title: Synthesis, properties, and reactivity of a series of non-heme {FeNO}(7/8) complexes: implications for Fe-nitroxyl coordination.
abstract: The biochemical properties of nitroxyl (HNO/NO(-)) are distinct from nitric oxide (NO). Metal centers, particularly Fe, appear as suitable sites of HNO activity, both for generation and targeting. Furthermore, reduced Fe-NO(-)/Fe-HNO or {FeNO}(8) (Enemark-Feltham notation) species offer unique bonding profiles that are of fundamental importance. Given the unique chemical properties of {FeNO}(8) systems, we describe herein the synthesis and properties of {FeNO}(7) and {FeNO}(8) non-heme complexes containing pyrrole donors that display heme-like properties, namely [Fe(LN(4)(R))(NO)] (R = C(6)H(4) or Ph for 3; and R = 4,5-Cl(2)C(6)H(2) or PhCl for 4) and K[Fe(LN(4)(R))(NO)] (R = Ph for 5; R = PhCl for 6). X-ray crystallography establishes that the Fe-N-O angle is ~155° for 3, which is atypical for low-spin square-pyramidal {FeNO}(7) species. Both 3 and 4 display ν(NO) at ~1700 cm(-1) in the IR and reversible diffusion-controlled cyclic voltammograms (CVs) (E(1/2)=~-1.20 V vs. Fc/Fc(+) (ferrocene/ferrocenium redox couple) in MeCN) suggesting that the {FeNO}(8) compounds 5 and 6 are stable on the CV timescale. Reduction of 3 and 4 with stoichiometric KC(8) provided the {FeNO}(8) compounds 5 and 6 in near quantitative yield, which were characterized by the shift in ν(NO) to 1667 and ~1580 cm(-1), respectively. While the ν(NO) for 6 is consistent with FeNO reduction, the ν(NO) for 5 appears more indicative of ligand-based reduction. Additionally, 5 and 6 engage in HNO-like chemistry in their reactions with ferric porphyrins [Fe(III)(TPP)X] (TPP = tetraphenylporphyrin; X = Cl(-), OTf(-) (trifluoromethanesulfonate anion or CF(3)SO(3)(-))) to form [Fe(TPP)NO] in stoichiometric yield via reductive nitrosylation.
authors.affiliation: Department of Chemistry, The University of Georgia, 1001 Cedar Street, Athens, GA 30602, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Sanders
authors.forename: Ashis K
authors.initials: AK
authors.lastname: Patra
authors.forename: Todd C
authors.initials: TC
authors.lastname: Harrop
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009569:Nitric Oxide / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011758:Pyrroles / Q000138:chemical synthesis / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D056831:Coordination Complexes; D009589:Nitrogen Oxides; D011758:Pyrroles; D009569:Nitric Oxide; D007501:Iron; C039900:nitroxyl