is the chemical compound
with the formula GaCl3
. Solid gallium trichloride exists as a dimer with the formula Ga2
. It is colourless and soluble in virtually all solvents, which is unusual for a metal halide. It is the main precursor to most derivatives of gallium
and a reagent in organic synthesis
As a Lewis acid, GaCl3 is milder than aluminium trichloride. Gallium(III) is easier to reduce than Al(III), so the chemistry of reduced gallium compounds is more extensive than for aluminium. Ga2Cl4 is known whereas the corresponding Al2Cl4 is not. The coordination chemistry of Ga(III) and Fe(III) are similar, and gallium(III) compounds have been used as diamagnetic analogues of ferric compounds.
Gallium trichloride can be prepared from the elements, heating gallium
metal in a stream of chlorine
, and purifying the product by sublimation under vacuum.
The dimeric structure involving two chlorine bridging atoms with the gallium atoms essentially tetrahedrally coordinated by chlorine is surprising, as the chlorides of the two members of group 13 above and below gallium, AlCl3
both contain 6 coordinate metal atoms in a three dimensional structure. As a consequence of its structure where there are no significant lattice forces, gallium trichloride has the lowest melting point of all of the aluminium, gallium and indium trihalides. The formula of Ga2
is often written as Ga2
. In the gas phase the dimers dissociate to trigonal planar
is the lightest member of Group 13 to have a full d
shell, (gallium has the electronic configuration Ar
1) below the valence electrons that could take part in d
-π bonding with ligands. This in terms, hard and soft acid-base theory
allows gallium(III) to behave as "soft" acid. The strength of the bonds between gallium halides and ligands have been extensively studied. What emerges is:
With a chloride ion as ligand the tetrahedral GaCl4− ion is produced, the 6 coordinate GaCl63− cannot be made. Compounds like KGa2Cl7 that have a chloride bridged anion are known
In a molten mixture of KCl and GaCl3, the following equilibrium exists:
- 2 GaCl4− Ga2Cl7− + Cl−
Use in detection of solar neutrinos
110 tons of gallium trichloride solution was used in the GALLEX
experiment performed by Laboratori Nazionali del Gran Sasso
in Italy to detect solar neutrinos
. In this experiment, isotope germanium
-71 was produced and its decay measured.
- Gallium. WebElements Periodic Table. .