The fragmentation mechanism of iron complexes bearing a bidentate ligand, dimethoxyethane (CH(3)OCH(2)CH(2)OCH(3), labeled as DXE) has been investigated by means of FT-ICR mass spectrometry (ion-molecule reactions) and infrared multiphoton dissociation spectroscopy. Two possible reaction mechanisms were envisioned for the Fe(DXE)(+) + DXE reaction, leading to the formation of the Fe(CH(2)O)(DXE)(+) ion. The two mechanisms differ in the nature of the neutral molecules formed: CH(3)OC(2)H(5) or CH(2)=CH(2) + CH(3)OH. The combination of ion-molecule reactions, thermochemistry considerations, and IRMPD spectra leads us to suggest that the mechanism involves successive elimination of the neutrals CH(2)=CH(2) and CH(3)OH, the first step of the mechanism being the insertion of the iron atom in the O-C(central) bond.