Organotellurium chemistry

Functional groups

The Te analogues of common organosulfur functional groups are known. Tellurols are unstable. Diorganomono- and ditellurides are the most commonly encountered organotellurium compounds. Telluroxides (R₂TeO) are also known.

Synthesis

Commonly used tellurium based reagents are hydrogen telluride, NaHTe, sodium telluride, and PhTeLi. Because Te is insoluble and polymeric, it is often not a useful precursor to organotellurium compounds, but it is attacked by hydride reducing agents:

Te + 2LiBHEt₃ → Li₂Te + H₂ + 2 BEt3

and organolithium compounds:

Te + RLi → RTeLi

One departure from S and Se chemistry, is the availability of the tetrachloride TeCl4. Tellurium tetrachloride reacts with alkenes and alkynes to the chloro tellurium trichloride addition product:

RCH=CH₂ + TeCl₄ → RCH(Cl)-CH₂TeCl₃

These organotellurium derivatives are susceptible to further reactions.

Applications

Organotellurium compounds have few applications. Dimethyl telluride is used to in the metalorganic vapour phase epitaxy where it serves as a volatile source of Te. It is the only organotellurium compound that has been quantified in environmental samples.

Organic synthesis

Diphenyl ditelluride is used as a source of PhTe⁻ in organic synthesis. Some of its reactions are:

Organic reduction of aldehydes, alkenes, alkynes, nitro compounds, oxiranes to alkenes

Debromination of vicinal dibromides with E2 elimination

Other methods in organotellurium chemistry include:

Tellurium in vinylic tellurium trichlorides can be replaced by halides with a variety of reagents (iodine, NBS)

Detellurative cross-coupling reaction: Compounds of the type Ar₂TeCl₂ engage in a coupling reaction to the corresponding biaryls with Raney nickel or palladium

Another type is this Stille reaction:

Hydrotelluration: Compounds of the type RTeH react with alkynes R'CCH to R'HCCTeR with anti addition to a Z-alkene. In contrast hydrostannylation, hydrozirconation and hydroalumination in similar reactions react with syn addition.

Te/Li exchange in transmetallation is used in the synthesis of lithium reagents with demanding functional groups.

Allylic oxidation: like the selenium counterpart selenoxide oxidation, allylic telluroxides undergo [2,3]-sigmatropic rearrangements forming allylic alcohols after hydrolysis.

Olefin synthesis: Like the selenium counterpart selenoxide elimination, certain telluroxides (RTeOR) can form alkenes on heating.