Charge transfer initiated nitroxyl chemistry on free silver clusters Ag 2–5−: Size effects and magic complexes

Abstract

The reactivity of small silver cluster anions Ag 2–5 − toward nitric oxide and mixtures of nitric oxide with carbon monoxide is investigated under multi-collision conditions in a radio frequency octopole ion trap at temperatures of 100 and 300 K. A strongly cluster size dependent reaction behavior is observed, where reactive fragmentation dominates for clusters with four or fewer atoms and only Ag 5 − is able to form reaction products without dissociation of the metal cluster. The decisive role of charge transfer in the NO bond breakage, NO oxidation, and the formation of free NO 2 − and N 2O 4 − ions, as well as N x O ( y> x) -ligands on the silver clusters is discussed. The mass spectrometric data reveal the particular stability of the reaction products AgN 2O 4 − and Ag 3NO −. The reaction product mass spectra obtained for Ag 5 − in the presence of NO and CO show the depletion of the N x O ( y> x) -ligands on the metal cluster possibly involving the oxidation of CO to CO 2.