C–H Bond Activation by Oxygen-Centered Radicals over Atomic Clusters DOI
Xunlei Ding, Xiao‐Nan Wu, Yan‐Xia Zhao

et al.

Accounts of Chemical Research, Journal Year: 2011, Volume and Issue: 45(3), P. 382 - 390

Published: Oct. 21, 2011

Saturated hydrocarbons, or alkanes, are major constituents of natural gas and oil. Directly transforming alkanes into more complex organic compounds is a value-adding process, but the task very difficult to achieve, especially at low temperature. Alkanes can react high temperature, these reactions (with oxygen, for example) control usually proceed carbon dioxide water, thermodynamically stable byproducts. Consequently, great deal research effort has been focused on generating studying chemical entities that able with efficiently activate C-H bonds lower temperatures, preferably room To identify low-temperature methods bond activation, researchers have investigated free radicals, is, species open-shell electronic structures. Oxygen-centered radicals typical naturally occur in atmospheric, chemical, biological systems. In this Account, we survey atomic clusters contain oxygen-centered (O(-•)), an emphasis radical generation reaction near Atomic intermediate state matter, situated between isolated atoms condensed-phase materials. containing O(-•) moiety generated promising results activation. After brief introduction experimental compositions focus two important factors dramatically influence The first factor spin. O(-•)-containing unpaired spin density distributions over oxygen atoms. We show nature distribution, such as localization delocalization within clusters, heavily influences reactivity second charge. be negatively charged, positively neutral overall. discuss how charge may Moreover, given state, cationic it demonstrated local distribution around centers also significantly change Through judicious synthetic choices, readily controllable physical quantities clusters. adjustment properties impact thus constituting consideration rational design catalysts practical alkane transformations.

Language: Английский

Carboxylate-Assisted Ruthenium-Catalyzed Alkyne Annulations by C–H/Het–H Bond Functionalizations DOI
Lutz Ackermann

Accounts of Chemical Research, Journal Year: 2013, Volume and Issue: 47(2), P. 281 - 295

Published: Feb. 4, 2013

To improve the atom- and step-economy of organic syntheses, researchers would like to capitalize upon chemistry otherwise inert carbon–hydrogen (C–H) bonds. During past decade, remarkable progress in organometallic has set stage for development increasingly viable metal catalysts C–H bond activation reactions. Among these methods, oxidative functionalizations are particularly attractive because they avoid use prefunctionalized starting materials. For example, annulations that involve sequential heteroatom–H cleavages allow modular assembly regioselectively decorated heterocycles. These structures serve as key scaffolds natural products, functional materials, crop protecting agents, drugs. While other have devised rhodium or palladium complexes alkyne annulations, my laboratory focused on application significantly less expensive, yet highly selective ruthenium complexes.This Account summarizes evolution versatile ruthenium(II) alkynes via C–H/N–H, C–H/O–H, C–H/N–O cleavages. achieve functionalizations, we needed understand detailed mechanism crucial metalation with importance carboxylate assistance this process. As a consequence, our recent efforts resulted widely applicable methods preparation differently arenes heteroarenes, providing access among others isoquinolones, 2-pyridones, isoquinolines, indoles, pyrroles, α-pyrones. Most reactions used Cu(OAc)2·H2O, which not only acted oxidant but also served essential source acetate carboxylate-assisted ruthenation manifold. Notably, ruthenium(II)-catalyzed occurred under an ambient atmosphere air cocatalytic amounts Cu(OAc)2·H2O. Moreover, substrates displaying N–O bonds "internal oxidants" syntheses isoquinolones isoquinolines. Detailed experimental mechanistic studies provided strong support catalytic cycle relies initial ruthenation, followed by coordinative insertion alkyne, reductive elimination, reoxidation thus formed ruthenium(0) complex.

Language: Английский

Citations

1577
Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen DOI
Xiaoguang Guo,

Guangzong Fang,

Gang Li

et al.

Science, Journal Year: 2014, Volume and Issue: 344(6184), P. 616 - 619

Published: May 8, 2014

The efficient use of natural gas will require catalysts that can activate the first C-H bond methane while suppressing complete dehydrogenation and avoiding overoxidation. We report single iron sites embedded in a silica matrix enable direct, nonoxidative conversion methane, exclusively to ethylene aromatics. reaction is initiated by catalytic generation methyl radicals, followed series gas-phase reactions. absence adjacent prevents C-C coupling, further oligomerization, hence, coke deposition. At 1363 kelvin, reached maximum at 48.1% selectivity peaked 48.4%, whereas total hydrocarbon exceeded 99%, representing an atom-economical transformation process methane. lattice-confined delivered stable performance, with no deactivation observed during 60-hour test.

Language: Английский

Citations

1252
Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects DOI
Pierre Schwach, Xiulian Pan, Xinhe Bao

et al.

Chemical Reviews, Journal Year: 2017, Volume and Issue: 117(13), P. 8497 - 8520

Published: May 5, 2017

The quest for an efficient process to convert methane efficiently fuels and high value-added chemicals such as olefins aromatics is motivated by their increasing demands recently discovered large reserves resources of methane. Direct conversion these can be realized either oxidatively via oxidative coupling (OCM) or nonoxidatively dehydroaromatization (MDA), which have been under intensive investigation decades. While industrial applications are still limited low yield (selectivity) stability issues, innovations in new catalysts concepts needed. newly emerging strategy using iron single sites catalyze olefins, aromatics, hydrogen (MTOAH) attracted much attention when it was reported. Because the challenge lies controlled dehydrogenation highly stable CH4 selective C–C coupling, we focus mainly on fundamentals C–H activation analyze reaction pathways toward routes OCM, MDA, MTOAH. With this, intend provide some insights into mechanisms implications future development direct chemicals.

Language: Английский

Citations

1191
Green Carbon Science: Scientific Basis for Integrating Carbon Resource Processing, Utilization, and Recycling DOI
Mingyuan He, Yuhan Sun, Buxing Han

et al.

Angewandte Chemie International Edition, Journal Year: 2013, Volume and Issue: 52(37), P. 9620 - 9633

Published: July 26, 2013

How green was my valley: Green carbon science focuses on the transformations of carbon-containing compounds in entire cycle. The ultimate aim is to use resources efficiently and minimize net CO2 emission. This holistic view also has ramifications for related fields including petroleum refining production liquid fuels chemicals from coal, methane, CO2, biomass.

Language: Английский

Citations

840
Selective anaerobic oxidation of methane enables direct synthesis of methanol DOI
Vitaly L. Sushkevich, Dennis Palagin, Marco Ranocchiari

et al.

Science, Journal Year: 2017, Volume and Issue: 356(6337), P. 523 - 527

Published: May 4, 2017

Direct functionalization of methane in natural gas remains a key challenge. We present direct stepwise method for converting into methanol with high selectivity (~97%) over copper-containing zeolite, based on partial oxidation water. The activation helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars and then water 473 K, consistently produced 0.204 mole CH3OH per copper zeolite. Isotopic labeling confirmed as the source oxygen regenerate zeolite active centers renders desorption energetically favorable. On basis situ x-ray absorption spectroscopy, infrared density functional theory calculations, we propose mechanism involving CuII oxide centers, CuI reoxidation concurrent formation hydrogen.

Language: Английский

Citations

759
Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry DOI
Zhen Guo, Bin Liu, Qinghong Zhang

et al.

Chemical Society Reviews, Journal Year: 2014, Volume and Issue: 43(10), P. 3480 - 3480

Published: Jan. 1, 2014

Oxidation catalysis not only plays a crucial role in the current chemical industry for production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to establishment novel green sustainable processes. This review is devoted dealing with selective oxidation reactions, which are important from viewpoint chemistry still remain challenging. Actually, some well-known highly challenging reactions involve methane by oxygen. On other hand aerobic alcohols liquid phase preferential carbon monoxide hydrogen, have attracted much attention recent years because their high significance or energy chemistry. article summarizes advances development new catalytic materials systems these reactions. A deep scientific understanding mechanisms, active species structures discussed. Furthermore, connections among distinct highlighted, gain insight breakthrough rational design efficient

Language: Английский

Citations

727
Catalysis by clusters with precise numbers of atoms DOI
Eric C. Tyo, Štefan Vajda

Nature Nanotechnology, Journal Year: 2015, Volume and Issue: 10(7), P. 577 - 588

Published: July 1, 2015

Language: Английский

Citations

649
Methane Activation by Heterogeneous Catalysis DOI Open Access
Raimund Horn,

Robert Schlögl

Catalysis Letters, Journal Year: 2014, Volume and Issue: 145(1), P. 23 - 39

Published: Nov. 20, 2014

Language: Английский

Citations

583
Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C–H activation DOI

Matthew D. Marcinkowski,

Matthew T. Darby, Jilei Liu

et al.

Nature Chemistry, Journal Year: 2018, Volume and Issue: 10(3), P. 325 - 332

Published: Jan. 8, 2018

Language: Английский

Citations

551
Understanding trends in C–H bond activation in heterogeneous catalysis DOI
Allegra A. Latimer, Ambarish Kulkarni, Hassan Aljama

et al.

Nature Materials, Journal Year: 2016, Volume and Issue: 16(2), P. 225 - 229

Published: Oct. 10, 2016

Language: Английский

Citations

456