Types chalcogenide

LDH materials are not readily exfoliated in contrast to other layered materials such as smectite clays or MS2 type-chalcogenides (M0S2, NbSe2, etc...) [15-17] the delamination of LDH sheets requires elaborate syntheses as discussed above in Sect. 2.1. 

Surprisingly many spinel-type chalcogenides form with copper as an A element. In a ternary representative Cu should be divalent in order to satisfy the valence rules. The spinel structure, however, shows no Jahn-Teller distortions contrary to the oxides. Assuming the cation-anion bonds to be saturated, the metallic properties must be due either to a metallic de band of Cu2+ or to the simultaneous presence of T4+ and T3+. 

The important group of inclusion compounds based on the early transition metal layer and channel type chalcogenides has been investigated. The problems of the formation of Li intercalates by interacting n-bytyllithium hexene solutions with Nb, Mo, W and Re chalcogenides have been considered. 

Electrocatalysis of the ORR of various Chevrel type chalcogenide compounds was first studied by Alonso-Vante and Tributsch [19] in an acid medium and an enhancement in the ORR activity was observed when Mo was partially substituted by Ru. The compounds containing non-substituted octahedral Mo show metallic behavior while Ru substituted Mo octahedral (Moe-rM Xg, where X = S, Se, Te) systems show semiconducting behavior. The compound Mo4.2Rui,8Se8 displayed catalytic behavior comparable to that of Pt. The ORR overpotentials on catalysts of the series MogXg followed the trend Te[Pg.468]

Betyllium, because of its small size, almost invariably has a coordination number of 4. This is important in analytical chemistry since it ensures that edta, which coordinates strongly to Mg, Ca (and Al), does not chelate Be appreciably. BeO has the wurtzite (ZnS, p. 1209) structure whilst the other Be chalcogenides adopt the zinc blende modification. BeF2 has the cristobalite (SiOi, p. 342) structure and has only a vety low electrical conductivity when fused. Be2C and Be2B have extended lattices of the antifluorite type with 4-coordinate Be and 8-coordinate C or B. Be2Si04 has the phenacite structure (p. 347) in which both Be and Si... 

The chalcogenides of Ga, In and T1 are much more numerous and at least a dozen different structure types have been established by X-ray... 

All three metals form a wide variety of binary chalcogenides which frequently differ both in stoichiometry and in structure from the oxides. Many have complex structures which are not easily described, and detailed discussion is therefore inappropriate. The various sulfide phases are listed in Table 22.4 phases approximating to the stoichiometry MS have the NiAs-type structure (p. 556) whereas MS2 have layer lattices related to M0S2 (p. 1018), Cdl2, or CdCl2 (p. 1212). Sometimes complex layer-sequences occur in which the 6-coordinate metal atom is alternatively octahedral and trigonal prismatic. Most of the phases exhibit... 

No chalcogenide halides of zinc and cadmium are known. The phase diagrams of CdS-CdCl (7, 198, 210), CdSe-CdCl (220, 314), CdTe-CdClj 368), CdTe-CdBr2 (368), and CdTe-Cdl (323) are of a simple, eutectic type. The system CdS-CdCl shows a range of solubility of CdS in solid CdClj that extends to 5% of CdS at room temperature, and increases to a maximum of 12.5% of CdS at 500°C (7,210). 

The most important mercury chalcogenide halides are of the type HgaYjXj (Y = S, Se, Te X = Cl, Br, I). The corresponding sulfide halides have been known for over 150 years (326). Quite a lot of work has been performed concerning the preparation, structures, electronic and optical properties, and phototropic behavior of these compounds. Mercury chalcogenide halides of other compositions have been mentioned in the literature (141). As most of these compounds are not well established, they will not be treated in detail, with the exception of the latest contributions (see Table V). 

InSCl, InSBr, InSeCl, and InSeBr are isotypic, and crystallize in the hexagonal CdCU lattice type. The halide and chalcogenide ions are statistically distributed among the Cl sites. As in CdClj, the bonding within the InYs Xa/a octahedra should be predominantly ionic 162). 

Solid-state cluster chemistry is dominated by octahedral (M 5L8)L6 and (MsLi2)L units which are the focus of this paper. These two cluster types are different in the way the metal octahedral core is surrounded by the ligands. In (MsLg)L6-type clusters (Fig. 6.1a), typical for molybdenum and rhenium halides, chalcogenides, and chalcohalides, eight innei hgands (L ) cap the octahedron faces and six outer ligands (L ) are located in the apical positions [9]. For metals with a smaller number of valence electrons, the (M6L i2)L -type clusters... 

Fig. 7.1 Idealized structures of the trinuclear cluster chalcogenides M3Q4L9 (type I, (a)) and M3Q7U (type II, (b)).

Quaternary chalcogenides of the type A Ln M X, containing three metal elements from different blocks of the Periodic Table (A is an alkali or alkaline earth metal, Ln is an /-block lanthanide or scandium, M is a p-block main group or a r/-block transition metal, and X is S or Se) are also known [65]. 

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