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

Abstract

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), [{CpMe₅(dppe)Fe}₂(μ-adpc) (3) and their oxidized complexes [Cp(dppe)Fe(apc)][PF₆] (1[PF₆]), [{Cp(dppe)Fe}₂(μ-adpc)][PF₆] (2[PF₆]₂), [{CpMe₅(dppe)Fe}₂(μ-adpc)][PF₆]₂ (3[PF₆]₂) (Cp=1,3-cyclopentadiene, CpMe₅=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.

Keywords: Azo-Cyanamide Ligands; Crystal structure; Electron transfer.