1,721,009 research outputs found
The stereoselective polymerization of linear conjugated dienes
No full textPolydienes are amongst the largest worldwide produced and manufactured classes of polymers. This is because of their elastomeric properties, which make them suitable for many applications as synthetic rubbers.1
Recent Advancements in Metal-catalysts Design for CO2/Epoxide Reactions
Full text linkCarbon dioxide utilization is considered an effective strategy to mitigate the carbon footprint of chemical industry. Among other uses, the incorporation of carbon dioxide into cyclic organic carbonates (COCs) and aliphatic polycarbonates (APCs) has received great attention in the field of homogeneous catalysis. After few decades of research activity, a wide range of metal-based catalytic systems has been reported to promote this reaction. Nonetheless, a better comprehension of the apparently simple reaction mechanism of such transformations has been reached only in recent years. This, in turn, allowed for the design of new catalytic systems guided by a clearer mechanistic picture. In this review, we present the most recent advancements in this field, distinguishing between catalysts for COCs and APCs production classified on the bases of their ligand structures
Terpolymerization of co2 with epoxides and cyclic organic anhydrides or cyclic esters
No full textThe synthesis of polymeric materials starting from CO2 as a feedstock is an active task of research. In particular, the copolymerization of CO2 with epoxides via ring-opening copolymerization (ROCOP) offers a simple, efficient route to synthesize aliphatic polycarbonates (APC). In many cases, APC display poor physical and chemical properties, limiting their range of application. The terpolymerization of CO2 with epoxides and organic anhydrides or cyclic esters offers the possibility, combining the ROCOP with ring-opening polymerization (ROP), to access a wide range of materials containing polycarbonate and polyester segments along the polymer chain, showing enhanced properties with respect to the simple APC. This review will cover the last advancements in the field, evidencing the crucial role of the catalytic system in determining the microstructural features of the final polymer
Homogeneous Iron Catalysts for the Synthesis of Useful Molecules from CO2
No full textCarbon dioxide utilization is a hot topic in modern science, and chemical transformation of CO2 into useful molecules (e.g. fuels, solvents, polymers, drugs, and building blocks) has gained more and more attention during the past decades. The search for highly efficient catalytic systems plays a major role in the development of sustainable CO2 fixation. At the same time, catalyst design must be conducted following the green chemistry principles. For this reason, iron is emerging as a desired substitute of other transition metals (e.g. chromium, ruthenium, and rhodium) because of its Earth crust abundance and low toxicity. Here, we describe the use of iron-based homogeneous catalytic systems for the conversion of carbon dioxide into value-added products by means of both reductive and nonreductive processes
Synthesis and physical properties of elasomeric polypropylene obtained in the prersence of TiCl2(2-OC6H4OCH3)2 and methyl aluminoxane
No full text[OSSO]-bisphenolate metal complexes: A powerful and versatile tool in polymerization catalysis
No full textSince the report of the stereospecific polymerization of styrene dated 2003, metal complexes bearing [OSSO]-bisphenolate ligands have been successfully applied in different branches of homogeneous catalysis, de facto building a new research field. This review will focus on polymerization reactions promoted by these complexes, starting with those involving “traditional” monomers (such as fossil-derived olefins) up to more recent and green applications, like polymerization of terpenes or utilization of CO2 as a green building block
Metal complexes bearing sulfur-containing ligands as catalysts in the reaction of co2 with epoxides
No full textCoupling of CO2 with epoxides is a green emerging alternative for the synthesis of cyclic organic carbonates (COC) and aliphatic polycarbonates (APC). The scope of this work is to provide a comprehensive overview of metal complexes having sulfur-containing ligands as homogeneous catalytic systems able to efficiently promote this transformation with a concise discussion of the most significant results. The crucial role of sulfur as the hemilabile ligand and its influence on the catalytic activity are highlighted as well
SYNTHESIS AND PHYSICAL PROPERTIES OF ELASTOMERIC POPLYPROPYLENE OBTAINED IN THE PRESENCE OF OF TICL2(2-OC6H4OCH3)2 AND METHYL ALUMINOXANE
No full textSynthesis and physical properties of elasomeric polypropylene obtained in the prersence of TiCl2(2-OC6H4OCH3)2 and methyl aluminoxane
No full textAsymmetric hydrodimerization of styrene by a chiral zirconium complex containing a tetradentate [OSSO]-type bis(phenolato) ligand
No full textThe chiral non racemic (Λ,R,R)-[OSSO]Zr(CH2Ph) 2 (1a) activated by methylaluminoxane (MAO) and in presence of H 2 produces the chiral hydrodimer (S)-1,3-diphenylbutane with good selectivity respect to the achiral 1,4-diphenylbutane. The absolute configuration of the chiral dimer and the effect of the hydrogen pressure on the ratio between 1,3-diphenylbutane and 1,4-diphenylbutane give useful information about the regiochemistry and stereochemistry of insertion of the styrene into the Zr-H bond. © 2011 Elsevier B.V. All rights reserved
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