Mercury complexes sulfides

Dithiocoumarins (50) are generally prepared by treatment of thiocoumarins with phosphorus pentasulfide, isolation being best effected by formation of a mercury complex by addition of mercurous chloride, followed by decomposition of this complex with sodium sulfide. An alternative ring-closure approach involves heating o-allylphenols (49) with sulfur in... 

Four different thiourea complexes of mercury(II) are easily prepared from aqueous solutions of mercury(II) chloride and thiourea. The proportions of reagents are not as critical as the temperature, elevation of which results in precipitation of black mercury (II) sulfide. Electrical conductivities and freezing points provide evidence for the constitution of the complexes. 

Mercury(II) sulfide, red, 1 19 Metal complex compounds with diolefins, 6 216... 

Mercury(II) is a very soft Lewis acid, which forms stable complexes preferentially with soft Lewis bases such as sulfur ligands. You should remember here that the major natural form of mercury is sulfides. Increasing the pH of the aqueous solution due to... 

Mercury(ll) is a very soft Lewis acid, which forms stable complexes preferentially with soft Lewis bases such as sulfur ligands. You should remember here that the major natural form of mercury is sulfides. Increasing the pH of the aqueous solution due to pollution or river water discharge to marine water leads to precipitation of HgO. We know that HgO has finite solubility in water, and the solution may be described in terms of mercury(II) hydroxide as the following reactions (2)-(4)... 

GC analysis. However, Kanno et al. (1985) determined MeHg in environmental samples as dithizone complexes by GC-ECD. The samples were treated with an ethanol solution of potassium hydroxide and, after acidification, extracted with benzene-dithizone. The mercury complex was extracted into aqueous ethanoi containing sodium suifide. After acidification, the excess of sulfide was removed by air bubbling, MeHg was again extracted into benzene-dithizone, and analyzed by GC. The detection limit was 0.5 [Pg.443]

Fig. II.8.1 Anodic differential pulse voltammograms obtained after a preliminary reduction of complex sulfides at —1.0 V vs. Ag/AgCl for 60 s. The electrolyte solution was 1 M HCl with 10 M HgCl2. The mercury salt was used to simultaneously plate metallic mercury where the tin and thallium metals could dissolve (reprinted with permission from [14])...

Some metal thiosulfates are inherently unstable because of the reducing properties of the thiosulfate ion. Ions such as Fe " and Cu " tend to be reduced to lower oxidation states, whereas mercury or silver, which form sulfides of low solubiUty, tend to decompose to the sulfides. The stabiUty of other metal thiosulfates improves in the presence of excess thiosulfate by virtue of complex thiosulfate formation. 

Nitrogen triiodide a-Nitroguanidine Nitromethane Acids, bromine, chlorine, hydrogen sulfide, ozone Complex salts of mercury and silver Acids, alkylmetal halides, hydroxides, hydrocarbons, organic amines, formaldehyde, nitric acid, perchlorates... 

Zn(R-dtp)2 complexes have been characterized and their thermal stabilities investigated 173,184,190,297-299,301-305) Zn(R-dtp)2 compounds are thermally degraded to volatile olefins and non-volatile residues and this serves as the basis for gas chromatographic determination of the compounds 304,30s) Several papers describing pyrolyses of Zn(R-dtp>2 complexes have discussed mechanisms for formation of olefins, sulfides, and other products 173,184,190,298,299, 304) Dakternieks and Graddon i8s,283)35 mentioned earlier, have reported thermodynamic measurements for depolymerization and adduct formation reactions of zinc, cadmium and mercury R-dtp compounds. 

Li and coworkers synthesized the novel IL l-butyl-3-trimethylsilylimid-azolium hexafluorophosphate and demonstrated its utility for liquid/ liquid extraction of inorganic mercury. Using o-carboxyphenyl diazoamino p-azobenzene as a chelator to form a stable neutral complex with the metal ion, the authors demonstrated selective extraction into the hydrophobic IL phase [19]. When sodium sulfide was added to the IL phase, the mercury ion was back-extracted into the aqueous layer, providing an avenue for recycling the IL. The authors report extraction and back-extraction efficiencies of 99.9 and 100.1%, respectively, for a 5.0 pg/L aqueous mercury standard. The mercury detection limit was 0.01 ng/mL in water and the method was successfully applied to detecting trace mercury in natural water samples. 

Literally hundreds of complex equilibria like this can be combined to model what happens to metals in aqueous systems. Numerous speciation models exist for this application that include all of the necessary equilibrium constants. Several of these models include surface complexation reactions that take place at the particle-water interface. Unlike the partitioning of hydrophobic organic contaminants into organic carbon, metals actually form ionic and covalent bonds with surface ligands such as sulfhydryl groups on metal sulfides and oxide groups on the hydrous oxides of manganese and iron. Metals also can be biotransformed to more toxic species (e.g., conversion of elemental mercury to methyl-mercury by anaerobic bacteria), less toxic species (oxidation of tributyl tin to elemental tin), or temporarily immobilized (e.g., via microbial reduction of sulfate to sulfide, which then precipitates as an insoluble metal sulfide mineral). 

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