Efficient Palladium Catalyst Research Articles

Construction of Multiphase Concave Tetrahedral PdInMo Nanocatalyst for Enhanced Alcohol Oxidation

AbstractHeterogeneous palladium‐based catalysts show excellent catalytic properties for electrocatalytic oxidation of alcohols, but the construction of such heterogeneous catalysts is a challenge. Here, a multiphase tetrahedral PdInMo nanocatalyst is prepared by a one‐pot reaction method. And the multiphase tetrahedral PdInMo nanocatalyst consists of a face‐centered cubic structure and an intermetallic structure. Due to the oxygen affinity of indium and molybdenum atoms, the interface defects of internal multiphase structure, and intermetallic structure, the multiphase concave tetrahedral PdInMo nanocatalyst shows enhanced catalytic efficiency in the electrocatalytic oxidation reaction of methanol and ethanol. Compared with commercial Pd/C catalysts, PdIn0.117Mo0.037 nanocatalyst has the best mass activity and specific activity. In electrocatalysis of methanol oxidation, the mass activity (2205.57 mA mgPd−1) and specific activity (6.67 mA cm−2) are 4.81 and 3.40 times than that of a commercial Pd/C nanocatalyst (458.5 mA mgPd−1, 1.96 mA cm−2), respectively. In the electrocatalysis of ethanol oxidation, the mass activity (2668.49 mA mgPd−1) and specific activity (8.11 mA cm−2) are 4.06 and 3.14 times than that of the commercial Pd/C nanocatalyst (655.83 mA mgPd−1, 2.58 mA cm−2), respectively. This study provides a reference for the design of highly efficient palladium catalysts for alcohol oxidation.

Efficient palladium ion adsorption and catalyst preparation from pharmaceutical wastewater using amino-functionalized Ti3C2

This paper reports the recovery and reuse of Pd ions from pharmaceutical wastewater using amino-modified Ti3C2. Ti3C2–NH2 was synthesized by modifying (3-aminopropyl)triethoxysilane and the successful substitution of some surface functional groups of Ti3C2; the decrease in material thickness was verified by characterization. This study revealed that the presence of amino groups significantly enhanced the Pd(II) adsorption capacity of Ti3C2. The effects of the adsorbent material, adsorbent dosage, pH, initial concentration of Pd ions, presence of competing cations, and contact time on the adsorption performance were investigated. The maximum adsorption capacity of 20 mg of Ti3C2–NH2 was 986.65 mg/g in 100 ml of a Pd-ion solution with an initial concentration of 200 mg/l at pH 3. A pseudo-second-order kinetic model fitted well with the experimentally obtained rate data, indicating that the main mode of Pd-ion removal by Ti3C2–NH2 was via chemical reduction. Finally, the catalyst exhibited excellent performances during the photocatalytic and Suzuki coupling reactions with yields of 81 % and 95 %, respectively. The results demonstrated that Ti3C2–NH2 is an excellent material for adsorbing Pd ions and can effectively recycle these ions from pharmaceutical wastewater.

Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment

AbstractThis review summarizes the research progress of palladium (Pd) catalysts in electrocatalytic hydrodechlorination (ECH) for the removal of chlorinated organic pollutants (COPs). ECH technology is a new type of green water treatment technology without secondary pollution, which has excellent removal effect on COPs. Pd is widely used in the field of ECH due to its excellent catalytic properties. However, the easy deactivation and high price of Pd have limited the application of Pd catalysts in practical wastewater treatment. Researchers have improved the performance of Pd catalysts for ECH by improving the morphological structure (dispersion, particle size, crystalline surface) and electronic states (electron‐rich Pd, electron‐deficient Pd). It is also found that modulation of the adsorption abilities of Pd catalysts can greatly improve the catalytic activity. The factors affecting the stability of Pd catalysts are also investigated, and the future large‐scale mature application of ECH technology is envisioned. The ability to prepare single‐atom Pd catalysts in a relatively simple way is a future direction, which will achieve 100 % atom utilization and thus significantly reduce the cost of Pd. This review details the frontier research on Pd catalysts in the field of ECH, which can provide some good strategies for related researchers.

Palladium-catalyzed Heck reactions promoted by limonene-derived bicyclic phosphines

Tertiary bicyclic phosphines derived from (R)-(+)-limonene provided efficient palladium catalysts for Heck cross-coupling reactions. Overall, high yields of the desired aryl alkenes products were obtained for cross-coupling of sterically and electronically diverse substrates. The efficiency of the catalysts was further demonstrated in the synthesis of commercial ketones, such as raspberry ketone and its derivatives.

Visible light-driven efficient palladium catalyst turnover in oxidative transformations within confined frameworks

Palladium catalyst turnover by reoxidation of a low-valent Pd species dominates the proceeding of an efficient oxidative transformation, but the state-of-the-art catalysis approaches still have great challenges from the perspectives of high efficiency, atom-economy and environmental-friendliness. Herein, we report a new strategy for addressing Pd reoxidation problem by the fabrication of spatially proximate IrIII photocatalyst and PdII catalyst into metal-organic framework (MOF), affording MOFs based Pd/photoredox catalysts UiO-67-Ir-PdX2 (X = OAc, TFA), which are systematically evaluated using three representative Pd-catalyzed oxidation reactions. Owing to the stabilization of single-site Pd and Ir catalysts by MOFs framework as well as the proximity of them favoring fast electron transfer, UiO-67-Ir-PdX2, under visible light, exhibits up to 25 times of Pd catalyst turnover number than the existing catalysis systems. Mechanism investigations theoretically corroborate the capability of MOFs based Pd/photoredox catalysis to regulate the competitive processes of Pd0 aggregation and reoxidation in Pd-catalyzed oxidation reactions.

Sol-Gel Synthesis of Organically Modified Silica Particles as Efficient Palladium Catalyst Supports to Perform Hydrogenation Process

Modern approaches to the production of new materials require the improvement of synthesis techniques towards simplifying the processes of their preparation and reducing the number of stages. Thus, in this study, one-stage synthesis of organomodified silica materials is developed using a special surfactant—dodecyldimethylamin N-oxide (DDAO). The peculiarity of this approach is that there is no need for heat treatment of the material, since DDAO is removed by washing in alcohol. Amino-, mercapto-, methyl-, and phenyl-modified silicas were synthesized using this method. The SEM images showed the morphology of all the obtained materials is close, all particles are spherical, and the diameter of individual particles is about 500 nm. Palladium particles were precipitated on these supports, then the experiments were carried out to study the catalytic activity of these materials in a model reaction of nitroaniline reduction. The phenyl modified matrix-based materials showed very low activity. This is due to the fact that the support and the substrate contain aromatic fragments, thus, hydrophobic interactions arise between them, which complicates the diffusion of the products. The leader is a matrix with an amino fragment, which is associated with its electron-donor effect. The XPS method revealed the amount of fixed palladium, as well as the binding energy shifts, which are 0.68 eV for 5% Pd/SiO2–C6H5; 0.56 eV for 5% Pd/SiO2–C3H6–NH2; 0.26 eV for 5% Pd/SiO2–CH3; and 0.13 eV for 5% Pd/SiO2.

A highly controllable, effective, and recyclable magnetic-nanoparticle-supported palladium catalyst for the Suzuki–Miyaura cross-coupling reaction

In this work, a highly efficient palladium catalyst was facilely immobilized on the surfaces of magnetic nanoparticles with the coordination of N-heterocyclic carbene. The prepared Pd–NHC@NCPs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectrometry. With suitably designed emulsion polymerization and immobilization, the final palladium loading could reach 0.78 mmol/g. The catalyst showed outstanding catalytic performance in the Suzuki–Miyaura cross-coupling reaction among various substrates, with little catalyst usage (0.03 mol.%), short reaction time, and mild reaction conditions. In addition, the catalyst could be separated conveniently from the reacting system with an external magnet and show good catalytic performance even after being reused five times or more, indicating good recyclability.

Evaluation of P-bridged biaryl phosphine ligands in palladium-catalysed Suzuki–Miyaura cross-coupling reactions

A family of biaryl phosphacyclic ligands derived from phobane and phosphatrioxa-adamantane frameworks is described. The rigid biaryl phosphacycles are efficient for Suzuki–Miyaura cross-coupling of aryl bromides and chlorides. In particular, coupling reactions of the challenging sterically hindered and heterocyclic substrates were viable at room temperature.

Anchored Pd(0) Nanoparticles on Synthetic Talc for the Synthesis of Biaryls and a Precursor of Angiotensin II Inhibitors

AbstractThe palladium-catalyzed Suzuki–Miyaura cross-coupling reaction is one of the most important and efficient reactions to prepare a variety of organic compounds, including biaryls. Despite the overwhelming number of reports related to this topic, some methodological difficulties persist in terms of catalyst handling, recovery, and reuse, as well as the reaction media. This work reports the rational design of new, efficient, cost-effective, and reusable palladium catalysts supported on synthetic talc for the Suzuki–Miyaura reaction. From the results, key points were identified: both designed catalysts accelerated the reaction in EtOH and an open-flask setup, affording moderate to excellent yields within a short time (e.g., 30 min) even for deactivated aryl halides; the protocol can be applied to a great number of both cross-coupling partners, showing an excellent functional group tolerance; the catalysts can be recovered and reused without significant loss of activity. This protocol was used for the synthesis of a precursor of angiotensin II inhibitors such as valsartan, losartan, irbesartan, and telmisartan.

Fe3O4‐SAHPG‐Pd0 nanoparticles: A ligand‐free and low Pd loading quasiheterogeneous catalyst active for mild Suzuki–Miyaura coupling and CH activation of pyrimidine cores

This paper reports a green magnetic quasiheterogeneous efficient palladium catalyst in which Pd0 nanoparticles have been immobilized in self‐assembled hyperbranched polyglycidole (SAHPG)‐coated magnetic Fe3O4 nanoparticles (Fe3O4‐SAHPG‐Pd0). This catalyst has been used for effective ligandless Pd catalyzed Suzuki–Miyaura coupling reactions of different aryl halides with substituted boronic acids at room temperature and in aqueous media. Herein, SAHPG is used as support; it also acts as a reducing agent and stabilizer to promote the transformation of PdII to Pd0 nanoparticles. Also, this environmental friendly quasiheterogeneous catalyst is employed for the first time in the synthesis of new pyrimido[4,5‐b]indoles via oxidative addition/CH activation reactions on the pyrimidine rings, which were obtained with higher yield and faster than when Pd(OAc)2 was used as the catalyst. Interestingly, the above‐mentioned catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled several times with no significant decrease in the catalytic activity.

Quantifying Electrocatalytic Reduction of CO2 on Twin Boundaries

Summary A protocol relying on the use of silver nanostructures with well-defined dimensions and morphologies (e.g., nanocubes and nanowires) has been developed to differentiate and quantitatively determine the atom-specific activities of different surface atoms toward catalyzing electrochemical CO2 reduction reaction (CO2RR). The atom-specific activity of the twin-boundary edges (TBEs) is comparable to (or slightly higher than) that of the single-crystal edges (SCEs) formed from the crossing of two {100} surfaces, and it is on the order of ∼16 attoampere/atom (aA/atom) toward electrochemical CO2RR. This value is more than two orders higher than the atom-specific activity of the {100} surface atoms, i.e., ∼0.1 aA/atom. The high catalytic activity of the TBEs, which represent a class of commonly existing surface defects in stable metal nanostructures with face-centered cubic lattices, is consistent with the DFT calculations, in which the bridge-type binding configuration of COOH∗ at the TBEs stabilizes this intermediate to promote overall CO2RR.

Discovery, Synthesis, and Scale-up of Efficient Palladium Catalysts Useful for the Modification of Nucleosides and Heteroarenes.

Nucleic acid derivatives are imperative biomolecules and are involved in life governing processes. The chemical modification of nucleic acid is a fascinating area for researchers due to the potential activity exhibited as antiviral and antitumor agents. In addition, these molecules are also of interest toward conducting useful biochemical, pharmaceutical, and mutagenic study. For accessing such synthetically useful structures and features, transition-metal catalyzed processes have been proven over the years to be an excellent tool for carrying out the various transformations with ease and under mild reaction conditions. Amidst various transition-metal catalyzed processes available for nucleoside modification, Pd-catalyzed cross-coupling reactions have proven to be perhaps the most efficient, successful, and broadly applicable reactions in both academia and industry. Pd-catalyzed C–C and C–heteroatom bond forming reactions have been widely used for the modification of the heterocyclic moiety in the nucleosides, although a single catalyst system that could address all the different requirements for nucleoside modifications isvery rare or non-existent. With this in mind, we present herein a review showcasing the recent developments and improvements from our research groups toward the development of Pd-catalyzed strategies including drug synthesis using a single efficient catalyst system for the modification of nucleosides and other heterocycles. The review also highlights the improvement in conditions or the yield of various bio-active nucleosides or commercial drugs possessing the nucleoside structural core. Scale ups wherever performed (up to 100 g) of molecules of commercial importance have also been disclosed.

Development of efficient palladium catalysts for alkoxycarbonylation of alkenes.

Herein, we report a general and efficient Pd-catalysed alkoxycarbonylation of sterically hindered and demanding olefins including a variety of tri-, tetra-substituted and 1,1-disubstituted alkenes. In the presence of 1,3-bis(tert-butyl(pyridin-2-yl)phosphanyl)propane L3 or 1,4-bis(tert-butyl(pyridin-2-yl)phosphanyl)butane L4 the desired esters are obtained in good yields and selectivities. Similar transformation is obtained using tertiary ether as showcased in the carbonylation of MTBE to the corresponding linear ester in high yield and selectivity.

Breaking Compromises in CO2 Reduction

Electrochemical reduction of CO 2 to formate is a promising approach to utilize intermittent renewable energy for high-value chemical storage and to mitigate carbon pollution. Demanding applied targets for this process require that the reaction is sustained at a high current density with near-unity product efficiency. In this issue of Joule , Zheng and De Luna et al. show that incorporating sulfur into tin catalysts greatly increases the reaction rate while maintaining high selectivity and robust stability.

Rational Design of Efficient Palladium Catalysts for Electroreduction of Carbon Dioxide to Formate

The electrochemical reduction of CO2 into renewable chemical products such as formic acid is an important and challenging goal. Traditional Pd catalysts suffer from CO poisoning, which leads to current density decay and short operating lifetimes. Here we explored the ability to control Pd nanoparticle surface morphology to amplify catalytic activity and increase stability in the electroreduction of CO2 to formate. Through computational studies we have elucidated trends in intermediate binding which govern the selectivity and catalytic activity. We then rationally synthesized Pd nanoparticles having an abundance of high-index surfaces to maximize electrocatalytic performance. This catalyst displays a record current density of 22 mA/cm2 at a low overpotential of −0.2 V with a Faradaic efficiency of 97%, outperforming all previous Pd catalysts in formate electrosynthesis. The findings presented in this work provide rational design principles which highlight morphological control of high-index surfaces for th...

Highly efficient palladium catalysts supported on nitrogen contained polymers for Suzuki-Miyaura reaction

Through Pd catalyzed CN coupling reaction, Pd nanoparticles and diadamantylphosphine ligand were immobilized in situ into the formed N contained polymers as heterogeneous Pd catalysts for Suzuki-Miyaura reaction. The Pd@NPad2-1.0 catalyst was found to be highly efficient and only 4ppm of Pd (Pd@NPad2-1.0) was required for the coupling of aryl bromides with phenylboronic acid, and the corresponding products were obtained in good to excellent yields with high TON and TOF as 250,000 and 41,666h−1 respectively. Moreover, the coupling of various aryl chlorides with phenylboronic acids gave the corresponding products in high yields also. And the Pd@NPad2-1.0 catalyst is reusable at least 5 times with only slight deactivation.

ChemInform Abstract: A Simple and Efficient Palladium Catalyst of Nitrogen‐Based Ligand for Cu(I)‐ and Amine‐Free Sonogashira Reaction.

AbstractA green approach for Sonogashira coupling of aryl halides and terminal alkynes is developed using copper‐, amine‐, and phosphine—free catalytic system based on palladium glycine ligand complex.

A Simple and Efficient Palladium Catalyst of Nitrogen-Based Ligand for Cu(I)- and Amine-Free Sonogashira Reaction

Glycine, as a kind of commercially available and inexpensive ligand, is used to prepare an air-stable and water-soluble catalyst used in Sonogashira reaction in our study. In the presence of 1% [PdCl2(NH2CH2COOH)2] as catalyst, excellent catalytic activity towards the Sonogashira coupling of aryl iodides with terminal alkynes without using any additive such as Cu(I)-cocatalyst is observed in a mixture of water and acetone (3/3 mL) under air at 60 °C with NaOH as a base, giving products in good to excellent yields.

Palladium Nanoparticles Supported on Fibrous‐Structured Silica Nanospheres (KCC‐1): An Efficient and Selective Catalyst for the Transfer Hydrogenation of Alkenes

AbstractAn efficient palladium catalyst supported on fibrous silica nanospheres (KCC‐1) has been developed for the hydrogenation of alkenes and α,β‐unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high‐resolution TEM, chemisorption) with analogous mesoporous (MCM‐41, SBA‐15) silica‐supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC‐1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC‐1‐supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.

Synthesis of diaryl thioethers from aryl halides and potassium thiocyanate

An efficient palladium catalyst was synthesized using nicotine, benzyl chloride and palladium chloride. The structure of this catalyst was characterized and it was then used for the synthesis of diaryl sufides. A variety of diaryl thioethers were synthesized under relatively mild reaction conditions. This protocol avoids foul‐smelling thiols via cross‐coupling of aryl halides with potassium thiocyanate and all substrates give the corresponding products in good to excellent yields in the presence of low amounts of the catalyst. Copyright © 2014 John Wiley & Sons, Ltd.