samarium(III) Chloride
Properties
| State | Solid (hygroscopic; commonly hydrated) |
| Color | pale yellow |
| Solubility | Very soluble in water; soluble in alcohols |
| Melting Point | 795 °C (anhydrous) |
About samarium(III) Chloride
Samarium(III) chloride is a pale yellow hygroscopic salt with the anhydrous formula SmCl3 and a molar mass of 256.71 g/mol. The form you actually pull off a stockroom shelf is almost always the heptahydrate or hexahydrate — getting the anhydrous compound from aqueous solution is genuinely difficult because heating SmCl3·xH2O in moist air gives SmOCl (the oxychloride) and HCl rather than the chloride you wanted. The two clean routes are vacuum sublimation and the NH4Cl-assisted dehydration trick: grind the hydrate with a 6-fold excess of ammonium chloride, heat slowly under inert gas to about 300 °C to drive off water and HNH4Cl, then ramp to 400–500 °C to sublime away the residual NH4Cl. In the crystal the Sm(III) center is 9-coordinate in a tricapped trigonal prismatic geometry, which is the standard arrangement for the larger trivalent lanthanides. The most common synthetic use of SmCl3 is as a precursor to samarium(II) iodide (Kagan's reagent), the workhorse one-electron reductant behind Barbier allylations, pinacol couplings, and ketyl-olefin cyclizations in natural-product total synthesis.
Where you'll encounter it
If you've ever opened a bottle of SmCl3·6H2O and watched it slump into a wet yellow paste within minutes on a humid bench, you've met its hygroscopic personality firsthand. In a synthetic methods lab the more common encounter is the SmI2 generation: dissolving anhydrous SmCl3 in dry THF, adding methyl iodide and a sliver of samarium metal, and watching the deep blue-violet color of Kagan's reagent develop over an hour. That blue solution will reduce a ketone to a ketyl radical and stitch together a five-membered ring with stereocontrol that's hard to match by other means. Industrially, samarium-doped strontium aluminate phosphors using SmCl3 as the dopant precursor give the orange-red afterglow you see in some emergency exit signs and watch dial markers, courtesy of the Sm3+ 4G5/2 to 6H7/2 transition near 600 nm.
Common Uses
- Precursor to SmI2 (Kagan's reagent) for one-electron reductions in natural-product total synthesis
- Dopant source for Sm-doped strontium aluminate phosphors with orange-red 600 nm emission
- Mild Lewis-acid catalyst for selected aldol and Mukaiyama-type reactions
- Feedstock for samarium metal production by molten-salt electrolysis
- Starting material for organosamarium reagents in lanthanide methodology research
Safety Information
GHS classification: Skin irritation Category 2 (H315), Eye irritation Category 2A (H319), STOT SE 3 respiratory (H335). Hydrolyzes on skin and in lungs to release HCl, which drives most of the irritation. Lanthanide salts have low acute oral toxicity (rat LD50 for SmCl3 is roughly 3.5 g/kg) but chronic inhalation of lanthanide dusts is associated with pulmonary granulomas. No formal OSHA PEL is set; ACGIH treats soluble lanthanide compounds under the general nuisance-dust TLV of 10 mg/m3 total / 3 mg/m3 respirable. Weigh in a fume hood with nitrile gloves, safety glasses, and an N95 if generating dust during transfers.
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.