Stabilized Palladium Nanoparticles Research Articles

ChemInform Abstract: Suzuki—Miyaura Cross‐Coupling of Arenediazonium Salts Catalyzed by Alginate/Gellan‐Stabilized Palladium Nanoparticles under Aerobic Conditions in Water.

ChemInform Abstract: Suzuki—Miyaura Cross‐Coupling of Arenediazonium Salts Catalyzed by Alginate/Gellan‐Stabilized Palladium Nanoparticles under Aerobic Conditions in Water.

REMOVED: Impact of UV Graft Polymerization on Stabilized Palladium Nanoparticles for Catalytic Reactions

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RETRACTED: Synthesis and characterization of chitosan and grape polyphenols stabilized palladium nanoparticles and their antibacterial activity

Based on enhanced effectiveness, the new age drugs are nanoparticles of polymers, metals or ceramics, which can combat conditions like cancer and fight human pathogens like bacteria. In this present study we aimed for a green approach to synthesize palladium nanoparticles by reducing palladium chloride salts with nontoxic and biodegradable polymeric chitosan and grape polyphenols and confirmed by FTIR, TEM, SEM and UV-spectroscopy. We also extended our study to show the efficacy of the grape and chitosan impregnated palladium nanoparticles as an antibacterial agent against Escherichia coli. Antibacterial assays were carried out with a representative gram-negative bacterium, E. coli and a gram-positive bacterium, Staphylococcus aureus. Commendable efforts have been made to explore this property using electron microscopy, which has revealed size dependent interaction of palladium nanoparticles conjugates with bacteria by disrupting cell membranes and the leakage of cytoplasm. Therefore, the observed results imply that grape and chitosan-based nano palladium conjugates prepared in our present system are promising candidates for a wide range of biomedical and general applications.

Synthesis of azamacrocycle stabilized palladium nanoparticles: Controlled size and one-dimensional growth

Palladium nanoparticles (PdNPs) of uniform size in the range of 3–5 nm are prepared in MeOH and MeCN:MeOH by solvent-assisted reduction of palladium acetate in presence of a hexaazamacrocyclic ligand, L1. For the mixed solvent system different ratio of the solvents was tried i.e., 1:1, 1:3 and 3:1. In all cases the concentration and ratio of Pd(II) to L1 was maintained at 2 mM:1 mM. In another experiment NPs were prepared in MeOH by lowering the concentration of L1 to 0.5 mM, where chain-like assemblies of PdNPs was observed. Importantly, the solutions are found to be stable at RT for months. Palladium nanoparticles of uniform size (3-5 nm range) are obtained by solvent-assisted reduction of 2mM palladium acetate in MeOH and MeCN: MeOH in presence of a hexaazamacrocyclic ligand. Chain-like arrangement of the nanoparticles was seen in MeOH medium by lowering the concentration of the ligand from 1 to 0.5 mM.

ChemInform Abstract: Conjugated Polymer Stabilized Palladium Nanoparticles as a Versatile Catalyst for Suzuki Cross‐Coupling Reactions for Both Aryl and Heteroaryl Bromide Systems.

AbstractThe preparation of a palladium‐polymer hydride material in which the metal nanoparticles are stabilized in a polymer matrix is described.

Amphiphilic ionic liquid stabilizing palladium nanoparticles for highly efficient catalytic hydrogenation

The highly water-soluble palladium nanoparticles (NPs) were synthesized by using the amphiphilic poly(ethylene glycol)-functionalized dicationic imidazolium-based ionic liquid (C(12)Im-PEG IL) as a stabilizing agent. The aqueous dispersed palladium NPs in the range of 1.9 ± 0.3 nm were observed by transmission electron microscopy (TEM). The physicochemical properties of C(12)Im-PEG IL in aqueous phase have been characterized by electrical conductivity, surface tension and dynamic light scattering (DLS) measurements. It was demonstrated that the amphiphilic ionic liquid can form micelles above its critical micelle concentration (CMC) in aqueous solution and the micelles played a crucial role in stabilizing the palladium NPs and thus promoted catalytic hydrogenation. Furthermore, the dicationic ionic liquid can also act as a gemini surfactant and generated emulsion between hydrophobic substrates and the catalytic aqueous phase during the reaction. The aqueous dispersed palladium NPs showed efficient activity for the catalytic hydrogenation of various substrates under very mild conditions and the stabilizing Pd(0) nanoparticles (NPs) can be reused at least eight times with complete conservation of activity.

Conjugated polymer stabilized palladium nanoparticles as a versatile catalyst for Suzuki cross-coupling reactions for both aryl and heteroaryl bromide systems

A simple and efficient procedure for Suzuki coupling of aryl bromides with phenylboronic acid, catalyzed by an in situ-generated palladium(0)–polymer composite in the absence of any phosphine ligand, has been reported. The catalyst is remarkably active having a high TOF value for both aryl and heteroaryl systems, and is recyclable up to three runs with minimum loss of efficiency.

Polyion complex stabilized palladium nanoparticles for Suzuki and Heck reaction in water

Palladium nanoparticles stabilized by a polyion complex composed of poly{4-chloromethylstyrene- co-(4-vinylbenzyl) tributylammonium chloride} and poly(acrylic acid) were easily recovered by filtration after pH treatment. The polyion complex stabilized palladium nanoparticles have high catalytic activity for the Suzuki and Heck reactions in water.

Direct Reductive Amination with Gum Acacia Stabilized Pd Nanoparticles

Gum acacia stabilized palladium nanoparticles (GA-Pd nanoparticles) were prepared and applied to a reductive amination reaction. The GA-Pd nanoparticles catalyzed the direct one-pot reductive amination of aldehydes 2 with nitroarenes 1 under atmospheric pressure of hydrogen to give the corresponding amines 3 in up to 96% yield (eq. 2, 18 examples).

Preparing water-dispersed palladium nanoparticles via polyelectrolyte nanoreactors

A counterion-induced polyelectrolyte collapse strategy has been developed for the preparation of poly(acrylic acid) stabilized palladium nanoparticles (NP-Pd-PAA). The structure and composition of the nanoparticles were investigated via transmission electron microscopy, dynamic light scattering, powder X-ray diffraction, and X-ray photoelectron spectroscopy. NP-Pd-PAA catalyzed fully aqueous Suzuki coupling reactions at loadings as low as 0.01 mol% Pd.

The functionalized poly(ethylene glycol) supported palladium nanoparticles as a highly efficient catalyst for aerobic oxidation of alcohols

The aerobic oxidation of various alcohols was studied with the stabilizing palladium nanoparticles as the catalyst under very mild conditions in poly(ethylene glycol) (PEG) media. The bidentate nitrogen ligand functionalized-PEG played an important role in stabilizing and immobilizing palladium nanoparticles. The stabilizing palladium nanoparticles were found to be highly active for the oxidation of benzyl alcohol. Finally, the scope and limitation of substrates have also been investigated for this novel catalytic system.

Air‐Stable and Highly Active Dendritic Phosphine Oxide‐ Stabilized Palladium Nanoparticles: Preparation, Characterization and Applications in the Carbon‐Carbon Bond Formation and Hydrogenation Reactions

AbstractDendrimer‐stabilized palladium nanoparticles were formed in the reduction of palldium bis(acetylacetonate) [Pd(acac)2] in the presence of phosphine dendrimer ligands using hydrogen in tetrahydrofuran. The resulting Pd nanoparticles were characterized by TEM, 31P NMR and 31P MAS NMR. The results indicated that the dendritic phosphine ligands were oxidized to phosphine oxides. These dendrimer‐stabilized Pd nanoparticles were demonstrated to be efficient catalysts for Suzuki and Stille coupling reactions and hydrogenations. The dendritic wedges served as a stabilizer for keeping the nanoparticles from aggregating, and as a vehicle for facilitating the separation and/or the recycling of the Pd catalyst. In the case of the Suzuki coupling reaction, these Pd nanoparticles exhibited high catalytic efficiency (TON up to 65,000) and air stability as compared with the commonly used homogeneous catalyst tetrakis(triphenylphosphine)palladium [Pd(PPh3)4]. In addition, the results obtained from the bulky dendritic substrate suggest that the Pd nanoparticles might act as reservoir of catalytically active species, and that the reaction is actually catalyzed by the soluble Pd(0) and/or Pd(II) species leached from the nanoparticle surface.

Sulphonated “Click” Dendrimer‐Stabilized Palladium Nanoparticles as Highly Efficient Catalysts for Olefin Hydrogenation and Suzuki Coupling Reactions Under Ambient Conditions in Aqueous Media

AbstractWater‐soluble 1,2,3‐triazolyl dendrimers were synthesized by “click chemistry” and used to stabilize palladium nanoparticles (PdNPs). These new “click” dendrimer‐stabilized nanoparticles (DSN) are highly stable to air and moisture and are catalytically active for olefin hydrogenation and Suzuki coupling reaction, in aqueous media, under ambient conditions using a low amount of palladium (0.01 mol% Pd). Kinetic studies show high catalytic efficiency and high stability for the new “click” DSN in both reactions. The complexation of potassium tetrachloropalladate (K2PdCl4) to the triazole ligands present in the dendritic structures was monitored by UV/vis and, after reduction, the nanoparticles were characterized by transmission electron microscopy (TEM).

Suzuki coupling reactions catalyzed by poly(N-ethyl-4-vinylpyridinium) bromide stabilized palladium nanoparticles in aqueous solution

In this work, it was investigated to use of poly(N-ethyl-4-vinylpyridinium) bromide stabilized palladium nanoparticles in the Suzuki reaction between phenylboronic acid and aryl halides in aqueous solution. The nanoparticles were isolated and re-used several times with low loss of activity.

PEG-stabilized palladium nanoparticles: An efficient and recyclable catalyst for the selective hydrogenation of 1,5-cyclooctadiene in thermoregulated PEG biphase system

Polyethylene glycol (PEG)-stabilized palladium nanoparticles were prepared and applied to the selective hydrogenation of 1,5-cyclooctadiene (1,5-COD) in thermoregulated PEG biphase system, which allows a reaction in a single-phase at a higher temperature followed by a phase split at a lower temperature. Under the optimized reaction conditions, the conversion of 1,5-COD and the selectivity of cyclooctene (COE) were 100 and 98%, respectively. The catalyst could be easily separated from the product by phase separation and reused for 6 times without evident loss in activity and selectivity.

Preparation and Characterization of 4-Dimethylaminopyridine-Stabilized Palladium Nanoparticles

4-Dimethylaminopyridine (DMAP)-stabilized palladium nanoparticles with a mean diameter of 3.4 +/- 0.5 nm are prepared from the aqueous phase reduction of Na2PdCl4 using NaBH4 in the presence of DMAP. TEM and UV-vis spectroscopy characterization of the nanoparticle dispersion shows no obvious change in the nanoparticles several months after preparation. 1H NMR spectroscopy of the nanoparticles shows that the nanoparticle dispersion also contains a boron/DMAP complex and two palladium/DMAP complexes. One of the palladium complexes crystallizes out of the dispersion and is identified as Pd(DMAP)4(OH)2 by X-ray crystallography. Following extensive analysis, it is believed that the palladium/DMAP complexes are formed following the oxidation of the palladium nanoparticles. The prepared nanoparticle dispersion promotes selective hydrogen/deuterium (H/D) exchange on the carbon atoms alpha to the endocyclic nitrogen atom on the DMAP-stabilizing ligands through reaction with D2O. This activity is attributed to the presence of the nanoparticles rather than to the presence of the oxidized palladium/DMAP complexes.

Phosphine Dendrimer Stabilized Palladium Nanoparticles: A Highly Active and Recyclable Catalyst for the Suzuki—Miyaura Reaction and Hydrogenation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Efficient Aerobic Oxidation of Alcohols Using a Recoverable Catalyst: The Role of Mesoporous Channels of SBA‐15 in Stabilizing Palladium Nanoparticles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Efficient Aerobic Oxidation of Alcohols Using a Recoverable Catalyst: The Role of Mesoporous Channels of SBA‐15 in Stabilizing Palladium Nanoparticles

Highly Efficient Aerobic Oxidation of Alcohols Using a Recoverable Catalyst: The Role of Mesoporous Channels of SBA‐15 in Stabilizing Palladium Nanoparticles

Highly Efficient Aerobic Oxidation of Alcohols Using a Recoverable Catalyst: The Role of Mesoporous Channels of SBA‐15 in Stabilizing Palladium Nanoparticles

Scaling down the activity: An efficient recyclable palladium-based catalyst has been developed for the aerobic oxidation of alcohols (see scheme). The combination of a substituted bipyridyl ligand and ordered mesoporous channels (in SBA) causes a synergistic effect that results in enhanced activity, the prevention of agglomeration of the palladium nanoparticles, and the generation of a durable catalyst.