Polytelluride anion

Smith DM, Ibers JA (2000) Syntheses and solid-state structural chemistry of polytelluride anions. Coord Chem Rev 200-202 187-205... 

Only species Te 2- with short chains (n = 2-4) are present in polytelluride solutions [57]. Despite this fact many Zintl-type valence precise tellurium dianions of higher nuclearity have been isolated in the solid state in the presence of suitable counter cations. The three general synthetic routes to such polytelluride anions can be summarized with representative examples as follows ... 

Polytelluride Anions With Cluster-like Building Units... 

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... 

The propensity of tellurium to form intermolecular interactions distinguishes its chemical properties from those of sulfur and selenium for which such secondary bonding is virtually nonexistent (see Ref 38 and references therein). By contrast to polysulfides and polyseleiudes, polytelluride anions can exhibit charges that deviate from -2. 

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. ... 

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. 

Dilution with water reverses the reaction, and heating the solution liberates sulfur dioxide. Upon being added to a solution of tellurides, tellurium forms colored polytellurides. Unlike selenium, tellurium is not soluble in aqueous sodium sulfite. This difference offers a method of separating the two elements. Like selenium, tellurium is soluble in hot alkaline solutions except for ammonium hydroxide solutions. Cooling reverses the reaction. Because tellurium forms solutions of anions, Te2-, and cations, Te4+, tellurium films can be deposited on inert electrodes of either sign. 

Tellurium, potassium hydroxide, water, phenylacetylene, a trialkylmethylammonium chloride as phase-transfer catalyst, either tin(IJ) chloride or hydrazine hydrate as reducing agent and toluene as the organic solvent upon heating at approximately 100 for six hours produced Z,Z-bis[2-phenylvinyl ditellurium in low yields. Polytelluride radical anions were postulated as intermediates2 3. 

Unlike sulfur and selenium, the charge of the polytellurides can vary from —2. This is exemphfied by RbTee, which is shown in Figure 7(d). It consists of Tee rings that show bond lengths of 2.777(3) 3.195(3) A. They are hnked together into a two-dimensional network by two pairs of Te- Te contacts of 3.214(3) and 3.449(3) A. Another example is [Cr(en)3]Tee containing a polymeric Tee anion (see Figure 7(e)). ... 

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