Indium(III) hydroxide

Indium(III) hydroxide is the chemical compound with the formula In(OH)₃. Its prime use is as a precursor to indium(III) oxide, In₂O₃.^[1] It is sometimes found as the rare mineral dzhalindite.

Indium(III) hydroxide

Names
IUPAC name Indium(III) hydroxide
Other names Indium hydroxide, indium trihydroxide
Identifiers
CAS Number	20661-21-6 Y
3D model (JSmol)	Interactive image
ChemSpider	79974
ECHA InfoCard	100.039.937
EC Number	243-947-7
PubChem CID	88636
UNII	09J170CMXV Y
CompTox Dashboard (EPA)	DTXSID2074825
InChI InChI=1S/In.3H2O/h;3*1H2/q+3;;;/p-3 Key: IGUXCTSQIGAGSV-UHFFFAOYSA-K
SMILES [OH-].[OH-].[OH-].[In+3]
Properties
Chemical formula	In(OH)3
Molar mass	165.8404 g/mol
Appearance	White solid
Density	4.38 g/cm3
Melting point	150 °C (302 °F; 423 K) (decomposes)
Solubility in water	insoluble
Refractive index (nD)	1.725
Structure
Crystal structure	cubic
Space group	Im3
Coordination geometry	octahedral
Hazards
NFPA 704 (fire diamond)	2 0 1
Related compounds
Related compounds	Boric acid Aluminium hydroxide Gallium hydroxide Thallium(III) hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Structure

Indium(III) hydroxide has a cubic structure, space group Im3, a distorted ReO₃ structure.^[2][3]

Preparation and reactions

Neutralizing a solution containing an In³⁺ salt such as indium nitrate (In(NO₃)₃) or a solution of indium trichloride (InCl₃) gives a white precipitate that on aging forms indium(III) hydroxide.^[4][5] A thermal decomposition of freshly prepared In(OH)₃ shows the first step is the conversion of In(OH)₃·xH₂O to cubic indium(III) hydroxide.^[4] The precipitation of indium hydroxide was a step in the separation of indium from zincblende ore by Reich and Richter, the discoverers of indium.^[6]

Indium(III) hydroxide is amphoteric, like gallium(III) hydroxide (Ga(OH)₃) and aluminium hydroxide (Al(OH)₃), but is much less acidic than gallium hydroxide (Ga(OH)₃),^[5] having a lower solubility in alkaline solutions than in acid solutions.^[7] It is for all intents and purposes a basic hydroxide.^[8]

Dissolving indium(III) hydroxide in strong alkali gives solutions that probably contain either four coordinate [In(OH)₄]⁻ or [In(OH)₄(H₂O)]⁻.^[8]

Reaction with acetic acid or carboxylic acids is likely to give the basic acetate or carboxylate salt, e.g. (CH₃COO)₂In(OH).^[7]

At 10 MPa pressure and 250-400 °C, indium(III) hydroxide converts to indium oxide hydroxide (InO(OH)), which has a distorted rutile structure.^[5]

Rapid decompression of samples of indium(III) hydroxide compressed at 34 GPa causes decomposition, yielding some indium metal.^[9]

Laser ablation of indium(III) hydroxide gives indium(I) hydroxide (InOH), a bent molecule with an In-O-H angle of around 132° and an In-O bond length of 201.7 pm.^[10]