Mercury single crystal preparation

In addition to these examples, several polynuclear mercury alkynyl derivatives have been prepared. Examples of such derivatives include compounds 50-56 which have been obtained by reaction of the MeHgGl with the primary alkyne in basic methanolic conditions.67,68 The phenyl analogs have also been isolated. Most of these compounds have been characterized by FTIR, NMR, and FABMS, and in the case of 51-53 by single crystal X-ray diffraction. 

The chemisorption of species occurs at specific sites on the electrode, for example on top of certain atoms, or in the bridge position between two atoms. Therefore, most adsorption studies are performed on well-defined surfaces, which means either on the surface of a liquid electrode or on a particular surface plane of a single crystal. Only fairly recently have electrochemists learned to prepare clean single crystal electrode surfaces, and much of the older work was done on mercury or on amalgams. 

The reaction between dimercury(I) salts and molecules with an electron-pair-donating atom normally destroys the metal-metal bond of the dimercury(I) ion Hg+—Hg+ by disproportionation, forming metallic mercury and a mercury(II) compound, but the use of nonpolar solvents, weak Lewis bases and dialytic crystallization methods has contributed to the successful preparation of single crystals of several dimercury(I) coordination compounds in the past 25 years.9,30,31 The myth that the dimercury(I) species Hg + forms few coordination compounds has been exploded. 

In Chapter 1, Antoinette Hamelin deals with the topic of characterization of the double layer at well-defined single-crystal faces of solid metals. She also gives valuable instructions for the preparation and characterization of single-crystal faces of known orientation and index which will be very useful to many workers in this field, especially those who are just entering it as novices or to those whose crystals are not always too accurately characterized Most of the work reported is concerned with crystal faces of gold and silver which this author has specialized in studying. It is her work in recent years that has taken experimental studies of doublelayer behavior well beyond the conventional area of research at liquid mercury. 

Most of the work in the previous sections of this chapter has dealt with mercury electrodes for the reasons discussed in Section 13.2.1. However, electrochemists are also interested in studying the interfacial structure of solids, because most electrochemical studies are carried out with solid electrodes (e.g., platinum or carbon). Such studies are difficult, because there are problems in reproducing a surface and in keeping it clean. Impurities in solution can diffuse to the electrode surface and adsorb, thereby significantly changing the interfacial properties. Moreover, the surfaces of solids, unlike those of mercury, are not atomically smooth, but have defects, such as dislocation lines, with a density of at least 10 to 10 cm. In comparison, a typical metal surface density has about 10 atoms cm. Especially important to the understanding of solid electrodes has been the use of so-called well-defined metal electrodes, that is, single crystal metals with very carefully prepared surfaces of known orientation (35). 

A silver- mercury centered cluster compound was prepared by Peringer etal. [96] (Scheme 12.41). The multi-component reaction led to quantitative formation of the complex 141, which was analyzed by X-ray single crystal diffraction. The Hg-Ag distances in this compound are 2.853(2) and 2.805(2) A, and the Hg-Hg distance is 2.6598(14) A. 

Single-stage chemical synthesis by annealing stoichiometric mixtures of individual oxides is often used for preparing ceramics. When highly volatile oxides are used (thallium- and mercury-based HTSCs), the process is carried out in hermetically sealed ampoules with an excess of the volatile component. The heating temperatures usually exceed those of the crystallization and can take up to lOh or more. 

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