N₂ Activation by Neutral Ruthenium Clusters

The activation of nitrogen molecules when forming complexes with neutral Ru clusters in the gas phase has been investigated by probing their N–N stretching frequencies using infrared multiple photon dissociation spectroscopy. The measured frequencies for Ru_nN_2m (n = 5–16; m = 1, 2) fall in the range between 2110 and 2201 cm^–1 and can be attributed to chemisorbed σ-bonded N₂, which corresponds to the γ-state on metal surfaces. The band positions are not dependent on the N₂ coverage, but significant variations are found depending on cluster size.