Thursday, February 15, 2018

Effect of Carboxylate Ligands on Alkane Dehydrogenation with (dmPhebox)Ir Complexes

Department of Chemistry, University of Rochester, Rochester, New York 14627, United States

ACS Catal.20188, pp 2326–2329
DOI: 10.1021/acscatal.7b04057

Abstract Image

A series of carboxylate-ligated iridium complexes (dmPhebox)Ir(O2CR)2(H2O) (R = −CH3, −CH2CH3, −CMe3, −CH2C6H5, and −CH═CMe2) were designed and synthesized to understand the carboxylate ligand effects on the reactivity of the complex for alkane dehydrogenation. Kinetic studies showed that the different R groups of the carboxylate iridium complexes can affect the reactivity with octane in the β-H elimination step. The rate constants for octene formation with different carboxylate ligands follow the order R = −CH═CMe2 > −CMe3 > −CH2CH3 > −CH3 > −CH2C6H5. In contrast, there is no significant effect of carboxylate ligand on the rate of the C–H activation step at 160 °C. These experimental results support the findings in the previously reported density functional theory study of the (dmPhebox)Ir complex in alkane C–H activation.

Hydrogen/Deuterium (H/D) Exchange Catalysis in Alkanes

Aaron Sattler*
Corporate Strategic Research, ExxonMobil Research & Engineering Company, 1545 Route 22 East, Annandale, New Jersey 08801, United States

ACS Catal., 2018, 8, pp 2296–2312
DOI: 10.1021/acscatal.7b04201


The catalytic exchange of hydrogen and deuterium (H/D exchange) in light alkanes has been studied for almost a century. While alkanes and their C–H bonds are relatively inert, H/D exchange studies have shown that a large number of materials can catalytically activate these bonds. These studies helped elucidate the mechanisms by which alkane C–H bonds interact with catalytic materials. This Review serves to highlight this area of research, focusing on two main classes of heterogeneous materials, metals and metal oxides, and their trends in reactivities and selectivities are described in detail. Furthermore, the ability of these materials to carry out C–H bond activation and H/D exchange catalysis is compared with that of molecular organometallic complexes, and the mechanistic relationships and similarities in these processes are proposed.

Friday, February 2, 2018

Light-Driven CH Oxygenation of Methane into Methanol and Formic Acid by Molecular Oxygen Using a Perfluorinated Solvent

Light-Driven CH Oxygenation of Methane into Methanol and Formic
Acid by Molecular Oxygen Using a Perfluorinated Solvent
Angew. Chem. Int. Ed. 2017, 56, 1-5


The chlorine dioxide radical (ClO2·) was found to act as an efficient oxidizing agent in the aerobic oxygenation of methane to methanol and formic acid under photoirradiation. Photochemical oxygenation of methane occurred in a two-phase system comprising perfluorohexane and water under
ambient conditions (298 K, 1 atm). The yields of methanol and formic acid were 14 and 85 %, respectively, with a methane conversion of 99% without formation of the further oxygenated products such as CO2and CO. Ethane was also photochemically converted into ethanol (19%) and acetic acid (80%). The methane oxygenation is initiated by the photochemical Cl-O bond cleavage of ClO2· to generate Cl· and O2. The produced Cl· reacts with CH4 to form a methyl radical (CH3·). Finally, the oxygenated products such as methanol and formic acid were given by the radical chain reaction. A fluorous solvent plays an important role of inhibiting the deactivation of reactive radical species such as Cl· and CH3·.

Monday, January 22, 2018

Buchwald–Hartwig Amination of Nitroarenes

  • First published: Full publication history
  • DOI: 10.1002/anie.201706982
  • Abstract
    The Buchwald–Hartwig amination of nitroarenes was achieved for the first time by using palladium catalysts bearing dialkyl(biaryl)phosphine ligands. These cross-coupling reactions of nitroarenes with diarylamines, arylamines, and alkylamines afforded the corresponding substituted arylamines. A catalytic cycle involving the oxidative addition of the Ar−NO2 bond to palladium(0) followed by nitrite/amine exchange is proposed based on a stoichiometric reaction.

Monday, January 15, 2018

Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C – H activation

Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C–H activation

M. D. Marcinkowski, M. T. Darby, J. Liu, J. M. Wimble, F. R. Lucci, S. Lee, A. Michaelides, M. Flytzani-Stephanopolous, M. Stamatakis, E. C. H. Sykes

Nature Chem. 2018, ASAP
DOI: 10.1038/nchem.2915


The recent availability of shale gas has led to a renewed interest in CH bond activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high CH activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine CH activation in a number of systems including methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate CH bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant CH activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.

Monday, January 1, 2018

Preparation and Characterization of Bimetallic Pd-Cu Colloids by Thermal Decomposition of Their Acetate Compounds in Organic Solvents

Preparation and Characterization of Bimetallic Pd-Cu Colloids by Thermal Decomposition of Their Acetate Compounds in Organic Solvents

Kunio Esumi, Takafumi Tano, Kanjiro Torigoe, and Kenjiro Meguro
University of Tokyo

Chem. Mater. 1990, 2, 564-567  (


Bimetallic Pd-Cu/Cu2O colloids are prepared by the thermal decomposition of their acetates dissolved in methyl isobutyl ketone and bromobenzene. In methyl isobutyl ketone, the average diameter of Pd-Cu2O colloids decreases from about 130 to 50 nm with an increase of molar fraction of palladium acetate, while in bromobenzene the size of Pd-Cu colloids increases from about 8 to 15 nm. The composition of Pd-Cu or Pd-Cu2O colloids is almost hte same as that of the feed ratio of their acetates. The dispersion stability of these colloids is further addressed by measuring their ζ potentials.

Sunday, November 26, 2017

Selective Activation of Methane on Single-Atom Catalyst of Rhodium Dispersed on Zirconia for Direct Conversion

Selective Activation of Methane on Single-Atom Catalyst of Rhodium
Dispersed on Zirconia for Direct Conversion 

Y. Kwon, T. Y. Kim, G. Kwon, J. Yi, and H. Lee

J. Am. Chem. Soc. ASAP


Direct methane conversion into value-added products has become increasingly important. Because of inertness of methane, cleaving the first CH bond has been very difficult, requiring high reaction temperature on the heterogeneous catalysts. Once the first CH bond becomes activated, the remaining CH bonds are successively dissociated on the metal surface, hindering the direct methane conversion into chemicals. Here, a single-atom Rh catalyst dispersed on ZrO2 surface has been synthesized and used for selective activation of methane. The Rh single atomic nature was confirmed by extended X-ray fine structure analysis, electron microscopy images, and diffuse reflectance infrared Fourier transform spectroscopy. A model of the single- atom Rh/ZrO2 catalyst was constructed by density functional theory calculations, and it was shown that CH3 intermediates can be energetically stabilized on the single-atom catalyst. The direct conversion of methane was performed using H2O2 in the aqueous solution or using O2 in gas phase as oxidants. Whereas Rh nanoparticles produced CO2 only, the single-atom Rh catalyst produced methanol in aqueous phase or ethane in gas phase.