Szewczyk, Marcin; Magre, Marc; Zubar, Viktoriia; Rueping, Magnus(ACS Catalysis, American Chemical Society (ACS), 2019-11-20)[Article]
Efficient reduction of cyclic and linear organic carbonates catalyzed by a readily available earth alkaline catalyst has been achieved. The described homogenous reaction based on a ligand-free magnesium catalyst provides an indirect route for the conversion of CO2 into valuable alcohols. The reaction proceeds with high yields under mild reaction conditions, with low catalyst loading and short reaction times, and shows a broad applicability toward various linear and cyclic carbonates. Additionally, it can be applied for the depolymerization of polycarbonates.
Kenyon, Philip; Falivene, Laura; Caporaso, Lucia; Mecking, Stefan(ACS Catalysis, American Chemical Society (ACS), 2019-11-18)[Article]
The influence of the labile ligand on the rate of β-hydride elimination (BHE) for salicylaldiminato Ni(II) complexes is shown using a series of precatalysts which differ only in the labile ligand but produce polyethylenes with a range of molecular weights (Mn = 466 to 100 kg mol-1), degrees of branching (1.7 to 7.3 branches/1000 C), and melting temperatures (from 132 to 123 °C) under the same conditions. The use of a weakly coordinating solvent (diethyl ether) was able to suppress this increase in BHE. DFT studies on a related salicylaldiminato Ni(II) complex show that BHE can feasibly occur following recombination of the labile ligand with the catalyst.
Lebedev, Yury; Polishchuk, Iuliia; Maity, Bholanath; Dinis Veloso Guerreiro, Miguel; Cavallo, Luigi; Rueping, Magnus(Journal of the American Chemical Society, American Chemical Society (ACS), 2019-11-09)[Article]
A series of methyl aluminum complexes bearing chiral biphenol-type ligands were found to be highly active catalysts in the asymmetric reduction of heterocyclic ketones (S/C = 100-500, ee up to 99%). The protocol is suitable for a wide range of substrates and has a high tolerance to functional groups. The formed 2-heterocyclic-alcohols are valuable building blocks in drug discovery or can be used as ligands in asymmetric catalysis. Isolation and comprehensive characterization of the reaction intermediates support a catalysis cycle proposed by DFT calculations.
Vollmer, Ina; Ould-Chikh, Samy; Aguilar-Tapia, Antonio; Li, Guanna; Pidko, Evgeny A.; Hazemann, Jean-Louis; Kapteijn, Freek; Gascon, Jorge(Journal of the American Chemical Society, American Chemical Society (ACS), 2019-11-04)[Article]
Producing aromatics directly from the smallest hydrocarbon building block, methane, is attractive because it could help satisfy increasing demand for aromatics while filling the gap created by decreased production from naphtha crackers. The system that catalyzes the direct methane dehydroaromatization (MDA) best so far is Mo supported on zeolite. Mo has shown to outperform other transition metals (TMs). Here we attempt to explain the superiority of Mo by directly comparing Fe and Mo supported on HZSM-5 zeolite. To determine the most important parameters responsible for the superior performance of Mo, detailed characterization using X-ray absorption spectroscopy (XAS) techniques combined with catalytic testing and theoretical calculations are performed. The higher abundance of mono- and dimeric sites for the Mo system, their ease of carburization in methane, as well as intrinsically lower activation energy barriers of breaking the methane C–H bond over Mo explain the better catalytic performance. In addition, a pretreatment in CO is presented to more easily carburize Fe and thereby improve its catalytic performance.
Chatupheeraphat, Adisak; Rueping, Magnus; Magre, Marc(Organic Letters, American Chemical Society (ACS), 2019-10-31)[Article]
A simple and efficient catalytic system for a chemo- and regioselective ortho-alkenylation of anilines is presented. The new magnesium-catalyzed reaction allows the use of a wide range of alkynes and anilines with different electronic and steric properties and provides free as well as protected anilines with excellent yields.
Shoinkhorova, Tuiana; Dikhtiarenko, Alla; Galilea, Adrian; Chowdhury, Abhishek Dutta; Caglayan, Mustafa; Vittenet, Jullian; Bendjeriou-Sedjerari, Anissa; Ali, Ola S; Morales-Osorio, Isidoro; Xu, Wei; Gascon, Jorge(ACS applied materials & interfaces, American Chemical Society (ACS), 2019-10-16)[Article]
Shaping and optimal compositional formulation are major challenges in the successful industrial application of heterogeneous catalysts. The choice of components during formulation plays a vital role in endowing the final catalyst's mechanical strength, durability, and lifetime and may even affect activity and selectivity. Herein, we evaluate the application of spray drying to manufacture spherical ZSM-5-based catalysts and their applicability in the methanol-to-olefins process. Several critical parameters of the spray drying process and various aspects related to catalyst formulation (binder, zeolite, and clay) are investigated. Chemical composition and structure of the clay matrix substantially influence the catalytic performance.
Samantaray, Manoja; D’Elia, Valerio; Pump, Eva; Falivene, Laura; Harb, Moussab; Ould-Chikh, Samy; Cavallo, Luigi; Basset, Jean-Marie(Chemical Reviews, American Chemical Society (ACS), 2019-10-15)[Article]
Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis. The predictive character of SOMCat was just the result of intuitive mechanisms derived from the elementary steps of molecular chemistry. This review article will compare the aspects of single atom catalysis and surface organometallic catalysis by considering several specific catalytic reactions, some of which exist for both fields, whereas others might see mutual overlap in the future. After a definition of both domains, a detailed approach of the methods, mostly modeling and spectroscopy, will be followed by a detailed analysis of catalytic reactions: hydrogenation, dehydrogenation, hydrogenolysis, oxidative dehydrogenation, alkane and cycloalkane metathesis, methane activation, metathetic oxidation, CO2 activation to cyclic carbonates, imine metathesis, and selective catalytic reduction (SCR) reactions. A prospective resulting from present knowledge is showing the emergence of a new discipline from the overlap between the two areas.
Ming, Jun; Cao, Zhen; Wu, Yingqiang; Wahyudi, Wandi; Wang, Wenxi; Guo, Xianrong; Cavallo, Luigi; Hwang, Jang-Yeon; Shamim, Atif; Li, Lain-Jong; Sun, Yang-Kook; Alshareef, Husam N.(ACS Energy Letters, American Chemical Society (ACS), 2019-10-11)[Article]
Solid electrolyte interphase (SEI)-forming agents such as vinylene carbonate, sulfone, and cyclic sulfate are commonly believed to be film-forming additives in lithium-ion batteries that help to enhance graphite anode stability. However, we find that the film-forming effect and the resultant SEI may not be the only reasons for the enhanced graphite stability. This is because the as-formed SEI cannot inhibit Li+–solvent co-intercalation once the additive is removed from the electrolyte. Instead, we show that the Li+ solvation structure, which is modified by these additives, plays a critical role in achieving reversible Li+ (de)intercalation within graphite. This discovery is confirmed in both carbonate and ether-based electrolytes. We show that the problem of graphite exfoliation caused by Li+–solvent co-intercalation can be mitigated by adding ethene sulfate to tune the Li+ coordination structure. This work brings new insight into the role of additives in electrolytes, expanding the prevailing thinking over the past 2 decades. In addition, this finding can guide the design of more versatile electrolytes for advanced rechargeable metal-ion batteries.
Hall, Ryan; Desai, Priyanka S.; Kang, Beom-Goo; Huang, Qifan; Lee, Sanghoon; Chang, Taihyun; Venerus, David C.; Mays, Jimmy; Ntetsikas, Konstantinos; Polymeropoulos, George; Hadjichristidis, Nikolaos; Larson, Ronald G.(Macromolecules, American Chemical Society (ACS), 2019-10-10)[Article]
We blend newly synthesized nearly monodisperse four-arm star 1,4-polybutadienes with various well-entangled linear polymers, confirming the conclusions in Desai et al. [ Macromolecules201649 (13)49644977] that advanced tube models, namely, the hierarchical 3.0 and branch-on-branch models [Wang, Z.; J. Rheol.201054 (2)223260], fail to predict the linear rheological data when the pure linear polymers have shorter relaxation times, but within 3–4 orders of magnitude of the star polymer. However, when the linear polymer has a longer relaxation time than the star, our new work, surprisingly, finds that non-monotonic dependence of terminal relaxation behavior on composition is both observed experimentally and captured by the models. Combined with previous data from the literature, we present results from over 50 1,4-polybutadiene star–linear blends, suitable for thorough testing of rheological models of entangled polymers.
Jang, Yoon Kyung; Magre, Marc; Rueping, Magnus(Organic Letters, American Chemical Society (ACS), 2019-10-07)[Article]
The chemoselective reduction of α,β-unsaturated ketones by use of an economic and readily available Mg catalyst has been developed. Excellent yields for a wide range of ketones have been achieved under mild reaction conditions, short times, and low catalyst loadings (0.2-0.5 mol %).
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