Polyanionic hydrides from polar intermetallics AeE2 (Ae = Ca, Sr, Ba; E = Al, Ga, In)

Area of Science:

• Materials Science
• Solid State Chemistry
• Inorganic Chemistry

Background:

• Polar intermetallic compounds AeE2 (Ae = Ca, Sr, Ba; E = Al, Ga, In) are known for their diverse structural and chemical properties.
• Investigating their hydrogenation behavior can lead to the discovery of novel hydride materials with potential applications.

Purpose of the Study:

• To systematically investigate the hydrogenation of polar intermetallic systems AeE2.
• To synthesize and characterize new hydride compounds formed from these systems.
• To elucidate the structural and electronic properties of the resulting hydrides.

Main Methods:

• Systematic hydrogenation experiments on AeE2 systems.
• X-ray powder diffraction and neutron diffraction for structural characterization of synthesized hydrides (SrGa2H2, BaGa2H2) and their deuterides.
• First-principles electronic structure calculations.

Main Results:

• Successful synthesis of new hydrides SrGa2H2 and BaGa2H2.
• Structural characterization revealed these compounds are isostructural to SrAl2H2, crystallizing in space group P3m1.
• Electronic structure calculations confirmed the presence of a novel two-dimensional polyanion [E2H2]2- with both E-E and E-H bonds.
• The hydrides decompose around 300°C and hydrogenation occurs at low temperatures (~200°C).

Conclusions:

• The synthesized compounds AeE2H2 are classified as polyanionic hydrides, featuring hydrogen as a terminating ligand within a polymeric anion.
• The polyanion [E2H2]2- exhibits unprecedented structural arrangements with E-E and E-H bonds.
• The low-temperature hydrogenation suggests the utility of the polar intermetallic polyanion precursor ([E2]2-) for hydride synthesis.