Cationic tetranuclear macrocyclic CaCo3 complexes as highly active catalysts for alternating copolymerization of propylene oxide and carbon dioxide

We found that a cationic hetero tetranuclear complex including a calcium and three cobalts exhibited high catalytic activity toward alternating copolymerization of propylene oxide (PO) and carbon dioxide (CO2). The tertiary anilinium salt [PhNMe2H][B(C6F5)4] was the best additive to generate the cationic species while maintaining polymer selectivity and carbonate linkage, even under 1.0 MPa CO2. Density functional theory calculations clarified that the reaction pathway mediated by the cationic complex is more favorable than that mediated by the neutral complex by 1.0 kcal mol-1. We further found that the flexible ligand exchange between Ca and Co ions is important for the alternating copolymerization to proceed smoothly.

Cyclic polylactide synthesis initiated by a lithium anthraquinoid: understanding the selectivity through DFT and diffusion NMR

We present herein the application of a lithium anthraquinoid in the catalytic synthesis of cyclic PLA, showing that the aggregation plays a critical role in cyclic vs. linear selectivity.

Aluminum porphyrins with quaternary ammonium halides as catalysts for copolymerization of cyclohexene oxide and CO2: metal-ligand cooperative catalysis

Bifunctional Al porphyrins worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO₂.

Bifunctional Al^III porphyrins with quaternary ammonium halides, 2-Cl and 2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO₂ at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h^–1 and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional Mg^II and Zn^II counterparts, 3-Cl and 4-Cl, as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [2-Br] and zero-order in [CO₂], and the activation parameters were determined: ΔH^‡ = 12.4 kcal mol^–1, ΔS^‡ = –26.1 cal mol^–1 K^–1, and ΔG^‡ = 21.6 kcal mol^–1 at 80 °C. Comparative DFT calculations on two model catalysts, Al^III complex 2′ and Mg^II complex 3′, allowed us to extract key factors in the catalytic behavior of the bifunctional Al^III catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (ΔH^‡ = 13.3 kcal mol^–1, ΔS^‡ = –3.1 cal mol^–1 K^–1, and ΔG^‡ = 14.4 kcal mol^–1 at 80 °C).

Macrocyclic multinuclear metal complexes acting as catalysts for organic synthesis

Recent progress in homogeneous catalysis with macrocyclic multinuclear metal complexes (categories A–C) is overviewed.

Rare-earth/zinc heterometallic complexes containing both alkoxy-amino-bis(phenolato) and chiral salen ligands: synthesis and catalytic application for copolymerization of CO2 with cyclohexene oxide

Ten rare-earth/zinc heterometallic complexes were synthesized and their catalytic application for copolymerization of CO₂ with cyclohexene oxide was explored.

Advances in the use of CO2 as a renewable feedstock for the synthesis of polymers

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds.

Recyclable Single-Component Rare-Earth Metal Catalysts for Cycloaddition of CO2 and Epoxides at Atmospheric Pressure

Ionic rare-earth metal complexes 1-4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO₂. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60-97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40-95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity. This is the first recyclable rare-earth metal-based catalyst in cyclic carbonate synthesis.

Synthesis of Polycarbonates and Poly(ether carbonate)s Directly from Carbon Dioxide and Diols Promoted by a Cs2CO3/CH2Cl2 System

Recently, polycarbonates have attracted considerable research interest because of their potential biodegradability and sustainability. Here, we present a direct route for the synthesis of polycarbonates and poly(ether carbonate)s from carbon dioxide (CO₂) and diols, promoted by Cs₂CO₃ and CH₂Cl₂ under 1 atm of CO₂. Quantitative conversion of diols and polymers with up to 11 kg/mol molecular weight could be obtained. While benzylic diols lead to predominantly carbonate linkage, aliphatic diols result in the incorporation of the methylene unit of CH₂Cl₂ that produces poly(ether carbonate)s. Both primary and secondary diols have been successfully incorporated into the polymer chain.

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide

The choice of the anion has a surprisingly strong effect on the incorporation of CO2 into the polymer obtained during the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide. The product span ranges from polyethercarbonates, where short polyether sequences alternate with carbonate linkages, to polycarbonates with a strictly alternating sequence of the repeating units. Herein, we report on the influence of the coordination ability of the anion on the selectivity and kinetics of the copolymerisation reaction.

Carbon dioxide capture and utilization: using dinuclear catalysts to prepare polycarbonates

The copolymerization of epoxides, including cyclohexene oxide and vinyl-cyclohexene oxide with carbon dioxide are presented. These processes are catalyzed using a homogeneous di-zinc complex that shows good activity and very high selectivities for polycarbonate polyol formation. The polymerizations are investigated in the presence of different amounts of exogenous reagents, including water, diols and diamines, as models for common contaminants in any carbon dioxide capture and utilization scenario.

Ring-opening polymerization of cyclohexene oxide using aluminum amine–phenolate complexes

Al(iii) catalysts at concentrations as low as 0.001% ring-open cyclohexene oxide to yield high molecular weight polyether with narrow dispersity.

Dinuclear zinc catalysts with unprecedented activities for the copolymerization of cyclohexene oxide and CO2

New dinuclear zinc catalysts reveal by far the highest polymerization rates for the copolymerization of cyclohexene oxide and CO₂.

Kinetics of the (salen)Cr(iii)- and (salen)Co(iii)-catalyzed copolymerization of epoxides with CO2, and of the accompanying degradation reactions

The catalytic cycle of the (salen)M(iii)-catalyzed copolymerization for a variety of epoxides with CO₂ is elucidated using computational chemistry, and factors that control the kinetics and product distribution of these reactions are described.

A concise review of computational studies of the carbon dioxide–epoxide copolymerization reactions

The production of polycarbonates from carbon dioxide and epoxides is an important route by which waste CO₂ is converted into useful products. This review surveys the use of computational chemistry toward understanding this reaction.

Chemical datuments as scientific enablers

This article is an attempt to construct a chemical datument as a means of presenting insights into chemical phenomena in a scientific journal. An exploration of the interactions present in a small fragment of duplex Z-DNA and the nature of the catalytic centre of a carbon-dioxide/alkene epoxide alternating co-polymerisation is presented in this datument, with examples of the use of three software tools, one based on Java, the other two using Javascript and HTML5 technologies. The implications for the evolution of scientific journals are discussed.