Iron complexes nitrosyls

The nitrosyl iron complex Fe( J-mph) NO shows a spin-state transition between the S = f and S = ground states. The structure of the complex is characterized by ... 

Volodin, A.M., Dubkov, K.A. and Lund, A. (2001) Direct ESR detection of S = 3/2 states for nitrosyl iron complexes in FeZSM-5 zeolites, Chem. Phys. Lett., 333, 41. 

There is interest in the possible use of other metal nitrosyl complexes as vasodilators, but from the series KJM(CN)6NO] where M = V, Cr, Mn, and Co (n = 3) or M = Mo (n = 4) neither the Cr nor the Mn complexes exhibit any hypotensive action (504). Iron-sulfur-nitrosyl clusters such as [Fe4S4(NO)4] are active, and their effects can be potentiated by visible light (505). 

Iron-sulfur-nitrosyl complexes (continued) from tetranuclear precursors, 32 343 tellurium analogs, 32 350 tetrairon complexes, N NMR spectroscopy, 32 365 x-ray crystallography [Fe(NO)(S2CNR2)2 and related clusters, 32 359-361... 

Nitric oxide and iron nitrosyl complexes have been observed in the reduction of nitrite by bacterial nitrite reductases, which contain iron chlorin or iron isobac-terichlorin [151]. A specific nitric oxide reductase also exists to convert NO to nitrous oxide [9]. Iron complexes of chlorins, isobacteriochlorins, and porphyrins, as well as ruthenium and osmium polypyridines, and cobalt and nickel... 

Drapier, j. C., Pellat, C., and Henry, Y. (1991). Generation of EPR-detectable nitrosyl-iron complexes in tumor target cells cocultured with activated macrophages. ]. Biol. Chem. 266, 10162-10167. 

Butler, A. R., Glidewell, C., Hyde, A. R., and Walton, J. C. (1985). Formation of paramagnetic mononuclear iron nitrosyl complexes from diamagnetic di- and tetranuclear iron-sulphur nitrosyls Characterization by EPR spectroscopy and study of thiolate and nitrosyl ligand exchange reactions. Polyhedron 4, 797-809. 

Vanin, A. F., and Varich, V. Y. (1980). Formation of nitrosyl complexes of non-haeme iron (complexes 2.03) in animal tissues in vivo. Biophysics (USSR) 24. 686-690. 

Sodium nitroprusside was first prepared and investigated in the middle of the nineteenth century, and a comprehensive summary of the earlier chemical investigations has been published (17). Up to 1910-1930, the addition reactions of bases to NP were explored, involving the characterization of colored intermediates (e.g., with SH-, SR-, and SO3 ), useful for analytical purposes. The hypotensive action of NP was first demonstrated in 1929, and a considerable research effort has attempted to establish the mode of action of NP and its metabolic fate. Questions still arise on the mechanism of NO release from NP in the biological fluids, and we refer to them below. New accounts dealing with modern structural and reactivity issues associated with the coordination of nitrosyl in NP and other complexes have appeared (18-20). From the bioinorganic and environmental viewpoint, nitrosyl iron complexes have been studied with... 

The recent upsurge of interest in iron-sulfur-nitrosyl complexes has been stimulated in part by the reported isolation of [Fe2(SMe)2(NO)4] from natural sources (12), by the obvious resemblances between these complexes and the naturally occurring [2Fe-2S] and [4Fe-4S] clusters of iron sulfur proteins (23, 14), and by the connections between tetrairon-sulfur-nitrosyls and cubane-type clusters (15). Most of the work in this area has been published in the past 5 years or so, and no review has previously been made. However, a number of excellent reviews of the wider aspects of metal-nitrosyl chemistry have appeared (16 19). 

The number of iron-selenium-nitrosyl complexes is substantially smaller than the iron-sulfur-nitrosyl species, as considerably less work in this area has been reported. However there are a number of differences between the sulfur systems and their analogs containing selenium or tellurium. For selenium it is convenient to divide the complexes into three classes, dependent upon the stoichiometry of the metal-chalcogen framework. 

The principal objective of the earliest X-ray studies to be carried out on iron-sulfur-nitrosyl complexes, those on [Fe2(SEt)2(NO)4] (10) and Cs[Fe4S3(NO)7] (11), was the establishment of their gross chemical constitution. More recent X-ray studies have been concerned not only with gross structure, but additionally with detailed comparisons within series of similar species as a possible probe of electronic structure. 

The diamagnetic behavior of the diiron and tetrairon complexes, despite the presence of formally d1 and/or d9 iron centers, indicates very strong coupling between the individual paramagnetic centers all theoretical treatments of polynuclear iron-sulfur-nitrosyl complexes to date have been based on the assumption of diamagnetism in even-electron species and have employed molecular orbital methods at various levels of approximation. 

The reactions of the anion [Fe2S2(NO)4]2 with electrophiles have already been described (Section II,B,2). Apart from these reactions, most of the chemistry so far reported for iron-sulfur-nitrosyl systems involves the dinuclear complexes [Fe2(SR)2(NO)4], the tetranuclear [Fe4S3(NO)7] and [Fe4S4(N0)4], and the paramagnetic mononuclear species [Fe(NO)2(SR)2] and [Fe(NO)(SR)3] , which prove to be important reactive intermediates in a wide range of reactions. 

Although many of the details remain to be clarified, transfer of nitrosyl groups onto preformed iron-sulfur frameworks of the natural type is well established (107,108). The transfer of nitrosyl groups from iron-sulfur-nitrosyl complexes to atoms other than iron is more problematical, as reported work on the ability of these complexes to nitrosate secondary amines RR NH, with formation of secondary nitrosamines RR NNO, has provided conflicting conclusions. 

The central role of the complexes [Fe(NO)2(SR)2]- in the reaction chemistry of iron-sulfur-nitrosyl complexes and their very ready formation both in in vitro and in vivo (108,123-125,128,129) suggest that the antimicrobial activity of nitrite depends not only upon the disruption of respiration [by destruction of the natural iron-sulfur clusters of redox proteins (70S)] but also specifically upon the formation... 

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