A mixed oxidation state, binuclear iron complex containing an unsymmetrically coordinating ligand. A ligand-induced switch in redox behavior

Binuclear [FeIIFeIII(BMDP)(O2CPh)3](BF4) (1) was obtained by treating an acetonitrile solution of the fully reduced [FeIIFeII(BMDP)(O2CPh)(MeOH)1.5(H2O)0.5](BF4)2 with 5 equiv of benzoate and then exposing the mixture to oxygen. Examination of [FeIIFeIII(BMDP)(O2CPh)3](BF4) by X-ray crystallography reveals the localized, mixed oxidation state nature of the cation in the solid state. 1H NMR and magnetic susceptibility data for the new complex are also reported. In the absence of dioxygen and other oxidants, treatment of FeIIFeII(BMDP)(O2CPh)(MeOH)1.5(H2O)0.5](BF4)2 with excess benzoate results in the formation of [FeIIFeII(BMDP)(O2CPh)2](BF4)2, which has also been characterized by X-ray diffraction.