Catalyst For Heck Reaction Research Articles

In situ preparation of palladium nanoparticles in ionic liquid crystal microemulsion and their application in Heck reaction

A simple and an efficient approach for in situ preparation of palladium nanoparticles (Pd NPs) in ionic liquid crystal (ILC) microemulsion is described. Microemulsion was formed by using a ternary mixture of triton X-100/ILC/water (in the ratio of 1.4:0.1:8.5). Three such microemulsions-1, 2 and 3 were formed by using three different ILCs namely ammonium ILC containing a cholesterol core (ILC-1), imidazolium ILC bearing a cholesterol core (ILC-2) and imidazolium ILC containing a biphenyl core (ILC-3), respectively. The Pd NPs were characterised using UV–vis spectroscopy, transmission electron microscopy and X-ray diffraction studies. Among the three, microemulsion-2 which was prepared using ILC-2 yielded stable NPs with an average particle size of ~20 nm. The NPs prepared in all three emulsions were examined as catalyst for Heck reaction. The catalytic efficiency was analysed for four cross-coupling reactions involving iodobenzene with different substituted alkenes namely methyl acrylate, ethyl acrylate, butyl acrylate and styrene. The coupling reactions were completed in a shorter period with good yields. Further, the recyclability test of Pd NPs revealed that the particles showed good activity until third catalytic cycle. The Pd NPs prepared in microemulsion-2 showed better activity compared to those prepared in microemulsions-1 and -3.

Density functional theory study of N-doping effect on the stability and activity of Pd/NCNT catalysts for heck reaction

Carbon nanomaterial-supported Pd nanoparticles (Pd/CNS) are easily prepared and effective heterogeneous catalysts for the Heck reaction. However, the drawbacks of poor stability and lower activities compared to homogeneous catalysts limit their use in industrial applications. Chemical modification of carbon nanotubes (CNTs) by heteroatom doping, has been shown to be an effective way to improve the activities and stabilities of Pd/CNT catalysts. Herein we aimed to understand the role of nitrogen-doped carbon nanotubes (NCNTs) in improving the activity and stability of supported Pd catalysts based on density functional theory (DFT) calculations. The adsorption energies of Pdn (n = 1–6) clusters were investigated for three different types of NCNTs containing graphitic-N (NNTS), pyridinic-N (NNTY), and pyrrolic-N (NNTL). The activities of Pd/NNTS, Pd/NNTY, and Pd/NNTL as catalysts for the Heck reaction were also studied. The calculations regarding the stability and energies of the various interactions revealed that N-doping the CNT structure had important influences on NCNT activity and stability. It was found that NNTL was the most suitable for loading of Pd to catalyze the Heck reaction. Our results showed that the geometry and electronic structures of the heteroatom-doped CNTs were vital for the stability and activities of the catalysts. This work shows that regulation of the distribution of N-structures in N-doped CNTs could effectively enhance the stability and activities of these catalysts.

Heterogeneous palladium SALOPHEN onto porous polymeric microspheres as catalysts for heck reaction

Abstract Catalysts based on porous polymeric microspheres were prepared from N,N′-Bis(3,3′-allyl-salicylidene)-o-phenylenediamine Pd(II) (PdAS) metallo-monomer, styrene (STY), and divinylbenzene (DVB) as co-monomers. The effects of the STY/PdAS mass ratio of co-monomers were investigated to synthesize the optimal catalyst. All the prepared materials were characterized by scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, inductively coupled plasma optical emission spectroscopy (ICP-OES), thermogravimetric analysis (TGA), solid-state diffuse-reflectance UV Vis (DRS UV-Vis) spectrometry, and X-ray photoelectron spectroscopy (XPS). Increasing the PdAS content from 1 to 5 wt%, based on the mass feed of monomers, produced well-defined spherical polymer resins with particle diameters of ~200 μm and high surface areas (>500 m2/g). XPS spectra shown a unique Pd2+ signal associated with the PdAS complex immobilized on a porous resin matrix. The catalytic performances of porous polymer microspheres were evaluated for Heck reaction between iodobenzene and methyl acrylate to produce methyl cinnamate, giving up to 100 % selectivity for the trans-isomer. The resin with 5 wt% PdAS showed the best catalytic activity in methyl cinnamate synthesis. Finally, the best catalytic system was evaluated in octinoxate production producing the target product with the same levels of conversion and selectivity for trans-isomer as was detected for methyl cinnamate synthesis.

Self-assembly 3D needle-like nickel nanostructure growth on carbon fibers by regulating prepare conditions and exploited as bifunctional material

Three-dimensional (3D) needle-like nickel carbon nanofibers (Ni/CNFs) were successfully fabricated as bifunctional materials by controlling the conditions in the preparation process. The effects such as different molar ratio, carbonization temperature and carbonization time of nanofibers morphology structures were investigated in the experiments. 3D needle-like Ni/CNFs materials as catalyst were applied in Heck reaction which exhibited a certain catalytic activity. Furthermore, this material was oxidized into the nickel and nickel oxidized (Ni/NiO) carbon nanofibers in the air atmosphere, forming electrode material. The electrochemical tests were carried out in electrolyte of 4 M KOH, and it was demonstrated that Ni/NiO-5 was the best electrode material with a high specific capacitance of 676 F g−1 at the current density of 0.5 A g−1. Cycling performance as an index of evaluation material was also investigated and the capacitance retention kept of 108% after 5000 cycles, which exhibited the excellent stability. Furthermore, the Ni/NiO-5 as the positive electrode and CNFs as negative electrode were assembled into the asymmetric supercapacitor (ASC) in 4 M KOH solution. The resulting Ni/NiO-5//CNFs device represented maximum energy density of 90.9 Wh kg−1 at the power density of 1350 W kg−1. Bifunctional materials could not only be utilized in catalytic field, but also be applied as electrode materials for the supercapacitor. This work offers a novel 3D needle-like structure for improving the potential of metal oxides for energy storage applications and this material also can be used as catalyst in Heck reaction, which displayed widely prospects applications as bifunctional materials.

Carbonization of Chitosan in Palladium-Chitosan/ Montmorillonite Composites to Prepare Novel Heterogeneous Catalysts for Heck Reactions

ABSTRACTPalladium-carbon/montmorillonite (Pd-C/MMT) heterogeneous catalysts were prepared by carbonization of chitosan in palladium-chitosan/montmorillonite (Pd-CS/MMT) composites under a N2 atmosphere. The main purpose of this study was to determine the effects of the carbonization temperature (250, 450, and 650°C) on the material microstructure and its catalytic performance. X-ray diffraction patterns revealed that the formation of an intercalation of the carbonaceous material between the clay mineral layers which was also confirmed by Fourier transform infrared spectra results. The N content of the Pd-C/MMT catalyst decreased as the carbonization temperature was increased. Thermogravimetry curves revealed that the thermal stability of the Pd-C/MMT catalyst increased obviously as the carbonization temperature was increased. Pd nanoparticles, sized at about 20 nm, were mainly dispersed on the surface of the MMT, as observed by high-resolution transmission electron microscopy (HR-TEM). The prepared Pd-C/MMT catalysts had good catalytic activity when applied in Heck coupling reactions of aromatic halides and alkenes to produce aryl olefins. The relations between the recyclability and the material composition are discussed.

Palladium on Polydopamine: Its True Potential in Catalytic Transfer Hydrogenations and Heck Coupling Reactions

AbstractThe application of Pd–polydopamine and magnetic Fe3O4@Pd–polydopamine catalysts in catalytic transfer hydrogenation reactions and the Heck arylation is reported. The reduction of a wide range of aromatic nitro‐compounds bearing both electron‐donating and ‐withdrawing substituents to the corresponding anilines could be efficiently performed, although the reduction of carbonyl compounds was found to be less general. In the latter case, only aromatic ketones could be reduced to the corresponding alcohols, whereas aldehyde substrates were unaffected, which may be owing to their reaction with the catalyst support leading to catalyst deactivation. By using magnetic Fe3O4@Pd–polydopamine system, facilitated catalyst recovery and reuse for five consecutive cycles without considerable loss of activity in nitro‐group reduction. The efficiency of the catalyst in Heck reactions was comparable to that in transfer hydrogenation, however, no catalytic activity was observed upon reuse in this case, likely as a result of metal leaching. We also explored tandem Heck reaction/catalytic transfer hydrogenation sequences, however, the two reactions showed limited compatibility under the applied conditions.

Aminoclay decorated with nano-Pd(0) picolinic acid complex as a novel efficient, heterogeneous, and phosphine ligand-free catalyst in Heck reaction under solvent-free conditions

A new heterogeneous phosphine ligand-free nano-Pd(0) picolinic acid complex was synthesized under mild and ecofriendly conditions with a short and simple process in green solvent. In this work, as a novel functionalization method, the surface of aminoclay was decorated via ionic bond formation between the picolinic acid complex of nano-Pd(0) and the amino group on its surface. Then, the prepared heterogeneous catalyst was characterized by TEM, FE-SEM, ICP, IR, XRD, TGA, EDX, XPS and UV–visible techniques and was subsequently employed as an efficient and reusable heterogeneous catalyst for selective Heck coupling of aryl halide and n-butyl acrylate under solvent-free conditions. The catalyst was recoverable simply by centrifuging and was reusable for at least seven runs with a minimum amount of palladium leaching. Also, the mercury poisoning test confirmed the heterogenous nature of the catalyst.

Palladium nanoparticles immobilized on amphiphilic and hyperbranched polymer‐functionalized magnetic nanoparticles: An efficient semi‐heterogeneous catalyst for Heck reaction

To address the obstacles facing the use of palladium‐based homogeneous and heterogeneous catalysts in C─C cross‐coupling reactions, a novel semi‐heterogeneous support was developed based on hyperbranched poly(ethylene glycol)‐block‐poly(citric acid)‐functionalized Fe3O4 magnetic nanoparticles (Fe3O4@PCA‐b‐PEG). Because of the surface modification of the Fe3O4 nanoparticles with amphiphilic and hyperbranched polymers (PCA‐b‐PEG), these hybrid materials are not only soluble in a wide range of solvents (e.g. water, ethanol and dimethylformamide) but also are able to trap Pd2+ ions via complex formation of free carboxyl groups of the PCA dendrimer with metal ions. The reduction of trapped palladium ions in the dendritic shell of Fe3O4@PCA‐b‐PEG leads to immobilized palladium nanoparticles. The morphology and structural features of the catalyst were characterized using various microscopic and spectroscopic techniques. The catalyst was effectively used in the palladium‐catalysed Mizoroki–Heck coupling reaction in water as a green solvent. In addition, the catalyst can be easily recovered from the reaction mixture by applying an external magnetic field and reused for more than ten consecutive cycles without much loss in activity, exhibiting an example of a sustainable and green methodology.

Macrocyclic Pd(II) dithiolate complexes as catalysts in Heck reactions

The supramolecular palladium dithiolate complexes, [Pd2(dppe)2{S(C6H4)nS}]2(OTf)4 and [Pd2(dppe)2(SCH2C6H4CH2S)]4(OTf)8 (dppe=1,2-bis(diphenylphosphino)ethane) has been investigated as highly stable and robust catalysts in Heck C-C coupling reactions. The arylation of butyl acrylate and styrene with various aryl bromides under optimized catalytic systems, showed excellent yield and turnover number (410,000) of the products. The tetranuclear complexes showed slightly higher catalytic activity than the octanuclear complex.

Controllable preparation of one-dimensional hybrid catalytic materials of nickel nanoparticles/porous carbon fibers and study of their performance as catalyst for Heck reaction

Ni(0) porous carbon nanofibers (Ni(0)/PCNFs) were successfully synthesized by a simple electrospinning technique with subsequent process of reduction and calcination. The as-prepared continuous Ni(0)/PCNFs which had a uniform particles diameter of 5 nm and porous structure were adopted as a catalyst in Heck reaction, which effectively improved the conversion and the selectivity of the product. Compared with Ni(0) supported on carbon nanofibers, the solid nanoporous catalyst obviously increases the efficiency of Heck reaction and also does not require ligands. Though five recycles, the catalyst remained a high catalytic activity.

Novel Pd-BTP/SiO2 as an Effective Heterogeneous Catalyst for Heck Reactions

A highly efficient and reusable catalyst, palladium (II) complex supported on functionalized silica, was prepared by anchoring palladium (II) onto 2,6-bis(5,6-dimethyl-1,2,4-triazine-3-yl)pyridine [BTP]-modified mesoporous silica (labeled as Pd-BTP/SiO2). The catalyst was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Brunauer Emmett Teller (BET) analysis. Its catalytic performance was tested for the Heck coupling reactions between aryl halides with acrylic acid or styrene, and good to excellent results (higher conversions 87–96% and yields 66–78%) were obtained. The catalyst system was stable under the reaction conditions and could be successfully reused more than five times without the loss of catalytic activity.

A novel bisoxazoline/Pd composite microsphere: a highly active catalyst for Heck reactions

A novel bisoxazoline/Pd microsphere catalyst was successfully prepared.

Synthesis, characterization, structure, redox property, antibacterial and catalytic activity of tridentate Schiff base cobalt(III), nickel(II) and palladium(II) complexes

Ligand, HL, 2-((2-(benzylthio)phenylimino)methyl)phenol, upon reaction with Co(NO3)3·6H2O, Ni(OAc)2·4H2O and PdCl2 separately afforded complexes [(L)2Co]NO3 (1), [(L)2Ni] (2) and [(L)PdCl] (3) respectively. The new complexes were characterized by usual spectroscopic studies like UV–Vis, IR and NMR and authenticated by X-ray structure determination on [(L)2Co]NO3, [(L)2Ni]. The analysis of crystal structures revealed that in all the complexes the ligand HL binds the metal center as uni-negative anion; L− dissociating phenolic proton and offers (O, N, S) tridentate binding mode to the metal. The compound [Co(L)2]NO3 is tested for in vitro antibacterial activity. Complex 3, acts as a catalyst in Heck reaction for a number of substrates. Complexes 1 and 2 exhibited a quasi reversible oxidative responses at 0.97 and 0.85V, respectively, versus SCE. The electronic spectra and redox properties of the complexes have been explained with DFT computation.

Research Progress in Supported Catalysts for Heck Reaction

Research Progress in Supported Catalysts for Heck Reaction

Preparation of Heterogeneous Palladium Catalysts Supported on Sporopollenin for Heck Coupling Reactions

The immobilized Schiff bases, S-[N-(2-aminoethyl)salicylal diimino] (1a), S-[N-(2-aminoethyl)cinnamaldiimino] (1b), S-[N-(2-aminoethyl)acetaldiimino] (1c), and their palladium(II) (2a–c) complexes, were synthesized onto a chemically modified sporopollenin with ethylenediamine. These complexes were investigated as catalysts in a Heck reaction of aryl halide with olefins. These immobilized palladium complexes is an efficient catalysts for Heck reaction of aryl halides with methyl and butyl acrylate.

Insight into PdCl2(bipy) Complex as an Efficient Catalyst for Heck Reaction and Kinetic Investigations in Homogeneous Medium

Insight into PdCl₂(bipy) Complex as an Efficient Catalyst for Heck Reaction and Kinetic Investigations in Homogeneous Medium

Use of benzimidazolium salts for in situ generation of palladium catalysts in Heck reactions in water

Abstract A new tetramethylene linked bis(benzimidazole) ligand has been obtained by a simple method. The in situ formed catalytic system derived from the benzimidazolium salt and Pd(OAc) 2 was used in the Heck reaction between aryl halides and styrene in water. The corresponding Heck products were obtained in good yields.

Synthesis of polyphenol microsphere-supported palladium complex and evaluation of its catalytic performance for Heck reaction

Polyphenol microspheres were prepared by template polymerization of phenol in the presence of horseradish peroxidase as bio-enzyme catalyst and aqueous 1,4-dioxane as solvent. The morphology of polyphenol microspheres thus obtained was observed with a scanning electron microscope. Further, polyphenol microspheres as obtained were loaded with palladium to generate polyphenol microsphere-supported Pd complex. Resultant Pd complex catalyst supported by polyphenol microspheres was characterized by means of Fourier transformation infrared spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy, and its thermal stability was examined. Moreover, the catalytic activity of polyphenol microsphere-supported Pd catalyst as synthesized for the Heck reactions of acrylic acid with aryl iodides was evaluated. Results indicate that the polyphenol microsphere as obtained has a diameter of about 500 nm. Polyphenol microsphere-supported Pd catalyst, as synthesized, at a dosage of 0.37 mol% Pd, possesses good catalytic activity for the Heck reactions of acrylic acid with aryl iodides in air at a low temperature of 50°C, and it also exhibits catalytic activity for bromide and activated chlorobenzene. The polyphenol microsphere-supported Pd complex has good thermal stability, and it can be readily separated and reused; the yield of the reaction of iodobenzene with acrylic acid remains at 82% after five recycle runs, showing promising potential as a catalyst for Heck reactions. Copyright © 2012 John Wiley & Sons, Ltd.

Ethylenediamine-functionalized activated carbon anchored palladium complex: a recyclable catalyst for Heck reaction

Ethylenediamine-functionalized activated carbon anchored palladium catalyst was prepared via grafting ethylenediamine onto chemically modified activated carbon, followed by the reaction with palladium chloride and then the reduction with potassium borohydride. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results indicated that palladium immobilized on the carrier via coordination bond in this catalyst. Transmission electron microscopy images showed that the supported palladium is in the form of near spherical particles smaller than 10 nm diameter and evenly dispersed on the surface of the carrier. This catalyst was applied for the Heck reaction of aryl halides with olefins. The influences of solvents, bases, reaction temperatures and times on catalytic property of the catalyst were investigated by using the coupling of iodobenzene and styrene as a probe reaction. By varying the combination of aryl halides and olefins, this catalyst showed effective catalytic activities to produce corresponding coupling products with moderate to excellent yields. Moreover, it can be recovered by simple filtration and reused several times without significant loss of activity and selectivity.

Preparation of high-magnetization Fe3O4–NH2–Pd (0) catalyst for Heck reaction

Abstract A magnetically separable Fe 3 O 4 –NH 2 –Pd (0) catalyst was easily synthesized by immobilizing Pd nanoparticles on the surface of magnetic Fe 3 O 4 –NH 2 microspheres. It was found that the combination of Fe 3 O 4 and triethylene tetramine (TETA) could give rise to structurally stable catalytic sites. Furthermore, the high-magnetization Fe 3 O 4 –NH 2 –Pd(0) catalyst can be recovered by magnet and reused for six runs for Heck reaction without significant loss in catalytic activity.