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Tellurium tetraiodide (TeI4) is an inorganic chemical compound. It has a tetrameric structure which is different from the tetrameric solid forms of TeCl4 and TeBr4.[2] In TeI4 the Te atoms are octahedrally coordinated and edges of the octahedra are shared.[2]

Preparation

Tellurium tetraiodide can be prepared by reacting Te and iodomethane, CH3I.[2] In the vapour TeI4 dissociates:[3]

TeI4 → TeI2 + I2

It can be also obtained by reacting telluric acid with hydrogen iodide.[4]

Te(OH)6 + HI → TeI4 + I2 + 6 H2O

It can also be obtained by reacting the elements, which can also produce tellurium diiodide and tellurium monoiodide, depending on the reaction conditions:[5]

Te + 2 I2 → TeI4
TeI4 → TeI2 + I2

Properties

Tellurium tetraiodide is an iron-gray solid that decomposes slowly in cold water and quickly in warm water to form tellurium dioxide and hydrogen iodide.[6] It is stable even in moist air and decomposes when heated, releasing iodine. It is soluble in hydriodic acid to form H[TeI5] and it is slightly soluble in acetone.[4]

Tellurium tetraiodide is a conductor when molten, dissociating into the ions TeI3+ and I−. In solvents with donor properties such as acetonitrile, CH3CN ionic complexes are formed which make the solution conducting:[3]

TeI4 + 2 CH3CN → (CH3CN)2TeI3+ + I−

Five modifications of tellurium tetraiodide are known, all of which are composed of tetrameric molecules.[7] The δ form is the most thermodynamically stable form. This is structurally derived (as well as the α, β and γ forms) from the ε form.

References

  1. ^ "Tellurium tetraiodide". pubchem.ncbi.nlm.nih.gov. Retrieved 13 December 2021.
  2. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. ^ a b Inorganic Chemistry,Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0-12-352651-5
  4. ^ a b Handbuch der präparativen anorganischen Chemie. 1 (3., umgearb. Aufl ed.). Stuttgart: Enke. 1975. p. 435. ISBN 978-3-432-02328-1.
  5. ^ Hagen, A. P. (2009-09-17). Inorganic Reactions and Methods, The Formation of Bonds to Halogens (Part 1). John Wiley & Sons. ISBN 978-0-470-14538-8.
  6. ^ Tellurium(IV) iodide, 99% (metals basis) at AlfaAesar, accessed on 2013-12-17 (PDF) (JavaScript required).[dead link]
  7. ^ Riedel, Erwin; Janiak, Christoph (2011). Anorganische Chemie: Zusatzmaterial online. Studium (8. Aufl ed.). Berlin: de Gruyter. ISBN 978-3-11-022567-9.
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