Neodymium(III) iodide

Neodymium(III) iodide is an inorganic salt of iodine and neodymium with the formula NdI3. Neodymium uses the +3 oxidation state in the compound. The anhydrous compound is a green powdery solid at room temperature.

Preparation
Heating neodymium and iodine in an inert atmosphere produces this salt:
 * 2 Nd + 3 I2 → 2 NdI3

It can also be prepared by the reaction of neodymium(III) oxide and hydroiodic acid to make a hydrate:
 * Nd2O3 + 6 HI → 2 NdI3 + 3 H2O

The anhydrate can then be obtained by heating the nonahydrate with ammonium iodide:
 * NdI3 • 9 H2O + nNH4I → NdI3 + nNH3 + nHI + 9H2O

Physical properties
Neodymium(III) iodide forms green, water-soluble hygroscopic crystals. It has a melting point of 784°C. It forms a nonahydrate crystal NdI3.9H2O – belongs to the orthorhombic crystal system, space group Pmmn, lattice constants a = 1.16604 nm, b = 0.80103 nm, c = 0.89702 nm, Z = 4.

Other compounds
NdI3 also forms some compounds with N2H4, such as NdI3·3N2H4·2H2O which is a dark green crystal, soluble in methanol and ethanol and insoluble in water, benzene and toluene, d20°C = 3.42 g/cm³.

NdI3 also forms some compounds with urea, such as NdI35CO(NH2)2 which is a lavender color crystal.

NdI3 also forms some compounds with thiourea, such as NdI3·2CS(NH2)2·9H2O which is a pale pink crystal.