Heterogeneous catalysis on chitosan-based materials: a review

Polymer-supported Schiff base complexes in oxidation reactions

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

The preparation and catalytic applications of dispersed metal catalysts supported on organic functional polymers are presented. The advantages of these catalysts, such as the easy tailoring with respect to the nature of the used support, the “nanoscale” size control of metal crystallites by the polymer framework, the high accessibility and consequent catalytic activity in a proper liquid or liquid–vapor reaction systems are stressed. Various proposed catalytic processes making use of these materials are presented and evaluated, including multifunctional catalysis, e.g. redox-acid. Interesting peculiar aspects such as the enhancement of the hydrogenation rate by nitrogen containing moieties anchored to the polymer backbone are emphasised. When suitable, a comparison with catalysts based on inorganic supports is given.

Catalysis by metal nanoparticles supported on functional organic polymers

A heterogeneous catalytic assembly of Pd nanoparticles-in-SiO2 supported ionic liquid brushes has been developed. The catalytic assembly showed uniform Pd particles size distribution. The catalyst allowed the hydrogenation of nitrobenzenes to arylamines to proceed under solvent-free or in neat water, room temperature, and normal pressure, giving nearly 100% yield and selectivity. A clean and energy-efficient process can be thus created over the robust catalysts. The process employing such a catalytic assembly overcomes simultaneously the disadvantages of the requirement for organic solvents in the liquid hydrogenation process and for high temperature in the vapor hydrogenation process.

Pd Nanoparticles in Ionic Liquid Brush: A Highly Active and Reusable Heterogeneous Catalytic Assembly for Solvent-Free or On-Water Hydrogenation of Nitroarene under Mild Conditions

Polymer anchored metal complex catalysts of Pd(II) were synthesized using styrene divinyl benzene (PS–DVB) co-polymer of two different crosslinking (2% and 8%) by sequential attachment of chloromethyl group, bidentate ligand and treating the functionalized polymer with the metal chloride solution. The supports and the catalysts were characterized using conventional techniques as well as the spectroscopic methods such as UV-Vis reflectance, IR and DTA-TG analysis. Other physico chemical properties such as bulk density, moisture content, surface area by BET method and swelling of the catalysts in different solvents have also been studied. The morphology of the catalysts was seen using scanning electron microscope. A probable structure of the catalyst formed on polymer matrix was proposed on the basis of the above studies. The synthesized catalysts were tested for their catalytic activity for the hydrogenation of nitrobenzene as a model reaction. The influence on the rate of various factors such as the amount of catalysts, concentration of the substrate and temperature of the system has been studied. The recycling efficiency of catalysts has also been studied.

Hydrogenation of nitrobenzene using polymer anchored Pd(II) complexes as catalyst

Chloromethylated styrene-divinyl benzene copolymer with different types of cross-link was treated with glycine for the introduction of the ligand. The polymer modified with ligand was kept in contact with RuCl 3 to form the metal complex on the surface of the polymer. The catalysts thus prepared were characterised by techniques such as IR, UV-Vis reflectance spectroscopy and DTA-TG analysis. Other physico-chemical properties such as surface area, moisture content, bulk density and swelling were also studied. The morphology of the catalysts was observed by scanning electron microscope. The catalysts were tested for the hydrogenation of nitrobenzene as a model reaction. The influence of various parameters such as concentration of catalyst and substrate, temperature and different solvents on the rate of the reaction has been studied.

Preparation characterization and catalytic activity of polymer supported Ru(III) complexes

Chloromethylated styrene-divinyl benzene of 8% cross-link was functionalized using o-phenylene diamine and finally it . was treated with Mn II for the formation of metal complex on the surface. The metal content was estimated using atomic absorption spectroscopy. The thermal stability of the catalyst was seen by the use of DTA-TG analyses and the catalyst was found to be stable up to ; 1258C. The modern spectroscopic methods such as FT-IR, ESR were used in order to confirm the . probable structure of the catalyst. The catalytic activity of this supported Mn II -complex was investigated for aziridination of olefins with bromamine-T as the source of nitrogen. The catalyst was found to be effective in this reaction and could be reused with no substantial loss of activity for up to three cycles. q 2000 Elsevier Science B.V. All rights reserved. .

Bromamine-T mediated aziridination of olefins with a new / polymer supported Manganese II complex as catalyst

Styrene-divinylbenzene copolymer with 2 and 5% crosslinking was chloromethylated by HCl and HCHO using AlCl3 as the catalyst. Polymer-bound Ru(III) complex catalysts were synthesized by sequential attachment of 1,2-diaminopropane to the copolymer beads followed by treatment with a metal salt. The catalysts were characterized by using various techniques: FT-IR, SEM, EPR, NMR, ESCA, TGA, and UV-Vis reflectance spectroscopy. Other physicochemical properties were determined: surface area by the BET method, swelling studies with different solvents, and moisture content. The catalytic behavior of the prepared catalysts was tested for hydrogenation of cyclohexene as a model reaction. The influence on catalytic behavior of various parameters was studied: temperature, concentration of catalyst and substrate, quantity of solvent, and the use of various solvents. The recycling efficiency of the catalysts was also studied. A probable reaction mechanism is proposed.

Preparation, Properties, and Catalytic Application of Polymer-Bound Ru(III) Complexes

Polymer bound Pd(II) complexes have been synthesised by sequential attachment of ethylenediaminetetraacetic acid (EDTA) ligand to chloromethylated styrene-divinyl benzene copolymer and treatment with palladium salt. The prepared catalysts were characterized by various techniques such as UV-Vis reflectance spectroscopy, IR, ESR, SEM and TG analysis. Various physico-chemical properties such as surface area (by BET method), moisture content, bulk density and swelling by different solvents have also been studied. Catalytic activity of these catalysts was tested for hydrogenation of 1-hexene as a model reaction. The influence on the rate of variation in temperature, concentration of the catalysts as well as the substrate and nature of solvent was studied. Entropy of activation was calculated from the kinetic data. The recycling efficiency of the catalysts was also studied. A probable reaction mechanism has been proposed.

Dilip R. Patel

Papers

Hydrogenation of nitrobenzene using polymer anchored Pd(II) complexes as catalyst

Preparation characterization and catalytic activity of polymer supported Ru(III) complexes

Bromamine-T mediated aziridination of olefins with a new / polymer supported Manganese II complex as catalyst

Preparation, Properties, and Catalytic Application of Polymer-Bound Ru(III) Complexes

Polymer-bound palladium (II)-EDTA complexes as hydrogenation catalysts