catalytically active Rh‐based organometallic complex incorporated inside the cavity of amorphous bipyridine‐based porous polymers is obtained. Small but significant differences in the structural properties of the polymers are highlighted depending on their backbone motifs.</jats:p