Palladium Nanoparticles In Water Research Articles

Highly Selective and Multigram Hydrogenation of Citral into Citronellal by Palladium Nanoparticles in Water

Highly Selective and Multigram Hydrogenation of Citral into Citronellal by Palladium Nanoparticles in Water

Effects of lipid bilayer encapsulation and lipid composition on the catalytic activity and colloidal stability of hydrophobic palladium nanoparticles in water.

This article shows the preparation of a lipid-nanoparticle assembly (LNA) which contains hydrophobic palladium nanoparticles (PdNPs) within the hydrophobic regions of the liposomal micelles. To understand the colloidal stability and catalytic activity of LNAs, the structure–property relationships of LNAs are investigated by manipulating the lipid composition and reaction temperature. The studies of LNAs using dynamic light scattering (DLS), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) show decreased colloidal stability with the incorporation of PdNPs compared to their counterpart 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes without PdNPs. LNAs with PdNPs catalyze the hydrogenation of 1-octene and its isomers to octane under one atm hydrogen gas and at room temperature within 24 h. The kinetic studies show that the isomerization of 1-octene to 2-octene occurs more favorably in the early stage of the reactions, which is followed by the subsequent hydrogenation of all octene isomers. The studies on temperature effects indicate that there is a significant increase in conversion yield of substrates when the reaction temperature increases from 22 to 37 °C, which correspond to room temperature and biological temperature, respectively. Phase transition of DSPC-PdNP LNAs from gel to liquid crystalline phase changing the fluidity of the bilayer is proposed to be the main reason for dramatic increases in the catalytic activity of the LNAs. It is also found that the rate of hydrogenation is dependent on the lipid composition of LNAs with the presence of cholesterol having a negative influence on the catalytic activity of LNAs while increasing their colloidal stability.

Selective Aerobic Oxidation of Benzyl Alcohols with Palladium(0) Nanoparticles Suspension in Water

This study concerns one of the rare applications of a suspension of palladium nanoparticles in water for oxidation reactions. The aqueous suspension containing well dispersed nanoparticles of 3.85 nm was obtained following a straightforward procedure involving the reduction of Na2PdCl4 with NaBH4 in the presence of PVP as stabilizing agent. In the way of oxidative catalytic valorisation of lignin, the aqueous suspension was directly applied as catalytic medium for the selective oxidation of vanillic alcohol into vanillin (80 °C, O2, 1 h) with more than 90% yield. Reusability of the catalytic medium has been demonstrated, acting as “quasi-homogeneous catalyst”. More sophisticated lignin-derived substrates like veratryl alcohol and hydrobenzoin gave yields of 50–80% to the respective aldehyde and ketone. In parallel, this as-synthesized suspension was directly used to prepare a Pd/TiO2 catalyst, the latter showing less efficiency for the catalytic transformations.

Selective Deprotection of Benzyl Carbamates on Micellar Nickel–Palladium Nanoparticles in Water

Key words palladium catalysis - nickel catalysis - micelles - deprotection - Cbz group

Tsuji–Trost Allylation with Palladium Nanoparticles in Water

Tsuji–Trost Allylation with Palladium Nanoparticles in Water

Influence of Graphene Oxide Supports on Solution-Phase Catalysis of Thiolate-Protected Palladium Nanoparticles in Water.

The influence of graphene oxide supports and thiolate surface ligands on the catalytic activity of colloidal Pd nanoparticles for alkyne hydrogenation in water is investigated. The studies show that unsupported, water-soluble thiolate-capped Pd nanoparticle catalysts favor the semi-hydrogenation over full-hydrogenation of dimethyl acetylene dicarboxylate (DMAD) under the atmospheric pressure and at room temperature. Pd nanoparticles supported on graphene oxide exhibit a similar activity for the hydrogenation of DMAD, but they show an improved long-term colloidal stability in aqueous solution after multiple catalytic cycles. After the heat treatment of Pd nanoparticles supported on graphene oxide at 300 °C, these heated hybrids exhibit an enhanced catalytic activity towards the full-hydrogenation. Overall, the studies suggest some influences of graphene oxide supports on the stability and thiolate surface ligands on the activity and selectivity of Pd nanoparticle catalysts.

ChemInform Abstract: Cross‐Coupling of Vinylethylene Carbonates with Arylboronic Acids Catalyzed by in situ Generated Palladium Nanoparticles in Water.

AbstractIt is found that Pd(OAc)2 is reduced to form Pd‐nanoparticles by homo‐coupling of phenylboronic acid.

Efficient Hydrogenation of Nitrogen Heterocycles Catalyzed by Carbon‐Metal Covalent Bonds‐Stabilized Palladium Nanoparticles: Synergistic Effects of Particle Size and Water

AbstractWe reveal here the first hydrogenation of nitrogen heterocycles catalyzed by carbon–metal covalent bonds‐stabilized palladium nanoparticles in water under mild conditions. Using a one‐phase reduction method, smaller metal–carbon covalent bond‐stabilized Pd nanoparticles were prepared with a size distribution of 2.5±0.5 nm, which showed extraordinary synergistic effects with water in the catalytic hydrogenation of nitrogen heterocycles. Water was supposed to accelerate substrate absorption and synergistic activation of molecular hydrogen on the Pd nanoparticles surface. The nanosized Pd catalyst could be easily recovered and reused for 5 runs.magnified image

Cross-coupling of vinylethylene carbonates with arylboronic acids catalyzed by in situ generated palladium nanoparticles in water

A practical and greener method of the cross-coupling of vinylethylene carbonates (VECs) with arylboronic acids has been described. The coupling reaction was catalyzed by in situ generated palladium nanoparticles (PdNPs) without any ligands and additional stabilizers in water under ambient conditions to provide useful 4-hydroxylprenylarenes and their derivatives in good to high yields.

Water soluble polymer–surfactant complexes-stabilized Pd(0) nanocatalysts: Characterization and structure–activity relationships in biphasic hydrogenation of alkenes and α,β-unsaturated ketones

A suitable approach to stabilize palladium nanoparticles in water as a green reaction medium for catalytic hydrogenation reactions is described. Supramolecular self-assemblies, obtained through the mixture of modified polyethyleneimines as amphiphilic polymers and water-soluble ammonium salts as surfactants, were used as efficient protective agents in the synthesis of Pd(0) nanospecies. The size and dispersion of the nanoparticles prepared with these original self-assemblies were characterized by TEM, SAXS and DLS techniques. The performances of the catalysts according to the polymer–surfactant mixtures were investigated in the hydrogenation of alkenes and α,β-unsaturated ketones in pure biphasic water/substrate medium, under mild conditions (room temperature and 1bar H2). The nanocatalysts showed efficient catalytic activities and selectivity towards CC bonds. From investigations, the polymer–surfactant complexes act as cooperative protective agents and a pertinent structure–activity relationship was proposed based on the zeta-potential values and the catalytic activity of the resulting colloids.

Palladium Nanoparticles in Water: A Reusable Catalytic System for the Cycloetherification or Benzannulation of α-Allenols

A convenient ligand-free catalytic system has been developed for the chemoselective cyclization reaction of various α-allenol derivatives by palladium nanoparticles (PdNPs) in an aqueous reaction medium.

L-Arginine-Triggered Self-Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water.

Pd@CeO2 core-shell nanostructures with a tunable Pd core size, shape, and nanostructure as well as a tunable CeO2 sheath thickness were obtained by a biomolecule-assisted method. The synthetic process is simple and green, as it involves only the heating of a mixture of Ce(NO3 )3 , l-arginine, and preformed Pd seeds in water without additives. Importantly, the synthesis is free of thiol groups and halide ions, thus providing a possible solution to the problem of secondary pollution by Pd nanoparticles in the sheath-coating process. The Pd/CeO2 nanostructures can be composited well with γ-Al2 O3 to create a heterogeneous catalyst. In subsequent tests of catalytic NO reduction by CO, Pd@CeO2 /Al2 O3 samples based on Pd cubes (6, 10, and 18 nm), Pd octahedra (6 nm), and Pd cuboctahedra (9 nm) as well as a simply loaded Pd cube (6 nm)-CeO2 /Al2 O3 sample were used as catalysts to investigate the effects of the Pd core size and shape and the hybrid nanostructure on the catalytic performance.

L‐Arginine‐Triggered Self‐Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water

AbstractPd@CeO2 core–shell nanostructures with a tunable Pd core size, shape, and nanostructure as well as a tunable CeO2 sheath thickness were obtained by a biomolecule‐assisted method. The synthetic process is simple and green, as it involves only the heating of a mixture of Ce(NO3)3, l‐arginine, and preformed Pd seeds in water without additives. Importantly, the synthesis is free of thiol groups and halide ions, thus providing a possible solution to the problem of secondary pollution by Pd nanoparticles in the sheath‐coating process. The Pd/CeO2 nanostructures can be composited well with γ‐Al2O3 to create a heterogeneous catalyst. In subsequent tests of catalytic NO reduction by CO, Pd@CeO2/Al2O3 samples based on Pd cubes (6, 10, and 18 nm), Pd octahedra (6 nm), and Pd cuboctahedra (9 nm) as well as a simply loaded Pd cube (6 nm)–CeO2/Al2O3 sample were used as catalysts to investigate the effects of the Pd core size and shape and the hybrid nanostructure on the catalytic performance.

ChemInform Abstract: Copper‐ and Phosphine‐Free Sonogashira Coupling Reaction Catalyzed by Silica‐(acac)‐Supported Palladium Nanoparticles in Water.

AbstractCatalyst can be recycled and reused up to 5 times without appreciable loss in its activity.

Dual functionalized task specific ionic liquid promoted in situ generation of palladium nanoparticles in water: synergic catalytic system for Suzuki–Miyaura cross coupling

A new task specific ionic liquid with hydroxyl and prolinate functionalities acts as a reducing agent and serves as a ligand and stabilizer for in situ formed palladium nanoparticles. This system displays high catalytic activity for Suzuki–Miyaura cross-coupling in water.

Copper‐ and phosphine‐free Sonogashira coupling reaction catalyzed by silica–(acac)‐supported palladium nanoparticles in water

A palladium‐based catalyst supported on acac‐functionalized silica was used as a heterogeneous catalyst for the Sonogashira cross‐coupling reaction of various aryl halides and phenylacetylene under copper‐ and phosphine‐free conditions. This catalytic system serves as an efficient and stable catalyst for this cross‐coupling reaction and allows easy separation and recycling of the catalyst. The catalyst could be recycled for five runs without appreciable loss of its catalytic activity. In addition, the reaction was carried out in water as a green solvent. Copyright © 2014 John Wiley & Sons, Ltd.

ChemInform Abstract: Stereospecific Allyl—Aryl Coupling Catalyzed by in situ Generated Palladium Nanoparticles in Water under Ambient Conditions.

AbstractThe cross‐coupling of secondary allylic carbonates (I) and (IV) with arylboronic acids catalyzed by in situ generated Pd‐nanoparticles without any ligands and additional stabilizers is described.

Synthesis of phenanthridine and its analogues via aerobic ligand-free domino Suzuki coupling–Michael addition reaction catalyzed by in situ generated palladium-nanoparticles in water

Abstract A convenient methodology has been developed towards the synthesis of substituted phenanthridines and analogous benzo[ k ] and benzo[ i ] derivatives via aerobic ligand-free domino Suzuki coupling–Michael addition reaction in the presence of Pd(OAc) 2 and K 3 PO 4 as a catalytic system in H 2 O at 90 °C in good yields. Reaction was believed to be catalyzed by in situ generated palladium nanoparticles in water with the elimination of acetone.

ChemInform Abstract: Aerobic Ligand‐Free Domino Suzuki Coupling—Michael Addition Reaction Catalyzed by in situ Generated Palladium Nanoparticles in Water: A General Method for the Synthesis of Benzo[c]chromene Derivatives.

Abstract A general method has been developed for the synthesis of benzo[ c ]chromene derivatives via aerobic ligand-free domino Suzuki coupling and Michael addition reaction catalyzed by in situ generated palladium nanoparticles in water leading to C–C and C–O bond formations simultaneously.

Stereospecific Allyl–Aryl Coupling Catalyzed byin situGenerated Palladium Nanoparticles in Water under Ambient Conditions

AbstractA practical process for the stereospecific cross‐coupling of secondary allylic carbonates with arylboronic acids has been developed. The reaction is catalyzed byin situgenerated palladium nanoparticles (PdNPs) without any ligands and additional stabilizers in water under ambient conditions and furnishes the allyl–aryl coupling products in high isolated yields with high stereospecificities as well as excellent chemo‐, regio‐ andE/Z‐selectivities. Thein situgenerated PdNPs showed extraordinary catalytic activity (S/C up to 5000) even for the allyl–aryl coupling reactions of easily eliminated allylic carbonates under aqueous ambient conditions. The mechanism of the process has also been investigated.