Chemistry of (and on) Transition Metal Clusters: A Fourier Transform Ion Cyclotron Resonance Study of the Reaction of Niobium Cluster Cations with Nitric Oxide

The reactions of niobium cluster cations, Nb+ n ( n = 2–19), with nitric oxide have been investigated using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR). The overall reaction rate constants are found to be in reasonable agreement with collision rates calculated using the surface charge capture model. The dominant reaction for small clusters ( n < 9) involves reaction-induced fragmentation resulting in the loss of either NbO or NbN. By contrast, the main reaction observed for the larger clusters ( n > 11) is sequential NO chemisorption. Clusters n = 9, 10 exhibit both extremes of behaviour and are the only clusters upon which there is evidence of NO decomposition with N2 loss observed whenever multiple NO molecules are co-adsorbed. The rate constants for each process have been determined as a function of cluster size.