The [Re, O₈]⁺ potential energy surface: Fourier transform ion cyclotron resonance collision induced dissociation studies and density functional calculations

As potential model systems for organometallic oxidation reaction, ions of the composition [Re, O_n]⁺, n = 2-6, 8, are produced using a standard laser vaporization source and examined by Fourier transform ion cyclotron resonance collision induced dissociation mass spectrometry. Energy resolved collision induced dissociation (CID) in combination with density functional theory calculations is used to characterize the species and extract thermochemical properties. For the first time in FT-ICR, relative intensity data are converted to absolute cross sections, which are used for quantitative threshold evaluation. It is shown that [Re, O₅]⁺ and [Re, O₆]⁺ contain at least one, and [Re, O₈]⁺ at least two dioxygen ligands, bound with an energy of 50-90 kJ/mol. Threshold energies in combination with the theoretical results indicate that all even-numbered species [Re, O_2m]⁺ consist of O₂ ligands and can thus be written as Re(O₂)_m⁺. [Re, O₅]⁺ is identified as ReO₃(O₂)⁺, the calculation yielding an end-on coordinated ligand, whereas in the Re(O₂)_m⁺ species all ligands are side-on coordinated.