Structure and reactivity of metal clusters of the platinum group
Final Report Abstract
In conclusion, a comprehensive spectroscopic study of the structural and chemical properties of clusters of the platinum group metals (4d: Ru, Rh, Pd; 5d: Os, Ir, Pt) has been performed. Insights into the clusters’ structure and the behavior of adsorbed species are obtained mostly via vibrational spectroscopy in the gas phase. The clusters are investigated size-selectively using infrared multiple photon dissociation spectroscopy. As this requires an intense and tunable (far-) infrared source, the experiments are performed with Infrared Free Electron Lasers (FELs) as light sources. The wide tunability of FELs allows access to the characteristic vibrational modes of cluster-bound ligands in the mid-IR as well as internal vibrational modes of the metal clusters in the far-IR. The measured infrared multiple photon dissociation spectra are structural fingerprints and allow via comparison to spectra predicted, i.e. from DFT calculations, for structural assignments. The clusters of the platinum group metals are of particular interest due to the importance of the metals in catalytic applications, but also due to the surprising prediction of uncommon simple cubic structural motifs. However, for rhodium the stability of such cubic geometries appears to be an artifact of the GGA-DFT method and experimentally polytetrahedral structures are identified, similar to many other transition metals including platinum, while ruthenium and iridium indeed appear to follow the cubic growth motif for small cluster sizes. Insights into the activation and reactions of small molecules with metal clusters have been obtained from studying the IR spectra of metal cluster complexes. In many cases cluster sizespecific behavior is observed. The studied reactions include the binding of CO and N2 to ruthenium clusters as well as the activation of methane and carbon dioxide by platinum clusters. An interesting aspect in the IR spectroscopic studies of adsorbed molecules is the observation of IR induced (thermal) reactions, for instance the oxidation of CO by coadsorbed O species or the decomposition of N2O under release of N2. Finally, we have studied the platinum trimer by high resolution anion photoelectron spectroscopy using velocity map imaging and demonstrate with this example the wealth of information that is accessible by a detailed analysis of Franck-Condon patterns, intensities and angular distributions, and their dependence on the electron kinetic energy. By these means two structural isomers of the anionic trimer, the two corresponding neutral species and a number of excited states have been characterized.
Publications
- Probing C–O bond activation on gas-phase transition metal clusters: Infrared multiple photon dissociation spectroscopy of Fe, Ru, Re, and W cluster CO complexes. J. Chem. Phys. 131 (2009) 184706
J. T. Lyon, P. Gruene, A. Fielicke, G. Meijer, D. M. Rayner
(See online at https://doi.org/10.1063/1.3257687) - CO adsorption on neutral iridium clusters. Eur. Phys. J. D. 63 (2011) 231
C. Kerpal, D. J. Harding, G. Meijer, A. Fielicke
(See online at https://dx.doi.org/10.1140/epjd/e2010-10480-8) - Activated Methane on Small Cationic Platinum Clusters. Angew. Chem. Int. Ed. 51 (2012) 817
D. J. Harding, C. Kerpal, G. Meijer, A. Fielicke
(See online at https://doi.org/10.1002/anie.201107042) - Infra-red driven CO oxidation reactions on isolated platinum cluster oxides PtnOm+. Faraday Discussions 157 (2012) 213
A. C. Hermes, S. M. Hamilton, G. A. Cooper, C. Kerpal, D. J. Harding, G. Meijer, A. Fielicke, S. R. Mackenzie
(See online at https://doi.org/10.1039/c2fd20019h) - The structures of small cationic gas-phase platinum clusters. J. Chem. Phys. 136 (2012) 211103
D. J. Harding, C. Kerpal, D. M. Rayner, A. Fielicke
(See online at https://doi.org/10.1063/1.4726403) - N2 Activation by Neutral Ruthenium Clusters. J. Phys. Chem. C 117 (2013) 12153
C. Kerpal, D. J. Harding, J. T. Lyon, G. Meijer, A. Fielicke
(See online at https://doi.org/10.1021/jp401876b) - The structures of platinum oxide clusters in the gas phase. J. Phys. Chem. A 117 (2013) 1233
C. Kerpal, D. J. Harding, A. C. Hermes, G. Meijer, S. R. Mackenzie, A. Fielicke
(See online at https://doi.org/10.1021/jp3055137) - Unusual bonding in platinum carbido clusters. J. Phys. Chem. Lett. 4 (2013) 892
D. J. Harding, C. Kerpal, G. Meijer, A. Fielicke
(See online at https://doi.org/10.1021/jz400256d) - Platinum group metal clusters: from gas-phase structures and reactivities towards model catalysts. Chem. Eur. J. 20 (2014) 3258
D. J. Harding, A. Fielicke
(See online at https://doi.org/10.1002/chem.201304586) - Far-IR Spectra and Structures of Small Cationic Ruthenium Clusters: Evidence for Cubic Motifs. J. Phys. Chem. C 119 (2015) 10869
C. Kerpal, D. J. Harding, D. M. Rayner, J. T. Lyon, A. Fielicke
(See online at https://doi.org/10.1021/jp510471k) - The Nature of Bonding between Argon and Mixed Gold–Silver Trimers. Angew. Chem. Int. Ed. 54 (2015) 10675
A. Shayeghi, R. L. Johnston, D. M. Rayner, R. Schäfer, A. Fielicke
(See online at https://doi.org/10.1002/anie.201503845) - The effect of charge transfers on the adsorption of CO on small Mo doped Pt clusters. Chem. Eur. J. 23 (2017) 4120
P. Ferrari, J. Vanbuel, N. M. Tam, M. T. Nguyen, S. Gewinner, W. Schöllkopf, A. Fielicke, E. Janssens
(See online at https://doi.org/10.1002/chem.201604894)
