Infrared spectroscopy of N2 adsorption on size selected cobalt cluster cations in isolation.

We report IR active N2 stretching frequencies in isolated and size selected cobalt cluster nitrogen adsorbate complexes, [Con(N2)1](+) as recorded by virtue of InfraRed Photon Dissociation (IRPD) spectroscopy. The observed frequencies of the [Con(N2)1](+) complexes (n = 8-17) are significantly redshifted (2180 to 2290 cm(-1)) with respect to the IR inactive vibrations of free N2 (2359 cm(-1)). These bands are assigned to a μ1 head-on type of coordination of the N2 to the cobalt cluster surface, revealing remarkable cluster size dependent features to interpret.