Sulfite complexes

The kinetics of formation of [Co(tren)(C03)] from [Co(tren)(OH)2] have been investigated over the pH range 10.5-13. The tren system is very suitable for such a study, in a pH range where it is possible to assess the reactivity of CO3 as well as of HCOf and CO2, since it is stable both with respect to base hydrolysis and to redox reactions. Rate constants were measured over the temperature range 298-333 K at an ionic strength of 0.5 mol dm . It proved necessary to analyze the results in terms of three parallel reactions, since the high reactivity with carbon dioxide meant that reaction with this species had to be included despite its very low concentrations under these conditions. 

There has been much treatment of the kinetics and mechanism of decarboxylation of carbonatocobalt(III) complexes. Thus the results for decarboxylation of the [Co(tren)(C03)] cation mentioned above conflict to some extent with earlier results and interpretations in this area. Matters are more straightforward for decarboxylation of monodentate carbonate complexes, for instance, of trans-[Co(tn)2(C03)C ]. The reactivity pattern here, similar to that for other monodentate carbonate complexes, with rates on the stopped-flow time scale, corresponds to carbon-oxygen rather than to cobalt-oxygen bond rupture. Three papers deal with decarboxylate of complexes [Co(LLLL)(C03)], each 

In each case the acid-catalyzed path is dominant, the ki term of minor importance. The solvent isotope effects (D20)/ (H20) lie between 2.1 and 2.6. These values, and the activation parameters (Table 5.15), show that concerted attack by HsO is an unlikely mechanism, but indicate rather a two-stage mechanism in which rapid equilibrium protonation of the complex is followed by slow and rate-determining opening of the carbonate chelate ring (A1 mechanism with five-coordinate intermediate).In the case of the complex of ligand 39, effects of ligand unsaturation and substituent bulk were also assessed. 

Interpretation of kinetic patterns for decarboxylation of the d5-[Co(py)2(C03)2] anion is clouded by a slight uncertainty as to whether both carbonate ligands are indeed bidentate. Kinetic parameters, including the solvent isotope effect, for loss of the first carbonate ligand (Table 5.15) are consistent with decarboxylation of a bidentate group, but the activation parameters do fall within the narrow 

Substitution Reactions of Inert Metal Complexes—6 and Above 

---

In liquid S02 the basic species is S032 so [(CH3)4N]2S03 gives a basic solution in which aluminum sulfite dissolves by forming a sulfite complex, as shown in the equation... 

The reaction rate at pH = 9 could be followed only when the silver ion concentration was kept to a low value. This was accomplished by using as a source of silver ions the soluble silver sulfite complex ion which has a dissociation constant of about 3 X 10-9 at 25°. The undissociated complex itself is not involved in the reaction to any significant extent. The reaction rate varies as about the half power of the silver ion concentration under these conditions. The dependence upon the hydroquinone concentration, as indicated by the data in Table I, is somewhat greater than a direct proportionality (James, 7). 

Sodium stannite (which is not a developer) reacts very rapidly with silver nitrate or with the silver sulfite complex, and the rates have not... 

The cyanine dye, 3,3 -diethyl-9-methylthiacarbocyanine chloride, had a much greater effect than gelatin in decreasing the reaction rate of the silver chloride. The rate of reduction of silver chloride varied linearly with the amount of silver chloride surface not covered by the dye, and the rate attained at complete coverage was of the order of one-thousandth that for the undyed precipitate. The dye exerted scarcely any effect upon the reduction of silver ions from silver sulfite complex solution. 

Oxygen-bonded sulfito complexes of platinum(IV) can be prepared by the reaction of aqueous sulfite with [Pt(NH3)5(H20)]4+ to give the O-bonded sulfito complex [Pt(NH3)5(0S02)]2+. This compound rearranges to the S-bonded sulfite complex, or at elevated temperatures in addic solution a single-step two-electron reduction occurs to yield a platinum(II) complex Pt(S03)(NH3)3 (equation 480).1631 The O-bonded sulfite complexes show a series of IR bands in the range 460-960 cm-1.1632... 

The reaction of the chlorosulfite ester Xld with palladium(O) may take place by direct nucleophilic displacement of the chlorosulfite group at carbon by palladium or via an intermediate sulfite complex Xlld. The direct nucleophilic displacement would be expected to take place with inversion of configuration. The reaction of the chlorosulfite ester to afford... 

Sulfur dioxide can insert in various ways as shown in (21-XLVI). The usual product is the S-sulfinate (21-XLVIa), although the other isomers are known. The insertion of S02into M—OR bonds, e.g., of Ir(OR)(CO)L2, gives oxygen-coordinated sulfite complexes.211... 

Tegoni, M., and Cambillau, C., 1994. The 2.6 refined structure of the Escherichia coli recombinant Succ/turomycei cereviiiue flavocytochrome sulfite complex, Prot. Sci. 3 303n313. 

The mechanism of the reduction of Fe(III) is somewhat complicated,involving the intermediate formation of a red material that appears to be a sulfite complex of Fe(III). The reaction rate is slow in the presence of excess sulfuric acid. It is accelerated by the presence of thiocyanate, which apparently replaces part of the coordinated sulfite in the intermediate. The reduction then proceeds quantitatively even in 1 M sulfuric add when the cold solution is treated with sulfur dioxide and slowly heated to boiling. The excess reductant is removed with a stream of carbon dioxide. 

When trivalent gold is mixed with sulfite and thiosulfate, it is reduced to monovalent gold. Kato et al. studied the stoichiometry of the redox reaction and arrived at the conclusion that the predominant gold species in the system is [Au(S203)2], a monovalent gold thiosulfate complex. If the solution contains only sulfite but no thiosulfate, the gold complex takes the form of [Au(S03)2] , a monovalent gold sulfite complex ... 

The cathodic polarization curves were determined for the reduction of gold ions in solutions containing, respectively, sulfite alone, thiosulfate alone, and a mixture of sulfite and thiosulfate. These curves are shown in Fig. 39. Addition of thiosulfate to the solution of gold sulfite complex shifts the polarization curve to the potential range where the thiosulfate complex is reduced. This result shows that the reduction of gold in the sulfite-thiosulfate mixture takes place from the thiosulfate complex. This conclusion is consistent with the difference between the stability constants of the two complexes ... 

The Au(I) sulfite complex is well known to be the source of gold in an electroplating bath. Will the Au(I) sulfite complex in the absence of thiosulfate work as a source of gold for electroless plating ... 

The formation of these complexes profoundly affects the visible spectrum of TNP-amino acids. This complication is resolved in the spectrophotometric procedure of Plapp et al. (1971) by following TNP-amino acid formation at 367 nm, the isobestic point for e-trinitrophenyl-a-acetyllysine and its sulfite complex. The procedure described by Fields (1971, 1972) exploits the higher extinction coefficient of the sulfite complex at 420 mii. 

Better results can be obtained for the electroless deposition (ELD) in solutions. In this case the protective ligands can probably be dissolved in the liquid phase and thus diffuse away from the seeds. Of the several deposition baths considered, each consisting of a soluble gold salt and reducing reagent, only the one based on the sulfite complex of Au and hydroxylamine resulted in dense and relatively thick (up to 800 nm) gold layers. The reason for this behaviour remains unclear but there are hints that complex reactions are taking place in the autocatalytic deposition process. 

Attempts have been made to devise conditions of mild proteolysis to discover whether fragments of the whole molecule are active. Apo-pig M4-LDH is more susceptible to proteolysis than apo-H -LDH, although no active cleavage products were found (192). If the enzyme-NAD-sulfite complex is treated with trypsin, then 90% enzymic activity is retained... 

There is a preparative advantage in hydrolysing the osmic ester by aqueous-alcoholic sodium sulfite solution, for then the osmium is precipitated as sparingly soluble sulfite complex. 

KRUPA Dr. Stensland, I don t think you re really talking about sulfate. You re talking about sulfur equivalents. Some work done in the Lake Michigan area indicates that perhaps up to 30 in precipitation samples may be stable sulfite complexes of transition metals. 

Enemark et al. have studied the structure of an inhibited low-pH Mo(v) form of the Argl60Gln mutant of human SO with combined EPR measurements and DPT calculations.They used very large 250-atom cluster models, which were optimized with BP86/TZVP calculations, whereas EPR properties were calculated with B3LYP and the same basis set. The results indicated that the observed species is a five-coordinate sulfite complex. 

The peak potential for the cathodic reduction of the silver sulfite complex [Ag(S03)2] shifts towards more positive value as the... 

The oxygen-bound sulfate complex [Co(tren)(OH2)OS02] is formed by reaction of [Co(tren)(OH2)OH] with SO3 and undergoes internal electron transfer to give cobalt(II) and SO4 with a rate constant 1.0 X 10 s" at 25 C and pH less than 5.4. Activation parameters are MI 24 kcal moF and AS 8.2 cal moF. At higher pH a bis-sulfite complex which is not subject to internal redox is formed. Infrared evidence points to both S and O binding in this species. 

---