Solid state chemistry sulfides

K. Wold, K. Dwight, Solid State Chemistry - Synthesis, Structure and Properties of Selected Oxides and Sulfides. Chapman Hall, 1993. 

Group VIII sulfides are obtained by the low-temperature precipitation described above. However, a preferred synthesis involves the direct sulfidation with hydrogen sulfide of ammonium hexachlorometallates. A good example is found in the synthesis of RuS2 and Rh2S3 (28). However, synthetic techniques and the solid-state chemistry of the Group VIII sulfides are not as well developed as those for the Group VII sulfides, and much research needs... 

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... 

The Transition Metal Sulfides are a group of solids which form the basis for an extremely useful class of industrial hydrotreating and hydroprocessing catalysts. Solid state chemistry plays an important role in understanding and controlling the catalytic properties of these sulfide catalysts. This report discusses the preparation of sulfide catalysts, the role of disorder and anisotropy in governing catalytic properties, and the role of structure in the promotion of molybdenum disulfide by cobalt. 

Solid state chemistry plays an important role in the catalysis by Transition Metal Sulfides however, it is a role that is somewhat different than the role usually assigned to solid state chemistry in catalysis. In catalysis, by sulfides, the chemistry of ternary phases is not now important and thus, the usual role of solid state chemistry in preparing ternary phases and systematically studying the effect on catalytic properties through variation of the composition of these ternary phases is absent. Nevertheless, preparation of the Transition Metal Sulfides is crucial in controlling the properties of the catalysts. Low temperature solid state preparations are the key to obtaining good catalysts in reasonable surface area for catalytic measurements. 

In heterogeneous catalysis, there are many examples where addition of a second component can change the overall catalytic reactivity in the system by changing its solid-state chemistry. An example of this includes the addition of Co + to the M0S2 and NiS2 systems discussed in Chapter 5. The mixed metal sulfides offer significantly increased activity due to changes in the chemical reactivity of the sulfide surface. We introduce here the solid-state chemistry of oxide catalysts (see also reference 3). A more detailed discussion on mixed metal oxides is presented in Chapter 5. 

In solution this reaction is rather rapid but in the solid state autoxidation takes place much slower. Nevertheless, commercial sulfides and polysulfides of the alkali and alkali earth metals usually contain thiosulfate (and anions of other sulfur oxoacids) as impurities [6]. For all these reasons the chemistry of polysulfides is rather complex, and some of the earlier studies on polysulfides (prior to ca. 1960) are not very rehable experimentally and/or describe erroneous interpretations of the experimental results. 

The solid state and the surface chemistry of some of the solid Fe-phases impart to these oxides and sulfides the ability to catalyze redox reactions. Surface complexes and the solid phases themselves acting as semiconductors can participate in photoredox reactions, where light energy is used to drive a thermodynamically unfavorable reaction (heterogeneous photosynthesis) or to catalyze a thermodynamically favorable reaction (heterogeneous photocatalysis). 

Molecules and solids based on cubic rather than octahedral motifs are less abundant in chemistry. The former were treated in Section 5.2.5 and now we consider a few solid-state analogs. Similar cubic architectures are found in (Fe/Co/Ni Ss, or synthetic C09S8 transition-metal sulfide minerals called pentlandites. In a binary... 

The chemistry of Ru and Os1 bears little resemblance to that of Fe except in some solids such as sulfides or phosphides and in some complexes with 7r-bonding ligands. The higher oxidation states are much more easily obtained than for iron. There is an extensive chemistry of M=0 species for both elements. 

The complex nature of the HDS and HDN problems requires a broad, transdisciplinary approach in order to try to answer the most varied questions related to these important classes of reactions. The key issues include the practical aspects related to process and product engineering, a precise knowledge of the nature and the composition of petroleum and of refinery fractions, and the thermodynamics and detailed kinetics of the different processes involved. Also, a number of more fundamental solid-state and surface chemistry considerations regarding the preparation, the characterization, and the resulting properties of HDS and HDN catalysts, as well as the complicated reaction mechanisms involved for the various important families of substrates, need to be understood in depth. Even though some very impressive achievements have been disclosed over the last 30-40 years, it seems that some of the major new discoveries desired today may have been held back by the lack of a better understanding of some key issues. Of particular importance are the nature and the structure of HDS-HDN active sites on metal sulfide catalysts, and the intimate details of the elementary reactions implicated in the commonly accepted catalytic schemes. 

Both antimony tribromide and antimony triiodide are prepared by reaction of the elements. Their chemistry is similar to that of SbQ3 in that they readily hydrolyze, form complex halide ions, and form a wide variety of adducts with ethers, aldehydes, mercaptans, etc. They are soluble in carbon disulfide, acetone, and chloroform. There has been considerable interest in the compounds antimony bromide sulfide [14794-85-5], antimony iodide sulfide [13868-38-1], ISSb, and antimony iodide selenide [15513-79-8] with respect to their solid-state properties, ferroelectricity, pyroelectricity, photoconduction, and dielectric polarization. 

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. 

Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis, selectivity control in one-electron reduction, the photochemistry of fullerenes, photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxy-coordinated (tetraphenylporphyrinato)antimony(V) hexafluorophosphate, bio-mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photo-induced electron transfer, photoinduced electron transfer involving C o/CjoJ comparisons between the photoinduced electron transfer reactions of 50 and aromatic carbonyl compounds, recent advances in the chemistry of pyrrolidino-fullerenes, ° photoinduced electron transfer in donor-linked fullerenes," supra-molecular model systems,and within dendrimer architecture,photoinduced electron transfer reactions of homoquinones, amines, and azo compounds, photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group, photochemical and polymerisation reactions in solid Qo, photo- and redox-active [2]rotaxanes and [2]catenanes, ° reactions of sulfides and sulfenic acid derivatives with 02( Ag), photoprocesses of sulfoxides and related compounds, semiconductor photocatalysts,chemical fixation and photoreduction of carbon dioxide by metal phthalocyanines, and multiporphyrins as photosynthetic models. 

Molybdenum has a special affinity for sulfur and the close energy match of the Mo 4d and S 3p orbitals often leads to fascinating but unpredictable chemistry. " Molybdenum forms many solid-state sulfides, including the principal ore molybdenite (M0S2), MO2S3, M02SS, non-stoichiometric sulfides and Chevrel phases. These compounds enjoy increasing use as lubricants, electronic materials and catalysts. " ... 

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