title: Thermal N-H bond activation on anionic and cationic platinum clusters: non-predetermined reaction pathways indicate transitions to a bulk surface reactivity.
abstract: Reactions of cationic and anionic platinum clusters Pt(n)(+/-), n=1-5, with NH(3) are studied by FT-ICR mass spectrometry and DFT calculations. With cationic clusters, radiative association of an intact NH(3) is the dominant reaction channel. On anionic clusters, NH(3) undergoes reductive elimination of molecular hydrogen, with nitride and hydride bound at remote sites of the cluster. Nitride assumes a bridge position, while hydride is bound atop a single platinum atom. On the [Pt(n),NH(3)](-) potential energy surface, for n=4 fifteen local minima and connecting transition states were identified with relevance to the hydrogen formation reaction, and 12 local minima were identified for n=5. These potential energy surfaces offer a rich variety of pathways, illustrating a key feature of a successful bulk catalyst: The variety of pathways helps the catalyst to work over a wide range of temperatures and pressures.
authors.affiliation: J. Heyrovský Institute of Physical Chemistry, v.v.i. Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23, Prague 8 (Czech Republic).|Department of Physical Chemistry, Institute of Chemical Technology, Prague, Technická 5, 166 28, Prague 6 (Czech Republic).
authors.forename: Milan
authors.initials: M
authors.lastname: Ončák
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin (Germany), Fax: (+49) 30-314-21102.
authors.forename: Yali
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin (Germany), Fax: (+49) 30-314-21102.|Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany).
authors.forename: Robert F
authors.initials: RF
authors.lastname: Höckendorf
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin (Germany), Fax: (+49) 30-314-21102.|Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany).
authors.forename: Martin K
authors.initials: MK
authors.lastname: Beyer
authors.affiliation: J. Heyrovský Institute of Physical Chemistry, v.v.i. Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23, Prague 8 (Czech Republic).
authors.forename: Rudolf
authors.initials: R
authors.lastname: Zahradník
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623, Berlin (Germany), Fax: (+49) 30-314-21102.
authors.forename: Helmut
authors.initials: H
authors.lastname: Schwarz