Mercury chloride, complexes

Mercury-chloride complexes in dilute solutions. This slightly more difficult example will be useful in showing how to handle poorly conditioned systems of equations. It is assumed that mercury chloride HgCl2 is dissolved in pure water with a molality m = 10 5 mol kg-1. Given the equilibrium constants for chloride complex formation... 

In the indirect thiocyanate method (not very sensitive, e 5 10 ) the determination of chloride [20-28] has been based on the displacement of SCN ion from the mercury(II) thiocyanate complex by chloride ions, to give a stable mercury chloride complex. After addition of Fe(III) in excess, the red Fe(SCN) complex is formed, and the absorbance is measured at 480 nm. In the FIA method the UV detection has been applied in the absence of Fe(III) ions [29]. 

It is commonly accepted that one of the first publications on metallomesogens was by Vorlander, " who reported a number of mercury-based mesomorphic materials,such as the symmetrical Schiff-base complexes of diarylmercury(ll) (160a R = H, NO2, Me, OMe, OEt) and the related, asymmetric, monoaryl mercury chloride complexes 160b. Both series of organometallic compounds exhibited high-temperature smectic phases. 

The circulating brine contains mercury concentrations of 2-20mg/L. Mercury emissions from the brine system can occur through losses of brine into the wastewater, by brine vaporization in the resaturators, or by disposal of the residues from the brine purification filter. These emissions are minimal at a chlorine concentration < 30 mg/L, giving a redox potential > 500 mV vs. NHE. Under these conditions mercury remains dissolved in the brine as a mercury chloride complex even if the brine is alkaline. 

In a very recent contribution, Lai and Tiekink (235) isolated the mercury-chloride complex [HgCl(ri -S2CNEt2)(l,10-phen )] (500) from the reaction of [Hg(S2CNEt2)2] and 1,10-phen, which is presumed to result from the loss of a dithiocarbamate and chloride abstraction from the chloroform solvent. An X-ray crystal structure shows that the dithiocarbamate binds in a monodentate fashion, allowing the mercury center to adopt a highly distorted tetrahedral coordination geometry. 

The aqueous solution has a low conductivity, indicating that mercury(II) chloride dissolves essentially as molecules Cl—Hg—Cl and these linear molecules are found in the solid and vapour. A solution of mercury(II) chloride is readily reduced, for example by tin(ll) chloride, to give first white insoluble mercury(I) chloride and then a black metallic deposit of mercury, The complexes formed from mercury(II) chloride are considered below. 

Copper(II) ions in the presence of chloride ions are reduced at the dropping mercury electrode (dme) in two steps, Cu(II) -> Cu(I) and Cu(I) -> Cu(0) producing a double wave at -1-0.04 and 0.22 V versus sce half-wave potentials. In the presence of peroxydisulphate , when the chloride concentration is large enough, two waves are also observed the first limiting current corresponds to the reduction of the Cu(II) to Cu(I) plus reduction of a fraction of peroxydisulphate and the total diffusion current at a more negative potential is equal to the sum of the diffusion currents of reduction of Cu(II) to Cu(0) and of the peroxydisulphate. There is evidence that peroxydisulphate is not reduced at the potential of the first wave because of the adsorption of the copper(I) chloride complex at... 

Both models apply the same chemical scheme of mercury transformations. It is assumed that mercury occurs in the atmosphere in two gaseous forms—gaseous elemental HgO, gaseous oxidized Hg(II) particulate oxidized Hgpart, and four aqueous forms—elemental dissolved HgO dis, mercury ion Hg2+, sulphite complex Hg(S03)2, and aggregate chloride complexes HgnClm. Physical and chemical transformations include dissolution of HgO in cloud droplets, gas-phase and aqueous-phase oxidation by ozone and chlorine, aqueous-phase formation of chloride complexes, reactions of Hg2+ reduction through the decomposition of sulphite complex, and adsorption by soot particles in droplet water. 

Mercury chloride thioether complexes have been oxidized to the corresponding sulfoxide complexes by treatment with hydrogen peroxide (76) [Eq. (30)]... 

The X-ray crystal structures of the related, though less complex, anticrown mercury-containing macrocycles 45 and 46 have also recently been reported. Complex 45 may form either 1 1 complexes with Br or I" or a 3 2 complex with Cr. In the case of the bromo derivative, crystallographic results reveal an infinite chain of alternating Br and 45 with each halide bridging between six Hg atoms, Hg- Br 3.07-3.39 A. It is postulated that the related 3 2 chloride complex exhibits a similar, though finite layered structure. The related pentameric species 46 forms... 

Isocyanide-mercury(II) chloride complexes when reacted with acetylacetone in the presence of triethylamine yield furan derivatives (290) (75CPB2842). The aminofuranones (291)... 

Mercury represents a serious environmental risk, and the study of removal of mercury from wastewater has received considerable attention in recent years. Mercury concentration was usually reduced by deposition on a cathode with high surface area. Removal of mercury is studied using extended surface electrolysis which reduces the level of mercury to below acceptable concentrations of 0.01 ppm in wastes by employing a Swiss roll cell with a cadmium-coated, stainless-steel cathode. An industrial cell with a fluidized bed electrode has also been studied. Graphite, as an efficient porous electrode, has been used to remove traces of mercuric ions form aqueous electrolyte solutions. In order to apply the electrochemical method for some effluents, it is necessary to use sodium hypochlorite to convert elemental mercury and less soluble mercury compounds to water-soluble mercuric-chloride complex ions. 

Kamburova [134] has reported a spectrophotometric method based on the formation of the mercury-triphenyltetrazolium chloride complex for the determination of mercury in soils. 

Following the preparation of 4.79, a number of other cyclic mercury crown compounds have been synthesised, which do exhibit halide complexation behaviour. Compound 4.80, forms a 1 1 polymer with bromide in the solid state in which the Hr anions perch above the Hg3 plane. The Hg—Br distances of 3.07-3.39A are considerably longer than normal Hg—Br covalent bonds (about 2.54A).61 The compound also binds SCN- with similarly long bonds as shown in Figure 4.34.60 The analogous chloride complex has a 3 2 stoichiometry suggesting a triple-decker sandwich of type [4.80 Cl 4.80 Cl 4.80]2. ... 

Chloride ions react with mercury (II) thiocyanate to form a sparingly dissociating mercuric chloride complex and liberate a stoichiometrically equivalent amount of thiocyanate ions (2CT + Hg(SCN)2 - Hgd2 + 2SCN) die thiocyanate reacts with iron (III) ions, yielding die intensely red ferric thiocyanate complex (SCN + Fe3+ -> Fe(SCN)2+), which is determined at 460 nm. 

The extreme insolubility and high melting points of the mercuric chloride complexes suggest that they are polymeric as illustrated for N P (NHMe)g.2HgCl2 (VII)(Figure 3). A number of polymerio mercury complexes are known(4,.5) ... 

Thiourea, mercury(II) chloride complexes with, 6 26 Thorium, powder by reduction of oxide with calcium, 6 50 removal of, in extraction of... 

Anodic limits on mercury. Mercury is readily oxidized, particularly in the presence of anions that precipitate or complex mercury or mercury ) ions, such as the halides, cyanide, thiosulfate, hydroxide, or thiocyanate. For this reason, mercury is seldom used to study anodic processes except for those subtances that are easily oxidized, for example, Cr(II), Cu(I), and Fe(II). Under carefully controlled conditions, mercury can be coated with a thin layer of mercury chloride such that it does not interfere with electron transfer in the oxidation of a number of organic compounds, particularly amines.66... 

A systematic study of substitution reactions of oxazole itself has not been reported. Bromination of 2-methyl-4-phenyloxazole or 4-methyl-2-phenyloxazole with either bromine or NBS gave in each case the 5-bromo derivative, while 2-methyl-5-phenyloxazole was brominated at C(4). Mercuration of oxazoles with mercury(II) acetate in acetic acid likewise occurs at C(4) or C(5), depending on which position is unsubstituted 4,5-di-phenyloxazole yields the 2-acetoxymercurio derivative. These mercury compounds react with bromine or iodine to afford the corresponding halogenooxazoles in an electrophilic replacement reaction (81JHC885). Vilsmeier-Haack formylation of 5-methyl-2-phenyloxazole with the DMF-phosphoryl chloride complex yields the 4-aldehyde. 

Sodium hydrosulfide regenerates l,2-dithiole-3-thiones from their mercury(II) chloride complexes. This may be regarded as a nucleophilic attack <66AHC(7)39). 

Chlorophenyl Tellurium Trichloride1 A 100 ml one-necked flask is fitted with a reflux condenser carrying a calcium chloride drying tube and charged with 2.7 g (10 mmol) of tellurium tetrachloride, 3.5 g (10 mmol) of 4-chlorophenyl mercury chloride, and 30 ml of dry dioxane. The mixture is heated under reflux for 4 h, cooled to 20 , the mercury dichloride/dioxane complex is filtered off, and the filtrate is distilled under vacuum. The residue is recryslallized from glacial acetic acid yield 3.3 g (96%) m.p. 225°... 

Synthesis of unsubstituted mercuracarborands, as illustrated in Scheme 1, is a two-step process involving deprotonation of the acidic CH vertices of 1,2-carborane 7 followed by treatment with the appropriate mercury salt <1994JA7142, 1997ACR267>. Thus, -butyllithium efficiently deprotonates 1,2-carborane 7 giving doso-X.Z-VXz-1,2-C2BioHio 8, the pivotal intermediate. If treated with mercury acetate, neutral trimer 5 is formed. Using mercury chloride or bromide, however, leads to the formation of tetramer 9 and 10, respectively, as 1 1 anion-host complexes. 

---