Reactions of Nitric Oxide with a Low-Spin Fe(III) Center Ligated to a Tetradentate Dicarboxamide N₄ Ligand: Parallels between Heme and Non-heme Systems

Reaction of excess NO with the non-heme Fe(III) complex [(bpb)Fe(py)2]ClO4 in MeCN under strictly anaerobic conditions affords the {Fe−NO}6(nitro)(nitrosyl) complex [(bpb)Fe(NO)(NO2)] (1) via metal-promoted NO disproportionation, while in a MeOH/MeCN mixture, the same reaction leads to reductive nitrosylation and generation of the {Fe−NO}7 species [(bpb)Fe(NO)] (2). Exposure of a solution of 1 in DMF to dioxygen leads to formation of the ring-nitrosylated product [(bpb-NO2)Fe(NO3)(DMF)] (3). The present system therefore exhibits all the NO reactivities reported so far with the iron−porphyrins.