Infrared Spectroscopy and Binding Geometries of Oxygen Atoms Bound to Cationic Tantalum Clusters

The binding of isolated oxygen atoms to small tantalum clusters is investigated using vibrational spectroscopy. Infrared spectra of TanO0,1,2+ (n = 6−11) are reported in the range of 90−1100 cm−1, comprising both the internal cluster modes and the adatom’s vibrations. The vibrational spectra are compared to the results of DFT calculations for n = 6−8, which show that the oxygen atoms bind preferentially as 2-fold bridging adatoms. Addition of one or two O atoms induces only minor distortions of the underlying metal cluster core.