Thermal Chemistry of 1-Methyl-1-Cyclopentene and Methylene Cyclopentane on Pt(111) Surfaces:  Evidence for Double-Bond Isomerization

Morales, Ricardo; Zaera, Francisco

doi:10.1021/jp061004e

Cited by 22 publications

(46 citation statements)

References 53 publications

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“… 53 , 54 , 57 The dehydrogenation of MeCp, Cp, and Cp-like cyclical molecules such as benzene on Pt has also been studied. For example, dehydrogenation for MeCp on Pt(111) has been shown by Morales and Zaera to occur above 350 K. 58 Similar studies for other unsaturated cyclic hydrocarbons have been performed, finding similar temperature thresholds for dehydrogenation. 56 , 59 These dehydrogenation reactions do not directly show up during ALD (for example, as a gas-phase reaction product) but they do play a key role in the formation of CH 4 as this reaction is the most likely source of H(ads) required for the hydrogenation reactions discussed earlier and could contribute to the self-limiting nature of the ALD reactions.…”

Section: Discussionsupporting

confidence: 53%

Surface Chemistry during Atomic Layer Deposition of Pt Studied with Vibrational Sum-Frequency Generation

2022

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A detailed understanding of the growth of noble metals by atomic layer deposition (ALD) is key for various applications of these materials in catalysis and nanoelectronics. The Pt ALD process using MeCpPtMe 3 and O 2 gas as reactants serves as a model system for the ALD processes of noble metals in general. The surface chemistry of this process was studied by in situ vibrational broadband sum-frequency generation (BB-SFG) spectroscopy, and the results are placed in the context of a literature overview of the reaction mechanism. The BB-SFG experiments provided direct evidence for the presence of CH 3 groups on the Pt surface after precursor chemisorption at 250 °C. Strong evidence was found for the presence of a C=C containing complex ( e.g ., the form of Cp species) and for partial dehydrogenation of the surface species during the precursor half-cycle. The reaction kinetics of the precursor half-cycle were followed at 250 °C, showing that the C=C coverage saturated before the saturation of CH 3 . This complex behavior points to the competition of multiple surface reactions, also reflected in the temperature dependence of the reaction mechanism. The CH 3 saturation coverage decreased significantly with temperature, while the C=C coverage remained constant after precursor chemisorption on the Pt surface for temperatures from 80 to 300 °C. These SFG results have resulted in a better understanding of the Pt ALD process and also highlight the surface chemistry during thin-film growth as a promising field of study for the BB-SFG community.

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Section: Discussionsupporting

confidence: 53%

Surface Chemistry during Atomic Layer Deposition of Pt Studied with Vibrational Sum-Frequency Generation

2022

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“…It should also be said that the detection of even minority products in TPD experiments may be sufficient to speculate on possible catalytic processes provided that the proper reaction conditions are identified. 81,[87][88][89] In this example, the yields for the production of the alkane (n-butane) may be quite low, but still indicative of the potential self-hydrogenation of alkyl groups via the incorporation of hydrogen atoms produced by the b-hydride elimination step that leads to the production of the alkene. 66,77,80,90 TPD yield calculations are also used to estimate average stoichiometries in surface species.…”

Section: Yieldsmentioning

confidence: 95%

“…An example of the latter is provided by our study on carbon-carbon double bond migrations in cyclic olefins. 89 Fig. 13 shows TPD traces for the key masses followed in experiments with coadsorbed methylene cyclopentane (MeCp) and deuterium on a Pt (111) single-crystal surface.…”

Section: Deuterium As a Reactantmentioning

confidence: 99%

“…The TPD results are consistent with the initial incorporation of a deuterium atom in the methylene moiety of MeCp to form an intermediate 1-methyl-cyclopentyl intermediate. 89 That alkyl surface species can then either accept a second deuterium atom to form MCp-d 2 (as seen in the 71 and 86 amu traces), or undergo b-hydride elimination to return a new olefin. A complication arises from the fact that, depending on the regioselectivity of the dehydrogenation step, different products are possible.…”

Section: Deuterium As a Reactantmentioning

confidence: 99%

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Kinetic measurements of hydrocarbon conversion reactions on model metal surfaces

Wilson

Guo

Morales

et al. 2007

Phys. Chem. Chem. Phys.

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Examples from recent studies in our laboratory are presented to illustrate the main tools available to surface scientists for the determination of the kinetics of surface reactions. Emphasis is given here to hydrocarbon conversions and studies that rely on the use of model systems, typically single crystals and controlled (ultrahigh vacuum) environments. A detailed discussion is provided on the use of temperature-programmed desorption for the determination of activation energies as well as for product identification and yield estimations. Isothermal kinetic measurements are addressed next by focusing on studies under vacuum using molecular beams and surface-sensitive spectroscopies. That is followed by a review of the usefulness of high-pressure cells and other reactor designs for the emulation of realistic catalytic conditions. Finally, an analysis of the power of isotope labeling and chemical substitutions in mechanistic research on surface reactions is presented.

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“…More recently, we in our laboratory have also been using RAIRS, in conjunction with other techniques, to characterize the isomerization of double bonds. Both bond migration 184,185 and cis-trans isomerization (Fig. 7) have been investigated this way.…”

Section: Surface-science Experiments Using Model Catalysts: Uhvmentioning

confidence: 99%

New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions

2014

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Infrared absorption spectroscopy has proven to be one of the most powerful spectroscopic techniques available for the characterization of catalytic systems. Although the history of IR absorption spectroscopy in catalysis is long, the technique continues to provide key fundamental information about a variety of catalysts and catalytic reactions, and to also offer novel options for the acquisition of new information on both reaction mechanisms and the nature of the solids used as catalysts. In this review, an overview is provided of the main contributions that have been derived from IR absorption spectroscopy studies of catalytic systems, and a discussion is included on new trends and new potential directions of research involving IR in catalysis. We start by briefly describing the power of Fourier-transform IR (FTIR) instruments and the main experimental IR setups available, namely, transmission (TIR), diffuse reflectance (DRIFTS), attenuated total reflection (ATR-IR), and reflection-absorption (RAIRS), for advancing research in catalysis. We then discuss the different environments under which IR characterization of catalysts is carried out, including in situ and operando studies of typical catalytic processes in gas-phase, research with model catalysts in ultrahigh vacuum (UHV) and so-called high-pressure cell instruments, and work involving liquid/solid interfaces. A presentation of the type of information extracted from IR data follows in terms of the identification of adsorbed intermediates, the characterization of the surfaces of the catalysts themselves, the quantitation of IR intensities to extract surface coverages, and the use of probe molecules to identify and titrate specific catalytic sites. Finally, the different options for carrying out kinetic studies with temporal resolution such as rapid-scan FTIR, step-scan FTIR, and the use of tunable lasers or synchrotron sources, and to obtain spatially resolved spectra, by sample rastering or by 2D imaging, are introduced.

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Thermal Chemistry of 1-Methyl-1-Cyclopentene and Methylene Cyclopentane on Pt(111) Surfaces: Evidence for Double-Bond Isomerization

Cited by 22 publications

References 53 publications

Surface Chemistry during Atomic Layer Deposition of Pt Studied with Vibrational Sum-Frequency Generation

Surface Chemistry during Atomic Layer Deposition of Pt Studied with Vibrational Sum-Frequency Generation

Kinetic measurements of hydrocarbon conversion reactions on model metal surfaces

New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions

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