 The molar mass of the parent complex can be determined, as well as information about structural rearrangements involving loss of carbonyl ligands under ESI-MS conditions.Mass spectrometry combined with infrared photodissociation spectroscopy can provide vibrational informations for ionic carbonyl complexes in gas phase.In the investigation of the infrared spectrum of the Galactic Center monoxide vibrations of iron carbonyls in interstellar dust clouds were detected.