A dual catalytic setup based on N-heterocyclic olefins (NHOs) and magnesium bis(hexamethyldisilazide) (Mg(HMDS) ) was used to prepare poly(propylene oxide) with a molar mass (M ) >500 000 g mol , in some cases even >10 g mol , as determined by GPC/light scattering. This is achieved by combining the rapid polymerization characteristics of a zwitterionic, Lewis pair type mechanism with the efficient epoxide activation by the Mg species. Transfer-to-monomer, traditionally frustrating attempts at synthesizing polyethers with a high degree of polymerization, is practically removed as a limiting factor by this approach. NMR and MALDI-ToF MS experiments reveal key aspects of the proposed mechanism, whereby the polymerization is initiated via nucleophilic attack by the NHO on the activated monomer, generating a zwitterionic species. This strategy can also be extended to other epoxides, including functionalized monomers.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1002/anie.201904806 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Trapping Anions within Stacks of Tetra-Urea Macrocycles.
J Am Chem Soc
January 2025
School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia.
Designing molecular receptors that bind anions in water is a significant challenge, and an even greater difficulty lies in using these receptors to remove anions from water without resorting to the hazardous liquid-liquid extraction approach. We here demonstrate an effective and synthetically simple strategy toward these goals by exploiting ion-pair assembly of macrocycles. Our anion binding ensemble consists of an octa-chloro tetra-urea macrocyclic anion receptor (ClTU), which forms water-dispersible aggregates, and a tetra-cationic fluorescent dye 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (TMPyP4), which provides Coulombic stabilization and fluorescence reporting of anion binding in an ion-pair assembly.
View Article and Find Full Text PDFOrganoboron-Functionalized Metal-organic Nanosheets for Highly Efficient CO2 Fixation Mediated by Frustrated Lewis Pairs.
Angew Chem Int Ed Engl
January 2025
University of North Texas, Department of Chemistry, 1508 W Mulberry St, 76201, Denton, UNITED STATES OF AMERICA.
Converting CO2 to high-value fine chemicals represents one of the most promising approaches to combat global warming and subsequently achieve a sustainable carbon cycle. Herein, we contribute an organoboron functionalized ultra-thin metal-organic nanosheet (MON), termed TCPB-Zr-NS, featuring an abundance of exposed Lewis acidic B and formate sites, which can effectively promote CO2 conversion upon the addition of Lewis basic o-phenylenediamines. Compared with the prototypical 3D analogue TCPB-Zr-3D, the resultant TCPB-Zr-NS showcases dramatically improved catalytic activity for the cyclization of o-phenylenediamine as a result of the highly exposed active sites and efficient substrates/products diffusion.
View Article and Find Full Text PDFConstructing Atomic Tungsten-Based Solid Frustrated-Lewis-Pair Sites with d-p Interactions for Selective CO Photoreduction.
J Am Chem Soc
January 2025
State Key Laboratory of Fluorine & Nitrogen Chemicals, School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Solid frustrated Lewis pair (FLP) shows remarkable advantages in the activation of small molecules such as CO, owing to the strong orbital interactions between FLP sites and reactant molecules. However, most of the currently constructed FLP sites are randomly distributed and easily reunited on the surface of catalysts, resulting in a low utilization rate of FLP sites. Herein, atomic tungsten-based FLP (N···W FLP) sites are constructed for photocatalytic CO conversion through introducing W single-atoms into polymeric carbon nitride.
View Article and Find Full Text PDFUnraveling the Strength and Nature of Se∙∙∙O Chalcogen Bonds: A Comparative Study of SeF and SeF Interactions with Oxygen-Bearing Lewis Bases.
Molecules
December 2024
School of Basic Medical Sciences/School of Biology and Engineering, Guizhou Medical University, Guiyang 550025, China.
Chalcogen bonds (ChBs) involving selenium have attracted substantial scholarly interest in past years owing to their fundamental roles in various chemical and biological fields. However, the effect of the valency state of the electron-deficient selenium atom on the characteristics of such ChBs remains unexplored. Herein, we comparatively studied the σ-hole-type Se∙∙∙O ChBs between SeF/SeF and a series of oxygen-bearing Lewis bases, including water, methanol, dimethyl ether, ethylene oxide, formaldehyde, acetaldehyde, acetone, and formic acid, using ab initio computations.
View Article and Find Full Text PDFA Longitudinal Pediatric Residency Climate Justice Curriculum.
J Grad Med Educ
December 2024
is Associate Professor of Clinical Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Graduate medical education programs must prepare physicians to adapt their care for patients whose health equity and outcomes are being threatened by climate change. This article presents the implementation of a longitudinal climate justice curriculum within a pediatrics residency program. To measure the self-reported changes in attitudes and intentions for change in behavior after implementation of a climate justice curriculum.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!