Sulfites metal complexes

Sulfide oxidases, 773 Sulfinylamines imido metal complexes synthesis from, 167 Sulfites... 

Bridged or Through-space Magnetically Coupled Complexes of High-spin Iron(III) Porphyrins with Other Types of Metal Complexes Possible Models for Cytochrome Oxidase, Assimilatory Sulfite Reductases, and Sulfite Oxidase... 

In addition to its ability to react as a mild oxidant, SO," can also react as a reductant. This has been established clearly in its reactions with substitution-inert transition metal complexes [67]. Indeed, this appears to be the mechanism for sulfate formation in the oxidation of sulfite by oxidized metal ion complexes, whereas dithionite formation is a product of S(IV) oxidation only for inner sphere reactants. 

The Marcus equation correlates these two reactions and earlier data for [Fe(CN)6] as well. The sulfite radical anion, SOJ, is proposed as a later intermediate, although this was not tested directly. Oxidations of SOs by other metal complexes believed to proceed via SOJ, follow second-order kinetics > at 25°C, fc = 5.6 x 10 ([IrClef ), 3.18 x lO ([IrBr< f ), and 2.1 X 10 ([Fe(bipy)3] ) M" s . ... 

The synthesis of metal sulfite hydrazine complexes involves two steps. Firstly, hydrazine hydrate (99-100%) is saturated with SO2 gas and the resulting product, hydrazinium sulfite monohydrate (N2H5)2S03-H20, is... 

The prepared mixed metal hydrazine hydrates are light in color and insoluble in water. From the chemical analysis it is evident that all mixed metal complexes, including magnesium, are present as sulfite [21]. However, when magnesium alone is used without FeS04, a bisulfate hydrazine is obtained under the same preparative conditions. 

The combustion of mixed metal sulfite hydrazine complexes in the presence of air (—300 °C) gives homogenous ferrites (Table 3.18). This is confirmed by the observed weight loss and powder XRD. 

Similar to hydrazinium metal sulfates, hydrazinium metal sulfite complexes can be synthesized the procedure is, though, slightly different. Hydrazinium transition metal sulfite dihydrate complexes of the formula (N2H5)2M(S03)2(H20)2 where M = Fe, Co, Ni, Cu, and Zn are prepared from metal hydrazine carboxylates (described in Chapter 4) as the starting material. In this method, the anhydrous metal hydrazine carboxylate, M(N2H3C00)2, is added to distilled water previously saturated with sulfur dioxide gas. The complex decomposes with the liberation of carbon... 

Stmcture (1) explains the formation of sulfur and sulfite in the presence of acid stmcture (2) is consistent with the formation of sulfide and sulfate in the presence of heavy metals. The bonding in thiosulfate complexes and the chemistry of thiosulfates are normally explained on the basis of (2) (see also... 

Thiosulfates. The ammonium, alkaU metal, and aLkaline-earth thiosulfates are soluble in water. Neutral or slightly alkaline solutions containing excess base or the corresponding sulfite are more stable than acid solutions. Thiosulfate solutions of other metal ions can be prepared, but their stabiUty depends on the presence of excess thiosulfate, the formation of complexes, and the prevention of insoluble sulfide precipitates. 

In the presence of a metal ion (M " ), a metal chalcogenide phase M2Sen will be precipitated upon exceeding the solubility product of [M and [Se ] (or [HSe ]). The concentration of free metal ions must be controlled by an excess of complexing agent, determining the applicable solubility of the metal and the overall competitive chemical reaction, in order to prevent the formation of sulfite, sulfate, and... 

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