Organotellurium chemistry

Organotellurium chemistry describes the synthesis and properties of organotellurium compounds, chemical compounds containing a carbon-tellurium chemical bond. Organotellurium chemistry is a lightly studied area, in part because of it having few applications. The tellurium analogues of common organosulfur and organoselenium functional groups are known. Tellurols are however unstable with respect to oxidation to the ditellurides. Commonly encountered organotellurium compounds are diorganomono- and ditellurides, R2Te and (RTe)2, respectively. Two other families of organotellurium(IV) compounds are well developed: R4−xTeClx and the telluroxides (R2TeO). Reduced organotellurium compounds are commonly obtained from NaHTe and lithium telluride: Li2Te + 2 RBr → R2Te + 2 LiBr A direct route to organolithium compounds starts from reactions of organolithium or Grignard reagents and Te: Te + ArLi → ArTeLi Butyl lithium gives the telluride similarly: Te + BuLi → BuTeLi Organotelluride anions can be oxidized or alkylated: 2 RTeLi + 0.5 O2 + H2O → RTeTeR + 2 LiOH RTeLi + R'Br → RTeR' + LiBr Diorganoditellurides are valued intermediates, especially the aryl derivatives such as diphenyl ditelluride: Ar2Te2 + RLi → RTeAr + LiTeR Ph2Te2 + 2 Li → 2 LiTePh One departure from sulfur and selenium chemistry is the availability of the tetrachloride, TeCl4. It reacts with arenes to give aryltellurium trichlorides: ArH + TeCl4 → ArTeCl3 + HCl For electron-rich arenes, the disubstitution occurs ArH + ArTeCl3 → Ar2TeCl2 + HCl Tellurium tetrachloride adds across alkenes and alkynes to the chloro tellurium trichlorides: RCH=CH2 + TeCl4 → RCH(Cl)-CH2TeCl3 Organotellurium trichlorides adopt dimeric structures, reflecting the Lewis acidity of the Te(IV) center. The dimers are cleaved by halides and other Lewis bases: RTeCl3 + Cl− → RTeCl4− The anions RTeCl4− (and the related adducts RTeCl3L) adopt square pyramidal structures with the electronegative groups in the plane. Organotellurium(IV) chlorides are susceptible to substitution reactions where by chloride is replaced by other halides and pseudohalides.