Enhancing stability by trapping palladium inside N-heterocyclic carbene-functionalized hypercrosslinked polymers for heterogeneous C-C bond formations

Abstract

Catalyst deactivation caused by the aggregation of active metal species in the reaction process poses great challenges for practical applications of supported metal catalysts in solid-liquid catalysis. Herein, we develop a hypercrosslinked polymer integrated with N-heterocyclic carbene (NHC) as bifunctional support to stabilize palladium in heterogeneous C-C bond formations. This polymer supported palladium catalyst exhibits excellent stability in the one-pot fluorocarbonylation of indoles to four kinds of valuable indole-derived carbonyl compounds in cascade or sequential manner, as well as the representative Suzuki-Miyaura coupling reaction. Investigations on stabilizing effect disclose that this catalyst displays a molecular fence effect in which the coordination of NHC sites and confinement of polymer skeleton contribute together to stabilize the active palladium species in the reaction process. This work provides new insight into the development of supported metal catalysts with high stability and will also boost their efficient applications in advanced synthesis.

Metal Catalysis with Knitting Aryl Polymers: Design, Catalytic Applications, and Future Trends

“…The most recently NCH based Pd knitting polymers reported were prepared by reaction of 1,3-bis(2,6-diisopropyl-4-(chloromethyl)phenyl)-4,5-dihydro-1H-imidazol-3-ium chloride with tetramethylbenzene (1), triphenylmethane (2), and tetraphenylmethane (3) following method-1 and subsequent treatment with PdCl 2 , which results in the networks named as KAP-Pd-PEPPSI 1−3. 46 The catalysts showed specific surface areas from moderate to low (227, 10, and 7 m 2 • g −1 , respectively) attributed to the hyper-cross-linking structure which results in the decrease in the number of intrinsic pores. Despite this, the three catalysts showed good activity in the fluorocarbonylation of indoles.…”

Grafting Hypercrosslinked Polymers on TiO2 Surface for Anchoring Ultrafine Pd Nanoparticles: Dramatically Enhanced Efficiency and Selectivity toward Photocatalytic Reduction of CO2 to CH4

“…Pd NPs still possessed well dispersion with increase of average particle size to 8.63 nm (Figure S23, Supporting Information), due to the migration and aggregation of ultrafine Pd NPs especially on the edge of composite. [14,48,49] It is noted that the aggregations have been suppressed by the stabilization effect of HN platform. [50,51] The photochemical, electrochemical, and photoelectrochemical properties of these samples were investigated by photoluminescence (PL) spectra, electrochemical impedance spectra (EIS), and transient photocurrent technique.…”

Construction of H6PW9V3O40@rht‐MOF‐1 for deep oxidative desulfurization of fuel oil

“…[16,17] However, developing the effective heterogeneous catalysts is of great challenge. [18,19] Polyoxometalates (POMs) are discrete soluble anionic metal oxide clusters of d-block transition metals in high oxidation states (usually W VI , Mo V,VI , V IV,V ). POMs can realize multistep reversible oxidation-reduction under mild conditions so that they can be used as solid acid catalysts and electron transfer catalysts to catalyze many organic reactions.…”

“…[ 16,17 ] However, developing the effective heterogeneous catalysts is of great challenge. [ 18,19 ]…”