The reaction of the new dinucleating ligand susan6-Me with Fe(BF4)2·6H2O results in formation of the homovalent FeIIFeII complex [(susan6-Me){FeII(μ-F)2FeII}]2+ and the mixed-valence FeIIFeIII complex [(susan6-Me){FeIIF(μ-F)FeIIIF}]2+ depending on the absence or presence of dioxygen, respectively. Complex [(susan6-Me){FeIIF(μ-F)FeIIIF}]2+ is the first molecular mixed-valence complex with a fluorido bridge. The short FeIII-μ-F bond of 1.87 Å causes a large reorganization energy, resulting in a localized class II system with an intervalence charge-transfer band of high energy at 10000 cm-1.