Chemisorption bond energies of Lewis acids and bases on chemically modified Mo(100) surfaces

Deffeyes, J.E.; Smith, A. Horlacher; Stair, Peter C.

doi:10.1016/0169-4332(86)90123-6

Cited by 15 publications

(3 citation statements)

References 11 publications

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“…The studies conclude that at low temperatures propene on both surfaces forms a di-σ complex bonded to two metal atoms that dehydrogenates to form propylidyne at roughly room temperature. Temperature-programmed desorption (TPD) and ultraviolet photoelectron spectroscopy (UPS) of propene and trifluoropropene on oxidized Mo(100) − indicated that backbonding contributes to the chemisorption of the trifluoropropene but not the propene. The desorption energy of trifluoropropene was ∼3 kcal/mol higher than that of propene.…”

Section: Introductionmentioning

confidence: 99%

Orientation of Physisorbed Fluoropropenes on Cu(111)

Street

Gellman

1997

J. Phys. Chem. B

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Fourier transform infrared reflection absorption spectra (FT-IRAS) have been obtained for adsorbed monolayers of propene and a set of fluorinated propenes (CFH2CHCH2, CF3CHCH2, and CF3CFCF2) on the Cu(111) surface. These species interact weakly with the copper surface. The FT-IRAS spectra indicate that the molecules lie flat with the plane of the molecule defined by the CCC atoms essentially parallel to the surface regardless of the degree of fluorination. Quantitative analysis of the orientation of hexafluoropropene determines the tilt of the molecular plane with respect to the surface to be 11°. The results for propene indicate a molecular tilt of 20°. Where the ν(CC) mode can be identified in the spectra of the adsorbed molecules, there is no perturbation of its frequency, which indicates that there is little backdonation between the metal and the π* orbital of the propene.

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Section: Introductionmentioning

confidence: 99%

Orientation of Physisorbed Fluoropropenes on Cu(111)

Street

Gellman

1997

J. Phys. Chem. B

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“…The electron deficiency of Ti is enhanced by the presence of relatively more-electronegative N atoms surrounding the Ti surface sites. Conversely, as relatively less-electronegative C atoms are introduced into the surface, Ti atoms become less electron-deficient, or less acidic. , However, the fact that dimethylamine (which has a greater electron-donating ability than ethylene) desorbs at lower temperature than ethylene may indicate that electron back-donation from the Ti atom to the C 2 D 4 molecule takes place and contributes to enhanced adsorbate−substrate bonding, as described by the Dewar−Chatt−Duncanson model. , It has been previously stated that this happens when the Ti sites feature a metallic character, with Ti bound to N having a greater metallic character than Ti bound to C. , The lesser metallic character of Ti−C sites would also explain the observed weaker adsorption on TiNC sites. A detailed analysis of the reactivity of amines and π-donors on crystalline TiN and TiC surfaces has been performed by Didziulis et al…”

Section: Discussionmentioning

confidence: 99%

Reversible Tuning of the Surface Chemical Reactivity of Titanium Nitride and Nitride−Carbide Diffusion Barrier Thin Films

Rodríguez‐Reyes

Bui

et al. 2009

Chem. Mater.

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Titanium nitride-carbide (TiNC, as deposited) XPS spectraAlthough exposure to ambient conditions introduces substantial amount of oxygen and organic carbon in the film (therefore making the analysis difficult), valuable information can be extracted from the N 1s spectra, shown in Fig. 1 in the manuscript. Previous experiments in situ have assigned sets of components for N, C and Ti in nitride-based films, as shown in this table : Assignments of XPS components for in situ analysis of TiC X N Y films Components Janovska

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“…Since it is proposed above that methane forms via a carbon−carbon double-bond dissociation reaction to form carbenes, the variation in methane yield may be related to this dissociation probability. It has been suggested that, within the context of the Dewar−Chatt−Duncanson model, alkenes bond on Mo(100) primarily by donation of electrons from π-orbitals to the metal rather than via back-donation into vacant π* orbitals. , That is, alkenes behave like π-donors on Mo(100). Corroborative evidence for this idea comes from the effect on the energetics of alkene desorption, , where the desorption activation energies increase with the addition of oxygen to the surface in accord with the above proposal.…”

Section: Discussionmentioning

confidence: 99%

Surface and Catalytic Chemistry of Small Hydrocarbons on Oxidized Molybdenum

Bartlett

1998

Langmuir

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It is shown that model oxides grown on metallic substrates catalyze propylene metathesis to form ethylene and butene with an activity that mimics that of supported catalysts for reaction below ∼650 K. Another reaction regime is found for olefin metathesis above ∼650 K, where the reaction proceeds with a much higher activation energy of ∼60 kcal/mol. Unfortunately, alkenes do not react to any detecable extent on the model oxide surfaces in ultrahigh vacuum. However, the high-temperature (>650 K) metathesis rate is found to be affected by the presence of oxygen overlayers, which also modify the chemistry of alkenes on Mo(100) in ultrahigh vacuum. It is found that methane is formed by reaction of alkenes on O/Mo(100). The only other products detected are ascribed to either hydrogenation or total thermal decomposition into carbon and hydrogen. It is shown, using iodine-containing molecules to graft hydrocarbon fragments onto the surface, that alkenes can dissociate, forming carbenes which react to yield methane. This chemistry is in accord with that found catalytically at high temperatures, where the product distribution from the reaction of ethylene is well described by a Schulz-Florey distribution and the product distribution from propylene is well described by copolymerization of carbenes and methyl carbenes.

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Chemisorption bond energies of Lewis acids and bases on chemically modified Mo(100) surfaces

Cited by 15 publications

References 11 publications

Orientation of Physisorbed Fluoropropenes on Cu(111)

Orientation of Physisorbed Fluoropropenes on Cu(111)

Reversible Tuning of the Surface Chemical Reactivity of Titanium Nitride and Nitride−Carbide Diffusion Barrier Thin Films

Surface and Catalytic Chemistry of Small Hydrocarbons on Oxidized Molybdenum

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