Pentamagnesium digallide

Pentamagnesium digallide, also known as magnesium gallide(−V), is a chemical compound in the family of magnesium gallides (Mg_xGa_y). This compound has gallium in the rare oxidation state −5 and is produced by splat quenching of a molten mixture of magnesium and gallium metal then heating the resulting substance to 350 °C:^[1][2]

5Mg + 2Ga → Mg₅Ga₂

Pentamagnesium digallide

Names
IUPAC name Pentamagnesium digallide
Other names Magnesium gallide(−V)
Identifiers
CAS Number	12064-14-1 N
3D model (JSmol)	Interactive image
ChemSpider	24593579
PubChem CID	78062207
CompTox Dashboard (EPA)	DTXSID30779590
InChI InChI=1S/2Ga.5Mg Key: BHKRUXZCMMTJBB-UHFFFAOYSA-N
SMILES [Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Ga-5].[Ga-5]
Properties
Chemical formula	Mg5Ga2
Molar mass	260.97 g/mol
Appearance	White crystalline solid
Density	3.08 g/cm3
Melting point	456 °C (853 °F; 729 K)
Structure
Crystal structure	Orthorhombic
Space group	Ibam
Point group	mmm
Lattice constant	a = 13.71 Å, b = 7.02 Å, c = 6.02 Å
Lattice volume (V)	579.06 Å3
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	-206.5 kJ/mol (calculated)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

It is an unwanted product when magnesium-gallium alloys are exposed to high temperatures.^[3]