Structure, coordination, and solvation of V+(benzene)n complexes via gas phase infrared spectroscopy

V+(C6H6)(n) (n = 1-4) and V+(C6H6)(n)Ar (n = 1, 2) complexes are produced by laser vaporization in a pulsed nozzle cluster source. The clusters are mass-selected and studied by infrared laser photodissociation spectroscopy in the C-H stretch region of benzene. Photodissociation of V+(C6H6)(n) complexes occurs by the elimination of intact neutral benzene molecules, whereas V+(C6H6)(n)Ar complexes lose Ar. The dissociation process is enhanced on vibrational resonances and the spectrum is obtained by monitoring fragment yield versus the infrared wavelength. Vibrational bands in the 2700-3300 cm(-1) region are characteristic of the benzene molecular moiety with systematic shifts caused by the metal bonding. A dramatic change in the IR spectrum occurs at n = 3, confirming that two ligands complete the coordination sphere and that additional benzenes act as solvent. The comparison between experiment and theory provides fascinating new insight into the bonding in these prototypical organometallic complexes.