Tellurol
Tellurols are analogues of alcohols and phenols where tellurium replaces oxygen.[1] Tellurols, selenols, and thiols have similar properties, but tellurols are the least stable.[2] Although they are fundamental representatives of organotellurium compounds, tellurols are lightly studied because of their instability. Tellurol derivatives include telluroesters (RC(O)TeR') and tellurocyanates (RTeCN).
Properties
Alkyltellurols are colorless liquids with strong odors. Samples usually appear yellowish owing to the presence of dialkylditelluride impurities. Near room temperature, methanetellurol degrades with loss of elemental tellurium. It is reported to ignite in air.[3]
Aryltellurols are more robust and have been obtained as colorless crystals. Some of the most stable tellurols are the bulky silylated derivatives of tris(trimethylsilyl)methane and analogues. One series of readily isolable tellurols is (Me3Si)3CTeH, (Me3Si)3SiTeH, and (Me3Si)3GeTeH.[1]
Acid–base properties
The acidity of tellurols can be inferred by the acidity and dissociation constant of hydrogen telluride, H2Te, which has a (first) pKa of 2.64 corresponding to a dissociation constant of 2.3 × 10−3. H2Te has a lower pKa and higher dissociation constant than H2S and H2Se.[4] The pKa is 9.3 for (Me3Si)3CTeH vs 10.8 for (Me3Si)3CSeH.[1]
The absence of hydrogen-bonding explains the low boiling temperature of tellurols.[4]
Preparation
The first tellurol to be synthesized, ethanetellurol, was prepared in 1926 via the Grignard reagent.[1] The most frequently used method involves reduction of the ditellurides (R2Te2).
References
- ^ a b c d Sadekov ID, Zakharov AV (1999). "Stable tellurols and their metal derivatives". Russ. Chem. Rev. 68 (11): 909–923. Bibcode:1999RuCRv..68..909S. doi:10.1070/rc1999v068n11abeh000544. S2CID 250864006.
- ^ Khater B, Guillemin JC, Bajor G, et al. (2008). "Functionalized Tellurols: Synthesis, Spectroscopic Characterization by Photoelectron Spectroscopy, and Quantum Chemical Study". Inorg. Chem. 47 (5): 1502–1511. doi:10.1021/ic701791h. PMID 18257551.
- ^ Hamada, K.; Morishita, H. (1977). "The Synthesis and the Raman and Infrared Spectra of Methanetellurol". Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry. 7 (4): 355–366. doi:10.1080/00945717708069709.
- ^ a b Patai S, Rappoport Z, eds. (1986). The Chemistry of Organic Selenium and Tellurium Compounds. Vol. 1. Chichester England: John Wiley & Sons Ltd. doi:10.1002/9780470771761. ISBN 9780471904250.