Synthesis of recoverable palladium composite as an efficient catalyst for the reduction of nitroarene compounds and Suzuki cross-coupling reactions using sepiolite clay and magnetic nanoparticles (Fe3O4@sepiolite-Pd2+)

Magnetic bentonite decorated with Pd nanoparticles and cross-linked polyvinyl pyridine as an efficient nanocatalyst for Suzuki coupling and 4-Nitrophenol reduction reactions

This study reports the preparation of a novel type of support based on magnetically recyclable bentonite functionalized with divinylbenzene-polyvinyl pyridine (PVP-DVB) for Pd (II) nanocatalyst by a simple cost-effective method. Firstly, the conventional co-precipitation method synthesized Fe₃O₄ nanoparticles (NPs) onto bentonite sheets. Then the prepared magnetic support surface was functionalized by divinylbenzene-polyvinyl pyridine (PVP-DVB) to create a cross-linked polymer with a high coordination ability with palladium. Repeated nitrogen units in the PVP-DVB polymer chain increase the number of Pd bonds and thus lead to higher performance of the nanocatalyst. Finally, the palladium NPs were simultaneously synthesized and immobilized under mild conditions. The synthesized nanocatalyst was characterized by several methods such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometer, inductively coupled plasma mass spectrometry and thermogravimetric analysis. The efficiency of synthesized heterogeneous nanocatalyst was investigated in Suzuki-Miyaura cross-coupling reactions between a range of aryl halides (X = Cl, Br, I) with phenylboronic acid and in the reduction of 4-nitrophenol (4-NP). Moreover, the synthesized nanocatalyst could be easily recovered and reused several times with an efficiency greater than 90%.

Palladium Supported on Bioinspired Materials as Catalysts for C–C Coupling Reactions

In recent years, the immobilization of palladium nanoparticles on solid supports to prepare active and stable catalytic systems has been deeply investigated. Compared to inorganic materials, naturally occurring organic solids are inexpensive, available and abundant. Moreover, the surface of these solids is fully covered by chelating groups which can stabilize the metal nanoparticles. In the present review, we have focused our attention on natural biomaterials-supported metal catalysts applied to the formation of C–C bonds by Mizoroki–Heck, Suzuki–Miyaura and Sonogashira reactions. A systematic approach based on the nature of the organic matrix will be followed: (i) metal catalysts supported on cellulose; (ii) metal catalysts supported on starch; (iii) metal catalysts supported on pectin; (iv) metal catalysts supported on agarose; (v) metal catalysts supported on chitosan; (vi) metal catalysts supported on proteins and enzymes. We will emphasize the effective heterogeneity and recyclability of each catalyst, specifying which studies were carried out to evaluate these aspects.

Suzuki–Miyaura cross coupling reaction: recent advancements in catalysis and organic synthesis

Suzuki–Miyaura cross coupling reaction (SMCR) – A milestone in the synthesis of C–C coupled compounds.

Catalytic activity of maghemite supported palladium catalyst in nitrobenzene hydrogenation

A maghemite supported palladium catalyst was prepared and tested in nitrobenzene hydrogenation. The catalyst support was made by a newly developed combined technique, where sonochemical treatment and combustion have been used. As a first step, maghemite nanoparticles were synthesized. Iron(II) citrate was treated in polyethylene glycol by high-intensity ultrasound cavitation to get a homogeneous dispersion, then the product was combusted. The produced powder contained maghemite nanoparticles with 21.8 nm average particle size. In the second step of catalyst preparation, the magnetic nanoparticles were dispersed in the ethanolic solution of palladium(II) nitrate. The necessary energy for the reduction of Pd2+ ions was achieved in the “hot spots” by acoustic cavitation, thus catalytically active palladium was formed. The prepared maghemite supported Pd catalyst have been tested in nitrobenzene hydrogenation at three different temperatures (283 K, 293 K and 303 K) and constant pressure (20 bar). At 293 K and 303 K, the conversion and selectivity of nitrobenzene was above 99% and 96%, respectively. However, the selectivity was only 73% at 273 K because the intermediate species (azoxybenzene and nitrosobenzene) have not been transformed to aniline. All in all, the prepared catalyst is successfully applied in nitrobenzene hydrogenation and easily separable from the reaction media.