View source for Zirconium(II) hydride

{{For|the hydrogen-zirconium system|Zirconium hydride}}
{{chembox
| verifiedrevid = 412151745
| Name = Zirconium(II) hydride
| Reference = <ref name="hand">{{Citation | last = Lide | first = David R. | year = 1998 | title = Handbook of Chemistry and Physics | edition = 87 | publication-place = Boca Raton, FL | publisher = CRC Press | isbn = 0-8493-0594-2 | pages = 4–96}}</ref>
| ImageFile = Zirconium(II)_hydride_powder.jpg
| IUPACName = Zirconium(II) hydride<ref name=pubchem></ref><ref name=chemspider></ref>
| OtherNames = {{ubl|Hydride;zirconium(2+)<ref name=pubchem>{{cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/Zirconium-dihydride | title=Zirconium dihydride }}</ref>|Zirconium(2+) dihydride<ref name=pubchem></ref><ref name=chemspider>{{cite web | url=http://www.chemspider.com/Chemical-Structure.24771611.html | title=Zirconium hydride &#124; H2Zr &#124; ChemSpider }}</ref>|Zirconium dihydride<ref name=pubchem></ref><ref name=chemspider></ref>}}
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 7704-99-6
| ChemSpiderID = 24771611
| InChI = 1S/Zr.2H
| InChIKey = QSGNKXDSTRDWKA-UHFFFAOYSA-N
| SMILES = [ZrH2]
| SMILES1 = [H-].[H-].[Zr+2]
| PubChem = 4137802
| EC_number = 231-727-3
| UNII = YHL4O15288
 }}
| Section2 = {{Chembox Properties
| Formula = {{chem2|ZrH2}}
| MolarMass = 93.240 g/mol
| Appearance = Grey [[tetragonal]] crystals or dark gray to black metallic powder<ref name=njgov/>
| Odor = Odorless<ref name="haz-map">{{cite web |title=Zirconium hydride |url=https://haz-map.com/Agents/8471 |publisher=Haz-Map |access-date=18 February 2025}}</ref>
| Density = 5.60 g/cm<sup>3</sup>
| MeltingPt = 800°C (decomposes)
| BoilingPt =
| Solubility = Insoluble{{CN|date=February 2025}}
| SolubleOther = Soluble in [[hydrofluoric acid|HF]]
 }}
| Section3 = {{Chembox Structure
| CrystalStruct = tetragonal
| MolShape = [[Molecular symmetry#Common point groups|dihedral]] (C<sub>2v</sub>)
 }}
| Section7 = {{Chembox Hazards
| GHSSignalWord = Danger
| GHSPictograms = {{GHS02}}{{GHS07}}
| MainHazards = Skin irritation, eye irritation, flammable<ref name=njgov/></ref>
| AutoignitionPt = 270 °C
| NFPA-H = 1
| NFPA-R = 1
| NFPA-F = 3
| HPhrases = {{H-phrases|H228|H315|H319|H335}}
| PPhrases = {{P-phrases|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}}
 }}
}}
'''Zirconium(II) hydride''' is a molecular [[chemical compound]] with the [[chemical formula]] {{chem2|ZrH2|auto=1}}. It is a grey [[crystaline|crystalline]] solid or dark gray to black powder.<ref name=njgov>{{cite web |title=Hazardous substance fact sheet |url=https://nj.gov/health/eoh/rtkweb/documents/fs/2048.pdf |website=nj.gov |publisher=New Jersey Department of Health and Senior Services |access-date=18 February 2025}}</ref> It has been prepared by laser ablation and isolated at low temperature.<ref name="ChertihinAndrews1995">{{cite journal|last1=Chertihin|first1=George V.|last2=Andrews|first2=Lester|title=Reactions of laser-ablated Zr and Hf atoms with hydrogen. Matrix infrared spectra of the MH, MH<sub>2</sub>, MH<sub>3</sub>, and MH<sub>4</sub> molecules|journal=The Journal of Physical Chemistry|volume=99|issue=41|year=1995|pages=15004–15010|issn=0022-3654|doi=10.1021/j100041a014}}</ref>

Zirconium(II) hydride has repeatedly been the subject of [[dirac equation|Dirac]]–[[hartree-Fock method|Hartree–Fock]] [[relativistic quantum chemistry|relativistic calculation studies]], which investigate the stabilities, geometries, and relative energies of hydrides of the formula {{chem2|MH4}}, {{chem2|MH3}}, {{chem2|MH2}}, or MH.

Zirconium(II) hydride has a [[Molecular symmetry#Common point groups|dihedral (C<sub>2v</sub>)]] structure. In zirconium(II) hydride, the formal [[oxidation state]]s of [[zirconium]] and [[hydrogen]] are +2 and −1, respectively, because the [[electronegativity]] of zirconium is lower than that of hydrogen. The stability of [[metal hydride]]s with the formula {{chem2|MH2}} (M = [[Titanium|Ti]], [[Zirconium|Zr]], [[Hafnium|Hf]]) decreases from Ti to Hf.

==Uses==
Zirconium(II) hydride is used as a thermal [[neutron moderator]] in [[nuclear reactor]]s and as a material for [[neutron reflector]]s in [[Nuclear reactor#By type of nuclear reaction|fast reactors]].<ref name=haz-map/>

Zirconium(II) hydride in the form of a [[powder]] is used in [[powder metallurgy]] as a [[hydrogenation]] [[catalyst]], [[Vacuum tube#Vacuum|vacuum tube getter]], [[foaming agent]] in the production of [[metal foam]]s and as a [[reducing agent]].<ref name=haz-map/>
==References==

{{reflist}}

==See also==
* [[Zirconium hydride]]

{{zirconium compounds}}

[[Category:Metal hydrides]]
[[Category:Zirconium(II) compounds]]