Lanthanum(III) iodide

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Lanthanum(III) iodide
Names
Other names
Lanthanum triiodide
Identifiers
3D model (
JSmol
)
ECHA InfoCard
 100.034.045 Edit this at Wikidata
EC Number
  • 237-465-6
  • InChI=1S/3HI.La/h3*1H;/q;;;+3/p-3
    Key: KYKBXWMMXCGRBA-UHFFFAOYSA-K
  • I[La](I)I
Properties
LaI
3
Molar mass 519.62
Density 5.63 g/mL at 25 °C
Melting point 772 °C (1,422 °F; 1,045 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Lanthanum(III) iodide is an inorganic compound containing lanthanum and iodine with the chemical formula LaI
3.[1]

Synthesis

Lanthanum(III) iodide can be synthesised by the reaction of lanthanum metal with mercury(II) iodide:[2][3]

2 La + 3 HgI2 → 2 LaI3 + 3 Hg

It can also be prepared from the elements, that is by the reaction of metallic lanthanum with iodine:[2]

2 La + 3 I2 → 2 LaI3

While lanthanum(III) iodide solutions can be generated by dissolving lanthanum oxide in hydroiodic acid, the product will hydrolyse and form polymeric hydroxy species:[4]

La2O3 + 6 HI → 2 LaI3 + 3 H2O → further reactions

Structure

Lanthanum(III) iodide adopts the same crystal structure as plutonium(III) bromide, with 8-coordinate metal centres arranged in layers.[4][5] This orthorhombic structure is typical of the triiodides of the lighter lanthanides (La–Nd), whereas heavier lanthanides tend to adopt the hexagonal bismuth(III) iodide structure.[3]

Reactivity and applications

Lanthanum(III) iodide is very soluble in water and is

deliquescent.[4] Anhydrous lanthanum(III) iodide reacts with tetrahydrofuran to form a photoluminescent complex, LaI3(THF)4, with an average La–I bond length of 3.16 Å.[6][7] This complex is a starting material for amide and cyclopentadienyl complexes of lanthanum.[6][8]

Related compounds

Lanthanum also forms a diiodide, LaI2. It is an electride and is best formulated {LaIII,2I−,e−}, with the electron delocalised in a conduction band.[4] Several other lanthanides form similar compounds, including CeI2, PrI2 and GdI2.[9] Lanthanum diiodide adopts the same tetragonal crystal structure as PrI2.[10]

Lanthanum(III) iodide reacts with lanthanum metal under an argon atmosphere in a tantalum capsule at 1225 K to form the mixed-valence compound La2I5.[11]

Reduction of LaI2 or LaI3 with metallic sodium in an argon atmosphere at 550 °C gives lanthanum monoiodide, LaI, which has a hexagonal crystal structure.[12]

References

  1. doi:10.1021/cr60220a001
    .
  2. ^
    doi:10.1002/9780470132531.ch6
    .
  3. ^
    doi:10.1021/ic50018a015
    .
  4. ^
    ISBN 978-0-08-037941-8
    .
  5. ISBN 978-0-19-965763-6
    .
  6. ^
    PMID 35099940
    .
  7. S2CID 232232544
    .
  8. PMID 28915015
    .
  9. ISBN 978-0-19-965763-6
    .
  10. doi:10.1088/0022-3719/20/26/014
    .
  11. S2CID 94059677
    .
  12. PMID 16499368
    .
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