Gallium III Bromide

AnalaR bromine, which has been dried over phosphorus-(Y) oxide, is placed in flask A (see Fig. 3) and pellets of gallium (10 g.) are dropped into tube B which is then sealed at point 1. The apparatus, previously dried by flaming it under vacuum, is swept out with dry nitrogen and the gas is then passed through a sintered-glass bubbler under the bromine at a rate which is adjusted to give rapid reaction in tube B, though the flow rate should not be so fast that 

Gallium(III) bromide is a hygroscopic, white solid which sublimes readily and melts at 122.5° to a covalent, dimeric liquid. The solid is ionic and its electrical conductivity at the melting point is twenty-three times that of the liquid.5 The vapor pressure of the liquid at T°K is given by the equation log p(mm.) = 8.554 — 3129/T and the heat of dissociation of the dimer in the gas phase is 18.5 kcal./mol.3 At 125° the liquid has the following properties 5,6 density, 3.1076 dynamic viscosity, 2.780 c.p. surface tension, 34.8 dynes/cm. and specific conductivity, 7.2 X 10-7 ohm-1 cm.-1 Gallium(III) bromide readily hydrolyzes in water and forms addition compounds with ligands such as ammonia, pyridine, and phosphorus oxychloride. 

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In a three-necked flask equipped with a nitrogen inlet, pressure-equalized dropping funnel and a copper-coil reflex condenser and provided with magnetic stirring were placed dry pentane (100 mL) and gallium(III) bromide (29.3 g, 0.095 mol). Over a 90 min period, diethylzinc (18.2 g, 0.148 mol) was slowly introduced. The mixture deposited a precipitate, presumably zinc bromide, with a marked heat evolution. After a 2 h reflux period, the reaction suspension was centrifuged and the separated liquid phase was freed of pentane. Distillation of the residue yielded 10 g (66%) of triethylgallium. bp 43-44 X (16 mm). A hydrolyzed sample of this product still showed the presence of trace amounts of zinc. 

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