A diversified reactivity of the mononuclear bis(amidinato)iron(II) complex [Fe(MesC(NPri)(2))(2)] (1) toward oxidizing reagents has been disclosed. The bis(amidinato)iron(II) complex was synthesized from the reaction of [Fe(Mes)(2)](2) with 4 equiv of diisopropyl carbodiimide in good yield. Treatment of 1 with 1 equiv of benzyl chloride gives the high-spin ferric complex [FeCl(MesC(NPri)(2))(2)] (2), with 0.25 equiv of S-8 affords the sulfur-insertion product [Fe(MesC(NPri)((NPrS)-S-i))(2)] (3), with 1 equiv of 3,5-dimethylphenyl azide or phenyl azide yields nitrene-insertion product [Fe(MesC(NPri)(2))((PrNC)-N-i(Mes)N(Pr-i)NAr)] (Ar = 3,5-dimethylphenyl, 4a; phenyl, 4b), and with 1 equiv of oxo-transfer reagent, trimethylamine oxide or 2,6-dichloropyridine oxide, generates the oxo-bridged diferric complex [(MesC(NPri)(2))(2)FeOFe(MesC(NPri)(2))(2)] (5). Complexes 1-3, 4a, and 5 have been characterized by H-1 NMR, UV-vis, IR, elemental analysis, and single-crystal X-ray diffraction studies. The formations of these unusual sulfur- and nitrene-insertion products 3, 4a, and 4b, can be explained by the sequential redox reaction between 1 and the oxidants, followed by migratory insertion steps.