Nitrate-to-Nitrite-to-Nitric Oxide Conversion Modulated by Nitrate-Containing {Fe(NO)2}9 Dinitrosyl Iron Complex (DNIC)

摘要

Nitrosylation of high-spin [Fe(κ2-O2NO)4]2− (1) yieldsn{Fe(NO)}7 mononitrosyl iron complex (MNIC) [(κ2-O2NO)(κ1-ONO2)3Fe-n(NO)]2− (2) displaying an S = 3/2 axial electron paramagnetic resonancen(EPR) spectrum (g⊥ = 3.988 and g∥ = 2.000). The thermally unstable nitratecontainingn{Fe(NO)2}9 dinitrosyl iron complex (DNIC) [(κ1-ONO2)2Fe-n(NO)2]− (3) was exclusively obtained from reaction of HNO3 andn[(OAc)2Fe(NO)2]− and was characterized by IR, UV−vis, EPR, superconductingnquantum interference device (SQUID), X-ray absorptionnspectroscopy (XAS), and single-crystal X-ray diffraction (XRD). In contrastnto {Fe(NO)2}9 DNIC [(ONO)2Fe(NO)2]− constructed by two monodentatenO-bound nitrito ligands, the weak interaction between Fe(1) and the distalnoxygens O(5)/O(7) of nitrato-coordinated ligands (Fe(1)···O(5) andnFe(1)···O(7) distances of 2.582(2) and 2.583(2) Å, respectively) may playnimportant roles in stabilizing DNIC 3. Transformation of nitrate-containing DNIC 3 into N-bound nitro {Fe(NO)}6 [(NO)(κ1-nNO2)Fe(S2CNEt2)2] (7) triggered by bis(diethylthiocarbamoyl) disulfide ((S2CNEt2)2) implicates that nitrate-to-nitritenconversion may occur via the intramolecular association of the coordinated nitrate and the adjacent polarized NO-coordinatenligand (nitrosonium) of the proposed {Fe(NO)2}7 intermediate [(NO)2(κ1-ONO2)Fe(S2CNEt2)2] (A) yielding {Fe(NO)}7n[(NO)Fe(S2CNEt2)2] (6) along with the release of N2O4 (·NO2) and the subsequent binding of ·NO2 to complex 6. The Nboundnnitro {Fe(NO)}6 complex 7 undergoes Me2S-promoted O-atom transfer facilitated by imidazole to give {Fe(NO)}7ncomplex 6 accompanied by release of nitric oxide. This result demonstrates that nitrate-containing DNIC 3 acts as an activencenter to modulate nitrate-to-nitrite-to-nitric oxide conversion.