Cadmium hydride: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 431436444

| OtherNames = Cadmium(II) hydride<br>Cadmium dihydride

|Section1={{Chembox Identifiers

| CASNo = 72172-64-6

| CASNo_Ref = {{cascite|changed|??}}

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 29331616

| PubChem = <!--57459443

| PubChem_Comment = monohydride -->

| SMILES = [H-].[H-].[Cd+2]

| InChI = 1/Cd.2H/q+2;2*-1

| InChIKey = IVRSYBKJJXDUEX-UHFFFAOYAR

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChI = 1S/Cd.2H/q+2;2*-1

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = IVRSYBKJJXDUEX-UHFFFAOYSA-N

}}

|Section2={{Chembox Properties

| Formula = {{Chem|CdH|2}}

| MolarMass = 113.419 g mol⁻¹

}}

|Section3={{Chembox Hazards

| REL = Ca<ref name=PGCH>{{PGCH|0087}}</ref>

| PEL = [1910.1027] TWA 0.005 mg/m³ (as Cd)<ref name=PGCH/>

| IDLH = Ca [9 mg/m³ (as Cd)]<ref name=PGCH/>

}}

|Section4={{Chembox Related

| OtherCompounds = [[Mercury(II) hydride]]

}}

'''Cadmium hydride''' (systematically named '''cadmium dihydride''') is an [[inorganic compound]] with the [[chemical formula]] {{Chem|(CdH|2|)|''n''}} (also written as {{Chem|([CdH|2|]}}{{Chem|)|''n''}} or {{Chem|CdH|2}}). It is a solid, known only as a thermally unstable, insoluble white powder.

== Nomenclature ==

The systematic name ''cadmium dihydride'', a valid [[IUPAC]] name, is constructed according to the compositional nomenclature. ''Cadmium dihydride'' is also used to refer to the related molecular compound ''dihydridocadmium'' and its oligomers. Care should be taken to avoid confusing the two compounds.{{cn|date=September 2023}}

''Cadmium hydride'' is also used as a compositional IUPAC name for the compound with the chemical formula CdH.

== History ==

In 1950 a research group led by Glenn D. Barbaras, [[chemical synthesis|synthesized]] cadmium hydride for the first time. This reaction sequence consisted of [[demethylation]]{{dubious|date=December 2014}} of dimethylcadmium in [[diethyl ether]] at −78&nbsp;°C, to cadmium hydride.<ref name=Barbaras1951>{{Cite journal|last1=Barbaras|first1=Glenn D.|last2=Dillard|first2=Clyde|last3=Finholt|first3=A. E.|last4=Wartik|first4=Thomas|last5=Wilzbach|first5=K. E.|last6=Schlesinger|first6=Hermann I.|title=The Preparation of the Hydrides of Zinc, Cadmium, Beryllium, Magnesium and Lithium by the Use of Lithium Aluminum Hydride|journal=Journal of the American Chemical Society|date=October 1951|volume=73|issue=10|pages=4585–4590|doi=10.1021/ja01154a025|publisher=ACS Publications}}</ref>

== Chemical properties ==

Solid cadmium hydride, on the basis of its infrared spectrum, is believed to contain hydrogen-bridge bonds.<ref name=Wang2004>{{Cite journal|last1=Wang|first1=Xuefeng|last2=Andrews|first2=Lester|title=Infrared Spectra of Zn and Cd Hydride Molecules and Solids|journal=The Journal of Physical Chemistry A|date=December 2004|volume=108|issue=50|pages=11006–11013|doi=10.1021/jp046414m|publisher=ACS Publications|bibcode=2004JPCA..10811006W}}</ref> Other lower metal hydrides polymerize in a similar fashion. Unless cooled below {{Convert|−20|C|F}}, cadmium hydride rapidly decomposes to produce [[cadmium]] and [[hydrogen]]:<ref name=Barbaras1951 />

:{{Chem|(CdH|2|)|''n''}} → ''n'' Cd + ''n'' {{Chem|H|2}}

== Dihydridocadmium ==

Dihydridocadmium is the monomeric, molecular form with the chemical formula {{Chem|CdH|2}} (also written {{Chem|[CdH|2|]}}). It is a colorless gas that does not persist undiluted. Dihydridocadmium has a low activation barrier toward autopolymerisation into the standard form of cadmium hydride and would rapidly do so in undiluted concentrations. Since the activation barrier for the reverse reaction is much greater than that of the decomposition reaction, autopolymerisation of dihydridocadmium may be considered as irreversible for most intents and purposes. It was produced by the gas phase reaction of excited cadmium atoms with [[dihydrogen]], H₂, and the structure determined high-resolution infrared emission spectra. The molecule is linear, with a bond length of 168.3 pm.<ref name="ShayestehYu2005">{{cite journal|last1=Shayesteh|first1=Alireza|last2=Yu|first2=Shanshan|last3=Bernath|first3=Peter F.|title=Gaseous HgH2, CdH2, and ZnH2|journal=Chemistry: A European Journal|volume=11|issue=16|year=2005|pages=4709–4712|issn=0947-6539|doi=10.1002/chem.200500332|pmid=15912545}}</ref>

=== Chemical properties ===

The two-coordinate hydridocadmium group (-CdH) in hydridocadmiums such as dihydridocadmium can accept an electron-pair donating ligand into the molecule by adduction:<ref name=Wang2004 />

:{{Chem|[CdH|2}}] + L → {{Chem|[CdH|2|L]}}

Because of this acceptance of the electron-pair donating [[ligand]] (L), dihydridocadmium has [[lewis acids and bases|Lewis-acidic]] character. Dihydridocadmium can accept two electron-pairs from ligands, as in the case of the tetrahydridocadmate(2−) anion ({{Chem|CdH|4|2−}}).

The compound, Cs₃CdH₅, prepared by the reaction of caesium hydride, CsH, and cadmium metal powder at high temperature contains the {{Chem|CdH|4|2−}} ion, along with caesium cations, Cs⁺, and hydride anions, H⁻. The tetrahedral anion is an example of an ionic complex of CdH₂. The average Cd-H bond length in {{Chem|CdH|4|2−}} is 182pm.<ref name="BortzGutmann1999">{{cite journal|last1=Bortz|first1=M.|last2=Gutmann|first2=M.|last3=Yvon|first3=K.|title=Synthesis and structure determination of the first ternary cadmium hydride, Cs3CdH5|journal=Journal of Alloys and Compounds|volume=285|issue=1–2|year=1999|pages=L19–L21|issn=0925-8388|doi=10.1016/S0925-8388(99)00031-6}}</ref>

In gaseous dihydridocadmium, the molecules form groups ([[trimer (chemistry)|trimers]]), being connected by [[van der Waals force]]s. The dissociation enthalpy of the dimer is estimated at 8.8 kJ mol⁻¹.<ref name=Wang2004 />

== References ==

{{Cadmium compounds}}

{{Hydrides by group}}