Reactions of Fe-n(+) clusters (n=2-11) with C6H6 and C6D6. Ligand isomerization in the benzene precursor ion Fe-4(C2H2)(3)(+)

Even though Fe-4(+) clusters in the gas phase have been demonstrated to be able to induce the cylotrimerization of added C2H2 ligands to benzene, the precursor ion Fe-4(C2H2)(3)(+) has not yet been structurally characterized. To improve our understanding of this type of ion, we compare the products obtained by the direct reaction of benzene with bare Fe C clusters (n = 2-11) to those obtained by dehydrogenative addition of ethene. Additional mass spectrometric studies such as collision-induced dissociation (CID) and thermoneutral ligand exchange with C6D6 suggest that the reaction of C2H4 with Fe-4(+) produces at least two types of structural isomers, with a preformed benzene molecule existing only in one of them (Fe4C6H6+).