Indium(III) chloride

Indium(III) chloride is the chemical compound with the formula InCl₃ which forms a tetrahydrate. This salt is a white, flaky solid with applications in organic synthesis as a Lewis acid. It is also the most available soluble derivative of indium.^[2] This is one of three known indium chlorides.

Indium(III) chloride

Anhydrous
Tetrahydrate
Indium(III) chloride
Names
Other names Indium chloride Indium trichloride
Identifiers
CAS Number	10025-82-8 Y
3D model (JSmol)	Interactive image
ChemSpider	23197 Y
ECHA InfoCard	100.030.027
EC Number	233-043-0
PubChem CID	24812
RTECS number	NL1400000
UNII	31JB8MKF8Z Y
UN number	3260
CompTox Dashboard (EPA)	DTXSID8033566
InChI InChI=1S/3ClH.In/h3*1H;/q;;;+3/p-3 Y Key: PSCMQHVBLHHWTO-UHFFFAOYSA-K Y InChI=1/3ClH.In/h3*1H;/q;;;+3/p-3 Key: PSCMQHVBLHHWTO-DFZHHIFOAF
SMILES Cl[In](Cl)Cl
Properties
Chemical formula	InCl3
Molar mass	221.17 g·mol−1
Appearance	white flakes
Density	3.46 g/cm3
Melting point	586 °C (1,087 °F; 859 K)
Boiling point	800 °C (1,470 °F; 1,070 K)
Solubility in water	195 g/100 mL, exothermic
Solubility in other solvents	THF, Ethanol
Structure
Crystal structure	Monoclinic, mS16
Space group	C12/m1, No. 12
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
GHS labelling:
Pictograms	[1]
Signal word	Danger[1]
Hazard statements	H302, H314[1]
Precautionary statements	P260, P301+P330+P331, P303+P361+P353, P305+P351+P338, P405, P501[1]
NFPA 704 (fire diamond)	2 0 0
Related compounds
Other anions	Indium(III) fluoride Indium(III) bromide Indium(III) iodide
Other cations	Boron trichloride Aluminium chloride Gallium trichloride Thallium(III) chloride
Related compounds	Yttrium(III) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Synthesis and structure

Being a relatively electropositive metal, indium reacts quickly with chlorine to give the trichloride. Indium trichloride is very soluble and deliquescent.^[3] A synthesis has been reported using an electrochemical cell in a mixed methanol-benzene solution.^[4]

Like AlCl₃ and TlCl₃, InCl₃ crystallizes as a layered structure consisting of a close-packed chloride arrangement containing layers of octahedrally coordinated In(III) centers,^[5] a structure akin to that seen in YCl₃.^[6] In contrast, GaCl₃ crystallizes as dimers containing Ga₂Cl₆.^[6] Molten InCl₃ conducts electricity,^[5] whereas AlCl₃ does not as it converts to the molecular dimer, Al₂Cl₆.^[7]

Reactions

InCl₃ is a Lewis acid and forms complexes with donor ligands, L, InCl₃L, InCl₃L₂, InCl₃L₃. For example, with the chloride ion it forms tetrahedral [InCl₄]⁻, trigonal bipyramidal [InCl₅]²⁻, and octahedral [InCl₆]³⁻.^[5]

In diethyl ether solution, InCl₃ reacts with lithium hydride, LiH, to form lithium tetrahydroindate(III) Li[InH₄]. This unstable compound decomposes below 0 °C,^[8] and is reacted in situ in organic synthesis as a reducing agent^[9] and to prepare tertiary amine and phosphine complexes of InH₃.^[10]

Trimethylindium, InMe₃, can be produced by reacting InCl₃ in diethyl ether solution either with the Grignard reagent methylmagnesium iodide CH₃MgI or methyllithium LiCH₃. Triethylindium can be prepared in a similar fashion but with the grignard reagent EtMgBr.^[11]

InCl₃ + 3 LiMe → Me₃In·OEt₂ + 3 LiCl

InCl₃ + 3 MeMgI → Me₃In·OEt₂ + 3 MgClI

InCl₃ + 3 EtMgBr → Me₃In·OEt₂ + 3 MgBr₂

InCl₃ reacts with indium metal at high temperature to form the lower valent indium chlorides In₅Cl₉, In₂Cl₃ and InCl.^[5]

Catalyst in chemistry

Indium chloride is a Lewis acid catalyst in organic reactions such as Friedel-Crafts acylations and Diels-Alder reactions. As an example of the latter,^[12] the reaction proceeds at room temperature, with 1 mole% catalyst loading in an acetonitrile-water solvent mixture. The first step is a Knoevenagel condensation between the barbituric acid and the aldehyde; the second step is a reverse electron-demand Diels-Alder reaction, which is a multicomponent reaction of N,N'-dimethyl-barbituric acid, benzaldehyde and ethyl vinyl ether. With the catalyst, the reported chemical yield is 90% and the percentage trans isomer is 70%. Without the catalyst added, the yield drops to 65% with 50% trans product.