When highly dispersed, supported Fe oxides are selective alkane oxidation catalysts, but new syntheses are required to reliably produce such materials. Here, highly dispersed, supported Fe(3+) catalysts are prepared via incipient wetness impregnation of SiO(2) with aqueous Fe complexes of ethylenediaminetetraacetic acid (FeEDTA), followed by calcination. With Na(+) countercations, UV-visible diffuse reflectance spectra are entirely below 300 nm and H(2) temperature-programmed reduction only shows reduction at similar to 630 degrees C for all loadings up to 2.15 wt%, the maximum loading for a single impregnation cycle. These characteristics indicate isolated sites not seen for Fe(NO(3))(3) precursors even at 0.3 wt%. NH(4)(+) countercations lead to amorphous oxide oligomers and a minority species with unusual reducibility at 310 degrees C. countercations produce 'single-site' behavior in adamantane oxidation using H(2)O(2) with a specific turnover frequency of 9.2 +/- 0.8 ks(-1), constant for all Fe loadings and approximately 10 times higher than that of other well-dispersed Fe/SiO(2) materials. Similar turnover frequencies are obtained when counting only the highly reducible species on the NH(4)(+)-derived catalyst, allowing these sites to be tentatively assigned as small, undercoordinated clusters that are both easily reduced and participate in alkane oxidation, reminiscent of Fe-exchanged MFI zeolites. (C) 2011 Elsevier Inc. All rights reserved.