The structure of C5H5RFe+ (R = F,Cl, Br,I, O,OH, OCH3, C6H5, H) ions in the gas phase and the generation of their neutral counterparts by neutralization-reionization mass spectrometry

The structure of C₅H₅FeR^+˙ ions was studied by tandem mass spectrometry that included the neutralization-reionization (NR) method. Halogen-containing species (R = F, Cl, Br, I) showed fragmentation that was consistent with a structure that has the cyclopentadienyl ring and R as separate ligands at the metal atom (structure A). This structure also was identified for C₅H₅FeO⁺ and CpFeOH^+˙ ions, but these species also easily isomerized to metal-cyclopentadiene structure, RC₅H₅Fe^+˙ (B), followed by hydrogen rearrangement(s) and CO loss. B was the dominant structure of C₅H₅FeH^+˙ and C₅H₅FeC₆H^+˙₅ ions. All ions that have structure A showed recovery signals in their NR mass spectra that indicated that their stable neutral counterparts were generated. The NR mass spectra also provided complementary information about the structure of ions before neutralization and after reionization.