Ruthenium Single-Atom Anchored in Polyoxometalate-Ionic Liquids for N-Formylation of Amines with CO₂ and H₂

In this work, we have developed aRu single-atom substituted polyoxometalate-basedionic liquid ([TOMA(6)SiW(11)O(39)Ru(dmso)],TOMA = methyltrioctylammonium, named as Ru-POM-IL) and confirmed thatthe single-atom Ru is anchored into the framework of the POM. Thebinary ionic liquid (IL) system, composed of the POM-based IL and1-butyl-3-methyl-imidazolium acetate (BMImOAc), exhibits high efficiencyfor N-formylation of amines with CO2 and H-2,leading to formylamides with high yields in toluene-IL biphasic media.The characterization by laser confocal scanning microscopy revealsa specific sponge-like structure of the binary IL, facilitating theefficient contact between the catalytic active sites and the substratemolecules. Detailed investigations elucidate that the reaction proceedsvia a pathway with formate intermediates, including CO2 adsorption and activation by BMImOAc, morpholine-assisted heterolyticsplitting of H-2 into Ru-H & delta;- species and the H & delta;+ attachment to the morpholineN center; the coupling of CO2 with Ru-H & delta;- to afford formate species; and then the dehydration of the formateintermediates to formamides. The catalytic system exhibits offeredadvantages of high efficiency, robustness, and recyclability in theN-formylation reaction.