Polymer-supported Palladium Catalysts Research Articles

A Novel Reusable Polymer Supported Palladium Catalyst for HeckReaction

With the rapid development of “green” chemistry; researchers are highly interested towards more sustainable approaches and prefer to choose eco-friendly synthetic routes and materials. This paper deals with the development of a novel reusable heterogeneous palladium catalyst for Heck reaction. The catalyst (mPAN-Pd) was developed by a simple procedure via synthetic modification of polyacrylonitrile (PAN) with monoethanolamine (MEA) followed by complexation with palladium chloride (PdCl2). After detailed characteristic studies, the catalytic efficiency of mPAN-Pd in Heck coupling reaction was systematically evaluated and optimised the reaction condition through a set of experiments. This heterogeneous catalytic system was found be applicable over a series of aryl halides and terminal alkenes leading to corresponding coupling products in good yields. Furthermore, this catalyst offers easy recyclability by simple filtration and reused for at least 5 cycles of Heck reaction without losing much of its activity.

A Review on the Development of Polymer Supported Heterogeneous Palladium Materials for Organic Synthesis and Electrochemical Applications

Abstract:: This comprehensive review explores the advancements in catalytic transformation, focusing on the use of heterogeneous catalytic systems with a particular emphasis on polymeric-supported palladium (Pd) complexes. This study explores the limitations associated with conventional homogeneous reagents, emphasizes the transition to eco-friendly catalytic systems, and emphasizes the importance of Pd nanoparticles. These nanoparticles are particularly noteworthy for their distinctive properties, including elevated catalytic activity, making them promising for various applications in organic synthesis. The review thoroughly examines the design and synthesis of heterogeneous catalysts, emphasizing the crucial selection of safe and recyclable supports to augment the longevity and reusability of metallic catalysts. Diverse polymer varieties, including polystyrene (PS), polyethylene (PE), polyacrylate derivatives, polyethylene glycol (PEG), and grafted polymers, are investigated as viable supports for Pd complexes. The authors intricately describe the synthesis techniques for these polymer-supported Pd catalysts and furnish illustrative examples showcasing their effectiveness in organic transformation. This comprehensive review additionally highlights the synthesis of polymer-supported palladium (Pd) materials and discusses their applications in electrochemistry. The focus extends to the electrocatalytic properties of Pdbased polymeric nanomaterials, showcasing their effectiveness in glucose sensing, hydrogen peroxide detection, and the sensing of other biological analytes. Furthermore, the catalytic capabilities of Pd nanoparticles in various electrochemical applications, including wastewater treatment and electrochemical capacitors, are explored. Integrating polymer-supported Pd materials into these electrochemical processes underscores their versatility and potential contributions to advancements in catalysis and electrochemical sensing. Catalytic applications featuring polymer-supported palladium complexes with polymeric ligands in organic synthesis processes use the Sonogashira reaction, Suzuki-Miyaura coupling, Heck reaction, Catalytic asymmetric transformations, etc. The subsequent section of the paper focuses on the creation of polymeric palladium complexes, achieved by the complexation of polymeric ligands with palladium precursors. It delves into noteworthy examples of catalytic processes employing polymer-supported palladium complexes featuring polymeric ligands, emphasizing distinct polymers, such as PS, PE, polyacrylate derivatives, PEG, and grafting polymers. The review concludes by exploring catalytic asymmetric transformations using chiral palladium complexes immobilized on polymer supports and discusses various chiral ligands and their immobilization on polymer supports, emphasizing their application in asymmetric allylic alkylation. The review furnishes a comprehensive summary of recent advancements, challenges, and prospective avenues in catalytic oxidation facilitated by polymer- supported palladium catalysts with electrochemical applications.

Markovnikov selective hydroaminocarbonylation of alkenes over a porous monophoshine polymer supported palladium catalyst

Here we develop a porous monophoshine polymer supported Pd catalyst (Pd/POL-m-3vPPh3) for hydroaminocarbonylation of aromatic alkenes with amines, showing excellent catalytic activity (up to 97% yield) and Markovnikov selectivity (up to 99%).

An Efficient Recyclable Polymer Supported Palladium Catalyst for Suzuki Reaction in Water

AbstractThis work describes the development of an efficient and reusable heterogeneous polymer supported palladium catalyst for Suzuki reaction in water. This novel catalyst system was designed through monoethanolamine (MEA) modification of nitrile group in Polyacrylonitrile (PAN) followed by metal salt (PdCl2) complexation. The resulting polymer complex (mPAN‐Pd) was then successfully optimised as an efficient heterogeneous catalyst for Suzuki reaction under ligand free conditions. The supported catalyst provided excellent reactivity in the coupling reactions of a series of aryl halides with phenyl boronic acids under mild reaction condition. The reaction proceeded in presence of 2 mol % ofmPAN‐Pdcatalyst at 80 °C in water and the resulting products were isolated in moderate to excellent yields upto 98 %. Furthermore, this catalyst can be conveniently recovered by simple filtration and reused at least five times without an appreciable loss in its activity or Palladium leaching.

Palladium supported on pyrrole functionalized hypercrosslinked polymer: Synthesis and its catalytic evaluations towards Suzuki-Miyaura coupling reactions in aqueous media

Bearing the merits of convenient functionalization and versatile framework composition, hypercrosslinked polymers are employed as promising candidates in green catalysis. In this study, a new hypercrosslinked polymer supported palladium catalyst has been synthesized based on pyrrole functionalization from triphenyl benzene and pyrrole via Scholl reaction and palladium anchoring on the polymer surface. The structure of prepared Pd catalyst was confirmed by TEM, SEM, EDX, XRD, N2 adsorption–desorption, solid state 13C NMR, TGA, FT-IR, XPS, and ICP analyses. The novel complex can be served as an effective catalyst for the preparation of biphenyl compounds with the yields up to 100 % in EtOH: H2O (1:1) at 60 °C by using 0.07 mol% of catalyst in air. More importantly, the catalyst also has significant advantages in terms of facile availability of raw materials, chemical and thermal stability, and cost-effective synthesis. Due to the high specific surface area, and the coordination of pyrrole groups with palladium on the surface of this polymer, this catalyst could effectively prevent palladium leaching (<1.1 %). Furthermore, the catalyst could be recovered by simple centrifugation for four consecutive times. The study provides new insight into the immobilization of palladium on such polymer surface in other heterogeneous catalysis systems.

Highly Efficient and Reusable Polymer Supported Palladium Catalyst for Copper Free Sonogashira Reaction in Water

AbstractDevelopment of a novel, greener and efficient heterogeneous catalytic system for copper free Sonogashira reaction in water is described. This novel catalyst can be easily prepared by a simple method through synthetic modification of nitrile group in Polyacrylonitrile (PAN) using monoethanolamine (MEA) followed by its complexation with palladium chloride (PdCl2). The resulting polymer Pd complex (mPAN‐Pd) was characterized by means of Fourier Transform Infrared Spectroscopy (FTIR), Energy‐Dispersive X‐ray Spectroscopy (EDAX), Inductively Coupled Mass Spectrometry (ICP‐MS) and X‐ray Photo Electron Spectroscopy (XPS) analyses. mPAN‐Pd was then explored as highly efficient heterogeneous catalyst for Sonogashira coupling reaction under copper and ligand free conditions in water affording the corresponding coupling products up to 97 % isolated yield. Moreover, the catalyst was recovered by simple filtration after the reaction and reused for next 5 cycles with excellent stability and activity. This is the first report on the use of ethanolamine modified PAN Pd (II) complex as an efficient heterogeneous catalyst for a coupling reaction.

Cyanide-Free Cyanation of Aryl Iodides with Nitromethane by Using an Amphiphilic Polymer-Supported Palladium Catalyst

AbstractA cyanide-free aromatic cyanation was developed that uses nitromethane as a cyanide source in water with an amphiphilic polystyrene–poly(ethylene glycol) resin-supported palladium catalyst and an alkyl halide (1-iodobutane). The cyanation proceeds through the palladium-catalyzed cross-coupling of an aryl halide with nitromethane, followed by transformation of the resultant (nitromethyl)arene intermediate into a nitrile by 1-iodobutane.

Enhancing stability by trapping palladium inside N-heterocyclic carbene-functionalized hypercrosslinked polymers for heterogeneous C-C bond formations

Catalyst deactivation caused by the aggregation of active metal species in the reaction process poses great challenges for practical applications of supported metal catalysts in solid-liquid catalysis. Herein, we develop a hypercrosslinked polymer integrated with N-heterocyclic carbene (NHC) as bifunctional support to stabilize palladium in heterogeneous C-C bond formations. This polymer supported palladium catalyst exhibits excellent stability in the one-pot fluorocarbonylation of indoles to four kinds of valuable indole-derived carbonyl compounds in cascade or sequential manner, as well as the representative Suzuki-Miyaura coupling reaction. Investigations on stabilizing effect disclose that this catalyst displays a molecular fence effect in which the coordination of NHC sites and confinement of polymer skeleton contribute together to stabilize the active palladium species in the reaction process. This work provides new insight into the development of supported metal catalysts with high stability and will also boost their efficient applications in advanced synthesis.

An Efficient Polymer Supported Palladium Catalyst for ortho Selective C−H Olefination of Anilides

AbstractThe development of a novel heterogeneous polymer supported palladium catalyst for the oxidative C−H olefination of anilides is described. The catalyst was realized by immobilizing Palladium acetate over ethylene diamine modified Polyacrylonitrile (PAN) and characterized by means of FTIR, XRD and XPS analyses which evidenced the complexation of Pd(OAc)2 with the chelating groups in the polymer. The resulting supported complex (en‐PAN‐Pd) was then explored as an efficient and reusable heterogeneous catalyst for ortho selective C−H activation of anilides on reaction with a number of alkyl acrylates. This reaction protocol serves as a useful and greener method for the synthesis of o‐alkenyl anilides under mild reaction conditions. The catalyst also exhibited good recyclability and reusability without losing much catalytic activity.

Porous organic polymer-supported palladium catalyst for hydroesterification of olefins

Hydroesterification of olefins with alcohols and CO is an attractive approach to synthesize value-added carboxylic esters. The current manufactures are mainly based on the use of homogeneous catalytic systems, and developing a heterogeneous process enabling cost-effective catalyst separation is of potential interest, particularly for higher olefins. In this contribution, we reported a robust porous organic polymer-supported palladium catalyst that exhibited excellent hydroesterification performance approaching that of the homogeneous counterpart. In addition, the catalyst shows remarkable adaptability for a broad range of substrates (both olefins and alcohols) and recyclability. The catalysts are thoroughly characterized by a spectrum of characterization techniques including N2 sorption, SEM, TEM, HAADF-STEM coupled with elemental mapping, FTIR with CO probe, XPS, and solid-state 31P NMR. Based on these, the good catalytic performance can be attributed to the high surface area, highly dispersed active metal species, and the strong coordination bonds between palladium center and the exposed phosphorous ligands in Porous organic polymer (POPs) frame. The ICP-OES and hot filtration test further indicate that the reaction truly proceeds in a heterogeneous manner, thus exhibiting great potential for industrial applications.

Porous Organic Polymer-Supported Palladium Catalyst for Suzuki–Miyaura Coupling in Water

Porous Organic Polymer-Supported Palladium Catalyst for Suzuki–Miyaura Coupling in Water

Combining polymer-bound catalyst with polymeric substrate for reproducible pH oscillations in palladium-catalysed oxidative carbonylation of alkynes

Palladium-catalysed oxidative carbonylation (PCOC) of alkynes is a promising engine for building smart pulsatile polymeric systems, as it has demonstrated (in certain configurations) sustained regular oscillations in pH and redox potential for up to one month of monitoring in a batch reactor. Recent developments in polymer-supported palladium catalysts have demonstrated the full capacity of this reaction – in a macrogel that experienced oscillations in volume, while releasing a drug load. In this work, we demonstrate reproducible oscillations (more than 100 h duration) in a proline-functionalised chitosan-palladium system (Chi-Pro-Pd), using both small molecule (phenylacetylene) and polymeric (pegylated dialkyne) substrate, for the first time. Moreover, by functionalising chitosan with proline ligands, we dramatically reduced halide-mediated leaching of palladium, which readily occurred in non-functionalised chitosan-palladium catalysts (Chi-Pd). Oscillatory patterns for both systems confirm the need for fabricating functionalised chitosan supports to improve catalyst reusability and minimise loss of palladium.

Microporous Polymer Supported Palladium Catalyst for Oxidative Heck Reactions

Microporous Polymer Supported Palladium Catalyst for Oxidative Heck Reactions

Palladium supported on an amphiphilic porous organic polymer: a highly efficient catalyst for aminocarbonylation reactions in water

An amphiphilic porous organic polymer supported palladium catalyst was successfully prepared, showing excellent catalytic performance for aminocarbonylation reactions in water.

ChemInform Abstract: N‐Heterocyclic Carbene‐Based Microporous Organic Polymer Supported Palladium Catalyst for Carbon—Carbon Coupling Reaction.

AbstractHighly dispersed Pd(0) nanoparticles are successfully immobilized into stable N‐heterocyclic carbene‐based microporous organic polymer via a simple post‐treatment.

Esterification, transesterification and hydrogenation reactions of polyunsaturated compounds catalyzed by a recyclable polymer supported palladium catalyst

Aliphatic and aromatic carboxylic acids were converted into their corresponding esters using a polymer supported palladium(II) β-ketoesterate complex under hydrogen atmosphere in the presence of catalytic bromobenzene in alcohols. This method was also applicable to the transesterification of esters. Good to excellent yields were obtained for different aliphatic or aromatic starting materials. The esterification (or transesterification) was promoted by the in situ generation of HBr from bromobenzene, which provided a mild acidic reaction environment. Pd(II) centers were converted into polymer stabilized metal nanoparticles (the true active species) under reaction conditions. The palladium catalyst exhibited a remarkable activity and was reusable for eight consecutive cycles. The present system was also tested for the preparation of partially hydrogenated fatty acid methyl esters, starting from a mixture composed by highly polyunsaturated esters and free carboxylic acids, taken as a model acidic feedstock for biodiesel upgrading.

The 2V-P,N polymer supported palladium catalyst for methoxycarbonylation of acetylene

Heterogenization of homogeneous catalyst by immobilizing complex on the surface of polymer supports promotes the design of the catalysts which combine the advantages of heterogeneous and homogeneous catalysts. The porous 2-vinyl-functional diphenyl-2-pyridylphosphine (2V-P,N) polymer (POL-2V-P,N) was successfully synthesized under solvothermal conditions. The POL-2V-P,N polymer was characterized by nitrogen physisorption, thermogravimetry (TG), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The heterogenized homogeneous Pd/POL-2V-P,N catalyst was synthesized by immobilizing Pd(OAc)2 on the POL-2V-P,N, which was used as not only support but also as ligands. The catalyst was investigated by means of 31P NMR, X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopic (XPS) and FT-IR and tested for the methoxycarbonylation of acetylene. According to the results of 31P NMR, XPS and EXAFS, there existed coordination bonds between palladium and the exposed phosphorous and nitrogen atoms of the porous POL-2V-P,N support. The XPS and FT-IR results showed that Pd0 species were present on the Pd/POL-2V-P,N catalyst. The heterogenized Pd/POL-2V-P,N palladium complex catalyst with high surface area and large pore volume displayed excellent activity for the methoxycarbonylation of acetylene as compared with the corresponding homogeneous palladium diphenyl-2-pyridylphosphine complex (Pd-P,N) under the same conditions. The used Pd/POL-2V-P,N catalyst also exhibited excellent activity under the same conditions. In addition, the hot filtration tests indicated that the reaction occurred in a heterogeneous way.

A polymer supported palladium(II) β-ketoesterate complex as active and recyclable pre-catalyst for selective reduction of quinolines in water with sodium borohydride

A polymer supported palladium catalyst, obtained by copolymerization of Pd(AAEMA)2 [AAEMA−=deprotonated form of 2-(acetoacetoxy) ethyl methacrylate] with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker), exhibited excellent activity and selectivity for the hydrogenation of quinolines to 1,2,3,4-tetrahydroquinolines in the presence of NaBH4 as hydrogen donor in water. Both the activity and selectivity could be maintained for at least seven reaction runs. No metal leaching into solution occurred during recycles. TEM analyzes carried out on the catalyst showed that the active species were supported palladium nanoparticles having a mean size of 3nm, which did not aggregate with the recycles.

PdCl2 on modified poly(styrene-co-maleic anhydride): A highly active and recyclable catalyst for the Suzuki–Miyaura and Sonogashira reactions

The Suzuki–Miyaura and Sonogashira coupling were performed using a new, efficient, reusable and recyclable polymer-supported palladium catalyst. Poly(styrene-co-maleic anhydride) as polymer-support is modified with 2-aminothiazole. PdCl2 was immobilized on this prepared support and its appearance was confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy analysis of X-rays (EDAX), inductively coupled plasma (ICP) analysis, and FT-IR techniques. In addition, a quantitative description for metal–ligand interactions in the aforementioned polymer-supported palladium complex is investigated by performing theoretical calculations using density functional theory techniques.

Highly selective hydrogenation of quinolines promoted by recyclable polymer supported palladium nanoparticles under mild conditions in aqueous medium

Polymer supported palladium catalyst, obtained by copolymerization of Pd(AAEMA)2 [AAEMA−=deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker), exhibited excellent activity and selectivity for the hydrogenation of quinolines to 1,2,3,4-tetrahydroquinolines under mild temperature (80°C) and H2 pressure (10bar) in aqueous medium. Both the activity and selectivity could be maintained for at least nine reaction runs. No metal leaching into solution occurred during application. TEM analyses carried out on the catalyst showed that the active species were supported palladium nanoparticles having a mean size of 4nm, which did not aggregate with the recycles.