Catalytically Enhanced NMR of Heterogeneously Catalyzed Hydrogenations

Живонитко, Владимир В.; Kovtunov, Kirill V.; Skovpin, Ivan V.; Barskiy, Danila A.; Salnikov, Oleg G.; Koptyug, Igor V.

doi:10.1002/9783527678211.ch7

Cited by 14 publications

(9 citation statements)

References 158 publications

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“…High NMR signal enhancements were utilized to detect key intermediates and side products of homogeneous hydrogenation processes mediated by transition-metal complexes . Elucidation of the reaction mechanism using PHIP has also been attempted for heterogeneous hydrogenations. , The extension of PHIP applications to studies of chemical reactions other than hydrogenations would open a great opportunity for the further development of the technique as a mechanistic tool in chemistry. Only a few examples of observations of PHIP-enhanced NMR signals have been reported in hydroformylation, hydrodesulfurization, and acrolein hydrogenation accompanied by oligomerization .…”

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confidence: 99%

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

et al. 2016

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Substantial signal enhancements achieved by using parahydrogen in catalytic hydrogenations are powerful tools for mechanistic studies of chemical reactions involving molecular H2. Potentially, this technique can be extended to other reaction classes, providing new information about reaction mechanisms. Moreover, this can lead to new substances with highly polarized spins. Herein, we report strong signal enhancements of oligomerization reaction products observed during the selective hydrogenation of acetylene over Pd nanoparticles of different shapes and sizes supported on SiO2. C4 oligomeric products (1,3-butadiene, 1-butene, 2-butene) demonstrated a high degree of nuclear spin polarization, with the highest degree observed for 1-butene [more than 1.7% vs (2.4 × 10–3)% at thermal equilibrium], which was an order of magnitude larger than that of the triple CC bond hydrogenation products. No dependence of polarization on the metal surface statistics or, generally, on the nanoparticle morphology (cubic, octahedral, cuboctahedral) could be observed. In contrast, the particle size effect was such that larger particles provided higher signal enhancements. This observation is in line with the increased activity over larger Pd nanoparticles observed during acetylene hydrogenation over the same catalysts.

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confidence: 99%

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

et al. 2016

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“…The product substances hyperpolarized by these methods may boost the sensitivity of NMR spectroscopy and MRI by orders of magnitude. PHIP has been also exploited in mechanistic studies in homogeneous and heterogeneous catalysis. − Traditionally, metal-containing hydrogenation catalysts, such as metal complexes and metal nanoparticles, have been utilized to activate para -H 2 . ,− Recently, a number of systems based on main group elements have been documented as efficient metal-free hydrogenation catalysts as well. In particular, pairs of various sterically separated (“frustrated”) Lewis acids and Lewis bases (FLPs) were reported to split H 2 . , …”

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Spontaneous¹⁵N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers

Sorochkina

Живонитко

Chernichenko

et al. 2018

J. Phys. Chem. Lett.

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The ability of frustrated Lewis pairs (FLPs) to activate H2 is of significant interest for metal-free catalysis. The activation of H2 is also the key element of parahydrogen-induced polarization (PHIP), one of the nuclear spin hyperpolarization techniques. It is demonstrated that o-phenylene-based ansa-aminoboranes (AABs) can produce 1H nuclear spin hyperpolarization through a reversible interaction with parahydrogen at ambient temperatures. Heteronuclei are useful in NMR and MRI as well because they have a broad chemical shift range and long relaxation times and may act as background-free labels. We report spontaneous formation of 15N hyperpolarization of the N–H site for a family of AABs. The process is efficient at the high magnetic field of an NMR magnet (7 T), and it provides up to 350-fold 15N signal enhancements. Different hyperpolarization effects are observed with various AAB structures and in a broad temperature range. Spontaneous hyperpolarization, albeit an order of magnitude weaker than that for 15N, was also observed for 11B nuclei.

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“…30,31 The main disadvantage of this approach is the presence of the dissolved homogeneous catalyst, which is expensive and is challenging to separate from the hyperpolarized compounds. 32,33 Recently, however, PHIP was observed in the heterogeneous reactions in the gas 34 and in the liquid phases 35,36 over immobilized complexes, 37 supported metals 34,38 and ligand-capped nanoparticles. 39,40 Observation of 13 C HP resonance and therefore, production of 13 C-hyperpolarized molecules via heterogeneous hydrogenation with parahydrogen was so far shown only for 13 C HEP during hydrogenation of 2-hydroxyethyl acrylate over platinum nanoparticles capped with glutathione.…”

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Toward production of pure ¹³C hyperpolarized metabolites using heterogeneous parahydrogen-induced polarization of ethyl[1-¹³C]acetate

et al. 2016

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Here, we report the production of 13C-hyperpolarized ethyl acetate via heterogeneously catalyzed pairwise addition of parahydrogen to vinyl acetate over TiO2-supported rhodium nanoparticles, followed by magnetic field cycling. Importantly, the hyperpolarization is demonstrated even at the natural abundance of 13C isotope (ca. 1.1%) along with the easiest separation of the catalyst from the hyperpolarized liquid.

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Catalytically Enhanced NMR of Heterogeneously Catalyzed Hydrogenations

Cited by 14 publications

References 158 publications

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

Spontaneous¹⁵N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers

Toward production of pure ¹³C hyperpolarized metabolites using heterogeneous parahydrogen-induced polarization of ethyl[1-¹³C]acetate

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Catalytically Enhanced NMR of Heterogeneously Catalyzed Hydrogenations

Cited by 14 publications

References 158 publications

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

Spontaneous15N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers

Toward production of pure 13C hyperpolarized metabolites using heterogeneous parahydrogen-induced polarization of ethyl[1-13C]acetate

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Spontaneous¹⁵N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers

Toward production of pure ¹³C hyperpolarized metabolites using heterogeneous parahydrogen-induced polarization of ethyl[1-¹³C]acetate