Indium(I) chloride

Indium(I) chloride (also indium monochloride) is the chemical compound with the formula InCl. Indium monochloride occurs as a yellow cubic form below 120 °C and above this temperature as a red orthorhombic form. InCl is one of three known indium chlorides.

Synthesis and structure
InCl can be prepared by heating indium metal with indium trichloride in a sealed tube.

According to X-ray crystallography, the structure of the yellow polymorph resembles that of sodium chloride except that the Cl-In-Cl angles are not 90°, but range between 71 and 130°. The red (high T) polymorph crystallizes in the thallium(I) iodide motif.

Reactivity
The relatively high energy level of the 5s electrons of the indium center make InCl susceptible to oxidation as well as disproportionation into In(0) and InCl3. Tetrahydrofuran (THF) appears to facilitate the disproptionation of InCl as well as other indium(I) halides.

History
Indium(I) chloride was first isolated in 1926 as part of an investigation on the compounds formed between indium and chlorine.