Indium Halides - Intermediate Halides

Intermediate Halides

A surprising number of intermediate chlorides and bromides are known, but only one iodide, and no difluoride. Rather than the apparent oxidation state of +2, these compounds contain indium in the +1 and +3 oxidation states. Thus the diiodide is described as InIInIIIX₄. It was some time later that the existence of compounds containing the anion In₂Br₆2− were confirmed which contains an indium-indium bond. Early work on the chlorides and bromides involved investigations of the binary phase diagrams of the trihalides and the related monohalide. Many of the compounds were initially misidentified as many of them are incongruent and decompose before melting. The majority of the previously reported chlorides and bromides have now either had their existence and structures confirmed by X Ray diffraction studies or have been consigned to history. Perhaps the most unexpected case of mistaken identity was the surprising result that a careful reinvestigation of the InCl/InCl₃ binary phase diagram did not find InCl₂.
The reason for this abundance of compounds is that indium forms 4 and 6 coordinate anions containing indium(III) e.g. InBr₄−, InCl₆3− as well as the anion In₂Br₆2− that surprisingly contains an indium-indium bond.