Ligational and conformational effects on the rates of reductive cleavage of ligated forms of [Fe((DMG)BPh(2))(2)]O-2 by 4-tert-butylcatechol are elucidated. The site-differentiated LFeN(4)-O-FeN4 species is the redox-active form. Trans ligands which stabilize higher oxidation states enhance the rate of reduction by stabilizing a LFe(IV)-O-Fe-II resonance form.