Heterogeneous hydrogenation of phenylalkynes with parahydrogen: hyperpolarization, reaction selectivity, and kinetics

Pokochueva, Ekaterina V.; Kovtunov, Kirill V.; Salnikov, Oleg G.; Gemeinhardt, Max E.; Kovtunova, Larisa M.; Bukhtiyarov, Valerii I.; Chekmenev, Eduard Y.; Goodson, Boyd M.; Koptyug, Igor V.

doi:10.1039/c9cp02913c

Cited by 12 publications

(14 citation statements)

References 45 publications

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“…However, in that study the catalyst was Pt/pumice and the temperature range was 100–300 °C – thus, the results are not directly comparable. The slight decrease of methylenecyclobutane conversion with temperature is likely caused by formation of carbonaceous deposits [33,54] …”

Section: Resultsmentioning

confidence: 99%

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Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen‐Induced Polarization Technique

et al. 2022

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In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150-350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results.

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Section: Resultsmentioning

confidence: 99%

“…The slight decrease of meth-ylenecyclobutane conversion with temperature is likely caused by formation of carbonaceous deposits. [33,54] Figure 1. (a) Scheme of methylenecyclobutane hydrogenation over 1 wt.% Rh/TiO 2 catalyst.…”

Section: General Remarksmentioning

confidence: 99%

Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen‐Induced Polarization Technique

et al. 2022

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“…Later, a systematic investigation of several supported metal catalysts in hydrogenation of different phenylalkynes was carried out, and the selectivity to the pairwise addition in liquid phase was found to be affected by both the nature of active metal and the percentage of metal loading. [154] Importantly, in those studies the hydrogenation reactions were carried out in methanol, chloroform or benzene solutions, which strongly limits potential applications. The first observation of PHIP produced with supported metal nanoparticles in an aqueous phase hydrogenation was reported shortly after.…”

Section: Het Phip In Liquid Phase and Possible Biomedical Applicationsmentioning

confidence: 99%

“…In the first application of this approach, [153] modest PHIP effects were observed during the liquid‐phase hydrogenation of a number of unsaturated substrates (e. g. methyl propiolate, styrene, 1‐phenyl‐1‐propyne, diphenylacetylene, and vinyl acetate). Later, a systematic investigation of several supported metal catalysts in hydrogenation of different phenylalkynes was carried out, and the selectivity to the pairwise addition in liquid phase was found to be affected by both the nature of active metal and the percentage of metal loading [154] . Importantly, in those studies the hydrogenation reactions were carried out in methanol, chloroform or benzene solutions, which strongly limits potential applications.…”

Section: Applications Of Heterogeneous Phipmentioning

confidence: 99%

Heterogeneous Catalysis and Parahydrogen‐Induced Polarization

et al. 2021

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Parahydrogen‐induced polarization with heterogeneous catalysts (HET‐PHIP) has been a subject of extensive research in the last decade since its first observation in 2007. While NMR signal enhancements obtained with such catalysts are currently below those achieved with transition metal complexes in homogeneous hydrogenations in solution, this relatively new field demonstrates major prospects for a broad range of advanced fundamental and practical applications, from providing catalyst‐free hyperpolarized fluids for biomedical magnetic resonance imaging (MRI) to exploring mechanisms of industrially important heterogeneous catalytic processes. This review covers the evolution of the heterogeneous catalysts used for PHIP observation, from metal complexes immobilized on solid supports to bulk metals and single‐atom catalysts and discusses the general visions for maximizing the obtained NMR signal enhancements using HET‐PHIP. Various practical applications of HET‐PHIP, both for catalytic studies and for potential production of hyperpolarized contrast agents for MRI, are described.

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“…This strategy is efficient to produce heterogeneous catalysts for pairwise hydrogenation required for PHIP experiments. It is an excellent alternative compared to directly grafted rhodium or rhodium nanoparticles on oxidic supports 26 for which dispersion of small particles or poisoning of catalytic sites is required to use them for pairwise hydrogen transfer.…”

Section: ■ Introductionmentioning

confidence: 99%

A Novel Wilkinson’s Type Silica Supported Polymer Catalyst: Insights from Solid-State NMR and Hyperpolarization Techniques

et al. 2021

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The synthesis of a novel immobilized Wilkinson’s catalyst [SiO2∼PvPy-Wilk] is presented. The support material of this catalyst consists of silica particles that are modified with polymer brushes carrying pyridyl moieties that enable the coordination of Wilkinson’s catalyst. The synthesis of this catalyst is monitored by 1D and 2D multinuclear solid-state NMR techniques to confirm the success of the immobilization. The [SiO2∼PvPy-Wilk] catalyst is then tested in the hydrogenation of styrene, and its reusability is inspected showing that significant structural changes after several reaction cycles yield an activation of the catalyst. Finally, the catalyst is tested in PHIP experiments giving rise to about 200-fold enhancement of the signals of the hydrogenation product ethylbenzene.

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Heterogeneous hydrogenation of phenylalkynes with parahydrogen: hyperpolarization, reaction selectivity, and kinetics

Abstract: Parahydrogen-induced polarization (PHIP) is a powerful technique for studying hydrogenation reactions in both gas and liquid phases.

Cited by 12 publications

References 45 publications

Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen‐Induced Polarization Technique

Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen‐Induced Polarization Technique

Heterogeneous Catalysis and Parahydrogen‐Induced Polarization

A Novel Wilkinson’s Type Silica Supported Polymer Catalyst: Insights from Solid-State NMR and Hyperpolarization Techniques

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