Thallium triiodide

Thallium triiodide

Names
IUPAC name thallium(I) (triiodide)
Other names thallous triiodide
Identifiers
CAS Number	60488-29-1 Y
Properties
Chemical formula	TlI3
Molar mass	585.097 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Thallium triiodide is a chemical compound of thallium and iodine with formula ${\displaystyle {\ce {TlI3}}}$. Unlike the other thallium trihalides, which contain thallium(III), ${\displaystyle {\ce {TlI3}}}$ is a thallium(I) compound and contains the triiodide ion, I₃⁻.

An appreciation as to why Tl⁺ is not oxidised to Tl³⁺ in the reaction:

can be gained by considering the standard reduction potentials of the half cells which are:

The favoured reaction is therefore the reduction of Tl³⁺ (1.252 > 0.5355).

Using standard electrode potentials in this way must be done with caution as factors such as complex formation and solvation may affect the reaction. TlI₃ is no exception as it is possible to stabilise thallium(III) with excess I⁻ forming the TlI₄⁻ ion (isoelectronic with the tetraiodomercurate anion and with lead(IV) iodide).