Indium(III) Chloride
Properties
| State | Solid (anhydrous is hygroscopic; tetrahydrate is common commercial form) |
| Color | White to pale yellow |
| Solubility | Very soluble in water (1950 g/L as tetrahydrate); soluble in ethanol and ether |
| Melting Point | 586 °C (anhydrous) |
| Boiling Point | 800 °C (sublimes) |
About Indium(III) Chloride
Indium(III) chloride is the workhorse soluble In(III) source — a hygroscopic white salt that you almost always handle as the tetrahydrate InCl3·4H2O because the anhydrous form pulls water out of room air fast enough to liquefy on the bench. The anhydrous solid has a layered YCl3-type structure with octahedrally coordinated In(III); dissolve it in water and you get [In(H2O)6]^3+ at low chloride, sliding to [InCl4]- as you add Cl-. Its synthetic niche comes from where it sits on the Lewis-acid hardness scale: harder than the late transition metals and softer than Al(III) or Ti(IV), and water-tolerant where most strong Lewis acids are not. Strong classical Lewis acids (AlCl3, BF3, TiCl4) hydrolyze the moment they see a hydroxyl, which kills any chemistry in protic solvents. InCl3 keeps catalyzing through aqueous and wet-organic conditions, which has made it the go-to catalyst for green-chemistry versions of the Mukaiyama aldol, Sakurai allylation, Mannich reaction, Friedel-Crafts acylation of activated arenes, Markovnikov alkyne hydration, and acetal protection/deprotection. Beyond catalysis, InCl3 is the standard In(III) feedstock for solution-phase nanocrystal syntheses of InP, InAs, and CuInS2 quantum dots, and it shows up as the indium source in electroplating baths and as a dopant precursor for indium-doped phosphors and glasses.
Where you'll encounter it
If you've ever run an indium-mediated Barbier allylation in water at room temperature instead of fighting an anhydrous Grignard setup — or pulled red InP quantum dots out of an octadecene flask at 300 °C for a Cd-free LED — InCl3 was the indium source you weighed out. In a Mukaiyama aldol screen, a few mol% of InCl3·4H2O in wet THF will activate the silyl enol ether without the moisture-exclusion ritual that AlCl3 demands. In an indium-electroplating bath formulating bearing surfaces for aerospace bushings, InCl3 plus boric acid plus a brightener is the classical sulfate-free recipe. And if your nano-lab sintered an InP/ZnS core-shell QD batch for a QLED prototype tube, the InCl3 you started with traced through every step of the synthesis.
Common Uses
- Water-tolerant Lewis-acid catalyst for Mukaiyama aldol, Sakurai allylation, and Mannich reactions
- In(III) precursor for InP, InAs, and CuInS2 colloidal quantum-dot synthesis
- Indium source for In-doped phosphors and high-refractive-index optical glasses
- Electrolyte component in indium electroplating baths for bearing surfaces and solder finishes
- Indium reagent for Barbier-type allylations in aqueous media (organoindium chemistry)
Safety Information
GHS: Skin Corr. 1B, Eye Dam. 1, STOT-RE Cat 1 (respiratory tract). OSHA PEL 0.1 mg/m³ as In. Indium compounds cause 'indium lung' (pulmonary alveolar proteinosis with interstitial fibrosis) on chronic dust inhalation — first reported in ITO production workers and now established across all soluble In compounds. Use a fume hood with HEPA-filtered exhaust for any dry powder handling, and wear nitrile gloves and safety goggles for solutions. Hydrolyzes vigorously in moist air, releasing HCl gas; store in a desiccator under N2 or Ar.
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.