Chalcogen compounds bases

Perspectives for fabrication of improved oxygen electrodes at a low cost have been offered by non-noble, transition metal catalysts, although their intrinsic catalytic activity and stability are lower in comparison with those of Pt and Pt-alloys. The vast majority of these materials comprise (1) macrocyclic metal transition complexes of the N4-type having Fe or Co as the central metal ion, i.e., porphyrins, phthalocyanines, and tetraazaannulenes [6-8] (2) transition metal carbides, nitrides, and oxides (e.g., FeCjc, TaOjcNy, MnOx) and (3) transition metal chalcogenide cluster compounds based on Chevrel phases, and Ru-based cluster/amorphous systems that contain chalcogen elements, mostly selenium. 

TBP are four-coordinated, whereas MC are three. Therefore, the bulkiness around E will be more severe for TBP than for MC. The increased bulkiness around E prefers MC to TBP.21b e Namely, it is possible to prepare hypervalent chalcogen compounds other than those predicted from the general rule based on x, by modulating electronic and/or steric conditions around chalcogens in organic chalcogen compounds. 

The heavier chalcogens are more prone towards secondary interactions than sulfur. In particular, the chemistry of tellurium has numerous examples of intramolecular coordination in derivatives such as diazenes, Schiff bases, pyridines, amines, and carbonylic compounds. The oxidation state of the chalcogen is also influential sulfur(IV) centres engender stronger interactions than sulfur(II). For example, the thiazocine derivative 15.9 displays a S N distance that is markedly longer than that in the corresponding sulfoxide 15.10 (2.97 A V5. 2.75-2.83 A, respectively). ... 

More complicated structural situations are observed in di-halogen-rich adducts of chalcogen-donor molecules when further soft-soft halogen halogen interactions intervene, thus generating multidimensional networks (see Chapter 13.1). A clear example is represented by the structure of the compound (dithizone)2 7I2 46 Based on structural data the authors have described the repeating unit in this polymeric compound as a... 

Abstract In this chapter, selected results obtained so far on Fe(III) spin crossover compounds are summarized and discussed. Fe(III) spin transition materials of ligands containing chalcogen donor atoms are considered with emphasis on those of M,f T-disubsti-tuted-dithiocarbamates, Ar,N-disubstituted-XY-carbamates (XY=SO, SSe, SeSe), X-xan-thates (X=0, S), monothio-/J-diketonates and X-semicarbazones (X=S, Se). In addition, attention is directed to Fe(III) spin crossover systems of multidentate Schiff base-type ligands. Examples of spin inter-conversion in Fe(III) compounds induced by light irradiation are given. 

Chalcogenation of a divalent germanium compound with styrene sulfide has been examined as an alternative route to the first free germanethione Tbt(Tip)Ge = S 165142 (Scheme 32) and later on allowed the synthesis of new base-stabilized germanethiones 187 and 188156 [Eq. (37)]. Phenyl isocyanate also may serve as a sulfur source leading to 165, which was evidenced by electronic spectroscopy and underwent a subsequent [2 + 2] cycloaddition with phenyl isocyanate157 (Scheme 36). 

Chalcogenides, 5 94-96 berkelium, 28 49, 53-54 lattice energies of, 1 192, 193 ligands, 45 16 Chalcogen(II) compounds binary halides, 35 274—280 complexes with Lewis bases, 35 293-295 halo-chalcogenates(ll), 35 280-288 mixed-valence compounds, 35 288-293 cationic species, 35 291-293... 

In order to make these points clearer, interatomic distances in representative compounds are listed in Table VII. The distortion of Mo6 should be caused by electronic effects from the individual cluster units and/or steric effects due to the linkage of the clusters. At one time the electronic effects were considered more important based on the band calculations (58, 84). The strong eg Mo rf-bonding character of the conduction band causes contraction of the Mo octahedron, and the filling of the tlu(Oh) - eu (S6) and t2u (Oh) —> au (S6) band is related to the smaller intratriangle distance. Namely, the larger shift of electrons from Mx and chalcogen atoms to the molybdenum atoms is related to smaller distortion of the Mo6 octahedra. 

In contrast to the chalcogen-bridged complexes, no similar oxygen-bridged compounds of iron, cobalt, or nickel exist. However, we obtained such oxo or i-ol-carbonyl complexes of chromium and its homologs, as well as of rhenium. The compounds are the products of the reactions of the respective metal carbonyls with bases (VII). 

Based on the ADC model, we proposed a kinetic model for defect formation in II-VI compounds. A system of rate equations describing the interaction between a II-VI crystal and chalcogen vapor was set up and solved under the assumption that only the atomic component of the vapor phase reacts with the crystal surface. In calculating the ADC equilibrium on... 

Much of this work has been directed towards materials-based applications, as volatile compounds might be CVD precursors see Chemical Vapor Deposition) and the ability of the thiolates and their fellows to react with the free chalcogens may assist doping lanthanide ions into optical and electrical materials. Thus, thermolysis of the [Ln(SePh)3(thf)3] (Ln =... 

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