20696-89-3Relevant academic research and scientific papers
Revealing Hydrogenation Reaction Pathways on Naked Gold Nanoparticles
Luza, Leandro,Rambor, Camila P.,Gual, Aitor,Alves Fernandes, Jesum,Eberhardt, Dario,Dupont, Jairton
, p. 2791 - 2799 (2017)
Gold nanoparticles (AuNPs) display distinct characteristics as hydrogenation catalysts, with higher selectivity and lower catalytic activity than group 8-10 metals. The ability of AuNPs to chemisorb/activate simple molecules is limited by the low coordination number of the surface sites. Understanding the distinct pathways involved in the hydrogenation reactions promoted by supported AuNPs is crucial for broadening their potential catalytic applications. In this study, we demonstrate that the mechanism of the hydrogenation reactions catalyzed by AuNPs with "clean" surfaces may proceed via homolytic or heterolytic hydrogen activation depending on the nature of the support. The synthesis of naked AuNPs employing γ-Al2O3 and ionic liquid (IL)-hybrid γ-Al2O3 supports was accomplished by sputtering deposition using ultrapure gold foils. This highly reproducible and straightforward procedure furnishes small (～6.6 nm) and well-distributed metallic gold nanoparticles (Au(0)NPs) that are found to be active catalysts for the partial and selective hydrogenation of substituted conjugated dienes, alkynes, and α,β-unsaturated carbonyl compounds (aldehydes and ketones). Kinetic and deuterium labeling studies indicate that heterolytic hydrogen activation is the primary pathway occurring on the AuNPs imprinted directly on γ-Al2O3. In contrast, AuNPs supported on IL-hybrid γ-Al2O3 materials cause the reaction to proceed via a homolytic hydrogen activation pathway. The IL layer surrounds the AuNPs and acts as a cage, influencing the frequency of the interaction of the catalytically active species and the metal surface and, consequently, the catalytic performance of the AuNPs. The IL layer is shown to improve the product selectivity by the enhancement of the substrate/product discrimination, and to decrease the catalytic activity by shifting the rate-determining step to the H2 and substrate competitive adsorption/activation on the same active sites. A series of kinetic experiments suggest that AuNPs imprinted on an IL-hybrid γ-Al2O3 support are more efficient (lower activation energy, Ea) than group 8-10 metal based catalysts for hydrogenation reactions at moderate to high temperatures (75-150 °C).
Distinguishing between abstraction and addition as the first step in the reaction of a nitroxyl radical with cyclohexene
Coseri, Sergiu,Ingold, Keith U.
, p. 1641 - 1643 (2004)
An unambiguous method for distinguishing between abstraction-addition and addition-abstraction mechanisms (and mixtures thereof) in the reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl with a specifically deuterated cyclohexene, 1,2-dideuteriocyclohexene, is demonstrated.
Well-Defined Cobalt(I) Dihydrogen Catalyst: Experimental Evidence for a Co(I)/Co(III) Redox Process in Olefin Hydrogenation
Tokmic, Kenan,Markus, Charles R.,Zhu, Lingyang,Fout, Alison R.
supporting information, p. 11907 - 11913 (2016/10/07)
The synthesis of a cobalt dihydrogen CoI-(H2) complex prepared from a CoI-(N2) precursor supported by a monoanionic pincer bis(carbene) ligand, MesCCC (MesCCC = bis(mesityl-benzimidazol-2-ylidene)phenyl), is described. This species is capable of H2/D2 scrambling and hydrogenating alkenes at room temperature. Stoichiometric addition of HCl to the CoI-(N2) cleanly affords the CoIII hydridochloride complex, which, upon the addition of Cp2ZrHCl, evolves hydrogen gas and regenerates the CoI-(N2) complex. Furthermore, the catalytic olefin hydrogenation activity of the CoI species was studied by using multinuclear and parahydrogen (p-H2) induced polarization (PHIP) transfer NMR studies to elucidate catalytically relevant intermediates, as well as to establish the role of the CoI-(H2) in the CoI/CoIII redox cycle.
Iridium-catalyzed H/D exchange at vinyl groups without olefin isomerization
Zhou, Jianrong,Hartwig, John F.
scheme or table, p. 5783 - 5787 (2009/03/11)
(Chemical Equation Presented) Making the switch: The title reaction represents a rare example of olefinic C-H activation without olefin isomerization. The conditions are sufficiently mild so that functional groups such as ketones, esters, nitriles, amines, sulfides, and alcohols are tolerated. This selectivity is demonstrated by deuterium labeling of several complex molecules.
Desymmetrization of N-Sulfonated Aziridines by Alkyllithium Reagents in the Presence of Chiral Ligands
Mueller, Paul,Riegert, David,Bernardinelli, Gerald
, p. 227 - 239 (2007/10/03)
The stereochemical course of the rearrangement of the N-sulfonylaziridines 5, 15, and 25 in the presence of s-BuLi/(-)-sparteine to the bicyclic sulfonamides 4, 16, and 17, respectively, has been investigated chemically and by X-ray structure analysis. Th
