Halide complexes gallium

Gallium(I), Halides of Ga(I) are known only in the vapor phase. Coordination complexes of GaCl and GaBr have been obtained with dioxane, morpholine, and acetylacetone. 

Gallium (Ga, at. mass 69.72) forms colourless Ga " ions. It occurs in solution exclusively in the III oxidation state. Gallium resembles aluminium and zinc in its properties. The hydroxide, Ga(OH)3, precipitates at pH 3, but dissolves in weakly alkaline media (pH 8-9). Gallium forms halide, oxalate, tartrate, acetate, and EDTA complexes. 

The choice of acid or base for solvent is simplified appreciably for melts containing complex ions (as a rule, they are anions), which are prone to the acid-base dissociation. Dissociation of this ion is assumed as the intrinsic acid-base equilibrium of a melt of such kind. In this case, the simpler eliminated anion will be considered as the base of the solvent and the coordinationally unsaturated residue will be the acidic particle of the solvent. Naturally, the division of particles formed by the auto-dissociation into acids and bases is made on the basis of the Lewis definition [13] an acid is the acceptor of an electron pair and a base is the donor of this electron pair. Ionic melts based on complex halides of gallium(III) [28], aluminium(III) [29] and boron(III) [30,31] may serve as examples of successful application of the above approach. The electron-deficient covalent halide (e.g. A1C13, BF3) in these melts is the solvent acid, and the corresponding halide ion is the base of the solvents ... 

Electrolytic procedures employing gallium metal in the form of a sacrificial anode can also be conveniently used to synthesize salts of the gallium(Ill) complex halide ions, [GaX4]. A straightforward procedure described here involves electrolysis of gallium in aqueous acid, HX, followed by heating to oxidize any Ga(II) species to Ga(III) ... 

The formation of molecular complexes between aluminum trihalides and pyridine or alkylpyridines has been the subject of systematic studies.35,36 Calorimetric data yield bond dissociation energies D(X3Al—py) of 323, 308 and 264 kJ mol-1 for X = C1, Br and I, respectively, and this same order is found for alkylpyridine adducts, although the A1—N bond is weakened in the case of lutidine by the effects of steric hindrance. For gallium halides the values of D(X3M—py) are smaller 248, 237 and 195 kJ mol-1 for chloride, bromide and iodide adducts, respectively. 

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