Collisional Activation of N2O Decompositionand CO Oxidation Reactions on Isolated Rhodium Clusters.

The reactions of nitrous oxide decoratedrhodium clusters, RhnN2O+(n= 5, 6), have been studied by Fouriertransform ion cyclotron resonancemass spectrometry. Collision induced dissociation with Ar is shownto lead to one of two processes; desorption of the intact N2O moiety (indicating molecular adsorption in the parent cluster)or N2O decomposition liberating molecular nitrogen withthe latter becoming increasingly dominant at higher collision energies.Consistent with the results of earlier studies, which employed infraredexcitation [Hermes, A. C.; et al.J. Phys. Chem. Lett. 2011, 2, 3053], Rh5ON2O+is observed to behave qualitatively differentlyto Rh5N2O+with decomposition ofthe nitrous oxide dominating the chemistry of the former. In otherexperiments, the reactivity of RhnN2O+clusters with CO has been studied. Chemisorptionof 13CO is calculated to deposit ca.2eV into the parent cluster, initiating a range of chemical processeson the cluster surface, which are fit to a simple reaction mechanism.Clear differences are again observed in the reaction branching ratiosfor Rh5N2O+and Rh6N2O+parent cluster ions. For the n= 5 cluster, the combined N2O reduction/CO oxidationis the most significant reaction channel, while the n= 6 cluster preferentially is oxidized to Rh6O+with loss of N2and CO. Even larger differences are observedin the reactions of the N2O decorated cluster oxides, RhnON2O+, for which morereaction possibilities arise. The results of all studies are discussedin relation to infrared driven processes on the same parent clusterspecies [Hamilton, S. M.; et al.J. Am. Chem. Soc.2010, 132, 1448; J. Phys.Chem. A, 2011, 115, 2489]. [ABSTRACT FROM AUTHOR]