Zirconium(III) iodide

Zirconium(III) iodide is an inorganic compound with the formula ZrI₃.

Zirconium(III) iodide

Ball-and-stick model of a polymer chain of face-sharing octahedra in the crystal structure of zirconium(III) iodide
Ball-and-stick model of the packing of polymer chains in the crystal structure of zirconium(III) iodide
Names
IUPAC name Zirconium triiodide
Identifiers
CAS Number	13779-87-8 Y
3D model (JSmol)	Interactive image
PubChem CID	157424840
InChI InChI=1S/3HI.Zr/h3*1H;/q;;;+3/p-3 Key: BPVKTQRLRAVYEX-UHFFFAOYSA-K
SMILES [Zr+3].[I-].[I-].[I-]
Properties
Chemical formula	I3Zr
Molar mass	471.937 g·mol−1
Appearance	dark blue crystals[1]
Melting point	727 °C (1,341 °F; 1,000 K)
Structure
Crystal structure	Orthorhombic
Space group	Pmmn, No. 59
Lattice constant	a = 12.594 Å, b = 6.679 Å, c = 7.292 Å
Related compounds
Other anions	Zirconium(III) chloride Zirconium(III) bromide
Other cations	Titanium(III) iodide Hafnium(III) iodide
Related compounds	Zirconium(IV) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Like other group 4 trihalides, zirconium(III) iodide can be prepared from zirconium(IV) iodide by high-temperature reduction with zirconium metal, although incomplete reaction and contamination of the product with excess metal often occurs.^[2]

3 ZrI₄ + Zr → 4 ZrI₃

An alternative is to crystallise zirconium(III) iodide from a solution of zirconium(III) in aluminium triiodide. The solution is prepared by reducing a eutectic solution of ZrI₄ in liquid AlI₃ at a temperature of 280–300 °C with metallic zirconium or aluminium.^[3][4]

Structure and bonding

Zirconium(III) iodide has a lower magnetic moment than is expected for the d¹ metal ion Zr³⁺, indicating non-negligible Zr–Zr bonding.^[2]

The crystal structure of zirconium(III) iodide is based on hexagonal close packing of iodide ions with one third of the octahedral interstices occupied by Zr³⁺ ions.^[2] The structure consists of parallel chains of face-sharing {ZrI₆} octahedra^[5] with unequally spaced metal atoms. The Zr–Zr separation alternates between 3.17 Å and 3.51 Å.^[6]

ZrCl₃, ZrBr₃ and ZrI₃ adopt structures very similar to the β-TiCl₃ structure.^[2] In all three ZrX₃ there is some elongation of the octahedra along the metal-metal axis, partly due to metal-metal repulsion,^[4] but the elongation is most pronounced in the chloride, moderate in the bromide and negligible in the iodide.^[4]