Lanthanum(III) iodide

Lanthanum(III) iodide
Names
	Other names Lanthanum triiodide
Identifiers
CAS Number	13813-22-4 ;
3D model (JSmol)	Interactive image;
ECHA InfoCard	100.034.045
EC Number	237-465-6;
PubChem CID	24870325;
CompTox Dashboard (EPA)	DTXSID0065640 ;
	InChI InChI=1S/3HI.La/h3*1H;/q;;;+3/p-3 Key: KYKBXWMMXCGRBA-UHFFFAOYSA-K;
	SMILES I[La](I)I;
Properties
Chemical formula	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). Infobox references

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 {La^III,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

^ Taylor, Moddie D. (1962). "Preparation of Anhydrous Lanthanon Halides". Chem. Rev. 62 (6): 503–511. doi:10.1021/cr60220a001.
^ ^a ^b Corbett, John D. & Simon, Arndt (1984). "Chapter 6: Lanthanum Triiodide (and Other Rare Earth Metal Triiodides)". In Holt Jr., Smith L. (ed.). Inorg. Synth. Vol. 22. pp. 11–16. doi:10.1002/9780470132531.ch6.
^ ^a ^b Asprey, L. B.; Keenan, T. K.; Kruse, F. H. (1964). "Preparation and Crystal Data for Lanthanide and Actinide Triiodides". Inorg. Chem. 3 (8): 1137–1141. doi:10.1021/ic50018a015.
^ ^a ^b ^c ^d Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 949–950. ISBN 978-0-08-037941-8.
^ Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. p. 420. ISBN 978-0-19-965763-6.
^ ^a ^b Ortu, Fabrizio (2022). "Rare Earth Starting Materials and Methodologies for Synthetic Chemistry". Chem. Rev. 122 (6): 6040–6116. doi:10.1021/acs.chemrev.1c00842. PMC 9007467. PMID 35099940.
^ Li, Yangjuan; Chen, Xiuting; Gong, Yu (2021). "Photoluminescence of LaI₃ switched on and off by association and dissociation of non-luminescent tetrahydrofuran". Dalton Trans. 50 (11): 3797–3800. doi:10.1039/D1DT00162K. PMID 33720234. S2CID 232232544.
^ Windorff, Cory J.; Dumas, Megan T.; Ziller, Joseph W.; Gaunt, Andrew J.; Kozimor, Stosh A.; Evans, William J. (2017). "Small-Scale Metal-Based Syntheses of Lanthanide Iodide, Amide, and Cyclopentadienyl Complexes as Analogues for Transuranic Reactions". Inorg. Chem. 56 (19): 11981–11989. doi:10.1021/acs.inorgchem.7b01968. PMID 28915015.
^ Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. p. 1250. ISBN 978-0-19-965763-6.
^ Burrow, J. H.; Maule, C. H.; Strange, P.; Tothill, J. N.; Wilson, J. A. (1987). "The electronic conditions in the 5d¹ layer-metal LaI₂ making comparison with the iso-electronic tantalum dichalcogenides, with the other RE di-iodides, and with the RE monochalcogenides". J. Phys. C: Solid State Phys. 20 (26): 4115–4133. Bibcode:1987JPhC...20.4115B. doi:10.1088/0022-3719/20/26/014.
^ Mattausch, Hj.; Oeckler, O.; Simon, A. (2003). "Crystal structure of dilanthanum pentaiodide, La₂I₅". Z. Kristallogr. NCS. 218 (3): 281. doi:10.1524/ncrs.2003.218.3.281. S2CID 94059677.
^ Ryazanov, Mikhail; Kienle, Lorenz; Simon, Arndt; Mattausch, Hansjürgen (2006). "New Synthesis Route to and Physical Properties of Lanthanum Monoiodide". Inorg. Chem. 45 (5): 2068–2074. doi:10.1021/ic051834r. PMID 16499368.

[1] Taylor, Moddie D. (1962). "Preparation of Anhydrous Lanthanon Halides". Chem. Rev. 62 (6): 503–511. doi:10.1021/cr60220a001.

[Corbett&Arndt-2] Corbett, John D. & Simon, Arndt (1984). "Chapter 6: Lanthanum Triiodide (and Other Rare Earth Metal Triiodides)". In Holt Jr., Smith L. (ed.). Inorg. Synth. Vol. 22. pp. 11–16. doi:10.1002/9780470132531.ch6.

[AspreyKeenanKruse-3] Asprey, L. B.; Keenan, T. K.; Kruse, F. H. (1964). "Preparation and Crystal Data for Lanthanide and Actinide Triiodides". Inorg. Chem. 3 (8): 1137–1141. doi:10.1021/ic50018a015.

[G&E-4] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 949–950. ISBN 978-0-08-037941-8.

[Wells420-5] Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. p. 420. ISBN 978-0-19-965763-6.

[Ortu-6] Ortu, Fabrizio (2022). "Rare Earth Starting Materials and Methodologies for Synthetic Chemistry". Chem. Rev. 122 (6): 6040–6116. doi:10.1021/acs.chemrev.1c00842. PMC 9007467. PMID 35099940.

[7] Li, Yangjuan; Chen, Xiuting; Gong, Yu (2021). "Photoluminescence of LaI₃ switched on and off by association and dissociation of non-luminescent tetrahydrofuran". Dalton Trans. 50 (11): 3797–3800. doi:10.1039/D1DT00162K. PMID 33720234. S2CID 232232544.

[8] Windorff, Cory J.; Dumas, Megan T.; Ziller, Joseph W.; Gaunt, Andrew J.; Kozimor, Stosh A.; Evans, William J. (2017). "Small-Scale Metal-Based Syntheses of Lanthanide Iodide, Amide, and Cyclopentadienyl Complexes as Analogues for Transuranic Reactions". Inorg. Chem. 56 (19): 11981–11989. doi:10.1021/acs.inorgchem.7b01968. PMID 28915015.

[Wells1250-9] Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. p. 1250. ISBN 978-0-19-965763-6.

[10] Burrow, J. H.; Maule, C. H.; Strange, P.; Tothill, J. N.; Wilson, J. A. (1987). "The electronic conditions in the 5d¹ layer-metal LaI₂ making comparison with the iso-electronic tantalum dichalcogenides, with the other RE di-iodides, and with the RE monochalcogenides". J. Phys. C: Solid State Phys. 20 (26): 4115–4133. Bibcode:1987JPhC...20.4115B. doi:10.1088/0022-3719/20/26/014.

[11] Mattausch, Hj.; Oeckler, O.; Simon, A. (2003). "Crystal structure of dilanthanum pentaiodide, La₂I₅". Z. Kristallogr. NCS. 218 (3): 281. doi:10.1524/ncrs.2003.218.3.281. S2CID 94059677.

[12] Ryazanov, Mikhail; Kienle, Lorenz; Simon, Arndt; Mattausch, Hansjürgen (2006). "New Synthesis Route to and Physical Properties of Lanthanum Monoiodide". Inorg. Chem. 45 (5): 2068–2074. doi:10.1021/ic051834r. PMID 16499368.

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