New Members of the {Fe(NO)₂}¹⁰ Dinitrosyliron Complexes Bound with [Thiolate, Thiolate] and [Amide, Amide] Ligations

The first dianionic {Fe(NO)2}10 dinitrosyliron complexes (DNICs) [Fe(SC7H4SN)2(NO)2]2− (1) and [Fe(OC7H4SN)2(NO)2]2− (2), coordinated with thiolates and amides, were prepared by the reaction of Fe(TMEDA)(NO)2 with 2 equiv of ligands [SC7H4SN]− and [OC7H4SN]−, respectively. The reversible interconversion between the dianionic {Fe(NO)2}10 DNICs 1/2 and the anionic {Fe(NO)2}9[Fe(SC7H4SN)2(NO)2]− (3)/[Fe(OC7H4SN)2(NO)2]− (4), respectively, was demonstrated. The transformation of DNICs 2 and 3 into the thermally stable DNICs 1 and 4, respectively, via the ligand-exchange reaction reveals that [OC7H4SN]− shows a high binding affinity toward the {Fe(NO)2}9 motif and [SC7H4SN]− prefers the {Fe(NO)2}10 motif. This result rationalizes that the intermolecular electron transfer from DNIC 2 to DNIC 3 occurs to lead to the formation of the more thermally stable DNICs 1 and 4 upon the reaction of DNICs 2 and 3 in tetrahydrofuran.