Chalcogen elements

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. 

In the cationic systems, the positive charges are delocalized over almost all atoms, even if the individual structures may be described by the Zintl concept that assigns localized positive charges to tricoordinate E atoms. It appears that the Zintl concept is better suited, yet not sufficient, to describe the structures of the heavier chalcogen elements. 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

Butylallene, which fails to react with (PhSe)2 under palladium catalysis, undergoes the diselenide addition upon photo-irradiation (Equation (80)).215 Using the (PhS)2/(PhSe)2 binary system, introduction of two different chalcogen elements into allenic C=C bond is also viable (Equation (81)). 

Ligands based on chalcogen elements (elements of Group 16) ... 

Enium Ions of Other Group 16 Elements. Furukawaetal.316,320 have obtained enium ions of the heavier chalcogen elements stabilized by intramolecular complexation with dimethylamino groups (322). Resonances of the benzylic and methyl protons in the 1H NMR spectrum of cation 322a are shifted downfield... 

Stability of homopolyatomic cations of chalcogen elements in superacid media... 

Terminal Multiple Bonds Between Chalcogen Elements and Ge... 

While the chemistry of tellurium compounds is still in its infancy, the rapid recent progress has shown that tellurium has many unique properties compared to other chalcogen elements. The advent and development of modem... 

These solvents dissolve the chalcogen elements sulfur, selenium, and tellurium, and therefore can be used for the solvothermal synthesis of metal chalcogenides by the reaction of metal oxalate with chalcogens at 120°C-200°C. It has been reported that the reaction also proceeds in tetrahydrofuran or pyridine, but the reaction in polyamines having more than two chelating atoms proceeds more completely. ... 

Polonium is the heaviest element in the chalcogen family. It is in Group 16 (VIA) in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. The other chalcogen elements are oxygen, sulfur, selenium, and tellurium. 

PTN(Me) is a white microcrystalline material, which is air stable in the solid state. The corresponding oxide cannot be obtained by classical P-phosphine oxidation with hydrogen peroxide, while the sulfide and selenide derivatives are easily and quantitatively prepared by reaction with the appropriate chalcogen element.6 PTN (Me) is soluble in nonpolar and polar solvents including water. At 20°C, PTN(Me), 1.18 g dissolves in 1 mL of water (6.81 x 10 2M). 

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