Azo-Cyanamide Bridged Dinuclear Iron Complexes Exhibiting no Electronic Coupling but Moderate Magnetic Coupling between the two Iron Centers.

To investigate the effect of long-distance organic ligand on electronic coupling between metallic atoms, the mononuclear and dinuclear complexes [Cp(dppe)Fe(apc)] (1), [{Cp(dppe)Fe} ₂ (μ-adpc)] (2), [{CpMe ₅ (dppe)Fe} ₂ (μ-adpc) (3) and their oxidized complexes [Cp(dppe)Fe(apc)][PF ₆ ] (1[PF ₆ ]), [{Cp(dppe)Fe} ₂ (μ-adpc)][PF ₆ ] (2[PF ₆ ] ₂ ), [{CpMe ₅ (dppe)Fe} ₂ (μ-adpc)][PF ₆ ] ₂ (3[PF ₆ ] ₂ ) (Cp=1,3-cyclopentadiene, CpMe ₅ =1,2,3,4,5-pentamethylcyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane), apc ^- =4-azo(phenylcyanamido)benzene and adpc ^2- =4,4'-azodi(phenylcyanamido)) were synthesized and characterized by cyclic voltammetry, UV-vis, single-crystal X-ray diffraction and Mössbauer spectra. Electrochemical measurements showed no electronic coupling between the two terminal Fe units, However, the investigation results of the magnetic properties of the two-electron oxidized complexes indicate the presence of moderate antiferromagnetic coupling across 18 Å distance.
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