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

摘要

Two sets of Fe ~(III/II) dithione complexes [Fe ~(II) ( ~( i ) Pr _(2) Dt ~(0) ) _(3) ][PF _(6) ] _(2) ([ 1 ][PF _(6) ] _(2) ), [Fe ~(II) (Me _(2) Dt ~(0) ) _(3) ][PF _(6) ] _(2) ([ 2 ][PF _(6) ] _(2) ), and [Fe ~(III) ( ~( i ) Pr _(2) Dt ~(0) ) _(3) ][PF _(6) ] _(3) ([ 3 ][PF _(6) ] _(3) ), [Fe ~(III) (Me _(2) Dt ~(0) ) _(3) ][PF _(6) ] _(3) ([ 4 ][PF _(6) ] _(3) ), and compound [Fe ~(III) ( ~( i ) Pr _(2) Dt ~(0) ) _(3) ][FeCl _(4) ][PF] _(2) ([ 3 ][FeCl _(4) ][PF _(6) ] _(2) ) were synthesized from N , N ′-diisopropyl piperazine-2,3-dithione ( ~( i ) Pr _(2) Dt ~(0) ) and N , N ′-dimethyl piperazine-2,3-dithione (Me _(2) Dt ~(0) ) ligands. Complexes [ 1 ][PF _(6) ] _(2) –[ 4 ][PF _(6) ] _(3) have been characterized by NMR, IR, and UV-visible spectroscopies, and by electrochemistry. The molecular structures of [ 2 ][PF _(6) ] _(2) and [ 3 ][FeCl _(4) ][PF _(6) ] _(2) have been determined by X-ray crystallography. Complexes [ 2 ][PF _(6) ] _(2) and [ 3 ][FeCl _(4) ][PF _(6) ] _(2) both crystallized in the monoclinic space group P 2 _(1) / n . Both complexes exhibit distorted octahedral geometry and the three coordinated ligands in each complex exhibit different dithione folding. Complexes [ 1 ][PF _(6) ] _(2) –[ 4 ][PF _(6) ] _(3) exhibit a single Fe ~(III/II) based couple and three quasi-reversible ligand-based redox couples. The electronic spectra of [ 1 ][PF _(6) ] _(2) –[ 4 ][PF _(6) ] _(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 electronic origin of their redox chemistry and spectroscopic features.