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.

Ion–molecule reactions of CoAr6+ with nitrogen oxides N2O, NO, and NO2: measuring absolute pressure by shock-freezing of the collision complex

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is a well suited tool to investigate bimolecular cluster ion-molecule reactions [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In order to determine absolute rate constants one should know the absolute pressure in the ICR-cell accurately, because the pressure is the main uncertainty.…”