that, unlike the parent complex, which exhibits a conductivity value expected for a 2:1 electrolyte (AM = 240 "1 cm"1 mol"1 for 8 X 10"4 M complex in acetonitrile), the peroxide complex behaves like a 1:1 electrolyte ( = 147 "1 cm"1 mol"1 for 8 X "4 M complex in acetonitrile).64 We thus propose that peroxide binding appears to result in the replacement of the µwith a µ-1:»!1 peroxide moiety with the retention of the basic ligand coordination around the dibridged dinuclear center (Figure 7a). This proposed structure for [Fe2(HPTB)(02)(N03)2]N03 is different from that proposed for the dioxygen adduct of [Fe2(iV-Et-HPTB)-(OBz)](BPh4)2,27 which consists of a tribridged diferric core analogous to the 2+ cation in Figure 7b with benzoate replacing nitrate. The structural differences in the two peroxide complexes may be reflected in the subtle changes in their UV-vis, Raman, and Mdssbauer parameters (Tables III and IV).All of the diferric peroxide complexes studied thus far appear to favor peroxide bridge formation, and none of these complexes model the dioxygen-binding mode found for oxyhemerythrin- 56 Those capable of reversible dioxygen binding derive from (63) Brennan, B. A.; Chen, Q.; Que, L., Jr. Unpublished results.