Preparation of siloxene nanosheet‐supported palladium as sustainable catalyst for Mizoroki–Heck reaction

Siloxene nanosheets were successfully modified with palladium nanoparticles by reducing palladium chloride with hydrazine hydrate. The palladium nanoparticles–siloxene nanosheets as a catalyst for the Mizoroki–Heck reaction exhibited high activity, recoverability and stability. The structural morphology of the catalyst was investigated using transmission electron microscopy. High efficiency of the catalyst was proved in the Mizoroki–Heck reaction after five catalytic recycles. Copyright © 2014 John Wiley & Sons, Ltd.     

Suzuki Reaction of Aryl Bromides Using a Phosphine-Free Magnetic Nanoparticle-Supported Palladium Catalyst

A palladium catalyst immobilized on superparaganetic nanoparticles was prepared with a palladium loading of 0.30 mmol/g. The catalyst was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared, atomic absorption spectrophotometry, and nitrogen adsorption. The immobilized palladium catalyst was an efficient catalyst without added phosphine ligands for the Suzuki cross-coupling reaction of several aryl bromides with phenylboronic acid. The recovery of catalyst was simply by magnetic decantation in the presence of a magnet. The immobilized palladium catalyst can be reused many times without significant degradation in catalytic activity. No leaching of active palladium species into the reaction solution was detected.     

Magnetically separable Pd catalyst for carbonylative Sonogashira coupling reactions for the synthesis of alpha,beta-alkynyl ketones

A magnetically separable palladium catalyst was simply synthesized through a wet impregnation incorporating palladium nanoparticles and superparamagnetic Fe3O4 nanoparticles in KBH4 solution, which is a highly efficient catalyst for the carbonylative Sonogashira coupling reaction of aryl iodides with terminal alkynes under phosphine-free conditions. This catalyst is completely magnetically recoverable due to the super paramagnetic behavior of Fe3O4 and can be reused with sustained selectivity and activity.     

Palladium nanoparticles supported on mesoporous natural phosphate: An efficient recyclable catalyst for nitroarene reduction

We report the preparation of palladium nanoparticles supported on mesoporous natural phosphate (Pd@NP) using a wetness impregnation method. The prepared catalyst was characterized using various techniques. Furthermore, the reduction and preparation of the palladium nanoparticles was followed using UV–visible spectra. Based on the Scherrer equation, the crystallite size of the as‐synthesized palladium nanoparticles was 10.88 nm. The performance of the synthesized catalyst was investigated in the reduction of 4‐nitrophenol as a model substrate to 4‐aminophenol using NaBH₄ as a hydrogen source. Moreover, catalytic reduction of various nitroarenes was studied and monitored using UV–visible spectroscopy and gas chromatography. The Pd@NP catalyst showed a high activity for the selected reaction and could be recycled.     

Synthesis of small palladium nanoparticles stabilized by bisphosphine BINAP bearing an alkyl chain and their palladium nanoparticle-catalyzed carbon-carbon coupling reactions under room-temperature

A new bisphosphine ligand, C8-BINAP, and C8-BINAP-stabilized palladium nanoparticles have been prepared; C8-BINAP was found to be an effective protecting ligand for preparing and stabilizing palladium nanoparticles with very small core size and narrow size distribution and the C8-BINAP-Pd nanoparticles behave as an efficient catalyst for carbon-carbon coupling reactions at room temperature.     

Silica–acetylacetone‐supported palladium nanoparticles as an efficient and reusable catalyst in the Heck–Mizoroki C–C cross‐coupling reaction

The preparation of palladium nanoparticles supported on acetylacetone‐modified silica gel and their catalytic application for Heck olefination of aryl halides were investigated. The catalyst was characterized using X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission and scanning electron microscopies. The supported palladium nanoparticles are demonstrated to be a highly active and reusable catalyst for the Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. The heterogeneity of the catalytic system was investigated with results indicating that there is a slight palladium leaching into the reaction solution under the applied reaction conditions. Despite this metal leaching, the catalyst can be reused nine times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Quasi-homogeneous hydrogenation with platinum and palladium nanoparticles stabilized by dendritic core-multishell architectures

Platinum and palladium nanoparticles, supported and stabilized by polymeric core-shell architectures, proved to be active catalysts for hydrogenation reactions. Here, two different reactions were used as probes to investigate the influence of the polymeric support: the hydrogenation of α-methyl styrene (AMS) to cumene and the partial hydrogenation of 1,5-cyclooctadiene (COD). We found that the stability of the nanoparticles and the rate of reaction are higher in the presence of a hydrophobic octadecyl shell within a three-shell polymer system. The kinetic study of AMS hydrogenation showed much higher activities for palladium nanoparticles than for platinum nanoparticles, and the obtained results (e.g., 35 kJ/mol for the activation energy) are of the same order of magnitude as reported earlier for palladium supported on alumina. A methanol/n-heptane biphasic mixture was tested for catalyst recycling and allowed for highly efficient catalyst separation with very low metal leaching.     

A new strategy to design a graphene oxide supported palladium complex as a new heterogeneous nanocatalyst and application in carbon–carbon and carbon‐heteroatom cross‐coupling reactions

The palladium nanoparticles were successfully stabilized with an average diameter of 6–7 nm through the coordination of palladium and terpyridine‐based ligands grafted on graphene oxide surface. The graphene oxide supported palladium nanoparticles were thoroughly characterized and applied as an efficient heterogeneous catalyst in carbon–carbon (Suzuki‐Miyaura, Mizoroki‐Heck coupling reactions) and carbon–heteroatom (C‐N and C‐O) bond‐forming reactions. The catalyst was simply recycled from the reaction mixture and was reused consecutive four times with small drop in catalytic activity.     

Efficient synthesis of 5‐substituted tetrazoles catalysed by palladium–S‐methylisothiourea complex supported on boehmite nanoparticles

An efficient and general method is reported for the synthesis of 5‐substituted 1H ‐tetrazole derivatives in the presence of S ‐methylisothiourea complex of palladium immobilized on boehmite nanoparticles (Pd‐SMTU@boehmite) as an efficient and recyclable nanocatalyst. Boehmite nanoparticles were not sensitive to air or moisture and were prepared without inert atmosphere in water at room temperature. Then a novel type of phosphine‐free palladium complex was immobilized on these nanoparticles. This catalyst was characterized using Fourier transform infrared, thermogravimetric, Brunauer–Emmett–Teller, transmission and scanning electron microscopic, energy‐dispersive X‐ray spectroscopic, X‐ray diffraction and inductively coupled plasma optical emission spectroscopic techniques. The catalyst was reused several times without palladium leaching or change in its structure.     

Atmospheric pressure aminocarbonylation of aryl iodides using palladium nanoparticles supported on MOF-5

An efficient amide synthesis by atmospheric pressure aminocarbonylation using palladium nanoparticles supported on MOF-5 is reported. Interestingly, only 0.5 wt% palladium loading was required to achieve high yields. The catalyst is recyclable and offers negligible palladium leaching.     

A new palladium nanoparticle catalyst on mesoporous silica prepared from a molecular cluster precursor

A promising approach to the controlled synthesis of supported nanoparticles involves the use of molecular carbonyl clusters as precursors. Molecular metal clusters consist of a defined number of structurally ordered atoms, and active monodisperse metal particles are formed after dispersing the molecules and removing the ligands. An octanuclear palladium cluster precursor with easily displaceable ligands was used to generate palladium nanoparticles on mesoporous MCM-41. The molecular cluster precursor, [Pd8(CO)8(PMe3)7], was directly adsorbed from solution onto MCM-41, followed by gentle thermolysis which yielded small metal nanoparticles. Compared to MCM-41-based catalysts prepared from palladium salts by conventional methods, this cluster-derived palladium catalyst has shown an efficient activity for liquid-phase hydrogenation of alkenes.     

Activity of palladium nanoparticles on graphene oxide in the Suzuki—Miyaura reaction

A convenient express method for obtaining palladium nanoparticles on the graphene oxide support was developed. The data of transmission electron microscopy and X-ray diffraction analysis indicated the formation of palladium nanoparticles with an average size of 2 nm. The obtained nanocomposite material showed high catalytic activity in the cross-coupling reaction of bromobenzene with phenylboronic acid. The efficiency of the catalyst increases when using a mixture of organic solvents with water.     

Synthesis,properties, and activity of nanosized palladium catalysts modified with elemental phosphorus for hydrogenation

The applicability of elemental phosphorus as a modifier of palladium catalysts for hydrogenation was demonstrated, and the conditions for the synthesis of nanoparticles that are highly efficient in hydrogenation catalysis were optimized. The modifying effect of elemental phosphorus depends on the P/Pd ratio; it is associated with changes in the catalyst dispersity and the nature of the formed nanoparticles containing various palladium phosphides (PdP₂, Pd5P₂, and Pd₆P) and Pd(0) clusters. The main stages of the formation of palladium catalysts for hydrogenation were determined, and a model of an active catalyst, in which the Pd₆P phosphide is the core of a nanoparticle and Pd(0) clusters form a shell, was proposed.     

Palladium particles from oxime-derived palladacycle supported on Fe3O4/oleic acid as a catalyst forthe copper-free Sonogashira cross-coupling reaction

An oxime-derived palladacycle was synthesized using4-bromobenzoxime and pyridine in CHCl3, and characterized by FT-IR and1H NMR spectroscopy. This Pd complex was supported on Fe3O4/oleic acid and shown to be an efficient catalyst for the copper-free Sonogashira cross-coupling reaction of various aryl halides with phenylacetylene in air and in ethanol or mixed aqueous medium. The oxime-derived palladacycle gave highly active palladium nanoparticles for the organicsynthesis. The coupling products were obtained in high yields with low Pd loading and theheterogeneous catalyst can be separated by an external magnet andreused six times without loss of its activity. The characterization of the catalyst wascarried out by XRD, SEM and TEM. Both TEM and XRD revealed that the palladium nanoparticles were well dispersed with diameters from 5 to 10 nm and average size 9.97 nm.     

Efficient Palladium‐Catalyzed Aminocarbonylation of Aryl Iodides Using Palladium Nanoparticles Dispersed on Siliceous Mesocellular Foam

A highly dispersed nanopalladium catalyst supported on mesocellular foam (MCF), was successfully used in the heterogeneous catalysis of aminocarbonylation reactions. During the preliminary evaluation of this catalyst it was discovered that the supported palladium nanoparticles exhibited a “release and catch” effect, meaning that a minor amount of the heterogeneous palladium became soluble and catalyzed the reaction, after which it re‐deposited onto the support.     

磁性纳米粒子负载钯催化有机合成反应研究进展

磁性纳米粒子负载钯催化的有机合成反应,由于具有催化活性高,催化剂在外加磁场作用下即可快速分离和重复使用等特点,已引起了人们的广泛关注.综述了近年来磁性纳米粒子负载钯催化有机合成反应的研究进展,载体包括Fe3O4纳米粒子、有机小分子修饰的磁性纳米粒子、SiO2包覆的磁性纳米粒子、碳修饰磁性纳米粒子、羟基磷灰石包覆的磁性纳米粒子和有机高分子修饰的磁性纳米粒子等.     

Mizoroki–Heck and Suzuki–Miyaura reactions mediated by poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐stabilized magnetically separable palladium catalyst

The purpose of this work was to synthesize and characterize a new magnetic polymer nanosphere‐supported palladium(II) acetate catalyst for reactions requiring harsh conditions. In this regard, an air‐stable, moisture‐stable and highly efficient heterogenized palladium was synthesized by the coordination of palladium(II) acetate with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐grafted modified magnetic nanoparticles with a core–shell structure. The structure of the newly developed catalyst was characterized using various techniques. The catalytic activity of the resultant nano‐organometallic catalyst was evaluated in Mizoroki–Heck and Suzuki–Miyaura reactions to afford the corresponding coupling products in good to excellent yields. High selectivity as well as outstanding turnover number (14 143, 4900) and turnover frequency (28 296, 7424) values were recorded for the catalyst in Suzuki–Miyaura and Mizoroki–Heck reactions, respectively. Magnetic separation and recycling of the catalyst for at least six runs became possible without any significant loss of efficiency or any detectable palladium leaching.     

Stabilized well-dispersed Pd(0) nanoparticles for aminocarbonylation of aryl halides

Well-dispersed palladium (0) nanoparticles stabilized with phosphonium based ionic liquid were synthesized conveniently and fully characterized. A catalyst system comprising of the Pd(0) nanoparticles and a base was found to be recyclable and efficient for the aminocarbonylation reaction of aryl iodide in ionic liquid media. In the presence of potassium tert-butyloxide, for the relatively stable aryl chloride and bromide substrates, medium activities were achieved for the catalyst. The catalyst composites can be recycled at least five times with sustained activity.     

准均相的铂钯合金纳米催化剂用于芳香族化合物脱卤反应

用一锅法合成的负载于聚酰胺酸盐上的铂钯纳米催化剂,可以通过调节溶液的p H值实现催化剂与反应体系的有效分离和循环利用.准均相的铂钯催化剂应用于水相中卤代芳香族化合物的氢化脱卤反应,转化率达到99%以上,并且在重复使用5次后仍然保持很高的活性.铂钯双金属催化剂拥有比单一金属铂或者钯更高的催化活性,这主要是由于铂钯合金在催化反应时具有协同效应.利用X射线衍射仪(XRD),透射电子显微镜(TEM)等方法对催化剂进行了表征.数据表明铂钯纳米粒子负载于聚酰胺酸上以后可以在水溶液中稳定存在并且处于均匀的分布状态,纳米粒子尺寸约为4 nm.     

A facile route for preparing a mesoporous palladium coordination polymer as a recyclable heterogeneous catalyst

To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica, polymers and nanoparticles. For the same purpose, we describe a general and facile method to immobilize palladium bis(phosphine) complexes on the basis of the technique widely used for metal-organic framework (MOF) synthesis, yielding a mesoporous coordination polymer palladium-CP1. Although palladium complexes are generally not stable enough to allow further manipulation, we succeeded in preparation of a palladium coordination polymer without by-product Pd clusters or nanoparticles. The fresh palladium-CP1 catalyst exhibits a yield close to 55% for tolane at room temperature and 24 h in Sonogashira coupling of iodobenzene and phenylacetylene, as compared with a yield of 89% for its homogeneous counterpart [Pd(PPh(3))(2)Cl(2)]. Furthermore, this catalyst is stable enough to be reused more than four times with no Pd and Zn leaching. Therefore this new immobilization method offers great promise for the produce of recyclable palladium heterogeneous catalysts with higher activity and higher thermal and chemical stability in the future.