Polychalcogenides formation

HgE may also be utilized as the source of the group VIB element (E = S, Se, Te), as in reaction (c). Indeed, this is the best means by which the Rb and Cs chalcogenides are formed. The alkali element is added in excess to prevent polychalcogenide formation. After excess reactants have been removed by sublimation the product is isolated as a solid. 

This means that addition of elemental E to alkali metal polychalcogenide fluxes (200-600°C) will promote the formation of longer chains as potential ligands, when such molten salts are employed as reaction media for the preparation of polychalcogenide complexes. Speciation analysis for polychalcogenides in solution has been performed by a variety of physical methods including UV/vis absorption spectroscopy, Raman spectroscopy, Se, Te and Te NMR, electron spin resonance and electrospray mass spectrometry. 

On the other hand, polytellurides only seem to oxidize metals to the +1 or +11 state. Reaction of equimolar amounts of Te4 with M(CO)6 results in disubstitution of CO forming a cu-complex (CO)4MTe4 (M = Cr (45), W (47)47). If an excess of metal carbonyl is used in the presence of poly-telluride anion, multinuclear products can be isolated and metal-metal bonds can also form, leading to clusters. Careful manipulation of reaction conditions and choice of the polychalcogenide anion used makes possible partial oxidation of the metal centers and cluster formation. The reaction of iron carbonyls with polytelluride anions can lead to a wide array of cluster compounds, the identities of which are controlled by the stoichiometries and compositions of the starting telluride anions. For instance, reaction of [Fe(CO)5] with Te2 leads to the formation of [Fe3(CO)9(ju.3-Te)]2 (48),48 whereas its reaction with increasing amounts... 

Some preliminary results on the electrochemical behaviour of elemental sulphur (and selenium) in AlCla-NaCl melts have been reported. The results for both elements were difficult to interpret, due in part to the low solubility of both elements in the melt and the modification of the electrode surfaces by the products of electrode reactions. In basic melts it was suggested that an cation is formed, in agreement with spectral studies. In acidic melts the results were more complex, and no exact conclusions could be drawn as to the nature of the species. A spectrophotometric study of the reactions of sulphur, selenium, and tellurium with aqueous solutions of NaOH at 150 °C (S, Se) and 300 °C (Te) has been carried out. From the experimental data the formation of the chain-like structure of polychalcogenide compounds was presumed. The spectra confirmed previous results concerning the mechanism of interaction of elemental chalcogens with aqueous NaOH solutions. 

---