Homogeneous Hydrogenation of CO₂ and CO to Methanol: The Renaissance of Low‐Temperature Catalysis in the Context of the Methanol Economy

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(42)

Опубликована: Авг. 3, 2022

The traditional economy based on carbon-intensive fuels and materials has led to an exponential rise in anthropogenic CO

Язык: Английский

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Cooperative approaches in catalytic hydrogenation and dehydrogenation

Chemical Society Reviews, Год журнала: 2022, Номер 51(6), С. 1881 - 1898

Опубликована: Янв. 1, 2022

This review uses catalytic hydrogenation and dehydrogenation processes as a platform to compare metal–ligand cooperativity metal–metal strategies in catalysis.

Язык: Английский

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Basic Promotors Impact Thermodynamics and Catalyst Speciation in Homogeneous Carbonyl Hydrogenation

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(18), С. 8129 - 8137

Опубликована: Апрель 27, 2022

Homogeneously catalyzed reactions often make use of additives and promotors that affect reactivity patterns improve catalytic performance. While the role reaction is discussed in view their chemical reactivity, we demonstrate they can be involved catalysis indirectly. In particular, adjust thermodynamics key transformations homogeneous hydrogenation enable would unfavorable otherwise. We identified this phenomenon a set well-established new Mn pincer catalysts suffer from persistent product inhibition ester hydrogenation. Although alkoxide base do not directly participate inhibitory transformations, equilibrium constants these processes. Experimentally, confirm by varying promotor concentration one control catalyst speciation inflict substantial changes to standard free energies steps cycle. Despite fact latter are universally assumed constant, state subject external control. These results suggest viewed as an integral component medium, on its own capable improving performance reshaping seemingly rigid thermodynamic landscape transformation.

Язык: Английский

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Molecular fluorophores for in vivo bioimaging in the second near-infrared window

European Journal of Nuclear Medicine and Molecular Imaging, Год журнала: 2022, Номер 49(9), С. 3226 - 3246

Опубликована: Янв. 28, 2022

Язык: Английский

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Near-Ambient-Temperature Dehydrogenative Synthesis of the Amide Bond: Mechanistic Insight and Applications

ACS Catalysis, Год журнала: 2021, Номер 11(12), С. 7383 - 7393

Опубликована: Июнь 7, 2021

The current existing methods for the amide bond synthesis via acceptorless dehydrogenative coupling of amines and alcohols all require high reaction temperatures effective catalysis, typically involving reflux in toluene, limiting their potential practical applications. Herein, we report a system this that proceeds under mild conditions (reflux diethyl ether, boiling point 34.6 °C) using ruthenium PNNH complexes. low-temperature activity stems from ability Ru–PNNH complexes to activate alcohol hemiaminals at near-ambient through assistance terminal N–H proton. Mechanistic studies reveal presence an unexpected aldehyde-bound species during reaction, which is also catalytic resting state. We further utilize synthesize several simple bond-containing commercially available pharmaceutical drugs corresponding method.

Язык: Английский

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Combined Computational and Experimental Investigation on the Mechanism of CO₂ Hydrogenation to Methanol with Mn-PNP-Pincer Catalysts

ACS Catalysis, Год журнала: 2022, Номер 12(24), С. 15310 - 15322

Опубликована: Ноя. 30, 2022

A theoretical and experimental mechanistic study is presented for the homogeneously catalyzed CO2 hydrogenation to methanol, using an Mn-PNP-Pincer catalyst in presence of a Lewis acid cocatalyst alcohol as solvent. Quantum chemical computations at density functional theory DLPNO-CCSD(T) level suggest formate resting state most stable intermediate. The concerted activation dihydrogen via proton shuttle mechanism decomposition hemiacetal intermediate computed define turnover-determining transition state. resulting energy span calculated 34.5 kcal mol–1 theory. An Eyring plot reveals barrier reaction 31.4 under catalytic turnover conditions, showing good agreement with slight overestimation computational model. Concentration–time profiles involved species also locate experimentally rate-determining states (RDSs) ester methanol. measured kinetic isotope effects use H2/D2 EtOH/D are hydrogen splitting RDS, giving further support mechanism. These insights provide guidance reference future improvement catalysts based on abundant 3d metals CO2-based production

Язык: Английский

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Kinetic modelling of cobalt-catalyzed propene hydroformylation: a combined ab initio and experimental fitting protocol

Catalysis Science & Technology, Год журнала: 2024, Номер 14(4), С. 961 - 972

Опубликована: Янв. 1, 2024

The mechanism of propene hydroformylation is studied with quantum chemistry and kinetic modelling. This yields detailed insight into mechanisms, reveals the essential role a complex between hydridocobalttricabonyl toluene.

Язык: Английский

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Highly Enantiomerically Enriched Secondary Alcohols via Epoxide Hydrogenolysis

Organometallics, Год журнала: 2024, Номер 43(13), С. 1490 - 1501

Опубликована: Июнь 17, 2024

In this article, we report the development of ruthenium-catalyzed hydrogenolysis epoxides to selectively give branched (Markovnikov) alcohol products. contrast previously reported catalysts, use Milstein's PNN-pincer-ruthenium complex at room temperature allows conversion enantiomerically enriched secondary alcohols without racemization product. The catalyst is effective for a range aryl epoxides, alkyl and glycidyl ethers first homogeneous system promote glycidol 1,2-propanediol, loss enantiomeric purity. A detailed mechanistic study was conducted, including experimental observations speciation under catalytically relevant conditions, comprehensive kinetic characterization catalytic reaction, computational analysis via density functional theory. Heterolytic hydrogen cleavage mediated by ruthenium center exogenous alkoxide base. Epoxide ring opening occurs through an opposite-side attack hydride on less-hindered epoxide carbon, giving product selectively.

Язык: Английский

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Epoxide Hydrogenolysis Catalyzed by Ruthenium PNN and PNP Pincer Complexes

Organometallics, Год журнала: 2022, Номер 41(8), С. 1025 - 1033

Опубликована: Апрель 12, 2022

The metal-catalyzed hydrogenolysis of epoxides to give alcohols has advanced rapidly in the past several years, with some catalysts selectively giving linear (anti-Markovnikov) products and other providing branched (Markovnikov) products. currently known branched-selective catalyst systems require loadings 1% or higher typically a strong base additive. We report herein that PNN- PNP-ruthenium pincer complexes containing N–H functional groups are highly active for epoxides. When isopropyl alcohol is used as solvent, excellent yields obtained without strongly basic additives, using low 0.03%. Epoxides directly attached secondary carbon very high (>99:1) selectivity Aryl-substituted branched:linear ratios ranging from 2.7 19.0. For aryl epoxides, PNP-Ru showed greater preference product than PNN-Ru catalyst, substrates electron-rich substituents lower product.

Язык: Английский

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The Mechanism of Markovnikov-Selective Epoxide Hydrogenolysis Catalyzed by Ruthenium PNN and PNP Pincer Complexes

Organometallics, Год журнала: 2023, Номер 42(5), С. 347 - 356

Опубликована: Фев. 27, 2023

The homogeneous catalysis of epoxide hydrogenolysis to give alcohols has recently received significant attention. Catalyst systems have been developed for the selective formation either Markovnikov (branched) or anti-Markovnikov (linear) alcohol product. Thus far, reported catalysts exhibiting selectivity all feature potential Noyori/Shvo-type bifunctional catalysis, with a RuH/NH FeH/OH core structure. proposed mechanisms ring-opening involved cooperative C–O bond involving metal hydride and acidic pendant group on ligand, in analogy well-documented mechanism polar double-bond hydrogenation exhibited by this type. In work, we present combined computational/experimental study catalyzed Noyori-type PNP PNN complexes ruthenium. We find that, at least these ruthenium systems, previously pathway is energetically inaccessible; instead, proceeds through opposite-side nucleophilic attack carbon, without involvement ligand N–H group. For both catalyst rate law overall barrier predicted density functional theory (DFT) are consistent results from kinetic studies.

Язык: Английский

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