Polytellurides sheet anions

Cs3Se22 has recently been prepared under methanolothermal conditions138 and is isostructural to Cs3Te2219. In contrast to the [Te ] sheets (Figure 10b) of the polytelluride, the anionic sheets in Cs3Se22 are best described as [(Se3-)(Se3-)], in which disordered pairs of bent Se3 radical anions and Sef anions are linked through secondary interactions. 

In contrast to the polysulfides and almost all the polyselenides (exception Cs4Sei6 ), a number of polytelluride anions are also known with total negative charges greater than 2, as, for instance, in NaTe with discrete [Tcs]" ions and in 83X022 with polymeric sheet-Uke [Tcg ] ions. These are examples for the striking variety of structural motifs and formula types (x/y = 5/3, 1/1, 2/3, 2/5, 1/3, 1/4, 1/6, 2/13, 1/7 and 3/22) that are known for the alkali metal polytellurides A TCj, and which reflect the propensity of tellurium both to catenate and to participate in hypervalent coordination polyhedra. Whereas discrete anions are observed for xjy > 2/3, polymeric chain and lamellar anionic networks are present in such tellurides when xfy < 2/5. ... 

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