title: Nitrate-to-nitrite-to-nitric oxide conversion modulated by nitrate-containing {Fe(NO)2}9 dinitrosyl iron complex (DNIC).
abstract: 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(∥) = 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.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan. fttsai@mx.nthu.edu.tw
authors.forename: Fu-Te
authors.initials: FT
authors.lastname: Tsai
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Lee
authors.forename: Ming-Hsi
authors.initials: MH
authors.lastname: Chiang
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008968:Molecular Conformation; D009566:Nitrates / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide