Ternary chalcogenide clusters

Tabic 12.15.A Dimensions of the nionoclinic unit cells for the ternary technetium chalcogenides [S26.  

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Lower formal oxidation states are stabilized, however, by M-M bonding in ternary chalcogenides such as M MeQn, M4M6Q13 (M = alkali metal M = Re, Tc Q = S, Se) and the recently reported M gMeS. Their structures are all based on the face-capped, octahedral MeXg cluster unit found in Chevrel phases (p. 1018) and in the dihalides of Mo and W... 

Most of the chalcogenide studies have involved binary, ternary, and pseudo ternary metal clusters. The ternary Chevrel-phases can be represented by MxMo6X8 (M = transition metal, X = chalcogen atom), where the transition metal fills the cavities in the Mo6X8 crystal structure. The pseudo-ternary (or pseudo-binary) Chevrel-phase clusters can be represented by MxMo6 xX8, where the Mo atoms are substituted by transition metal atoms.185 The crystal structure of ternary and pseudo ternary Chevrel phases are shown in Fig. 4. The carbonyl-chalcogenide clusters189 192 will be discussed in the next section. 

Ternary chalcogenides of rhenium and technetium containing isolated clusters... 

One-dimensionally linked Tce or Ree clusters have hitherto not been observed among the ternary chalcogenides discussed here (however, see Section 5.6.4). The compound Cs6Rc6Si2 is the only example so far of a two-dimensionally linked... 

The ability of tetrachalcogenometallates [ME4]" (M = V, Nb, = 3 M = Mo, W, n = 2 M = Re, n= 1) to act as multidentate ligands to a variety of transition metals has been well documented. " As a result of this coordinative versatility, these complexes have been widely implemented in the synthesis of homometallic and heterometallic metal chalcogenide clusters with intact or altered [ME4] - units. In particular, the synthesis of ternary polynuclear M-Fe-E and M-Cu(Ag)-E complexes has received much attention, due to their relevance to biological systems as well as interesting catalytic and physical properties. 

Ternary chalcogenides, M MoeXs (M = a transition metal, rare earth, etc. and X = S, Se, or Te) a class of ORR active materials, were for the first time synthesized by Chevrel et al. [167] and are referred as Chevrel compounds. These complex chalcogenides have a central octahedral metal cluster wherein the delocalization of the electrons leads to high electronic conductivity and these clusters act as a reservoir for electronic charge carriers. The substitution of Mo atoms by other transition metal atoms causes an alteration in the position of the Fermi level in such a way that it is suitable for the redox potential of the O2/H2O [19] couple. 

Chevrel R, Gougeon P, Potel M, Sergent M (1985) Ternary molybdenum chalcogenides A route to new extended clusters. J Solid State Chem 57 25-33... 

The situation is very similar in the Chevrel phases. These are ternary molybdenum chalcogenides A,.[Mo6Xg] (A = metal, X = S, Se) that have attracted much attention because of their physical properties, especially as superconductors. The parent compound is PbMo6Sg it contains Mo6Sg clusters that are linked with each other in such a way that the free coordination sites of one cluster are occupied by sulfur atoms of adjacent clusters (Fig. 13.9). The electric properties of Chevrel phases depend on the number of valence electrons. With 24 electrons per cluster (one electron pair for each edge of the... 

Trends in the electronic structure of the chalcogenide catalysts have proved to be helpful in the design and understanding of the catalyst clusters. During ORR, the molecular oxygen has been found to react with the cluster as a whole, rather than individual metal atoms.177 The overall number of electrons per cluster unit (NEC) in the valence bond has been shown to have a factor in the activity and stability of the cluster catalysts.177,181 The unsubstituted Chevrel phases have a NEC of 20.177,181 Substituting or intercalating other transition metals into the crystal lattice to make ternary or pseudo-binary Chevrel phases allows for the increase of NEC. It has been found that as the NEC approaches 24, the catalytic activity improves.181 Alonso-Vante compiled the results from his previous studies to show the effect of NEC in... 

There is also a series of ternary zirconium chalcogenides such as Zr6MTe2,57 M = Mn, Fe, Co, Ni, Ru, or Pt, which exhibit metal-centered tricapped trigonal prismatic clusters as the basic structural unit. 

Chevrel Phases Ternary molybdenum chalcogenides, M Mo X, are polynuclear clusters of special... 

We have included not only pure nitride materials but also many amides, azides, oxynitrides (but not nitrates and nitrites), nitride chalcogenides, and nitride halides. Specifically excluded are polymeric compounds (e.g. SxNy), cluster compounds (e.g. Sc2C12N), coordination compounds (e.g. [Pd(NS3)2]), ternary azides and amides, as well as ternary interstitial transition-metal nitrides. We have attempted to include all important structures and all type compounds. This review is also unique in that we attempt to evaluate the... 

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