Sulfides structural chemistry

Many of the most important naturally occurring minerals and ores of the metallic elements are sulfides (p. 648), and the recovery of metals from these ores is of major importance. Other metal sulfides, though they do not occur in nature, can be synthesized by a variety of preparative methods, and many have important physical or chemical properties which have led to their industrial production. Again, the solubility relations of metal sulfides in aqueous solution form the basis of the most widely used scheme of elementary qualitative analysis. These various more general considerations will be briefly discussed before the systematic structural chemistry of metal sulfides is summarized. 

The structural chemistry of the actinides is often similar to that of lighter transition metals, such as Zr and Hf, and to that of the lanthanides however, the diffuse nature of the 5/ orbitals leads to some differences and specifically to interesting magnetic and electrical properties. The actinide sulfides are generally isostructural with the selenides, but not with the analogous tellurides. The binary chalcogenides of uranium and thorium have been discussed in detail [66], but the structural... 

Many other structures of sulfide minerals have been determined. Most of them conform reasonably well to the structural principles described in this book, but some have surprising features that have not yet been incorporated in the system of structural chemistry,84 and in general the reasons for the choice of one structure rather than another are not yet evident. The general structure theory of the sulfide minerals still awaits formulation. 

Our knowledge concerning soluble metal complexes with sulfide ions as ligands has increased considerably during the last two decades and this kind of Compound is still of topical interest. Some of the reasons for this are the development of a very flexible and fascinating structural chemistry of multinuclear metal-sulfur complexes, the fact that the active sites of some electron transfer proteins contain metal ions and labile sulfur,41,42 and also the relation of metal-sulfur cluster compounds to some heterogeneous catalysts. In addition, apart from the numerous binary and ternary sulfides which occur in nature, we have at our disposal a rich solid state chemistry of metal sulfides, which has been reviewed elsewhere and will be excluded here.43"17... 

Metal sulfides belong to the most important classes of compounds because they are of general significance for geochemistry (they are the most important ores for many metals), analytical and structural chemistry, and biochemistry (metal sulfide systems act as electron transfer systems) as well as catalysis (a high percentage of industrially used heterogeneous catalysts are sulfides) and materials science. 

It is evident that the sulfides with the lowest solubility in water show the highest tendency to form discrete sulfido and polysulfido complexes and clusters corresponding to their solubility in bases, a fact which is interesting for future studies in synthetic and structural chemistry. 

The platinum metal chalcogenides in general are easier to prepare than the corresponding oxides. Whereas special conditions of temperature and pressure are required to prepare many of the oxides, the platinum metals react most readily with S, Se, and Te. A number of additional differences concerning the chemistry of the chalcogenides and the oxides are summarized as follows The metal—sulfur (selenium, tellurium) bond has considerably more covalent character than the metal-oxygen bond and, therefore, there are important differences in the structure types of the compounds formed. Whereas there may be considerable similarity between oxides and fluorides, the structural chemistry of the sulfides tends to be more closely related to that of the chlorides. The latter compounds... 

Although there are differences, the structural chemistry of the simpler selenides and tellurides is generally similar to that of sulfides. 

Ammonia complexes.. EflFect of complex formation on solubility. Cyanide complexes. The cyanide process of treating gold and silver ores. Complex halides and other complexes. Sodium thiosulfate as photographic fixer. Hydroxide complexes. Amphoteric hydroxides. Sulfide complexes. Equilibrium expressions for complex formation. Structural chemistry—tetrahedral, octahedral, square complexes. Existence of isomers. 

Wells, A. F., Structural Inorganic Chemistry, 3rd ed., Clarendon Press, Oxford, 1962. The third edition of this well-known book is an exceedingly comprehensive source book for experimental methods of structural chemistry and detailed solid-state structures of oxides, sulfides, silicates, metals and alloys, etc., as well as of compounds of a number of the elements. It can be strongly recommended as general reading for the student. 

The free-radical chemistry of fluoroalkanesulfenyl chlorides with hydrocarbons was also investigated [S, 9], Depending upon the structures of the sulfenyl chloride and the hydrocarbon, these reactions yield as major products up to three of the following four types of organic compounds thiols, disulfides, sulfides, and chlorohydrocarbons (equation 6), Perfluoroisobutanesulfenyl chloride is unique m that the only major products detected are the thiol and chlorohydrocarbon [ ] (equation 6) (Table 3). 

D. J. Vaughan and J. R. Craig, Mineral Chemistry of Metal Sulfides, Cambridge University Press, Cambridge, 1978, 493 pp. A comprehensive account of the structure bonding and properties of mineral sulfides. 

A detailed discussion of individual halides is given under the chemistry of each particular element. This section deals with more general aspects of the halides as a class of compound and will consider, in turn, general preparative routes, structure and bonding. For reasons outlined on p. 805, fluorides tend to differ from the other halides either in their method of synthesis, their structure or their bond-type. For example, the fluoride ion is the smallest and least polarizable of all anions and fluorides frequently adopt 3D ionic structures typical of oxides. By contrast, chlorides, bromides and iodides are larger and more polarizable and frequently adopt mutually similar layer-lattices or chain structures (cf. sulfides). Numerous examples of this dichotomy can be found in other chapters and in several general references.Because of this it is convenient to discuss fluorides as a group first, and then the other halides. 

Although desulfurization is a process, which has been in use in the oil industry for many years, renewed research has recently been started, aimed at improving the efficiency of the process. Envii onmental pressure and legislation to further reduce Sulfur levels in the various fuels has forced process development to place an increased emphasis on hydrodesulfurization (HDS). For a clear comprehension of the process kinetics involved in HDS, a detailed analyses of all the organosulfur compounds clarifying the desulfurization chemistry is a prerequisite. The reactivities of the Sulfur-containing structures present in middle distillates decrease sharply in the sequence thiols sulfides thiophenes benzothiophenes dibenzothio-phenes (32). However, in addition, within the various families the reactivities of the Substituted species are different. 

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