Resin loaded palladium nanoparticle catalyst, characterization and application in –C–C– coupling reaction (original) (raw)
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ChemCatChem, 2016
Macroporous ion exchange resin-supported palladium nanoparticles (Pd-NPs) catalysts are prepared via an intermatrix synthesis. For the first time, the effect of resin functionality (weak acid, strong acid, strong base) on the NP size, their catalytic activity and leaching is investigated in Suzuki cross-coupling of iodobenzene and phenylboronic acid. While the smallest NPs (1.34 nm) are found in the thiol Ambersep GT74 resin, the sulfonic acid Lewatit K2629 and quaternary amine Lewatit MP500 OH resins resulted in NPs of a similar size (2.42 and 2.59 nm respectively). Despite their smaller size, the NPs on Ambersep GT74 exhibited the lowest conversion (21.6%) which is attributed to a too strong coordination of the NPs by the thiol groups. The conversions obtained using Lewatit K2629 (76.8 %) and Lewatit MP500 OH (94.2%) were considerably higher, the excellent performance of the latter catalyst being ascribed to the promoting effect of the hydroxyl groups on the transmetallation and reductive elimination steps in Suzuki cross-coupling. No Pd leaching was observed when using Ambersep GT74 as support, compared to Pd leaching amounting to 1.1% and 4.8% when using Lewatit MP500 OH and Lewatit K2629 respectively. Such low values indicate that ion exchange resins are ideal supports to stabilize the NPs. Particularly the combination of high conversion and limited leaching on Lewatit MP500 OH opens up perspectives for catalyzing the Suzuki cross coupling with a heterogeneous catalyst.
Tetrahedron Letters, 2011
Solid-supported nano and microparticles of Pd(0) (SS-Pd) were prepared and used as heterogeneous catalysts for Suzuki-Miyaura cross coupling reactions of aryl halides (chloro, bromo and iodo) and phenyl boronic acid under mild and ligand-free conditions. Scanning electron microscope (SEM) and UV-vis based studies were performed to observe the distribution of nano and microparticles of palladium over solid surface and their oxidation states. In addition, the catalyst could be reused up to seven runs without significant loss of activity and stable enough under moist conditions. Ó 2011 Elsevier Ltd. All rights reserved.
Palladium (Pd) nanoparticles were synthesized using the dendrimer-template method and then immobilized on a silica support (SBA-15). The SBA-15 support material was specifically synthesized with a pore size large enough (d = 6.6 nm) to accommodate the dendrimer generation used (G-5 PAMAM-OH; d = 5.4 nm). The morphology of the Pd-supported catalyst (Pd 0 /SBA-15) was characterized by scanning electron microscopy coupled to an energy dispersive X-ray spectrometer which confirmed the elemental composition of the catalyst. Transmission electron microscopy confirmed the ordered array of the mesoporous SBA-15 and showed that the Pd NPs were indeed immobilized inside the pores. The catalyst had a pore size of 5.7 nm, a pore volume of 0.78 cm 3 /g and a surface area of 493 m 2 /g as determined by surface ad-sorption/desorption measurements from BET analysis. The prepared Pd 0 /SBA-15 catalyst was an efficient recyclable heterogeneous catalyst for Suzuki coupling. The catalytic activity was investigated using different experimental conditions such as temperature, catalyst loading, base and solvent variations. The catalyst gave high conversions and turnover frequencies even in aqueous solutions and at fairly low temperatures showing the potential for the green synthesis of important organic molecules through C–C bond formation.
Polymer-coated palladium nanoparticle catalysts for Suzuki coupling reactions
Journal of Colloid and Interface Science
A set of seven different palladium nanoparticle (PdNP) systems stabilized by small amounts (1.0 mg/mL) of structurally related macromolecular capping agents were comparatively tested as catalyst in p-nitrophenol (Nip) reduction and Suzuki cross-coupling reactions. The observed rate constants (kobs) for Nip reduction were in the range of 0.052–3.120 × 10−2 s−1, and the variation reflected the effects of polymer chain conformation, ionic strength and palladium–polymer complex coordination. Macromolecules featuring pendant pyridyl moieties or inverse temperature-dependent solubility were found to be unsuitable capping agents for PdNPs catalysts, despite being active. The catalytic activity in Suzuki cross-coupling reactions followed the same behavior; the most active particles in the Nip reaction also mediated the cross-coupling reaction providing the expected products in quantitative yields under relatively mild conditions after only 4 h at 50 °C. Experiments involving the successive ...
Chemical Engineering Journal, 2019
The Pd leaching behaviour of a strongly acid (Lewatit K2629) versus strongly basic (Lewatit MP500 OH) ion exchange resin supported Pd nanoparticle (Pd-NP) catalyst is elucidated in the Suzuki reaction between iodobenzene and phenylboronic acid with K 2 CO 3 as base in 1:1 (v/v) DMF/H 2 O at 40°C. Reaction and leaching kinetic analyses combined with hot filtration tests indicated heterogeneoushomogeneous catalysis for both Pd-NP catalysts. More particularly, leaching experiments showed that for Pd-NP Lewatit K2629, Pd-NP as well as molecular Pd 2+ leaching (as phenylpalladium(II)hydroxide complexes) occurred due to, respectively, the disturbance of the electrostatic NP stabilization by dissociated K 2 CO 3 and reaction with iodobenzene and hydroxide. For Pd-NP Lewatit MP500 OH, however, molecular Pd 2+ leaching induced by iodobenzene, dominates. Hence, the resin functionality determines the contribution of each leaching pathway. Furthermore, at high conversions, Pd redeposition occurred due to the decreased amount of leaching inducing reagents causing enlarged NPs in the resin which leached less in subsequent runs.
Journal of Organometallic Chemistry, 2013
A new catalytic system of bisphosphinite PCP-pincer palladium complex based on Merrifield resin was synthesized and characterized. The presence of highly active form of Pd (0) was proved by XRD and XPS techniques. Transmission electron microscopy (TEM) image of the catalyst showed that palladium particles are well-dispersed through the support in the range of 30e50 nm. This catalytic system exhibited excellent catalytic activity in MizorokieHeck, SuzukieMiyaura and SonogashiraeHagihara crosscoupling reactions with different aryl halides including inactive aryl chlorides. Short reaction times and good to excellent yields of the desired products express the effectiveness of this catalyst. The catalyst was successfully re-used up to 10 runs without appreciable change in its activity with high TON. Hot filtration test showed low leaching of the metal into solution from the supported catalyst which confirmed the full heterogeneous character of the catalytically active species.
Journal of Membrane Science, 2015
The elaboration of a polymeric catalytic membrane containing palladium nanoparticles is presented. The membrane was prepared using a photo-grafting process with imidazolium-based ionic liquid monomers as modifying agent and microPES s as support membrane. Ionic liquid serves as a stabilizer and immobilizer for the catalytic species, i.e. palladium nanoparticles. The Suzuki-Miyaura cross-coupling reaction was carried out on the catalytic membrane in flow-through configuration. Complete conversion was achieved in 10 s through one single filtration, without formation of byproducts. The apparent reaction rate constant was three orders of magnitude greater than in a batch reactor. No catalyst leaching was detected. This membrane offers the possibility of continuous production with no need for a separation step of the catalyst from the reaction medium.
Catalysts
Palladium nanoparticles (Pd NPs) synthesized by the metal vapor synthesis technique were supported on poly(4-vinylpyridine) 2% cross-linked with divinylbenzene (Pd/PVPy). Transmission electron microscopy revealed the presence of small metal nanoparticles (dm = 2.9 nm) highly dispersed on the PVPy. The Pd/PVPy system showed high catalytic efficiency in Suzuki-Miyaura carbon–carbon coupling reactions of both non-activated and deactivated aromatic iodides and bromides with aryl boronic acids, carried out under an air atmosphere. The high turnover of the catalyst and the ability of the PVPy resin to retain active Pd species are highlighted. By comparing the catalytic performances of Pd/PVPy with those observed by using commercially available Pd-based supported catalysts, the reported system showed higher selectivity and lower Pd leaching.
Nanoscale advances, 2024
A novel ligand-free heterogeneous catalyst was synthesized via pyrolysis of Samanea saman pods to produce carbon nanospheres (SS-CNSs), which served as a carbon support for immobilizing palladium nanoparticles through an in situ reduction technique (Pd/SS-CNS). The SS-CNSs effectively integrated 3% of Pd on their surfaces with no additional activation procedures needed. The nanomaterials obtained underwent thorough characterization employing various techniques such as FT-IR, XRD, FE-SEM, TEM, EDS, ICP-AES, and BET. Subsequently, the efficiency of this Pd/SS-CNS catalyst was assessed for the synthesis of biaryl derivatives via Suzuki coupling, wherein different boronic acids were coupled with various aryl halides using an environmentally benign solvent mixture of EtOH/H 2 O and employing only 0.1 mol% of Pd/SS-CNS. The catalytic system was conveniently recovered through centrifugation and demonstrated reusability without any noticeable decline in catalytic activity. This approach offers economic viability, ecological compatibility, scalability, and has the potential to serve as an alternative to homogeneous catalysis.