Roussins black salt

The interactions of NO with the iron-sulfur cluster moieties of several enzymes generate iron-sulfur-nitrosyl cluster compounds [156]. However, synthetic nitrosyl clusters such as Roussins black salt (RBS), Roussins red salt (RRS), Roussins red ester (RRE) and [FeNOS]4 (Fig. 5.3) are well known [129, 157] and can be synthesized easily [158-164]. For example, the RBS can be prepared by mixing FeS04 with NaN03 and (NH4)2S in aqueous solution [158]. RRE salts are generally insoluble in water, but recently the water soluble sulfonated derivative, Na2[Fe2(SCH2CH2S03)2(N0)4], has been prepared [165]. 

Jaworska M, Stasicka Z. Structure and UV-vis spectroscopy of Roussin black salt [Fe4S3(NO)7]-. / Mol Struct 2006 785 68-75. 

Several iron sulfide nitrosyl compounds are known. These have stmctures that in some cases are formally related to the FeS clusters by replacement of thiolate by NO. The compounds include the anions [Fe2S2(NO)4] and [Fe4S2(NO)2] (Roussin s red and black salts, respectively) and the neutral compounds [Fe2S2(NO)4] and [Fe4S4(NO)4]. Roussin s black salt has found use as a NO releasing vasodilator. 

These, and related, iron nitrosyl compounds have excited considerable interest because of their biological activity.Nitroprusside induces muscle relaxation and is therefore used to control high blood pressure. Roussin s black salt has antibacterial activity under conditions relevant to... 

Roseocobalt — see Cobalt, aquapentaammine-Roseopentaammine —see Aquapentaammine Roussin s black, 4, 1191 Roussin s red, 4, 1191 Roussin s salts, 4,240, 1243 Rubber vulcanization zinc complexes in, 5, 998 Rubeanic acid — see Dithiooxamid Rubidium complexes... 

Flash photolysis of the dianion of Roussin s Red Salt, [Fe2S2(NO)4]2, in particular the initial photoinitiated loss of NO (382) and the reverse recombination reaction, en route to the eventual product, the anion of Roussin s Black Salt, [Fe4S3(NO)7] , has been documented (383). A 4-RC6H4S group (R = H, Me, OMe, Cl, or CF3) replaces one of the chloride ligands in [Fe4S4Cl4]2 via a five-coordinated intermediate, with the detailed sequence of steps acid-dependent (384). Loss of chloride is... 

Figure 8 shows the molecular structure of the monoanion [Fe4S3 (NO)y], 12 a compound known as the black isomer of Roussin s salt . 

Flash photolysis of Roussin s Red Salt, Na2[Fe2S2(NO)4], and of Roussin s Black Salt, NH4[Fe4S3(NO)7], has been described. " Photolysis of [Fe2S2(NO)4] has been reviewed, in... 

Salts containing the anions [Fe2S2(NO)4]2 and [Fe4S3(NO)7] are often called, from their colors, Roussin s red and black salts, respectively similarly the organic derivatives [Fe2(SR)2(NO)4] are often called esters of Roussin s red salt. These names are nonsystematic and, in the case of [Fe2(SR)2(NO)4], scarcely accurate nonetheless they are convenient and they carry the sanction of long usage, and will on occasion be used here. 

Rousstn s red salt, Ferrous dinitrosyltrisulphide. Roussin s black salt. 

Figure 3.4 Iron-sulfur nitrosyl compounds (a) Roussin s black salt and (b) Roussin s methyl red ester.

Janczyk A, Wolnicka-Glubisz A, Chmura A, et al. NO dependent phototoxicity of Roussin s black salt against cancer cells. Nitric Oxide 2004 10 42-50. 

Although it is not strictly an organometallic cluster, Roussin s Black salt, [Fe4(S)3(NO)7] , represents the first nitrosyl compound prepared via nitrite. The reaction of FeS04, NaN02, and (NH4)2S is perhaps the most convenient method of synthesis of this cluster (29). A better defined approach to the use of N02 was first introduced by Hieber with Fe(CO)s [Eq. (15)] (30). The direct extension of this reaction to Mo(CO)6... 

Experimental work in model systems supplemented with theoretical investigations proved that the main photoreaction mode of Roussin s black salt is a photoredox reaction leading to generation of NO and a Fe(II) compound. The n NO-d transitions were assumed to be responsible for the photochemical reactivity of these compounds, which result in photodissociation of the NO group (33,36,50-52). It has been found, however, that irradiation of [Fe4(p3-S)3(NO)7] in the presence of S , thiolate anions or other S-nucleophiles produces Fe(III) species and N2O, instead of NO (53). 

---