摘要
Nitrosylation of high-spin [Fe(κ 2 -O 2 NO) 4 ] 2- (1) yields {Fe(NO)} 7 mononitrosyl iron complex (MNIC) [(κ 2 -O 2 NO)(κ 1 - ONO 2 ) 3 Fe(NO)] 2- (2) displaying an S = 3/2 axial electron paramagnetic resonance (EPR) spectrum (g ⊥ = 3.988 and g â̂¥ = 2.000). The thermally unstable nitrate-containing {Fe(NO) 2 } 9 dinitrosyl iron complex (DNIC) [(κ 1 -ONO 2 ) 2 Fe(NO) 2 ] - (3) was exclusively obtained from reaction of HNO 3 and [(OAc) 2 Fe(NO) 2 ] - and was characterized by IR, UV-vis, EPR, superconducting quantum interference device (SQUID), X-ray absorption spectroscopy (XAS), and single-crystal X-ray diffraction (XRD). In contrast to {Fe(NO) 2 } 9 DNIC [(ONO) 2 Fe(NO) 2 ] - constructed by two monodentate O-bound nitrito ligands, the weak interaction between Fe(1) and the distal oxygens O(5)/O(7) of nitrato-coordinated ligands (Fe(1)⋯O(5) and Fe(1)⋯O(7) distances of 2.582(2) and 2.583(2) Å, respectively) may play important roles in stabilizing DNIC 3. Transformation of nitrate-containing DNIC 3 into N-bound nitro {Fe(NO)} 6 [(NO)(κ 1 -NO 2 )Fe(S 2 CNEt 2 ) 2 ] (7) triggered by bis(diethylthiocarbamoyl) disulfide ((S 2 CNEt 2 ) 2 ) implicates that nitrate-to-nitrite conversion may occur via the intramolecular association of the coordinated nitrate and the adjacent polarized NO-coordinate ligand (nitrosonium) of the proposed {Fe(NO) 2 } 7 intermediate [(NO) 2 (κ 1 -ONO 2 )Fe(S 2 CNEt 2 ) 2 ] (A) yielding {Fe(NO)} 7 [(NO)Fe(S 2 CNEt 2 ) 2 ] (6) along with the release of N 2 O 4 (·NO 2 ) and the subsequent binding of ·NO 2 to complex 6. The N-bound nitro {Fe(NO)} 6 complex 7 undergoes Me 2 S-promoted O-atom transfer facilitated by imidazole to give {Fe(NO)} 7 complex 6 accompanied by release of nitric oxide. This result demonstrates that nitrate-containing DNIC 3 acts as an active center to modulate nitrate-to-nitrite-to-nitric oxide conversion. © 2012 American Chemical Society.