The Reactive Sites of Methane Activation: A Comparison of IrC3+ with PtC3+

The activation reactions of methane mediated by metal carbide ions MC3+ (M = Ir and Pt) were comparatively studied at room temperature using the techniques of mass spectrometry in conjunction with theoretical calculations. MC3+ (M = Ir and Pt) ions reacted with CH4 at room temperature forming MC2H2+/C2H2 and MC4H2+/H2 as the major products for both systems. Besides that, PtC3+ could abstract a hydrogen atom from CH4 to generate PtC3H+/CH3, while IrC3+ could not. Quantum chemical calculations showed that the MC3+ (M = Ir and Pt) ions have a linear M-C-C-C structure. The first C–H activation took place on the Ir atom for IrC3+. The terminal carbon atom was the reactive site for the first C–H bond activation of PtC3+, which was beneficial to generate PtC3H+/CH3. The orbitals of the different metal influence the selection of the reactive sites for methane activation, which results in the different reaction channels. This study investigates the molecular-level mechanisms of the reactive sites of methane activation.

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Consecutive Methane Activation Mediated by Single Metal Boride Cluster Anions NbB4−

Physical Chemistry Chemical Physics ◽

10.1039/d1cp01418h ◽

2021 ◽

Author(s):

Ying Li ◽

Ming Wang ◽

Yongqi Ding ◽

Chongyang Zhao ◽

Jia-Bi Ma

Keyword(s):

Mass Spectrometry ◽

Gas Phase ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Room Temperature ◽

Methane Activation ◽

Cluster Ions ◽

Metal Boride ◽

Cluster Anions ◽

Phase Cluster

Cleavage all C−H bonds in two methane molecules by gas-phase cluster ions at room temperature is a challenging task. Herein, mass spectrometry and quantum chemical calculations have been used to...

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Cyclic(Alkyl)(Amino) Carbene-Assisted Reduction of Carbon Dioxide: Isolation of Crystalline Alkali Metal Clusters of Supported CO2 Radical Anions and Dianions

10.26434/chemrxiv.12665336.v1 ◽

2020 ◽

Author(s):

Lucas A. Freeman ◽

Akachukwu D. Obi ◽

Haleigh R. Machost ◽

Andrew Molino ◽

Asa W. Nichols ◽

...

Keyword(s):

Alkali Metals ◽

Room Temperature ◽

Bond Activation ◽

Theoretical Calculations ◽

Chemical Reduction ◽

Structural Characteristics ◽

Open Shell ◽

X Ray Crystallography ◽

Earth Abundant ◽

Alkali Metal Clusters

The reduction of the relatively inert carbon–oxygen bonds of CO2to access useful CO2-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Achieving this reduction using earth-abundant main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere reactions and bond activation events between CO2and the MGE. Herein we report the first successful chemical reduction of a zwitterionic carbene-CO2adduct by either one or two equivalents of light alkali metals to form isolable, room-temperature-stable crystalline clusters exhibiting remarkably diverse electronic and structural characteristics. The reduction of a CAAC-CO2adduct [CAAC–CO2, 1, CAAC = cyclic (alkyl)(amino) carbene] with one equivalent of lithium, sodium or potassium metal yields the monoanionic radicals (THF)3Li2(CAAC–CO2)2(2), (THF)4Na4(CAAC–CO2)4(3), or (THF)4K4(CAAC–CO2)4(4). The reduction of 1by two or more equivalents of lithium, sodium, or potassium yields the open-shell, dianionic clusters (THF)2Li6(CAAC–CO2)3(5), Li12(CAAC–CO2)6(6), Na12(CAAC–CO2)6(7), and K10(CAAC–CO2)5(8). Each of the clusters was studied by a combination of X-ray crystallography, FTIR, UV-Vis, EPR and NMR spectroscopies, and theoretical calculations. <a>The synthetic transformation described in this report results in the facile net reduction of CO2at room temperature by lithium, sodium, and potassium metal without the need for additional metallic promoters, catalysts, or reagents – a process which does not occur in the absence of carbene.</a>

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Solvent-assisted osmium staining of butyl acrylate and ethylene-propylene-diene in a styrene acrylonitrile matrix

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150332 ◽

1993 ◽

Vol 51 ◽

pp. 900-901 ◽

Cited By ~ 1

Author(s):

Gudrun A. Hutchins

Keyword(s):

Butyl Acrylate ◽

Room Temperature ◽

Osmium Tetroxide ◽

Staining Procedure ◽

Reactive Site ◽

Ethylene Propylene ◽

Minimal Distortion ◽

Styrene Acrylonitrile ◽

Engineering Polymers ◽

Effective Reaction

In order to optimize the toughening effect of elastomers in engineering polymers, it is necessary to characterize the size, morphology and dispersion of the specific elastomer within the polymer matrix. For unsaturated elastomers such as butadiene or isoprene, staining with osmium tetroxide is a well established procedure. The residual carbon-carbon double bond in these materials is the reactive site and forms a 1,2-dilato complex with the OsO4. Incorporation of osmium tetroxide into the elastomer not only produces sufficient contrast for TEM, but also crosslinks the elastomer sufficiently so that ultramicrotomy can be accomplished at room temperature with minimal distortion.Blends containing saturated elastomers such as butyl acrylate (BA) and ethylene propylene diene monomer (EPDM) cannot be stained directly with OsO4 because effective reaction sites such as C=C or -NH2 are not available in sufficient number. If additional reaction sites can be introduced selectively into the elastomer by a chemical reaction or the absorption of a solvent, a modified, two-step osmium staining procedure is possible.

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Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

10.26434/chemrxiv.5717950 ◽

2017 ◽

Author(s):

Haibo Ge ◽

Lei Pan ◽

Piaoping Tang ◽

Ke Yang ◽

Mian Wang ◽

...

Keyword(s):

Bond Activation ◽

Theoretical Calculations ◽

Experimental Studies ◽

Bond Functionalization ◽

Aliphatic Ketones ◽

Site Selectivity ◽

Mechanistic Investigation ◽

Palladium Catalyzed ◽

Metal Catalyzed ◽

Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp3 carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp3)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp3)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.

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A Study on the Rearrangement of Dialkyl 1-Aryl-1-hydroxymethylphosphonates to Benzyl Phosphates

Current Organic Chemistry ◽

10.2174/1385272824666200226114306 ◽

2020 ◽

Vol 24 (4) ◽

pp. 465-471 ◽

Cited By ~ 2

Author(s):

Zita Rádai ◽

Réka Szabó ◽

Áron Szigetvári ◽

Nóra Zsuzsa Kiss ◽

Zoltán Mucsi ◽

...

Keyword(s):

Quantum Chemical ◽

Room Temperature ◽

Phase Transfer ◽

One Pot ◽

Substrate Dependence ◽

Triethylbenzylammonium Chloride ◽

One Step ◽

The Pudovik Reaction ◽

The One ◽

Solid Liquid

The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates (HPs) to the corresponding benzyl phosphates (BPs) has been elaborated under solid-liquid phase transfer catalytic conditions. The best procedure involved the use of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile as the solvent at room temperature. The substrate dependence of the rearrangement has been studied, and the mechanism of the transformation under discussion was explored by quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot version starting with the Pudovik reaction has also been developed. The conditions of this tandem transformation were the same, as those for the one-step HP→BP conversion.

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Nonreciprocal charge transport up to room temperature in bulk Rashba semiconductor α-GeTe

Nature Communications ◽

10.1038/s41467-020-20840-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yan Li ◽

Yang Li ◽

Peng Li ◽

Bin Fang ◽

Xu Yang ◽

...

Keyword(s):

Charge Transport ◽

Room Temperature ◽

Theoretical Calculations ◽

Ferromagnetic Layer ◽

Spin Splitting ◽

New Paradigm ◽

Rashba Spin ◽

Rashba Spin Splitting ◽

Fundamental Insight ◽

Insight Into

AbstractNonmagnetic Rashba systems with broken inversion symmetry are expected to exhibit nonreciprocal charge transport, a new paradigm of unidirectional magnetoresistance in the absence of ferromagnetic layer. So far, most work on nonreciprocal transport has been solely limited to cryogenic temperatures, which is a major obstacle for exploiting the room-temperature two-terminal devices based on such a nonreciprocal response. Here, we report a nonreciprocal charge transport behavior up to room temperature in semiconductor α-GeTe with coexisting the surface and bulk Rashba states. The combination of the band structure measurements and theoretical calculations strongly suggest that the nonreciprocal response is ascribed to the giant bulk Rashba spin splitting rather than the surface Rashba states. Remarkably, we find that the magnitude of the nonreciprocal response shows an unexpected non-monotonical dependence on temperature. The extended theoretical model based on the second-order spin–orbit coupled magnetotransport enables us to establish the correlation between the nonlinear magnetoresistance and the spin textures in the Rashba system. Our findings offer significant fundamental insight into the physics underlying the nonreciprocity and may pave a route for future rectification devices.

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Dissecting transmetalation reactions at the molecular level: C–B versus F–B bond activation in phenyltrifluoroborate silver complexes

Dalton Transactions ◽

10.1039/d0dt03309j ◽

2021 ◽

Vol 50 (4) ◽

pp. 1496-1506

Author(s):

Fiona Bathie ◽

Adam W. E. Stewart ◽

Allan J. Canty ◽

Richard A. J. O'Hair

Keyword(s):

Gas Phase ◽

Bond Activation ◽

Molecular Level ◽

Silver Complexes ◽

Fundamental Model ◽

Model Reactions

Gas-phase experiments and computation provide fundamental model reactions for aryl and fluoride transfer between silver and boron centres.

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A Quantum-Chemical DFT Approach to Elucidation of the Chirality Transfer Mechanism of the Enantioselective Suzuki–Miyaura Cross-Coupling Reaction

Journal of Chemistry ◽

10.1155/2017/3617527 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Radomir Jasiński ◽

Oleg M. Demchuk ◽

Dmytro Babyuk

Keyword(s):

Quantum Chemical ◽

Coupling Reaction ◽

Cross Coupling ◽

Palladium Complexes ◽

Initial Reaction ◽

Chiral Ligand ◽

Chirality Transfer ◽

Cross Coupling Reaction ◽

Enantioselective Reactions ◽

Selection Of

The DFT calculations of the simplified model of the asymmetric Suzuki–Miyaura coupling reaction were performed at the M062x/LANL2DZ theory level at first. It was found that enantioselective reactions mediated by the palladium complexes of chiral C,P-ligands follow a four-stage mechanism similar to that proposed previously as one of the most credible mechanisms. It should be underlined that the presence of substituents in the substrates and the chiral ligand at ortho positions determines the energies of possible diastereoisomeric transition states and intermediates in initial reaction steps. This suggests that, in practice, a sharp selection of theoretically possible paths of chirality transfer from the catalyst to the product should have a place and, therefore, the absolute configuration of the formed atropisomeric product is defined and can be predicted.

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Room-Temperature Selective Aliphatic Carbon–Carbon Bond Activation and Functionalization of Ethers by Rhodium(II) Porphyrin

Organometallics ◽

10.1021/om200280w ◽

2011 ◽

Vol 30 (14) ◽

pp. 3691-3693 ◽

Cited By ~ 13

Author(s):

Siu Yin Lee ◽

Tsz Ho Lai ◽

Kwong Shing Choi ◽

Kin Shing Chan

Keyword(s):

Room Temperature ◽

Bond Activation ◽

Carbon Bond ◽

Carbon Carbon Bond ◽

Aliphatic Carbon

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Broadening and shifting of the depolarized component of the Raman Q branch in D2 at room temperature

Canadian Journal of Physics ◽

10.1139/p95-077 ◽

1995 ◽

Vol 73 (7-8) ◽

pp. 530-536 ◽

Cited By ~ 6

Author(s):

P. M. Sinclair ◽

P. Duggan ◽

J. R. Drummond ◽

A. D. May

Keyword(s):

Spectral Data ◽

Direct Measurement ◽

Room Temperature ◽

Theoretical Calculations

We report the first direct measurement of the broadening and shifting of the depolarized component of the Raman Q branch in D2. Spectral data were recorded from 1.5 to 12 amagat at 305.2 K. Both the measured broadening and shifting of the depolarized component are significantly different from that for the polarized Q branch. These results can be used as a check of theoretical calculations when they become available. Here they are used to correct previously reported values of the broadening of the polarized part of the Q-branch spectrum. Measured values of the ratio of the depolarized to polarized intensity for the Q-branch lines are also given.

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