Zirconium(II) hydride

For the hydrogen-zirconium system, see Zirconium hydride.

Zirconium(II) hydride is a molecular chemical compound with the chemical formula ZrH₂. It is a grey crystalline solid or dark gray to black powder.^[4] It has been prepared by laser ablation and isolated at low temperature.^[6]

Zirconium(II) hydride^[1]

Names
IUPAC name Zirconium(II) hydride[2][3]
Other names Hydride;zirconium(2+)[2] Zirconium(2+) dihydride[2][3] Zirconium dihydride[2][3]
Identifiers
CAS Number	7704-99-6 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	24771611
ECHA InfoCard	100.028.844
EC Number	231-727-3
PubChem CID	4137802
UNII	YHL4O15288
CompTox Dashboard (EPA)	DTXSID10399770
InChI InChI=1S/Zr.2H Key: QSGNKXDSTRDWKA-UHFFFAOYSA-N
SMILES [ZrH2] [H-].[H-].[Zr+2]
Properties
Chemical formula	ZrH2
Molar mass	93.240 g/mol
Appearance	Grey tetragonal crystals or dark gray to black metallic powder[4]
Odor	Odorless[5]
Density	5.60 g/cm3
Melting point	800°C (decomposes)
Solubility in water	Insoluble[citation needed]
Solubility	Soluble in HF
Structure
Crystal structure	tetragonal
Molecular shape	dihedral (C2v)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Skin irritation, eye irritation, flammable[4]</ref>
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H228, H315, H319, H335
Precautionary statements	P210, P240, P241, P261, P264, P271, P280, P302+P352, P304+P340+P312, P305+P351+P338, P332+P313, P337+P313, P362, P370+P378, P403+P233, P405, P501
NFPA 704 (fire diamond)	1 3 1
Autoignition temperature	270 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Zirconium(II) hydride has repeatedly been the subject of Dirac–Hartree–Fock relativistic calculation studies, which investigate the stabilities, geometries, and relative energies of hydrides of the formula MH₄, MH₃, MH₂, or MH.

Zirconium(II) hydride has a dihedral (C_2v) structure. In zirconium(II) hydride, the formal oxidation states of zirconium and hydrogen are +2 and −1, respectively, because the electronegativity of zirconium is lower than that of hydrogen. The stability of metal hydrides with the formula MH₂ (M = Ti, Zr, Hf) decreases from Ti to Hf.

Uses

Zirconium(II) hydride is used as a thermal neutron moderator in nuclear reactors and as a material for neutron reflectors in fast reactors.^[5]

Zirconium(II) hydride in the form of a powder is used in powder metallurgy as a hydrogenation catalyst, vacuum tube getter, foaming agent in the production of metal foams and as a reducing agent.^[5]