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Dinitrosyl Iron Complexes (DNICs) Bearing O-Bound Nitrito Ligand: Reversible Transformation between the Six-Coordinate {Fe(NO) 2 } 9 [(1-MeIm) 2 (η 2 -ONO)Fe(NO) 2 ] ( g = 2.013) and Four-Coordinate {Fe(NO) 2 } 9 [(1-MeIm)(ONO)Fe(NO) 2 ] ( g = 2.03)

2009; American Chemical Society; Volume: 131; Issue: 10 Linguagem: Inglês

10.1021/ja808743g

1943-2984

Fu‐Te Tsai, Ting‐Shen Kuo, Wen‐Feng Liaw,

Nitric Oxide and Endothelin Effects

In contrast to the four-coordinate tetrahedral {Fe(NO)2}9 DNICs with an EPR g value of 2.03, the newly synthesized nonclassical six-coordinate {Fe(NO)2}9 DNIC [(1-MeIm)2(η2-ONO)Fe(NO)2] (1-MeIm = 1-methylimidazole) (1) displays an EPR signal g = 2.013. The temperature-dependent reversible transformation occurs between the six-coordinate chelating nitrito {Fe(NO)2}9 DNIC 1 and the four-coordinate monodentate nitrito {Fe(NO)2}9 DNIC [(1-MeIm)(ONO)Fe(NO)2] (2-MeIm). The chelating nitrito of DNIC 1, triggered by PPh3, undergoes O-atom transfer to yield O═PPh3, accompanied by reductive elimination of NO and the generation of {Fe(NO)2}10 DNIC [(1-MeIm)(PPh3)Fe(NO)2] (3), in contrast to the inertness of the nitrite-containing {Fe(NO)2}9 DNIC [(HIm)(ONO)Fe(NO)2] (HIm = imidazole) (2-HIm) toward PPh3. The findings, EPR signals of g = 2.013 for complex 1 and g = 2.03 for complexes 2-MeIm/2-HIm, imply that characterization of DNICs may be possible via their distinctive EPR signal g = 2.03 for the tetrahedral DNICs and EPR signal g = 2.01 for the six-coordinate DNICs. This study also implicates that the six-coordinate nitrite-containing {Fe(NO)2}9 DNICs may act as a transient intermediate (or an active center) to trigger the transformation of nitrite into nitric oxide.