Compounds of Indium

The usual valence of indium is three, although monovalent and bivalent compounds of indium with oxygen, halogens, and Group 15 (VA) and 16 (VIA) elements ate well known. The lower valence compounds tend to disproportionate into the trivalent compound and indium metal the trivalent compounds ate stable. 

Indiums low melting point is the major factor in determining its commercial importance. This factor makes it ideal for soldering the lead wires to semiconductors and transistors in the electronics industry. The compounds of indium arsenide, indium antimonide, and indium phosphide are used to construct semiconductors that have specialized functions in the electronics industry. 

There are many other compounds of indium, most of which are useful in the electronics and semiconductor industries. Some other examples are InP, Inj(SO )j, In Te, and InSb. 

Indium metal dust, particles, and vapors are toxic if ingested or inhaled, as are most of the compounds of indium. This requires the semiconductor and electronics industries that use indium compounds to provide protection for their workers. 

Renz 4 describes an additive compound of indium trichloride and pyridine, tripyridino-indium trichloride, [In(C5H5N)3]Cl3, which is prepared by adding pyridine to a solution of indium trichloride in alcohol. After standing for a short time, small needle-shaped crystals separate of melting-point 253° C. The compound is not hygroscopic like indium chloride, is somewhat sparingly soluble in alcohol, and is insoluble in ether. It decomposes on warming with water with formation of indium hydroxide, In(OH)3. Aluminium trichloride and iron trichloride form similar addition products. 

Salts of InCl2 and Ini2- (see Section 25.2.2.4) serve as the starting point for the synthesis of salts of [In(NCS)2], [In(NCO)2]- and [In(NCS)3]3 by metathesis in ethanol 13 the IR spectrum shows that both ligands are N-bonded in structures which are apparently bridged homopolymers in the solid state. No other pseudohalide compounds of indium(I) have been reported. 

Chapter 5 describes the chemistry of indium and thallium, including subvalent compounds of indium(II), thallium(II), and thallium(I). Applications of indium and thallium complexes are also described. 

Habeeb, J.J., Said, F.F. and Tuck, D.G. (1980) Coordination compounds of indium. Part XXXV. The direct electrochemical synthesis of adducts of indium(III) halides , 7. Chem. Soc., Dalton Trans., 1161-1163. 

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