Mercury complexes Subject

Other transition metals have received much less attention. Complexes of palladium and 2-amino-phenyl-containing formazans have been reported.397 Mercury complexes of tridentate formazans have been studied.398 Silver complexes of tridentate benzothiazolyl-containing formazans have also been studied.399 Recently, alkali and alkaline earth metals have been the subject of many studies. Formazans such as 228 and 229 as well as the macrocyclic 204 have received considerable attention as metal-specific analytical reagents.400-41 1... 

Chelate complexes could only be prepared in the case of platinum(II) as the metal ion, while the group V atom alone acted as a donor toward palladium(II) and mercury(II). The coordinated olefin in the chelate complexes was found to be readily displaced by monodentate ligands such as tertiary arsines, -toluidine and the thiocyanate ion. It was suggested by these workers that chelation would take place more readily if the olefinic phosphine or arsine were subject to greater steric restrictions than was the pentenyl ligand. 

Analytical Applications In addition to the above-mentioned analytical aspects of the processes at Hg electrodes, in this section, we briefly review the papers focused on the subject of the affinity of various compounds to the mercury electrode surface, which allowed one to elaborate stripping techniques for the analysis of inorganic ions. Complexes of some metal ions with surface-active ligands were adsorptively accumulated at the mercury surface. After accumulation, the ions were determined, usually applying cathodic stripping voltammetry (CSV). Representative examples of such an analytical approach are summarized as follows. 

When a liquid crystal is a metal-containing material, it is called a metallomesogen. It is commonly accepted that the first report on metallomesogens was by Vorlander in 1923, who reported a series of mercury mesomorphic complexes (Figure 7.4) [2]. The subject was not very popular until the end of the 1970s, then the number of reports increased regularly until the 1990s and then stabilized. 

Mercury forms a unique series of catenated polyatomic cations Hgj + that can be considered as complexes having monatomic Hg° as a ligand. These cations are the subject of Section 11.3. 

Electrolysis of complex salts. The essence of the technique is the following. The mixture of potassium tetraethylaluminate and complex salt of potassium phluoride with triethylaluminum is subjected to electrolysis the anode is lead, the cathode is mercury. Electrolysis dissolves the lead anode, forming tetraethyllead the cathode is covered with potassium amalgam ... 

The catalyst need not necessarily be a d square-planar complex, since the potential of the catalyzed rearrangement was first revealed by rfickel(O) complexes or mercury(II) trifluoroacetate, both d species. The pioneering work in this area has been the subject of two reviews. ... 

Soluble starch, available from chemical supply houses, is readily dispersed in water. The iodine-starch complex has limited water solubility, and it is therefore important not to add the starch indicator until near the end point when the iodine concentration is low. Because starch is subject to attack by microorganisms, the solution usually is prepared as needed. Among the products of hydrolysis is dextrose, which can cause large errors because of its reducing action. Various substances have been recommended as preservatives, including mercury(II) iodide and thymol. With formamide a clear solution containing 5% starch is obtained that is stable indefinitely. 

The catalytic activity of Hg in elimination and substitution reactions of transition-metal complexes continues to be the subject of study. Kinetic studies on the Hg" catalysed aquation of both cis-[Co(en)2(CN)Cl], cis-[(chloro)(aniline)CO(en)2], and [PdLX] (L = tetramethyldiethylenetriamine X = Cl, Br, or I) are consistent with intermediate adduct formation at the halide substituent. Mercury(ii) reacts reversibly with the [Co(NH3)5SCN] ion to yield [Co(NH3)5(SCN)Hg] which irreversibly undergoes either aquation to yield [Co(NH3)sH20] or isomerization to yield [Co(NH3)5(NCS)Hg] at approximately equal rates. The kinetics of the reaction... 

Mercury is a soft metal and as such it is expected to form secondary bonds, most readily with sulfur, selenium, and other heavy non-metals. The situation is, however, more complex and secondary interactions with other electronegative atoms have also been observed in the solid state. Interatomic distances longer than the expected van der Waals distances are, moreover, sometimes observed between molecules orientated such that weak interactions lead to particular arrangements in the crystal [69]. The are numerous examples of secondary bonds in organomercury chemistry although most are intramolecular there are several examples of inter-molecular secondary bonds leading to supramolecular self assembly. A review has been published on this subject [70] and many new examples have subsequently been reported. 

The interaction of selenium and methylmercury in the brain appears to be very complex. Despite the clear protective effect of selenite on methylmercury toxicity, selenium increases the mercury content of brain (Prohaska and Ganther, 1977 Chen et al, 1975a). Methylmercury tends to cause a shift in the concentration of selenium from the cytosol to the mitochondrial fraction in the brain. Gel filtration of the brain cytosol, however, revealed that mercury followed a pattern more closely related to protein than to selenium (Prohaska and Ganther, 1977). Therefore, the mechanism of the protective effect of selenium against methylmercury toxicity is still a subject for speculation. 

Here again we know today that KuCera was trying to cope with a complex of electrochemical problems of which he could not have been fully aware in his time. Hence he was unable to bring his method, based on sound principles, to its due perfection. In 1918 he suggested to his student, J.Heyrovsky, that he take up the surface tension measurements with the dropping mercury electrode as a subject for research. 

A range of mercury-transition metal bonded complexes have been subjected to X-ray structural analysis complexes with M-Hg-M links include CHg cis-RuMe(PMe )4 [Hg Pt(2,4,6-CgH2Cl3)(PPh-)2 2 ... 

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