Telluride ions

H2Se (hydrogen selenide, colorless), HSe (acid telluride ion, colorless), Se (selenide ion, colorless), H2Se03 (selenous acid, colorless), HSeOJ (acid selenite ion, colorless), SeO (selenite ion, colorless), H2Se04 (selenic acid, colorless), HSeOJ (acid selenate ion, colorless), SeO " (selenate ion, colorless). 

H2Te (hydrogen telluride, colorless), HTe (hydrogen telluride ion, colorless), Te (telluride ion, colorless), Te (ditelluride ion, red), Te" + (tellurous ion), HTeOj (telluryl ion), HTeO (acid tellurite ion, colorless), TeO " (tellurite ion, colorless), H2Te04 (telluric acid, colorless), HTeOJ (acid tellurate ion, colorless), TeO (tellurate ion, colorless). 

Data on the electrochemistry of the telluride ion in alkaline media are relatively limited. Mishra et al. [53] studied the oxidation of Te to Te° at solid electrodes, focusing on the intermediate step(s) of this process, and in particular, the possibility of detecting ditelluride Te via rotating ring disk electrode (RRDE) methodology. Oxidation beyond the elemental state to TeO and TeO was also studied using cyclic and hydrodynamic voltammetry. 

Mishra KK, Ham D, Rajeshwar K (1990) Anodic oxidation of telluride ions in aqueous base ... 

Fig. 3.5 Potential vs. pH diagram for the CdTe-H20 system at 25 °C. Solid CdTe is thermodynamically stable over the entire pH range. Consequently, CdTe does not hydrolyze at any H and OH activities of practical interest. In acidic solutions, the only process accompanying cathodic CdTe polarization is hydrogen release. Therefore, in the region of cathode potentials, CdTe is a sufficiently stable electrode material from the electrochemical point of view. The -1.35 V potential is the lowest limit of stabihty. Below this limit, CdTe corrodes in the whole pH range e.g., for pH < 2.8, H2Te vapor is produced at -1.25 V. For pH > 2.8, diteUuride or telluride ions are formed with disintegration of the compound. (With kind permission from Springer Science+Business Media [82])...

Telluro-cyanide (presumably TeCN ) has been explored as a source of tellurium for electrodeposition of CdTe [14], on account of the possible advantage that this species is less likely than tellurium dioxide to oxidize the cathodically produced telluride ion. Bath solutions were prepared by dissolving powdered Te in a concentrated aqueous solution of KCN and adding CdCb and EDTA. Stoichiometric CdTe deposits, free of excess Te, were reported. 

In a range of anions PhZ (Z = O, S, Se, Te), for example, the thiophenolate ion (PhS ) effectively traps aryl radicals (Ar ), whereas the anion of phenyl selenide (PhSe ) is 20 times less active, and the phenolate anion (PhO ) is absolutely inactive. The reaction of aryl radicals with phenyl-telluride ions (PhTe ) proceeds in an abnormal fashion—both asymmetrical and symmetrical tellurides are produced (Rossi and Pierini 1980). 

Elemental tellurium, treated with strong aqueous alkali, undergoes an oxido-reduction disproportionation giving the corresponding telluride ion which reacts with acetylenes to give divinylic tellurides in modest yields. ... 

In accordance with a Reformatsky reaction mechanism, the telluride ion attacks the bromine atom to generate an ester enolate which reacts in seqnence with the aldehyde to afford the a, -nnsatnrated ester. 

Treatment of 1,3,2-dioxathiolane. 7,.7-dioxides with telluride ion, generated in situ by reduction of the elemental Te, yields alkenes rapidly (10min-2h) under mild conditions (0°C to rt) <1995TL7209>. The reduction may be performed with 0.1 equiv or less of Te in the presence of a stoichiometric amount of LiEt3BH or NaH. The reaction is stereospecific, for example, / >-2,3-diphenylethane-2,3-diol produces ar-stilbene, and d,l-2,3-diphenylethane-2,3-diol gives trans-stilbene. The sulfates of m-diols are readily converted to ar-alkenes, as shown in Equation (12) <1995TL7209>. 

The reaction of sodium telluride with epoxides bearing a leaving group in a suitable position, such as in chloromethyl epoxides 44, gives allylic alcohols 45. This process has been performed under mild conditions due to the high nucleophilicity of the telluride ion (Scheme 22).100... 

Nucleophilic reduction by telluride ion of oxirane tosylates provides allylic alcohols, presumably via telluriranes as shown in Equation (12) and Table 7 <1997T12131>. When used in conjunction with the Sharpless-Katsuki asymmetric epoxidation, optically active transposed allylic alcohols can be made in high enantiomeric excess <1993JOC718, 1994JOC4311, 1994JOG4760>. 

In an analogous fashion to the reaction of telluride ion with oxirane tosylates (Section 1.07.10.2), aziridinemethanol-sulfonates form allylic amines as shown in Equation (14). It is suggested that telluriranes are intermediates as shown <1997JOC7920, 1997T12131>. The related reaction using sulfonates of 5-hydroxymethyl-2-oxazolidinones, shown in Equation (15), has also been reported (see Table 8) <1999TL2255>. 

Elimination. Under phase-transfer conditions, the NaBH4-Te combination is effective for the removal of all the oxygen function of 5-tosyloxyoxazolidin-2-ones to afford allyl amines. Probably the displacement by a telluride ion initiates the process (with subsequent loss of elemental Te in the elimination step). 

The four Fe(CO)4 fragments of [Fe4Te(CO)i6] are bonded to a central telluride ion in a tetrahedral fashion. The resulting coordination of iron is trigonal-bipyramidal with tellurium defining a common axial position for each FeTe(CO)4 fragment. 

Interestingly, several cyclic sulfates react with telluride ion generated in situ by reduction of elemental tellurium to yield alkene under mild conditions (0°C) [Eq. (23)]. For example, 4,5-diphenyl-l,3,2-dioxathiolane 2,2-dioxide gave irum-stilbene. Similarly, sugar derivatives can be converted into an unsaturated sugar (95TL7209) [Eq. (24)]. 

Startg. oxido compd. in methanol added via syringe to a soln. of Na2Te (generated in situ from Te and NaBH4 in 17 1 methanol/water) at —40°, the mixture allowed to react for ca. 3-4 h, oxygen or air introduced to promote oxidation of residual telluride ion to tellurium, aq. KOH added, and stirred at room temp, for 1 h - 2-( -butyl)-4-hydroxymethyltellurophene. Y 68%. Where Te is incompletely reduced to monomeric telluride ion, e.g. with Na-formaldehyde sulfoxylate, the primary product is the corresponding 2-hydroxymethyl-1,3-enyne. F.e.s.. R.P. Discordia, D.C. Dittmer, Tetrahedron Letters 29, 4923-6 (1988). 

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