Matrix infrared spectra of the Fe + N2 system show that laser-ablated Fe atoms react with nitrogen atoms and molecules to give the FeN and NFeN molecules and Fe(N2)x complexes. The iron nitride molecules FeN and NFeN were identified from nitrogen and iron isotopic shifts and splittings and density functional frequency calculations. Sharp 934.8 and 903.6 cm-1 bands are assigned to the 56FeN and N56FeN molecules in solid nitrogen. The NFeN molecule is bent with valence angle 115 ± 5° as determined from iron and nitrogen isotopic shifts. Nitrogen-to-argon matrix shifts for FeN and NFeN are small. The cyclic Fe2N molecule is observed at 779 and 719 cm-1 in solid nitrogen. Strong bands in the 2200-2000 cm-1 region are associated with end-bonded Fe(NN)x complexes; the FeNN molecule absorbs at 2017.8 cm-1 in solid argon. New absorptions at 1826.8 and 1683.7 cm-1 in argon matrix experiments, identified as side-bonded Fe(N2) and (Fe2)(N2), respectively, agree very well with earlier CASSCF frequency calculations and approach the frequency of N2 adsorbed on Fe(111). Structure and frequency calculations were done using density functional theory to support the identification of these new Fe(N2)x molecular complexes.