The thermal chemistry of adsorbed ethyl on the Pt(111) surface: infrared evidence for an ethylidene intermediate in the ethyl to ethylidyne conversion

Newell, Helen; McCoustra, Martin R. S.; Chesters, M.A.; Cruz, Carlos de la

doi:10.1039/a806786d

Cited by 30 publications

(20 citation statements)

References 35 publications

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“…Contact with this reactant stream led to the rapid disappearance of the bands at 3038 and 3057 cm −1 (Figure 3c), characterizing the π-bonded ethylene ligands, and the concomitant growth of bands at 2860, 2874, 2930, and 2960 cm −1 , ascribed to ethyl ligands on iridium ( Figure S2 in Supporting Information). 37,38 These results are consistent with those characterizing the isostructural Ir(C 2 H 4 ) 2 complex supported on dealuminated zeolite HY, but they are contrasted Calculated from differential conversions at time on stream = 0 (extrapolated from the corresponding conversion vs time-on-stream curves), assuming that all the Ir atoms were accessible to reactants (Supporting Information Figure S3). c Fractional conversion relative to equilibrium in the H−D exchange in the presence of C rates within the ranges allowed by our apparatus.…”

Section: Reaction Of Iridium Diethylene Complexes With Cosupporting

confidence: 84%

Site-Isolated Molecular Iridium Complex Catalyst Supported in the 1-Dimensional Channels of Zeolite HSSZ-53: Characterization by Spectroscopy and Aberration-Corrected Scanning Transmission Electron Microscopy

Lu¹,

Aydin²,

Liang

et al. 2012

ACS Catal.

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Zeolite HSSZ-53, which has 1-dimensional channels with 14-ring extra-large pores, was used as a support for a molecular iridium complex synthesized from Ir(C 2 H 4 ) 2 (C 5 H 7 O 2 ) and characterized with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies and atomic-resolution aberration-corrected scanning transmission electron microscopy (STEM). The spectra show that Ir(C 2 H 4 ) 2 (C 5 H 7 O 2 ) reacted readily with the bridging OH groups of the zeolite, leading to the removal of C 5 H 7 O 2 ligands and the formation of mononuclear Ir(C 2 H 4 ) 2 complexes bonded to the zeolite by Ir−O bonds at the framework aluminum sites. STEM images confirm the spectra, showing site-isolated iridium centers within the zeolite channels, with no evidence of iridium clusters. The samples constitute a highly uniform, well-defined array of essentially molecular catalytic species in a highly uniform, confined environment, allowing precise investigations of the chemistry of the iridium complex in the absence of solvents. IR spectra show that the supported Ir(C 2 H 4 ) 2 complexes were converted to Ir(C 2 H 5 ) 2 , Ir(CO) 2 , Ir(CO)(C 2 H 4 ), and Ir(CO)(C 2 H 4 ) 2 as various mixtures of H 2 , CO, and C 2 H 4 reacted with the sample. The sample was tested as a catalyst for ethylene hydrogenation and for H−D exchange in the reaction of H 2 + D 2 . The data, combined with results reported for isostructural iridium complexes bonded to zeolite HY and to MgO, demonstrate how the catalytic activity can be tuned by choice of the support, with the support being characterized as a ligand with electron-donating or electronwithdrawing properties. The results demonstrate that the rate of ethylene hydrogenation catalyzed by the supported iridium complexes is limited by H 2 activation when the iridium is electron rich (on the MgO support), whereas the rate-limiting step is C 2 H 4 adsorption when the iridium is electron deficient (on either zeolite support).

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Section: Reaction Of Iridium Diethylene Complexes With Cosupporting

confidence: 84%

Site-Isolated Molecular Iridium Complex Catalyst Supported in the 1-Dimensional Channels of Zeolite HSSZ-53: Characterization by Spectroscopy and Aberration-Corrected Scanning Transmission Electron Microscopy

Lu¹,

Aydin²,

Liang

et al. 2012

ACS Catal.

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“…Individual ligands on the gold centers observed by IR spectroscopy during steady‐state ethene hydrogenation were characterized by varying the reaction conditions26 and comparing against published spectra 29. The 2961, 2920, and 2870 cm −1 bands suggest the formation of ethyl ligands on the gold, consistent with the IR bands characterizing ethyl on metal surfaces29a,b,c and with CH 3 CH 2 Cl 29d. The 3085 cm −1 band is consistent with the formation of π‐bonded ethene, as observed for Pt, Pd, Ir, and Rh complexes 30…”

Section: Infrared Spectra Representing Samples 1 Andsupporting

confidence: 77%

Structure and Reactivity of a Mononuclear Gold‐Complex Catalyst Supported on Magnesium Oxide

2003

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A golden age of catalysis? A structural model of a MgO‐supported complex [AuIII(CH3)2{OMg}2] (where the MgO ligands are part of the MgO support) has been established based on distances and coordination numbers determined by EXAFS spectroscopy (see picture). This compound is the precursor of a mononuclear gold complex that catalyzes ethene hydrogenation. For comparison, a family of supported gold clusters was also prepared.

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“…EID of physisorbed hydrocarbons is useful for synthesis of symmetrical alkyl and cycloalkyl species [20][21][22][23][24][25][26], but condensation of ethane requires a LHecooled probe. In heroic efforts, supersonic molecular beams [27] and hyperthermal collisions [28] have been used to cleanly create adsorbed ethyl species on Pt(111). Perhaps the most versatile approach is one pioneered by Bent and coworkers [29][30][31] in which incident gas-phase H atoms undergo radical addition to the p-bond in weakly adsorbed ethylene to form ethyl groups.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Ethyl Groups on a Sn/Pt(111) Surface Alloy

Zhao

Koel

2005

Catal Lett

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In order to probe the thermal stability and reactivity of ethyl intermediates on Pt-Sn alloy catalysts, we have synthesized these species by reaction of H atoms with adsorbed ethylene on a ( ffiffi ffi (111) surface alloy. Adsorbed ethyl groups are stable until 376 K where they react to evolve ethane, ethylene, and H 2 . The activation energy for ethyl dehydrogenation is E dehyd Ã ¼ 97 kJ/mol, which is twice that reported on Pt(111). In addition, we place a lower limit of E hydr * > 70 kJ/mol on the barrier to ethyl hydrogenation on this alloy.

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The thermal chemistry of adsorbed ethyl on the Pt(111) surface: infrared evidence for an ethylidene intermediate in the ethyl to ethylidyne conversion

Cited by 30 publications

References 35 publications

Site-Isolated Molecular Iridium Complex Catalyst Supported in the 1-Dimensional Channels of Zeolite HSSZ-53: Characterization by Spectroscopy and Aberration-Corrected Scanning Transmission Electron Microscopy

Site-Isolated Molecular Iridium Complex Catalyst Supported in the 1-Dimensional Channels of Zeolite HSSZ-53: Characterization by Spectroscopy and Aberration-Corrected Scanning Transmission Electron Microscopy

Structure and Reactivity of a Mononuclear Gold‐Complex Catalyst Supported on Magnesium Oxide

Reactivity of Ethyl Groups on a Sn/Pt(111) Surface Alloy

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