neodymium(III) Chloride
Properties
| State | Solid (hygroscopic; commonly hydrated) |
| Color | pink to rose |
| Solubility | Very soluble in water; soluble in alcohols |
| Melting Point | 763 °C (anhydrous) |
About neodymium(III) Chloride
NdCl3 (250.59 g/mol anhydrous) is the workhorse soluble Nd(III) salt — the gateway compound between the bulk neodymium oxide that comes out of mineral separation and the laser crystals, NdFeB precursor alloys, and butadiene-rubber catalysts that consume neodymium downstream. Commercially it ships as the rose-pink hexahydrate NdCl3·6H2O (358.68 g/mol), which is strongly hygroscopic and has to be stored in a desiccator or sealed container or it deliquesces overnight. Preparing the anhydrous form is harder than it looks: heat the hydrate in air and you get neodymium oxychloride NdOCl plus HCl, not NdCl3. The clean routes are vacuum sublimation, NH4Cl-assisted dehydration under inert gas (the ammonium chloride scavenges adsorbed water as gaseous HCl and NH3), or direct synthesis from Nd metal turnings and Cl2 at 700 °C. In the crystal, each Nd(III) center sits in 9-coordinate tricapped trigonal prismatic geometry with chloride — a typical coordination number for the early lanthanides where ionic radius is still large enough to support 8 or 9 nearest neighbors. The pink color comes from sharp, narrow 4f-4f transitions of the Nd(III) 4f3 configuration that absorb selectively around 580 nm, leaving red and blue to transmit through.
Where you'll encounter it
If you've ever set up a polymerization run for cis-1,4-polybutadiene rubber on the bench, you've probably used NdCl3 or one of its alkyl-aluminum-activated derivatives as the Ziegler-Natta catalyst — Nd-based systems give 96-98% cis content versus 92-94% for the older Ti-based ones, and most modern tire-grade BR comes from an Nd catalyst. In a teaching lab, dissolving a few crystals of NdCl3·6H2O in water gives a striking pink solution that turns lavender under fluorescent light versus pink under incandescent — the same alexandrite color-change effect that makes Nd-doped glass so distinctive. And in a magnetics-research group, anyone who has run reduction experiments on Nd salts has handled the hexahydrate as the starting point for converting back to anhydrous fluoride or to metal via molten-salt electrolysis.
Common Uses
- Catalyst for cis-1,4-polybutadiene rubber production for tire compounds
- Starting material for Nd:YAG and Nd:YVO4 laser-crystal growth
- Lewis-acid catalyst for selected Diels-Alder and aldol condensations
- Dopant precursor for phosphor and infrared-laser glass synthesis
- Feedstock for Nd metal via NdF3 conversion and calciothermic reduction
- Analytical reference for lanthanide ion-exchange and chromatography research
- Coordination-chemistry source of Nd(III) for crown ether and EDTA complex studies
Safety Information
GHS classifications: Skin Irritation Category 2, Eye Irritation Category 2A. Acute toxicity is moderate; the main hazard on the bench is HCl vapor evolved when the hygroscopic hydrate contacts moist air or when residues are dried in air rather than under vacuum. No OSHA PEL is set for soluble Nd compounds specifically, but ACGIH treats the entire rare-earth chloride family as nuisance dust requiring 5 mg/m3 respirable control. Use nitrile gloves, safety glasses, and a fume hood when weighing or recrystallizing. Store in a desiccator with silica gel or molecular sieves — exposed to humid lab air, the hexahydrate will pick up water and eventually deliquesce to a sticky pink slurry within days.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.