Mononitrosyl iron

Closely related are the 1-benzylamino-l-deoxylactitol dithiocarbamate salts developed by Eybl and co-workers316 317 for the same purpose. However, the most important application of 175 is, probably, its use as a nontoxic, water-soluble nitric oxide probe in vivo. In view of the central importance that this gaseous free-radical species plays in regulating a broad range of important biological functions, its detection and quantification near its site of production and action is of prime importance. For this purpose, the ferrous salt of MGD, which forms a stable water-soluble mononitrosyl iron-dithiocarbamate complex (176) with a characteristic electron spin resonance (ESR) spectrum at room temperature, is currently used.318-323... 

Similar to the reaction course of the allylic substitution, which involves formation of tr-allyl moieties followed by subsequent nucleophilic addition across the Jt-bond, the mononitrosyl iron(—II) complex was expected to be active in transesterifications involving activation of carbonyl group and nucleophilic addition to the electrophilic carbon atom [100]. This assumption could be verified by experimental tests. Under neutral conditions without addition of a ligand co-catalyst, the iron complex 31 exhibited high activity in the transesterification of vinyl acetate. Good to excellent yields were obtained affording a new ester bond, as depicted in Scheme 39. 

Remarkably, mononitrosyl iron(—II) complexes displayed great potential in the activation of diazo compormds and carbene-transfer reactions [102]. Generally, the activation of diazo compound can be realized by electrophilic transition metal complexes. However, according to the concept of Umpoirmg [103], the electron-rich, nucleophilic iron(—II) compound 31 is expected to react with diazo compounds of electron-poor carbenes, such as ethyl diazoacetate (Scheme 42). At first the iron center would add the C=N bond of the diazo compound followed by release of N2 and formation of the electrophilic iron carbene moiety. The nitrosyl group in such transformations is assumed to support as an ancillary ligand the N2 release by pulling electron density to the iron center. 

Significantly, the limits in the activation of allylic C-C bond could be pursued further to include also electron-poor moieties by applying catalyses with nucleophilic iron complexes [104]. The combination of mononitrosyl iron(—II) complex... 

To a culture of NO-producing macrophages from murine bone marrow (5 x 10 cells in 2 ml of cultural medium) superoxide dismutase (10" M), Na-DETC (Img/ml) and FeS04 7H2O (10 M) are added successively (Vanin et al. 1991,1993). In 2 h, the cells harvested with the medium are centrifuged for 10 min at l,500xg, reconstituted in 0.3 ml of supernatant, and frozen in liquid nitrogen for the EPR analysis. The formed hydrophobic mononitrosyl iron complexes with DETC are located in membranous compartments of all cells. 

Flavodi-iron proteins containing a distinctive nonheme diiron/ flavin mononucleotide active site, catalyze reductive scavenging of dioxygen and NO in air sensitive microorganisms. Anaerobic addition of NO up to one NO per diferrous rmit results in formation of a diiron mononitrosyl complex, whereas further addition of NO results in two reaction pathways, one of which produces N2O and the diferric site and the other which produces a stable diiron-dinitrosyl complex. The production of N2O upon addition of NO to the mononitrosyl deflavo-protein was interpreted in terms of the li5rponitrite mechanism (71). 

These bands have been assigned according to Yuen et al. (22). The bands at 1815 and 1755 cm are assigned to mononitrosyl species, while those at 1897 and 1791 cm are assigned to the symmetric and asymmetric stretching modes, respectively, of an iron dinitrosyl species. The dinitrosyl species is converted to the mononitrosyl species at 1755 cm by evacuation. This will be discussed in more detail below. 

Mononitrosyl species attributable to NO adsorbed on iron cations were observed for all of the supported iron oxide samples studied (see Table III). Typically one mononitrosyl species was observed at 1850-1800 cm , and a second mononitrosyl was observed... 

Fe " " accompanied by the formation of N2O, while this reaction may be negligible over iron on the other three supports. The intensity of the band at 1745 cm decreased while that at 1800 cm" increased during prolonged exposure of Fe/MgO to NO. The site at 1745 cm could accordingly be assigned to a mononitrosyl species adsorbed on Fe " and the band at 1800 cm to a mononitrosyl species adsorbed on... 

Lu TT, Chiou SJ et al (2006) Mononitrosyl tris(thiolate) iron complex [Fe(NO) (SPh)3] and dinitrosyl irrai ctnnplex [(EtS)2Fe(NO)2] formation pathway of dinitrosyl iron complexes (DNICs) frmn nibosylatirai of biomimetic rubredoxin [Fe(SR)4] (R = Ph, Et). Inorg Chem 45 8799-8806... 

For example, in mononitrosyl complexes, most M-N-O interactions are linear for hexacoordinate complexes containing the configuration M(NO) . Thus, Fe(NO) possesses a linear coordination [53, 58] and such a compound would form with an Fe(III) porphyrinate (where iron is 3d ) which binds to NO. By contrast, the primary NO adduct of Fe(II) porphyrinates (3d ), such as is found in the reduced heme which binds O2 in blood or muscle (deoxyhemoglobin or deoxymyoglobin, respectively) possesses the (Fe(NO) configuration and such species are bent see examples with structural and spectroscopic data (Table 2.2). 

---