Syntheses, spectroscopic, redox, and structural properties of homoleptic Iron(III/II) dithionecomplexes

Abstract

Two sets of FeIII/II dithione complexes [FeII(iPr2Dt0)3][PF6]2([1][PF6]2),[FeII(Me2Dt0)3][PF6]2 ([2][PF6]2), and [FeIII(iPr2Dt0)3][PF6]3 ([3][PF6]3), [FeIII(Me2Dt0)3][PF6]3 ([4][PF6]3), and compound [FeIII(iPr2Dt0)3][FeCl4][PF]2 ([3][FeCl4][PF6]2) were synthesized from N,N0-diisopropyl piperazine-2,3-dithione (iPr2Dt0) and N,N0-dimethyl piperazine-2,3-dithione (Me2Dt0) ligands. Complexes [1][PF6]2 [4][PF6]3 have been characterized by NMR, IR, and UV-visible spectroscopies, and by electrochemistry. The molecular structures of [2][PF6]2 and [3][FeCl4][PF6]2 have been determined by X-ray crystallography. Complexes [2] [PF6]2 and [3][FeCl4][PF6]2 both crystallized in the monoclinic space group P21/n. Both complexes exhibit distorted octahedral geometry and the three coordinated ligands in each complex exhibit different dithione folding. Complexes [1][PF6]2 [4][PF6]3 exhibit a single FeIII/II based couple and three quasireversible ligand-based redox couples. The electronic spectra of [1][PF6]2 [4][PF6]3 show intense MLCT bands that indicate strong mixing between metal and ligand orbitals. DFT calculations were used to provide a framework for understanding the electronicorigin of their redox chemistry and spectroscopic features.