Magnetic Palladium Research Articles

Recent advances in the development of magnetic catalysts for the Suzuki reaction

Suzuki reactions are one of the most important carbon-carbon bond forming reactions found in organic chemistry, with current methodologies offering excellent yields for a wide range of substrates. Further optimisation of such reactions involves incorporation of iron oxide nanoparticles into the catalytic system leading to the formation of highly efficient, recyclable catalysts. This review will focus on the recent development of magnetic palladium catalysts (palladium on magnetite with carbon-based supports and silicon coatings, and palladium on maghemite). Their application and recyclability in Suzuki coupling reactions will also be presented.

Reusable and Magnetic Palladium and Copper Oxide Catalysts in Direct ortho and meta Arylation of Anilide Derivatives

We report a general, direct C–H arylation of anilide derivatives using reusable palladium or copper oxide on magnetite as heterogeneous precatalysts. Highly selective ortho and meta arylations are achieved using electronically and sterically diverse diaryliodonium salts. Catalytically active soluble species from the heterogeneous precursors were detected by experimental techniques. Preliminary mechanistic investigation suggests different reaction pathways for each of the catalysts.

Synergistic persulfate activation as an efficient and cost-effective approach for removal of organic synthetic-dyes from aqueous solutions using magnetic Pd-Fe3O4-flyash composite particles as catalyst

Magnetic palladium (Pd)-magnetite (Fe3O4)-flyash composite particles have been recently utilized for the removal of industrial azo reactive dyes from the aqueous solutions. The mechanism of dye-removal involves advanced oxidation process (AOP) such as the activation of costlier and hazardous oxidizer such as hydrogen peroxide (H2O2). The process also requires further backing-up with the adsorption treatment of activated carbon (AC) to control the enhanced chemical oxygen demand (COD) level of treated aqueous solution which not only increases the number of steps involved in the dye-removal process but also results in the generation of large amount of sludge. There is an urgent need to replace H2O2 with an efficient, cost-effective, and non-hazardous oxidizer which can resolve the aforementioned issues in the present dye-removal application. In this investigation, we utilize the magnetic Pd-Fe3O4-flyash composite particles for the decoloration of aqueous solutions containing industrial azo reactive dye such as Corafix Red ME4B via synergistic activation of persulfate anions (S2O82−) involving the catalytic and thermal contributions. In contrast to the activation of H2O2, the synergistic activation of S2O82− anions is noted to significantly reduce the COD level almost in a single step which reduces the dependency on the post adsorption treatment of AC. Moreover, the regeneration of AC in the present dye-removal application has also been demonstrated using the synergistic activation of S2O82− anions. The latter, hence, appears to be an efficient, cost-effective, and non-hazardous approach for the removal of organic synthetic-dyes from aqueous solutions by using the magnetic Pd-Fe3O4-flyash composite particles as catalyst.

Efficient transfer hydrogenation of nitro compounds over a magnetic palladium catalyst

Magnetic hydroxyapatite (HAP) supported Pd nanoparticles (γ-Fe2O3@HAP-Pd) were used for the transfer hydrogenation of nitro compounds with HCOONH4 as hydrogen donors. Aniline was produced in an excellent yield (>99%) in water at 25 °C with 6 equiv. HCOONH4. This process is suitable to a wide range of nitro compounds with excellent yields for most cases. Both the HAP support and the Pd nanoparticles showed a synergistic effect on the transfer hydrogenation of nitro compounds. Furthermore, the γ-Fe2O3@HAP-Pd catalyst was stable.

One‐pot synthesis of magnetic palladium–NiFe2O4–graphene oxide composite: an efficient and recyclable catalyst for Heck reaction

A magnetically separable NiFe2O4@GO–Pd composite (GO = graphene oxide) was successfully prepared by a facile one‐pot hydrothermal strategy. This new kind of hybrid material was fully characterized using powder X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy and vibrating sample magnetometry. Structural characterizations confirmed the formation of NiFe2O4 and Pd nanocrystals, and the close anchoring between nanoparticles and GO sheets. Additionally, the as‐prepared NiFe2O4@GO–Pd nanocomposite was effectively employed in the palladium‐catalyzed Heck reaction in an ethanol–water system as a green solvent. The catalyst was completely recoverable with the simple application of an external magnetic field and with no obvious loss of catalytic activity even after six repeated cycles. Copyright © 2016 John Wiley & Sons, Ltd.

In situ synthesis of self-assembled three-dimensional graphene-magnetic palladium nanohybrids with dual-enzyme activity through one-pot strategy and its application in glucose probe.

The self-assembled three-dimensional graphene nanohybrids with in situ-formed Fe3O4 and Pd nanoparticles on it (3DRGO_Fe3O4-Pd) are first synthesized by the one-pot solvothermal method, which have intrinsic peroxidase-like and oxidase-like activity. The catalytic mechanism is analyzed by the electron spin resonance (ESR), fluorescence, and electrochemical methods. The mimic enzyme catalytic activity of 3DRGO_Fe3O4-Pd is much higher than those of monometallic loaded nanohybrids and their physical mixture, probably caused by synergistic effect between Pd and Fe3O4 nanoparticles. The 3DRGO_Fe3O4-Pd nanohybrids was reproducible, stable, and reusable. After 10 cycles, the catalytic activity was still higher than 90%, and the morphology and structure were basically unchanged. Based on its high peroxidase-like activity, especially the enhanced affinity toward H2O2, a new colorimetric detection method for reduced glutathione (GSH) and glucose has been designed using H2O2 as an intermediary, which provides a simple, sensitive, and selective way to detect urine glucose of diabetes with a wide linear range and low detection limit.

Selective aerobic oxidation of the biomass-derived precursor 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid under mild conditions over a magnetic palladium nanocatalyst

High yield of 2,5-furandicarboxylic acid was achieved from the aerobic oxidation of 5-hydroxymethylfurfural over a magnetic palladium nanocatalyst.

A magnetically separable palladium catalyst containing a bulky N-heterocyclic carbene ligand for the Suzuki–Miyaura reaction

Bulky NHC ligands were employed for preparing magnetic palladium catalysts, which showed excellent activity, stability and reusability towards the Suzuki–Miyaura reaction.

A novel magnetic palladium catalyst for the mild aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid in water

Magnetically separable, graphene oxide-supported palladium nanoparticles showed high catalytic activity for the aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid.

Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions

A carbon-coated magnetic Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross-coupling reaction).

Rapid, Microwave‐Assisted, and One‐Pot Synthesis of Magnetic Palladium–CoFe2O4–Graphene Composite Nanosheets and Their Applications as Recyclable Catalysts

Here, a microwave‐assisted approach has been demonstrated to rapidly prepare magnetic Pd–CoFe2O4–graphene (GE) composite nanosheets in ethylene glycol (EG) solvent. The generation of both Pd and CoFe2O4 nanoparticles is accompanied with the reduction process of graphene oxide (GO) by EG. The surface morphologies and chemical composition of the composite nanosheets are characterized by transmission electron microscopy (TEM), energy‐dispersive X‐ray spectrometer (EDS), powder X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) measurements. The as‐prepared Pd–CoFe2O4–GE composite nanosheets exhibit a remarkable catalytic activity towards the reduction of 4‐nitrophenol by sodium borohydride (NaBH4) at room temperature. The apparent kinetic rate constant (K app) of this catalytic reaction could reach about 11.0 × 10−3 s−1. Moreover, the CoFe2O4 component exhibits a magnetic property, which could make the Pd–CoFe2O4–GE composite nanocatalysts separated from the suspension system. The catalytic conversion of the 4‐nitrophenol to 4‐aminophenol could reach 87.2% after four cycles. This work presents a simple, rapid, and versatile method to fabricate both metal and spinel‐type complex oxides on GE nanosheets, providing a new opportunity for their applications in the recyclable catalytic reaction.

Glucose Stabilized Magnetic Palladium Nanoparticles Exhibiting Enhanced Magnetic Properties Under Exposure to Hydrogen

H 2 [Pd II (Cl) 4 ] and [Pd IV (NH 3 ) 4 Cl 2 ]Cl 2 as starting materials produce palladium nanoparticles (Pd NPs) using hydroxylamine as reducing agent in aquous solvent in the presence of D-glucose as stabiliser and capping agent. Pd NPs with average 6 nm size was isolated from Pd(II) complex whereas the average Pd NPs of 8 nm was produced from Pd(IV) under similar reaction condition. These Pd NPs are characterized by UV–Vis, FT-IR, XRD, TEM and SEM and EDX studies. Magnetism of 6 nm sized Pd NPs show enhanced ferromagnetic behavior compared to those from 8 nm sized Pd NPs. On hydrogen exposure smaller sized Pd NPs show an increase in magnetization.