Corroding the chromium cation

Two [Cr,O2]+ isomers have been selectively produced and studied by FT-ICR mass spectrometry. The Cr(O2)+ complex was formed by supersonically expanding a plasma produced by laser vaporization of chromium metal with the helium carrier gas, which was seeded with traces of oxygen, while the chromyl cation is formed in an expansion with N2O. The complex is stable against thermal collisions, but in a bimolecular reaction with water it is rapidly converted to the chromyl cation, with ligand exchange being only a minor side reaction. Isotopic studies suggest a side-on geometry for Cr(O2)+, in accordance with density functional (B3LYP) calculations. The present work indicates that an investigation of the selected isomers can indeed be carried out, if appropriate chemical methods for the ion generation are applied.