A new biomimetic model of the sulfur-ligated non-heme enzyme superoxide reductase (SOR) has been synthesized.  This complex, [Fe^II(cyclam-PrS)]⁺, has an N₄S ligand based on the cyclam macrocycle, and adopts a square pyramidal geometry with an open site trans to the thiolate.  It reacts at -78^oC with O₂^- in the presence of protons to afford a metastable peroxo intermediate, [Fe^III(cyclam-PrS)OOH]⁺.  During this reaction O₂^- is reduced to H₂O₂, which is liberated by the addition of acetic acid, affording the acetate-bound complex [Fe^III(cyclam-PrS)OAc]⁺.  The ability of this system to act as a catalyst for the reduction of O₂^- to H₂O₂ is also demonstrated by the use of cobaltocene as a sacrificial reductant.  This work represents the first reported example of a non-heme iron peroxo intermediate with a thiolate bound trans- to the peroxo moiety, and is the most analogous synthetic model of the active site of SOR to date.