Electronic mercury compounds

Fig. 7.92 Mercury compounds arranged according to increasing isomer shift values. Using the calculated electron densities, the isomer shifts expected for free Hg - and Hg -ions are shown. The experimental error is given by the bars at the right side (from [485])...

Successful thermal decarboxylation of metal arenoates other than poly-halogenoarenoates are restricted to mercury compounds and fall into three categories, namely (i) those where electron-withdrawing substituents other than halogens are present in the organic groups, (ii) those where substituents and/or conditions are used which favor a different mechanism, e.g., classic electrophilic aromatic substitution, or (iii) those where the conditions are sufficiently forcing for both mercuration and decarboxylation to occur. 

The high sensitivity and selectivity of some gas chromatographic detectors are used to advantage in the measurement of organic mercury compounds. In the simplest approach, methyl mercury is extracted from seawater and converted to the iodide for electron capture gas chromatography [74],... 

Ealy [ 75 ] also used conversion to alkyl mercury iodides for the gas chromatographic determination of organomercury compounds in benzene extracts of water. The iodides were then determined by gas chromatograph of the benzene extract on a glass column packed with 5% of cyclohexane-succinate on Anakron ABS (70-80 mesh) and operated at 200 °C with nitrogen (56 ml min-1) as carrier gas and electron capture detection. Good separation of chromatographic peaks was obtained for the mercury compounds as either chlorides, bromides, or iodides. The extraction recoveries were monitored by the use of alkylmer-cury compounds labelled with 203 Hg. 

Phosphoryl radicals [10, 18, 38-42] tend to add to double bonds. Owing to the exceptionally high constants of hyperfine coupling of the unpaired electron with the phosphorus nucleus, phosphoryl radicals can be utilized as paramagnetic reporters [10]. Phosphoryl radicals have been prepared by photolysis of diphosphoryl mercury compounds (Scheme 6.5). 

There are three important routes to the formation of the mercury-transition metal bond (a) displacement of halogen or pseudohalogen from mercury(II) salts with carbonyl metallate anions (b) reaction of a halo-phenylmercury compound with a transition metal hydride and (c) oxidative addition of a mercury halide to neutral zero valent metals.1 We report here the syntheses of three compounds containing three-centre, two-electron, mercury-ruthenium bonds utilizing trinuclear cluster anions and mercury(II) halides.2-4... 

The (/-block elements tend to lose their valence s-electrons when they form compounds. Most of them can also lose a variable number of d-electrons and show variable valence. The only elements of the block that do not use their (/-electrons in compound formation are the members of Group 12 (zinc, cadmium, and mercury). The ability to exist in different oxidation states is responsible for many of the special properties of these elements and plays a role in the action of many vital biomolecules (Box 16.1). 

The limiting polarographic current was not proportional to the substrate concentration and a slightly soluble mercury compound was formed . The nature of the product and the number of electrons involved in the process were not determined. Chemical oxidation of 9 by I2 in an overall six-electron process (corresponding to two-electron oxidation of each As atom) leads to formation of the partly ionic hexaiodide . 

A mercury cathode mostly functions only as an electron donor numerous examples of such simple reductions have been reported. In some cases, however, the electrode is attacked with the formation of organic mercury compounds, e.g., by radicals during the reduction of a halide. When using mercury, suitable precautions must be taken to avoid mercury poisoning and environmental pollution. 

The sensitivity of plants to mercury compounds are different. In general, the fungitoxic concentration does not harm the seeds and bulbs of the plants the therapeutic index of mercury compounds for seed treatment is therefore satisfactory. Potato seed is an exception because it is susceptible to many species. However, only aryl mercury compounds are suitable for foliage application, and these only in the case of certain plants or in certain stages of development. Thus, phenylmercury acetate or chloride are not phytotoxic to apple trees in the prebloom period. Arylmercury compounds are not phytotoxic to the rice plant at all. Phytotoxicity is mainly caused primarily by mercury vapours formed on the reduction of mercury compounds (Hitchcock and Zimmermann, 1957). According to Lee et at. (1973), mercury compounds inhibit the biochemical reactions of the electron transport of photosynthesis, depending on the pH value and on the concentration. 

Gas chromatography has been the most frequently used technique for the determination of organic mercury compounds. In conventional GC, the compounds are chromatographed as halogenides, and determined by use of the highly halogene-sensi-tive electron capture detector (ECD). Better mercury specificity is obtained with detectors based on the principles of AAS, AFS or OES, but, for positive identification of the compounds, mass selective detectors have to be used. 

Solutions of sodium metal in liquid ammonia are blue and have high electrical conductivities the main current carrier of such solutions is the solvated electron. Such solutions are used in both organic and inorganic chemistry as efficient reducing agents. Sodium also forms a number of alkyl and aryl derivatives by reaction with the appropriate mercury compound, e.g. ... 

Cinnabar Electron tubes containing mercury Mercuric salt Mercurous compound Mercury compound, liquid, n.o.s, 6.1 Mercury compound, solid, n.o.s., 6.1 Mercury contained in manufactured articles, 8 Mercury vapour tubes Phenylmercuric compound, n.o.s., 6.1 Quicksilver... 

Several systems for selective catalytic reactions based on Shilov s system have been developed with oxidants more practical than platinum(IV). Periana reported two different systems for the oxidation of methane in sulfuric acid containing SO,. One of the catalysts is a simple mercuric halide, and reactions catalyzed by this mercury compound generated methyl sulfate with turnover frequencies of 10" s" . The second system is more reactive and is based on a platinum complex containing a bipyrimidine ligand (Equation 18.7). In this case, methane is converted to methyl bisulfate with 81% selectivity, greater than 500 turnovers, and a turnover frequency of 10 s" . These reactions are selective for the functionalization of methane to this methanol derivative because the electron-withdrawing... 

Table i. .1-182 Effective masses of electrons (in units of the electron mass mo) for mercury compounds... 

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