The crucial role of CO as a ligand in the formation of long-lived neutral iron complexes in the gas phase

Neutralization reionization (NR) mass spectra of mono- and bis-ligated iron cations Fe(L)(n)(+) (n = 1, 2) are reported for the simple ligands L = H2O , CO, C2H4, C4H6, C6H6, and NH3. Most of these iron complexes do not surviv e the NR process, and dissociation of the neutrals into Fe(+)nL prevails. I nterestingly, those complexes containing CO ligands exhibit much more prono unced recovery signals in the NR spectra. Electronic arguments imply that t he carbonyl ligand favors the generation of low-spin complexes of neutral i ron which are less prone to dissociate and are not accessed with the other Ligands. (C) 1999 Elsevier Science B.V. All rights reserved.