The Fe-2 + CO reaction has been reinvestigated using deposition of ground-state iron atoms and carbon monoxide in solid argon. The iron carbonyl products observed without activation energy are Fe2CO and higher carbonyl species Fe(CO)(x). The Fe2CO Molecule, has been characterized through the observation of four fundamental transitions assigned to the three stretching (nu(1), nu(2), and nu(4)) and the highest frequency bending vibration (nu(3)). Isotopic data on nu(1), nu(2), nu(3), nu(4), nu(1) + nu(2), and 2nu(1) have been measured in the near- and fare infrared regions. From the experimental data, a-linear structure can be excluded and precise C-O, Fe-C, and Fe-Fe bond force constants can be determined. Geometrical and electronic configurations of the lowest energy states for each possible spin multiplicity of Fe2CO, Fe2CO-, and Fe2CO+ have been calculated using density functional theory with the generalized approximation for the exchange-correlation functional (DFT-GGA). The calculation results also predict an end-on, but highly-bent, Fe-Fe-C-O ground-state structure for the neutral species ((7)A'). Comparison of the DFT force field computed harmonic frequencies with the experimental frequencies. obtained for Fe2CO isolated in, solid argon show a very good agreement, which validates the ground-state DFT prediction. Computed ionization energies and electron affinities are also reported, along with the vibrational harmonic frequencies for the predicted ionic ground states.