Syntheses, spectroscopic, redox, and structural properties of homoleptic Iron(III/II) dithione complexes.

Two sets of Fe dithione complexes [Fe( PrDt)][PF] ([1][PF]), [Fe(MeDt)][PF] ([2][PF]), and [Fe( PrDt)][PF] ([3][PF]), [Fe(MeDt)][PF] ([4][PF]), and compound [Fe( PrDt)][FeCl][PF] ([3][FeCl][PF]) were synthesized from ,'-diisopropyl piperazine-2,3-dithione ( PrDt) and ,'-dimethyl piperazine-2,3-dithione (MeDt) ligands. Complexes [1][PF]-[4][PF] have been characterized by NMR, IR, and UV-visible spectroscopies, and by electrochemistry. The molecular structures of [2][PF] and [3][FeCl][PF] have been determined by X-ray crystallography. Complexes [2][PF] and [3][FeCl][PF] both crystallized in the monoclinic space group 2/. Both complexes exhibit distorted octahedral geometry and the three coordinated ligands in each complex exhibit different dithione folding. Complexes [1][PF]-[4][PF] exhibit a single Fe based couple and three quasi-reversible ligand-based redox couples. The electronic spectra of [1][PF]-[4][PF] show intense MLCT bands that indicate strong mixing between metal and ligand orbitals. DFT calculations were used to provide a framework for understanding the electronic origin of their redox chemistry and spectroscopic features.