Hydrogen ditelluride

Hydrogen ditelluride or ditellane is an unstable hydrogen dichalcogenide containing two tellurium atoms per molecule, with structure HTeTeH or (TeH)2. Hydrogen ditelluride is interesting to theorists because its molecule is simple yet asymmetric (with no centre of symmetry) and is predicted to be one of the easiest to detect parity violation, in which the left handed molecule has differing properties to the right handed one.

Hydrogen ditelluride
Names
Other names
ditellane
Dihydrogen ditellanide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
239518
Properties
H2Te2
Molar mass 257.22 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Production

Hydrogen ditelluride can possibly be formed at the tellurium cathode in electrolysis in acid.[2] When electrolysed in alkaline solutions, a tellurium cathode produces ditelluride Te22− ions, as well as Te2− and a red polytelluride. The greatest amount of ditelluride is made when pH is over 12.[3]

Apart from its speculative detection in electrolysis, ditellane has been detected in the gas phase produced from di-sec-butylditellane.[1][4]

Properties

Hydrogen ditelluride has been investigated theoretically, with various properties predicted. The molecule is twisted with a C2 symmetry. There are two enantiomers. Hydrogen ditelluride is equal simplest in its unsymmetrical molecule, any simpler molecule will not have the required low symmetry. The equilibrium geometry (not counting zero point energy or vibrational energy) has the molecule with 2.879 Å between the tellurium atoms, and 1.678 Å between hydrogen and tellurium. The H-Te-Te angle is 94.93°. The angle of lowest energy between the two H-Te bonds (dihedral angle) is 89.32°. The trans cofiguration is higher in energy (3.71 kcal/mol), and the cis would be even higher (4.69 kcal/mol).[5]

Being chiral the molecule is predicted show evidence of parity violation, however this may get interference from stereomutation tunneling, where the P enantiomer and M enantiomer spontaneously convert into each other by quantum tunneling. The parity violation effect on energy comes about from virtual Z boson exchanges between the nucleus and electrons.[6] It is proportional to the cube of the atomic number, so is stronger in tellurium molecules than others higher up in the periodic table (eg O, S, Se). Because of parity violation, the energy of the two enantiomers differs, and is likely to be higher in this molecule than most molecules. So an effort is underway to observe this so-far undetected effect. The tunneling effect is reduced by higher masses, so that the deuterium form, D2Te2 will show less tunneling. In a tortional vibrational mode the molecule can twist back and forward storing energy. Seven different quantum vibration levels are predicted below the energy to jump to the other enantiomer. The levels are numbered vt=0 up to 6. The sixth level is predicted to be split into two energy levels because of quantum tunneling.[7] The parity violation energy is calculated as 3×10−9 cm−1 or 90 Hz.[7]

The different vibrational modes for H2Te are symmetrical stretch of H-Te, symmetrical bend of ∠H-Te-Te, torsion, stretch Te-Te, asymmetrical stretch H-Te, asymmetrical bend of ∠H-Te-Te.[7] The time to tunnel between enantiomers is only 0.6 ms for H2Te2, but is 66000 seconds for the tritium isotopomer T2Te2.[7]

There are organic derivatives, in which the hydrogen is replaced by organic groups. One example is bis-(2,4,6-tributylphenyl)ditellane.[8] Others are diphenylditellane and 1,2-bis(cyclohexylmethyl)ditellane.

References
  1. Macintyre, Jane E. (1995). Dictionary of Inorganic Compounds, Supplement 3. CRC Press. p. 287. ISBN 9780412491108.
  2. Awad, S. A. (May 1962). "Poisoning Effect of Telluride Ions on Hydrogen Evolution and Cathodic Formation of Hydrogen Ditelluride". The Journal of Physical Chemistry. 66 (5): 890–894. doi:10.1021/j100811a031.
  3. Alekperov, A I (30 April 1974). "Electrochemistry of Selenium and Tellurium". Russian Chemical Reviews. 43 (4): 235–250. Bibcode:1974RuCRv..43..235A. doi:10.1070/RC1974v043n04ABEH001803.
  4. Hop, Cornelis E. C. A.; Medina, Marco A. (April 1994). "H2Te2 Is Stable in the Gas Phase". Journal of the American Chemical Society. 116 (7): 3163–3164. doi:10.1021/ja00086a072.
  5. BelBruno, Joseph J. (1997). "Ab Initio Calculations of the Rotational Barriers in H2Te2 and (CH3)2Te2". Heteroatom Chemistry. 8 (3): 199–202. doi:10.1002/(SICI)1098-1071(1997)8:3<199::AID-HC1>3.0.CO;2-8.
  6. Senami, Masato; Inada, Ken; Soga, Kota; Fukuda, Masahiro; Tachibana, Akitomo (2018). "Difference of Chirality of the Electron Between Enantiomers of H$$_$$X$$_$$". Concepts, Methods and Applications of Quantum Systems in Chemistry and Physics. Springer, Cham. pp. 95–106. doi:10.1007/978-3-319-74582-4_6. ISBN 9783319745817.
  7. Gottselig, Michael; Quack, Martin; Stohner, Jürgen; Willeke, Martin (April 2004). "Mode-selective stereomutation tunneling and parity violation in HOClH+ and H2Te2 isotopomers". International Journal of Mass Spectrometry. 233 (1–3): 373–384. Bibcode:2004IJMSp.233..373G. doi:10.1016/j.ijms.2004.01.014.
  8. Lickiss, P. D. (1988). "Chapter 9. Organometallic chemistry. Part (II) Main-group elements". Annu. Rep. Prog. Chem., Sect. B: Org. Chem. 85: 263. doi:10.1039/OC9888500241.
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