The interaction of ethylene with free gold cluster cations: infrared photodissociation spectroscopy combined with electronic and vibrational structure calculations

Abstract

The interaction of ethylene with free gold clusters of different sizes and charge states has been previously shown theoretically to involve two different adsorption modes of the C 2 H 4 molecule, namely: the di-and-bonded ethylene adsorption configurations. Here, we present the first experimental investigation of the structure of a series of gas-phase gold-ethylene complexes, Au x (C 2 H 4) y + (x =2-4, y =1-3). By employing infrared multiple-photon dissociation spectroscopy (IR-MPD) in conjunction with first-principles calculations it is uncovered that up to three C 2 H 4 molecules bind to gold cations exclusively in a-bonded configuration. The binding of all ethylene molecules is found to be dominated by partial electron donation from the ethylene molecules to the gold clusters leading to an activation of the CC bond. The cooperative action of multiple coadsorbed C 2 H 4 on Au 4 + is shown to enable additional charge back-donation and an enhanced CC bond activation. In contrast, the strong C-H bond is not weakened and the experimental spectra do not give any indication for C-H bond dissociation. The possible correlations of the CC bond stretch vibration with the CC bond length and the net charge transfer are discussed.

Non‐covalent Interactions and Charge Transfer between Propene and Neutral Yttrium‐Doped and Pure Gold Clusters

“…The donation/back‐donation mechanism of ethylene adsorption on gold clusters was inferred from changes in the total charge of the adsorbate and the clusters bond lengths . It was shown that CO adsorption on Pd clusters elongates the Pd−Pd and C−O bonds, which supports a donation/back‐donation mechanism .…”

“…The bond formation and bond breaking processes are confined to the catalytically active sites, which can be modelled by small clusters. [27] Beside the calculation of the reactione nergy,t he analysisa nd the understanding of the chemicali nteractions between catalyst andr eagents is important for rational catalyst design.F or cluster-adduct complexes, the changes in bond lengths and charges, [28][29][30] the frontier orbital and population analysis, [31][32][33] ionization potentials and electron affinities, [34] and NBO analysis, [35] are commonlyu sed to analyse the chemical bonding.…”

Cluster Size Dependent Interaction of Free Manganese Oxide Clusters with Acetic Acid and Methyl Acetate

“…In contrast, νC−C is known to be very sensitive to the C−C bond lengths. 12 For example, for small hydrocarbons νC−C blue-shifts almost linearly from 995 cm −1 for C 2 H 6 with d(C−C) = 1.535 Å to 1623 cm −1 for C 2 H 4 with d(C = C) = 1.339 Å and 1974 cm −1 for C 2 H 2 with d(C C) = 1.203 Å. 31,32 This suggests that the blue-shift of ν s OCO + νC−C is mainly caused by a shortening of the C−C bond; the observed shift of about 30−45 cm −1 might already be caused by a change of the C−C bond length of <0.05 Å.…”

Infrared Study of OCS Binding and Size-Selective Reactivity with Gold Clusters, Aun+ (n = 1–10)

“…65 The NO stretching frequency of AunNO + complexes exhibits marked odd-even alternation, as the unpaired electron in the l Aun + (n = even) clusters efficiently donates into the NO * orbital, efficiently activating it. 7 Infrared studies of other adsorbates (e.g., CO, 7,66 methane, 67 methanol, [68][69][70] ethanol, 71 and ethene 72 ) on gold clusters suggest alternative binding mechanisms for which odd-even size effects are less clear. All small gold clusters selectively dissociate a single C-H bond in CH4 but, whilst CH4 binding energies to Aun + show a clear size dependence, 73 this is not reflected in the IR-MPD spectra.…”