Pd immobilized on thiol-modified magnetic nanoparticles: A complete magnetically recoverable and highly active catalyst for hydrogenation reactions

A palladium-based catalyst supported on thiol-modified superparamagnetic nanoparticles was successfully prepared by co-precipitation method. These magnetic nanomaterials were characterized by elemental analysis (EA), inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fourier transform-infrared (FT-IR), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM). The conversions of various aromatic nitro and unsaturated compounds can receive a really high yield with the existence of magnetic nanomaterials. The turn-over frequency (TOF) can be 66.46 h⁻¹ in ethanol under a H₂ atmosphere at room temperature. In this paper, the conversions of aromatic nitro bearing a variety of substituents were 93.56–100%, moreover, the catalyst afforded over 90% yield in the reducing unsaturated compounds. Another advantage is that the magnetite nanoparticles modified by thiol group can be separated just through the external magnetic force and can be reused atleast ten times without any significant loss in activity.     

Graphene-supported hemin as a highly active biomimetic oxidation catalyst

Well supported: stable hemin-graphene conjugates formed by immobilization of monomeric hemin on graphene, showed excellent catalytic activity, more than 10 times better than that of the recently developed hemin-hydrogel system and 100 times better than that of unsupported hemin. The catalysts also showed excellent binding affinities and catalytic efficiencies approaching that of natural enzymes.     

Ultra-deep desulfurization of diesel: oxidation with a recoverable catalyst assembled in emulsion

A [(C(18)H(37))(2)N(+)(CH(3))(2)](3)[PW(12)O(40)] catalyst, assembled in an emulsion in diesel, can selectively oxidize the sulfur-containing molecules present in diesel into their corresponding sulfones by using H(2)O(2) as the oxidant under mild conditions. The sulfones can be readily separated from the diesel using an extractant, and the sulfur level of the desulfurized diesel can be lowered from about 500 ppm to 0.1 ppm without changing the properties of the diesel. The catalyst demonstrates high performance (>/=96 % efficiency of H(2)O(2), is easily recycled, and approximately 100 % selectivity to sulfones). Metastable emulsion droplets (water in oil) act like a homogeneous catalyst and are formed when the catalyst (as the surfactant) and H(2)O(2) (30 %) are mixed in the diesel. However, the catalyst can be separated from the diesel after demulsification.     

Pd nanoparticles immobilized on PNIPAM–halloysite: highly active and reusable catalyst for Suzuki–Miyaura coupling reactions in water

Poly(N‐isopropylacrylamide)–halloysite (PNIPAM‐HNT) nanocomposites exhibited inverse temperature solubility with a lower critical solution temperature (LCST) in water. Palladium (Pd) nanoparticles were anchored on PNIPAM‐HNT nanocomposites with various amounts of HNT from 5 to 30 wt%. These Pd catalysts exhibited excellent reactivities for Suzuki–Miyaura coupling reactions at 50–70 °C in water. In particular, Pd anchored PNIPAM/HNT (95:5 w/w ratio) nanocomposites showed excellent recyclability up to 10 times in 96% average yield by simple filtration. Copyright © 2014 John Wiley & Sons, Ltd.     

Pd on amine-terminated ferrite nanoparticles: a complete magnetically recoverable facile catalyst for hydrogenation reactions

[structure: see text]. The present communication reports a facile route for Pd(0) immobilization on the surface of amine-terminated Fe3O4 and NiFe2O4 nanoparticles for a series of hydrogenation reactions. The catalysts are completely recoverable with the simple application of an external magnetic field, and the efficiency of the catalyst remains unaltered even after 10 repeated cycles for each of the reactions.     

Facile preparation of highly stable and active hybrid palladium nanoparticles: effectual,reusable and heterogeneous catalyst for coupling reactions

Palladium nanoparticles were supported on a bed of Fe₃O₄@‐NH₂@Murexide using a simple and efficient method, and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies and inductively coupled plasma optical emission spectrometry. The catalytic system showed great efficiency in cross‐coupling reaction of aryl iodides and arylboronic acid and in Sonogashira cross‐coupling reaction in the green solvent EtOH–H₂O (1:1). The isolation and recovery of the catalyst were simple and facile and it could be used for several successive Suzuki–Miyaura coupling and Sonogashira cross‐coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

WO3/C hybrid material as a highly active catalyst support for formic acid electrooxidation

The hybrid material based on WO₃ and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO₃/C catalysts in a large range of WO₃ content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO₃/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd.     

Suzuki-Miyaura coupling catalyzed by polymer-incarcerated palladium, a highly active, recoverable, and reusable Pd catalyst

[reaction: see text] Suzuki-Miyaura coupling using a highly efficient and reusable polymer-incarcerated palladium (PI Pd) is described. Various coupling reactions proceeded smoothly using PI Pd with phosphine ligands, and the catalyst could be recovered by simple filtration and reused several times without loss of activity.     

An assembled complex of palladium and non-cross-linked amphiphilic polymer: a highly active and recyclable catalyst for the Suzuki-Miyaura reaction

An insoluble and assembled catalyst of palladium and a non-cross-linked amphiphilic polymer were developed. In the presence of 50-500 ppm mol equiv of catalyst, the Suzuki-Miyaura reaction proceeded efficiently under organic solvent-free conditions. The catalyst was reused 10 times without any decrease in activity and was recycled without any special treatment.[structure: see text]     

Computational study-led organocatalyst design: a novel, highly active urea-based catalyst for addition reactions to epoxides

An in silico study examined the stabilities of hydrogen-bonded complexes between simple thiourea catalysts and three different electrophiles and identified a novel, highly active N-tosyl urea catalyst for the promotion of addition reactions to epoxide electrophiles. Synthesis and evaluation of 6 revealed it to be a powerful catalyst for the addition of 1,2-dimethylindole to styrene oxide under conditions in which simple N,N-bis-aryl ureas and thioureas (including 1) are inactive. Subsequent studies determined 6 to be compatible with a range of indole and epoxide substrates (including (E)-stilbene oxide) and found that relatively poor nucleophiles such as sterically and electronically deactivated anilines, thiophenol, and benzyl alcohol could be efficiently and regioselectively added to oxiranes under mild conditions.     

Copper Schiff base complex immobilized on silica‐coated Fe3O4 nanoparticles: a recoverable and efficient catalyst for synthesis of polysubstituted pyrroles

In this work, a copper Schiff base complex immobilized on silica‐coated Fe₃O₄ nanoparticles is synthesized, and studied as a highly efficient, recyclable, green and heterogeneous catalyst for the preparation of polysubstituted pyrroles under solvent‐free and mild conditions. This new catalyst was characterized by different techniques, such as Fourier transform infrared (FT‐IR), X‐ray powder diffraction (XRD), field‐emission scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), inductively coupled plasma (ICP) and vibrating sample magnetometry (VSM). The simple and environmentally one‐pot multicomponent condensation of nitromethane, an aryl aldehyde, a 1,3‐dicarbonyl compound and an amine in the presence of above catalyst affords the title compounds at room temperature. At the end, we compared the results for the synthesis of polysubstituted pyrroles in the presence of our nanocatalyst with previously reported catalysts in the literature.     

Pd(OH)2/C (Pearlman's catalyst): a highly active catalyst for Fukuyama,Sonogashira, and Suzuki coupling reactions

Treatment of thiol esters 1 with zinc reagent 2 in the presence of a small amount (相似文献   

Copper immobilized onto polymer‐coated magnetic nanoparticles as recoverable catalyst for ‘click’ reaction

Copper supported on polymer‐coated magnetic nanoparticles was designed and synthesized as a separable heterogeneous catalyst. The catalyst was fully characterized using several techniques such as Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning and transmission electron microscopies, X‐ray diffraction, vibrating sample magnetometry, thermogravimetric analysis and inductively coupled plasma atomic emission spectrometry. All results showed that copper was successfully supported on the polymer‐coated magnetic nanoparticles. Also, results showed that the synthesized material can be used as an efficient catalyst for the preparation of a series of 1,4‐disubstituted 1,2,3‐triazoles from corresponding halides, alkynes and sodium azide. The catalyst can be easily isolated from the reaction solution by applying an external magnet and reused for nine runs without any significant loss of catalytic activity.     

Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener

With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.     

Pd on surface-modified NiFe2O4 nanoparticles: a magnetically recoverable catalyst for Suzuki and Heck reactions

This communication reports on the use of NiFe2O4-DA-Pd, a complete magnetically separable catalyst for Suzuki and Heck coupling reactions of aromatic halide derivatives. The catalyst efficiency for the coupling of chloro derivatives is as good as bromo and iodo derivatives. Catalytic efficiency remains unaltered even after three repeated cycles.     

New N-heterocyclic carbene palladium complex/ionic liquid matrix immobilized on silica: application as recoverable catalyst for the Heck reaction

[reaction: see text] A new concept of simultaneous covalent anchoring of a N-heterocyclic carbene palladium/ionic liquid matrix on the silica surface and the application of the resulting catalyst in the Heck reaction of a variety of different haloarenes is described. The catalyst shows high thermal stability (up to 280 degrees C) and could be recovered and reused for four reaction cycles, giving a total TON congruent with 36 600. Furthermore, TEM coupled with EDX analysis indicate the formation of Pd nanoparticles within the immobilized IL layer.     

Copper perchlorate hexahydrate: a highly efficient catalyst for the cyanosilylation of aldehydes

Cu(ClO₄)₂·6H₂O has been found to be an efficient catalyst for cyanosilylation reaction of aldehydes in THF at room temperature with low catalytic loading (1.0 mol%) in short reaction time (mostly within 10 min). Copyright © 2008 John Wiley & Sons, Ltd.     

一种杂化型分散剂对纳米碳酸钙分散作用的研究

本文制备了一种有机无机杂化型分散剂,该分散剂由聚(丙烯酰氧乙基三甲基氯化铵-丙烯酸钠)(P(DAC-AAS))与多金属簇硅钨酸H4O40Si W12·x H2O(Si W12)通过静电相互作用复合得到。研究了该类分散剂应用于纳米碳酸钙水溶液的分散过程,并使用动态光散射法进行监测。与此同时运用红外光谱及热重分析对包覆改性前后的纳米碳酸钙进行了表征,结果显示分散剂通过吸附和化学键合来包覆改性纳米碳酸钙。