Gallium compounds

The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium.

At room temperature, gallium metal is not reactive with air and water because it forms a passive, protective oxide layer.

At higher temperatures, however, it reacts with atmospheric oxygen to form gallium(III) oxide, Ga2O3.

[3]: 162  Alternatively, Ga(OH)3 can be used at 747 °C:[8] Reacting a mixture of alkali metal carbonates and Ga2O3 with H2S leads to the formation of thiogallates containing the [Ga2S4]2− anion.

[2]: 1034  GaP, GaAs, and GaSb can be synthesized by the direct reaction of gallium with elemental phosphorus, arsenic, or antimony.

[10] Gallium forms ternary nitrides; for example:[7]: 99 Similar compounds with phosphorus and arsenic are possible: Li3GaP2 and Li3GaAs2.

[4] Unlike the trifluoride, gallium(III) chloride exists as dimeric molecules, Ga2Cl6, with a melting point of 78 °C.

GaCl can also be produced by reacting Ga with HCl at 950 °C; the product can be condensed as a red solid.

For example:[4][2]: 1036 [11] Like aluminium, gallium also forms a hydride, GaH3, known as gallane, which may be produced by reacting lithium gallanate (LiGaH4) with gallium(III) chloride at −30 °C:[2]: 1031 In the presence of dimethyl ether as solvent, GaH3 polymerizes to (GaH3)n. If no solvent is used, the dimer Ga2H6 (digallane) is formed as a gas.

Its structure is similar to diborane, having two hydrogen atoms bridging the two gallium centers,[2]: 1031  unlike α-AlH3 in which aluminium has a coordination number of 6.

[14] These alkylgalliums are liquids at room temperature, having low melting points, and are quite mobile and flammable.

Triphenylgallium is monomeric in solution, but its crystals form chain structures due to weak intermolecluar Ga···C interactions.

[13] Gallium trichloride is a common starting reagent for the formation of organogallium compounds, such as in carbogallation reactions.