Indium(III) chloride

Indium chloride is the chemical compound with the formula 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. This is one of three known indium chlorides.

Synthesis and structure

Being a relatively electropositive metal, indium reacts quickly with chlorine to give the trichloride. Indium trichloride is very soluble and deliquescent. A synthesis has been reported using an electrochemical cell in a mixed methanol-benzene solution.
Like [Aluminium chloride|] and [Thallium(III) chloride|], crystallizes as a layered structure consisting of a close-packed chloride arrangement containing layers of octahedrally coordinated In centers, a structure akin to that seen in [Yttrium(III) chloride|]. In contrast, [Gallium trichloride|] crystallizes as dimers containing. Molten conducts electricity, whereas does not as it converts to the molecular dimer,.
The tetrahydrate, InCl₃·4H₂O, crystallises in the orthorhombic crystal system. It consists of a unit of interconnected by two water of crystallizations. It is produced by the evaporation of a solution of indium chloride.

Reactions

is a Lewis acid and forms complexes with donor ligands, L,,,. For example, with the chloride ion it forms tetrahedral, trigonal bipyramidal, and octahedral.
In diethyl ether solution, reacts with lithium hydride, LiH, to form lithium tetrahydroindate. This unstable compound decomposes below 0 °C, and is reacted in situ in organic synthesis as a reducing agent and to prepare tertiary amine and phosphine complexes of [indigane|].
Trimethylindium,, can be produced by reacting in diethyl ether solution either with the Grignard reagent methylmagnesium iodide or methyllithium. Triethylindium can be prepared in a similar fashion but with the grignard reagent EtMgBr.
reacts with indium metal at high temperature to form the lower valent indium chlorides, and InCl.

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, 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.