Solid-State Schikorr Reaction from Ferrous Chloride to Magnetite with Hydrogen Evolution as the Kinetic Bottleneck

The selective formation of meta-stable Fe3O4 from ferrous sources by suppressing its oxidative conversion to the most stable hematite (α-Fe2O3) is challenging under oxidative conditions for solid-state synthesis. In this work, we investigated the conversion of iron(II) chloride (FeCl2) to magnetite (Fe3O4) under inert atmosphere in the presence of steam, and the obtained oxides were analyzed by atomic-resolution TEM, 57Fe Mössbauer spectroscopy, and the Verwey transition temperature (Tv). The reaction proceeded in two steps, with H2O as the oxide source in the initial step and as an oxidant in the second step. The initial hydrolysis occurred at temperatures higher than 120 °C to release gaseous HCl, via substituting lattice chloride Cl- with oxide O2-, to give iron oxide intermediates. In the first step, the construction of the intermediate oxides was not topotactic. The second step as a kinetic bottleneck occurred at temperatures higher than 350 °C to generate gaseous H2 through the oxidation of FeII by H+. A substantially large kinetic isotope effect (KIE) was observed for the second step at 500 °C, and this indicates the rate-determining step is the hydrogen evolution. Quantitative analysis of evolved H2 revealed that full conversion of ferrous chloride to magnetite at 500 °C was followed by additional oxidation of the outer sphere of magnetite to give a Fe2O3 phase, as supported by X-ray photoelectron spectroscopy (XPS), and the outer phase confined the conductive magnetite phase within the insulating layers, enabling kinetic control of magnetite synthesis. As such, the reaction stopped at meta-stable magnetite with an excellent saturation magnetization (σs) of 86 emu g-1 and Tv > 120 K without affording the thermodynamically stable α-Fe2O3 as the major final product. The study also discusses the influence of parameters such as reaction temperature, initial grain size of FeCl2, the extent of hydration, and partial pressure of H2O.

Metal–Organic Framework Derived Cobalt Oxide Supported Bimetallic Pd/Cu Nanoparticles for Efficient Catalysis of the Sonogashira Reaction under Aerobic Conditions

A bimetallic Pd/Cu catalyst supported on a metal-organic-framework-derived cobalt oxide was prepared and characterized by SEM, EDS, XRD, XPS, and ICP-OES analyses. The catalyst promoted the Sonogashira reaction of aryl iodides with terminal alkynes at a low loading of the palladium (0.032 mol%) and copper species (0.012 mol%) to give the corresponding disubstituted alkynes in moderate to good yields. When the catalyst was recovered by using an external magnetic field, its catalytic activity decreased slightly in a second cycle.

A Pd NP-confined novel covalent organic polymer for catalytic applications

A novel unsymmetrical covalent organic polymer was synthesized via nucleophilic substitution reaction of 2,4,6-trichloro-1,3,5-triazine with p-amino phenol.

Microwave-assisted synthesis of palladium nanoparticles supported on copper oxide in aqueous medium as an efficient catalyst for Suzuki cross-coupling reaction

We report here a reliable green method for the synthesis of palladium nanoparticles supported on copper oxide as a highly active and efficient catalyst for Suzuki cross-coupling reaction. The experimental synthetic approach is based on microwave-assisted chemical reduction of an aqueous mixture of palladium and copper salt simultaneously using hydrazine hydrate as reducing agent. The catalyst was fully characterized using various techniques showing well-dispersed palladium nanoparticles. The catalytic activity and recyclability of the prepared catalyst were experimentally explored in the ligand-free Suzuki cross-coupling reaction with a diverse series of functionalized substrates. The synthesized Pd/CuO catalyst shows many advantages beside its high catalytic efficiency such as the recyclability of up to five times with negligible loss of catalytic activity, short reaction times, use of environmentally benign solvent systems, and mild reaction conditions.

PEPPSI-SONO-SP2: a new highly efficient ligand-free catalyst system for the synthesis of tri-substituted triazine derivatives via Suzuki–Miyaura and Sonogashira coupling reactions under a green approach

Consecutive Suzuki–Miyaura and Sonogashira cross coupling reactions catalyzed by a new competent palladium catalyst PEPPSI-SONO-SP² under mild and green reaction conditions.

Synthesis and characterization of functionalized titania-supported Pd catalyst deriving from new orthopalladated complex of benzophenone imine: catalytic activity in the copper-free Sonogashira cross-coupling reactions at low palladium loadings

Efficient catalytic activity of TiO₂-supported Pd catalyst in the copper, amine and phosphine free Sonogashira cross-coupling reactions at low Pd-loadings.

Green synthesis of Pd/CuO nanoparticles by Theobroma cacao L. seeds extract and their catalytic performance for the reduction of 4-nitrophenol and phosphine-free Heck coupling reaction under aerobic conditions

We report the green synthesis of palladium/CuO nanoparticles (Pd/CuO NPs) using Theobroma cacao L. seeds extract and their catalytic activity for the reduction of 4-nitrophenol and Heck coupling reaction under aerobic conditions. The catalyst was characterized using the powder XRD, TEM, EDS, UV-vis and FT-IR. This method has the advantages of high yields, elimination of surfactant, ligand and homogeneous catalysts, simple methodology and easy work up. The catalyst can be recovered from the reaction mixture and reused several times without any significant loss of catalytic activity.

Tamarix gallica leaf extract mediated novel route for green synthesis of CuO nanoparticles and their application for N-arylation of nitrogen-containing heterocycles under ligand-free conditions

We report the green synthesis of CuO nanoparticles (CuO NPs) using Tamarix gallica leaf extract and their catalytic activity for N-arylation of nitrogen-containing heterocycles with aryl halides under ligand-free conditions.

Preparation of carbon supported CuPd nanoparticles as novel heterogeneous catalysts for the reduction of nitroarenes and the phosphine-free Suzuki–Miyaura coupling reaction

This paper reports on the synthesis and use of C/CuPd bimetallic NPs as heterogeneous catalysts for the phosphine-free Suzuki–Miyaura coupling and the reduction of nitroarenes.

Facile and surfactant-free synthesis of Pd nanoparticles by the extract of the fruits of Piper longum and their catalytic performance for the Sonogashira coupling reaction in water under ligand- and copper-free conditions

This work reports a facile synthesis of palladium nanoparticles (Pd NPs) by the extract of the fruits of Piper longum without any stabilizer or surfactant.

Preparation of Au nanoparticles by Anthemis xylopoda flowers aqueous extract and their application for alkyne/aldehyde/amine A3-type coupling reactions

This paper reports on the green synthesis of gold nanoparticles (Au NPs) by Anthemis xylopoda flowers aqueous extract without the addition of surfactant agents and their application as stable catalysts for the synthesis of propargylamines.

Synthesis and catalytic activity of carbon supported copper nanoparticles for the synthesis of aryl nitriles and 1,2,3-triazoles

Various substituted aryl nitrile and 1,2,3-triazole derivatives were prepared by using carbon supported copper nanoparticles (C/Cu NPs) as a heterogeneous catalyst under ligand-free conditions, which provided good to excellent yields.

Synthesis, characterization, structural, optical properties and catalytic activity of reduced graphene oxide/copper nanocomposites

This paper reports on the synthesis and use of copper nanoparticles supported on reduced graphene oxide, as separable catalysts for N-arylation of phenylurea with aryl halides under ligand-free and microwave conditions. Also, the structural and optical properties are studied.

One-pot three-component synthesis of 1,2,3-triazoles using magnetic NiFe2O4–glutamate–Cu as an efficient heterogeneous catalyst in water

A magnetic NiFe₂O₄ supported glutamate–copper catalyst is prepared and applied for the synthesis of a wide variety of 1,2,3-triazoles in water at room temperature.

Preparation of palladium nanoparticles using Euphorbia thymifolia L. leaf extract and evaluation of catalytic activity in the ligand-free Stille and Hiyama cross-coupling reactions in water

The yields of the reaction products were very high and no toxic organic solvents were needed in this method. The high efficiency of the catalyst remains unaltered even after five successive cycles.

Formation of dispersed palladium–nickel bimetallic nanoparticles in microemulsions: synthesis, characterization, and their use as efficient heterogeneous recyclable catalysts for the amination reactions of aryl chlorides under mild conditions

The amination cross-coupling reaction by Pd–Ni (1 : 1) bimetallic nanoparticles in water solvent.