Thallium triiodide

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Thallium triiodide
Thallium triiodide Thallium-triiodide-xtal-3D-SF.png
Thallium triiodide
Names
IUPAC name
thallium(I) (triiodide)
Other names
thallous triiodide
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 236-627-3
PubChem CID
  • InChI=1S/I3.Tl/c1-3-2;/q-1;+1
    Key: CFEVJLSKLTWQJS-UHFFFAOYSA-N
  • [Tl+].I[I-]I
Properties
I3Tl
Molar mass 585.09 g·mol−1
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H300, H330, H373, H411
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability (red): no hazard codeInstability (yellow): no hazard codeSpecial hazards (white): no code
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Thallium triiodide is a chemical compound of thallium and iodine with formula TlI3. Unlike the other thallium trihalides, which contain thallium(III), TlI3 is a thallium(I) salt and contains the triiodide ion, I−
3.

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

Tl3+ + 2 I− → Tl+ + I2

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

Tl3+ + 2
e−
 → Tl+; Er° = 1.252
I2 + 2
e−
 → 2 I−; Er° = 0.5355

The favoured reaction is therefore the reduction of Tl3+ to Tl+ (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 tetraiodothallate (TlI−
4) ion (isoelectronic with the tetraiodomercurate anion and with lead(IV) iodide).

Structure and preparation

TlI3 is formulated Tl+
I−
3, and has a similar structure to NH4I3, CsI3 and RbI3. [1] The triiodide ion in TlI3 is nearly linear but is asymmetric with one iodine–iodine bond longer than the other. For comparison the dimensions of the triiodide, Ia–Ib–Ic, ions in the different compounds are shown below:

compoundIa–Ib (pm)Ib–Ic (pm)angle (°)
TlI3306.3282.6177.90
RbI3305.1283.3178.11
CsI3303.8284.2178.00
NH4I3311.4279.7178.55

TlI3 can be prepared by the evaporation of stoichiometric quantities of thallium(I) iodide (TlI) and iodine in concentrated aqueous hydriodic acid, or by reacting TlI with iodine in ethanol.

Related Research Articles

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Hydrogen iodide (HI) is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the other is an aqueous solution of the gas. They are interconvertible. HI is used in organic and inorganic synthesis as one of the primary sources of iodine and as a reducing agent.

<span class="mw-page-title-main">Sodium iodide</span> Chemical compound

Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I−) in a crystal lattice. It is used mainly as a nutritional supplement and in organic chemistry. It is produced industrially as the salt formed when acidic iodides react with sodium hydroxide. It is a chaotropic salt.

Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point.

<span class="mw-page-title-main">Triiodide</span> Ion

In chemistry, triiodide usually refers to the triiodide ion, I−
3. This anion, one of the polyhalogen ions, is composed of three iodine atoms. It is formed by combining aqueous solutions of iodide salts and iodine. Some salts of the anion have been isolated, including thallium(I) triiodide (Tl+[I3]−) and ammonium triiodide ([NH4]+[I3]−). Triiodide is observed to be a red colour in solution.

<span class="mw-page-title-main">Thallium(I) iodide</span> Chemical compound

Thallium(I) iodide is a chemical compound with the formula TlI. It is exists as both a solid and high temperature red polymorph. Thallium(I) iodide is one of several water-insoluble metal iodides, along with AgI, CuI, SnI2, SnI4, PbI2, and HgI2.

Terbium(III) iodide (TbI3) is an inorganic chemical compound.

The thallium halides include monohalides, where thallium has oxidation state +1, trihalides in which thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. These salts find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 μm), whereas zinc selenide is opaque by 21.5 μm, and ZnSe optics are generally only usable to 650 cm−1 (15 μm).

<span class="mw-page-title-main">Molybdenum(III) iodide</span> Chemical compound

Molybdenum(III) iodide is the inorganic compound with the formula MoI3.

<span class="mw-page-title-main">Chromium(III) iodide</span> Chemical compound

Chromium(III) iodide, also known as chromium triiodide, is an inorganic compound with the formula CrI3. It is a black solid that is used to prepare other chromium iodides.

<span class="mw-page-title-main">Scandium triiodide</span> Chemical compound

Scandium triiodide, also known as scandium iodide, is an inorganic compound with the formula ScI3 and is classified as a lanthanide iodide. This salt is a yellowish powder. It is used in metal halide lamps together with similar compounds, such as caesium iodide, because of their ability to maximize emission of UV and to prolong bulb life. The maximized UV emission can be tuned to a range that can initiate photopolymerizations.

Cerium(III) iodide (CeI3) is the compound formed by cerium(III) cations and iodide anions.

Samarium(III) iodide is an inorganic compound, a salt of samarium and hydroiodic acid with the chemical formula SmI
3.

Iron(III) iodide is an inorganic compound with the chemical formula FeI3. It is a thermodynamically unstable compound that is difficult to prepare. Nevertheless, iron(III) iodide has been synthesised in small quantities in the absence of air and water.

<span class="mw-page-title-main">Praseodymium(III) iodide</span> Chemical compound

Praseodymium(III) iodide is an inorganic salt, consisting of the rare-earth metal praseodymium and iodine, with the chemical formula PrI3. It forms green crystals. It is soluble in water.

<span class="mw-page-title-main">Lanthanum(III) iodide</span> Chemical compound

Lanthanum(III) iodide is an inorganic compound containing lanthanum and iodine with the chemical formula LaI
3.

Europium(III) iodide is an inorganic compound containing europium and iodine with the chemical formula EuI3.

<span class="mw-page-title-main">Lutetium(III) iodide</span> Chemical compound

Lutetium(III) iodide or lutetium iodide is an inorganic compound consisting of iodine and lutetium, with the chemical formula of LuI3.

<span class="mw-page-title-main">Holmium(III) iodide</span> Chemical compound

Holmium(III) iodide is an iodide of holmium, with the chemical formula of HoI3. It is used as a component of metal halide lamps.

<span class="mw-page-title-main">Hafnium(III) iodide</span> Chemical compound

Hafnium(III) iodide is an inorganic compound of hafnium and iodine with the formula Hf I3. It is a black solid.

References

  1. ↑ Tebbe, K.F.; Georgy, U. (1985-12-15). "Die Kristallstrukturen von Rubidiumtriiodid und Thalliumtriiodid". Acta Crystallographica C (in German). 42 (12): 1675–1678. doi:10.1107/S0108270186090972.
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