1076-43-3Relevant articles and documents
Effect of solvent and ancillary ligands on the catalytic H/D exchange reactivity of Cp IrIII(L) complexes
Lehman, Matthew C.,Gary, J. Brannon,Boyle, Paul D.,Sanford, Melanie S.,Ison, Elon A.
, p. 2304 - 2310 (2013)
The reactivity of a series of Cp*lIrIII(L) complexes that contain a diverse set of ancillary ligands, L, (L = PMe3, N-heterocyclic carbene, NHC = 1,3-dimethylimidazol-2-ylidene, aqua, 4-t-butylpyridine, and 4-(2,4,6-tris-(4-t-butylphenyl)pyridinium)pyridine tetrafluoroborate) has been examined in catalytic H/D exchange reactions between C6H6 and a series of deuterated solvents (methanol-d 4, acetic acid-d4, and trifluoroacetic acid-d 1). These studies demonstrate that (1) the mechanism of catalytic H/D exchange is significantly influenced by the nature of the solvent; (2) electron-donating ligands (PMe3, NHC) promote the formation of Ir hydrides in methanol-d4, and these are critical intermediates in catalytic H/D exchange processes; and (3) weak/poorly donating ligands (4-t-butylpyridine, 4-(2,4,6-tris-(4-t-butylphenyl)pyridinium)pyridine tetrafluoroborate and aqua) can support efficient H/D exchange catalysis in acetic acid-d4.
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Adams,Tarbell
, p. 1260 (1938)
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Leitch
, p. 813 (1954)
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Coordination Chemistry of Benzene, Toluene, Cyclohexadienes, Cyclohexene, and Cyclohexane on Pt100)
Tsai, Min-Chi,Muetterties, E. L.
, p. 5067 - 5071 (1982)
The surface chemistry of benzene, toluene, cyclohexane, cyclohexene, and cyclohexadienes on Pt(100) is described.Benzene chemisorption was largely molecular although H-D exchange between chemisorbed C6H6 and C6D6 was observed at temperatures of 100 deg C and above.Toluene chemisorbed with bond breaking to give Pt-(100)-benzyl.This benzyl species (C6D5CD2) underwent H-D exchange with chemisorbed hydrogen.Exchange was more facile at the CH2 site than at aromatic C-H sites.Cyclohexane, cyclohexene, and cyclohexadienes chemisorbed on Pt(100) to form benzene with expected relative ease of dehydrogenation of cyclohexadienes >/= cyclohexene > cyclohexane.
H/D exchange processes catalyzed by an iridium-pincer complex
Iluc, Vlad M.,Fedorov, Alexey,Grubbs, Robert H.
, p. 39 - 41 (2012)
A PNP-pincer iridium dihydride performs the H/D exchange between aromatic substrates and tertiary hydrosilanes and D2O or C6D 6. Complete incorporation of deuterium into sterically accessible Car-H and Si-H bonds was observed at a moderate temperature of 80 °C.
Directing Reaction Pathways through Controlled Reactant Binding at Pd–TiO2 Interfaces
Zhang, Jing,Wang, Bingwen,Nikolla, Eranda,Medlin, J. Will
, p. 6594 - 6598 (2017)
Recent efforts to design selective catalysts for multi-step reactions, such as hydrodeoxygenation (HDO), have emphasized the preparation of active sites at the interface between two materials having different properties. However, achieving precise control over interfacial properties, and thus reaction selectivity, has remained a challenge. Here, we encapsulated Pd nanoparticles (NPs) with TiO2 films of regulated porosity to gain a new level of control over catalyst performance, resulting in essentially 100 % HDO selectivity for two biomass-derived alcohols. This catalyst also showed exceptional reaction specificity in HDO of furfural and m-cresol. In addition to improving HDO activity by maximizing the interfacial contact between the metal and metal oxide sites, encapsulation by the nanoporous oxide film provided a significant selectivity boost by restricting the accessible conformations of aromatics on the surface.
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Ingold,Raisin,Wilson
, (1936)
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Horiuti,Polanyi
, p. 847 (1934)
Synthesis of Hexalithiobenzene
Baran, J. R.,Hendrickson, C.,Laude, D. A.,Lagow, R. J.
, p. 3759 - 3760 (1992)
A new synthesis for hexalithiobenzene starting with hexachlorobenzene is reported.
Erlenmeyer,Lobeck
, p. 1464 (1935)
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Dixon,Schiessler
, p. 2197 (1954)
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Benzene as a Selective Chemical Ionization Reagent Gas
Allgood, Charles,Lin, Yi,Ma, Yee-Chung,Munson, Burnaby
, p. 497 - 502 (1990)
Dilute mixtures of C6H6 or C6D6 in He provide abundant +. or +. ions and small amounts of + or + ions as chemical ionization (CI) reagent ions.The C6H6 or C6D6 CI spectra of alkylbenzenes and alkylanilines contain predominantly M+. ions from reactions of +. or +. and small amounts of MH+ or MD+ ions from reactions of + or +.Benzene CI spectra of aliphatic amines contain M+., fragment ions and sample-size dependent MH+ ions from sample ion-sample molecules reactions.The C6D6 CI spectra of substituted pyridines contain M+. and MD+ ions in different ratios depending on the substituent (which alters the ionization energy of the substituted pyridine), as well as sample-size-dependent MH+ ions from sample ion-sample molecule reactions.Two mechanisms are observed for the formation of MD+ ions: proton transfer from +. or charge transfer from +. to give M+., followed by deuteron transfer from C6D6 to M+..The mechanisms of reactions were established by ion cyclotron resonance (ICR) experiments.Proton transfer from +. or +. is rapid only for compounds for which proton transfer is exothermic and charge transfer is endothermic.For compounds for which both charge transfer and proton transfer are exothermic, charge transfer is the almost exclusive reaction.
Bowman,Benedict,Taylor
, p. 960 (1935)
Catalytic deuteration of C(sp2)-H bonds of substituted (Hetero)arenes in a Pt(II) CNN-pincer complex/2,2,2Trifluoroethanol-d1 system: Effect of substituents on the reaction rate and selectivity
Kramer, Morgan,Watts, David,Vedernikov, Andrei N.
supporting information, p. 4102 - 4114 (2020/11/30)
Thirty four (hetero)arene derivatives have been tested in catalytic H/D exchange reactions involving their C(sp2)- H bonds and 2,2,2-trifluoroethanol-d1 (TFE-d1) in the presence of the homogeneous Pt(II) complex 1 supported by a sulfonated CNN-pincer ligand at 80 °C. The 18 substrates, including one pharmaceutical (naproxen), that are stable in the presence of 1 and are active in the H/D exchange reaction have been characterized by their position-specific extent of deuteration and, in a number of cases, the reaction kinetic selectivity. For the most reactive substrates the extent of deuteration approaches the expected statistical distribution of the exchangeable H and D atoms: e.g., 67-69% for phenol after 23 h and 88% for indole β-CH bonds after 45 min. For a few substrates (N,N-dimethylaniline, indole, nitrobenzene) the H/D exchange is highly position selective. No satisfactory correlation was found between the position-specific (meta, para) H/D exchange rate constants for X-monosubstituted benzenes and Hammett σX constants. This observation was proposed to be related to the concerted nature of the CH bond activation, the rate-determining CH bond oxidative addition at a Pt(II) center. A novel scale of Hammett σMX constants was introduced to characterize the reactivity of C(sp2)-H bonds in transition-metal-mediated reactions. The experimentally determined position-specific Gibbs energies of activation of the H/D exchange in substituted benzenes (meta and para positions) as well as in thiophene (α and β positions) were matched satisfactorily using DFT calculations.
Nickel-catalysed anti-Markovnikov hydroarylation of unactivated alkenes with unactivated arenes facilitated by non-covalent interactions
Hartwig, John F.,Nakao, Yoshiaki,Ohgi, Akito,Saper, Noam I.,Semba, Kazuhiko,Small, David W.
, (2020/02/18)
Anti-Markovnikov additions to alkenes have been a longstanding goal of catalysis, and anti-Markovnikov addition of arenes to alkenes would produce alkylarenes that are distinct from those formed by acid-catalysed processes. Existing hydroarylations are either directed or occur with low reactivity and low regioselectivity for the n-alkylarene. Herein, we report the first undirected hydroarylation of unactivated alkenes with unactivated arenes that occurs with high regioselectivity for the anti-Markovnikov product. The reaction occurs with a nickel catalyst ligated by a highly sterically hindered N-heterocyclic carbene. Catalytically relevant arene- and alkene-bound nickel complexes have been characterized, and the rate-limiting step was shown to be reductive elimination to form the C–C bond. Density functional theory calculations, combined with second-generation absolutely localized molecular orbital energy decomposition analysis, suggest that the difference in activity between catalysts containing large and small carbenes results more from stabilizing intramolecular non-covalent interactions in the secondary coordination sphere than from steric hindrance.
