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Polonium hydride

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Polonium hydride
Structural formula of hydrogen polonide
Space-filling model of the hydrogen polonide molecule
  Polonium, Po  Hydrogen, H
Names
Preferred IUPAC name Polonium hydride
Systematic IUPAC name Polane
Other names
  • Hydrogen polonide
  • Polonium dihydride
  • Dihydridopolonium
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
Gmelin Reference 25163, 169602
PubChem CID
CompTox Dashboard (EPA)
SMILES
Properties
Chemical formula PoH2
Molar mass 210.998 g/mol
Melting point −35.3 °C (−31.5 °F; 237.8 K)
Boiling point 36.1 °C (97.0 °F; 309.2 K)
Conjugate base Polonide
Structure
Molecular shape Bent
Related compounds
Other anions H2O
H2S
H2Se
H2Te
Other cations TlH3
PbH4
BiH3
HAt
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

Polonium hydride (also known as polonium dihydride, hydrogen polonide, or polane) is a chemical compound with the formula PoH2. It is a liquid at room temperature, the second hydrogen chalcogenide with this property after water. It is very unstable chemically and tends to decompose into elemental polonium and hydrogen. It is a volatile and very labile compound, from which many polonides can be derived. Additionally, it is radioactive.

Preparation

Polonium hydride cannot be produced by direct reaction from the elements upon heating. Other unsuccessful routes to synthesis include the reaction of polonium tetrachloride (PoCl4) with lithium aluminium hydride (LiAlH4), which only produces elemental polonium, and the reaction of hydrochloric acid with magnesium polonide (MgPo). The fact that these synthesis routes do not work may be caused by the radiolysis of polonium hydride upon formation.

Trace quantities of polonium hydride may be prepared by reacting hydrochloric acid with polonium-plated magnesium foil. In addition, the diffusion of trace quantities of polonium in palladium or platinum that is saturated with hydrogen (see palladium hydride) may be due to the formation and migration of polonium hydride.

Properties

Polonium hydride is a more covalent compound than most metal hydrides because polonium straddles the border between metals and metalloids and has some nonmetallic properties. It is intermediate between a hydrogen halide like hydrogen chloride and a metal hydride like stannane.

It should have properties similar to that of hydrogen selenide and hydrogen telluride, other borderline hydrides. It is expected to be an endothermic compound, like the lighter hydrogen telluride and hydrogen selenide, and therefore would decompose into its constituent elements, releasing heat in the process. The amount of heat given off in the decomposition of polonium hydride is over 100 kJ/mol, the largest of all the hydrogen chalcogenides.

It is predicted that, like the other hydrogen chalcogenides, polonium may form two types of salts: polonide (containing the Po anion) and one from polonium hydride (containing –PoH, which would be the polonium analogue of thiol, selenol and tellurol). However, no salts from polonium hydride are known. An example of a polonide is lead polonide (PbPo), which occurs naturally as lead is formed in the alpha decay of polonium.

Polonium hydride is difficult to work with due to the extreme radioactivity of polonium and its compounds and has only been prepared in very dilute tracer quantities. As a result, its physical properties are not definitely known. It is also unknown if polonium hydride forms an acidic solution in water like its lighter homologues, or if it behaves more like a metal hydride (see also hydrogen astatide).

References

  1. ^ Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). Lehrbuch der Anorganischen Chemie (in German) (102 ed.). Walter de Gruyter. p. 627. ISBN 978-3-11-017770-1.
  2. Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, p. 594, ISBN 0-12-352651-5
  3. ^ Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry. New York: Academic Press. pp. 197–230. ISBN 9780120236046. Retrieved June 7, 2012.
  4. Weigel, F. (1959). "Chemie des Poloniums". Angewandte Chemie. 71 (9): 289–316. Bibcode:1959AngCh..71..289W. doi:10.1002/ange.19590710902.
Polonium compounds
Polonium(−II)
Polonium(II)
Polonium(IV)
Polonium(VI)
Hydrogen compounds
Binary compounds of hydrogen
Alkali metal
(Group 1) hydrides
Alkaline
(Group 2)
earth hydrides
Monohydrides
Dihydrides
Group 13
hydrides
Boranes
Alanes
Gallanes
Indiganes
Thallanes
Nihonanes (predicted)
  • NhH
  • NhH3
  • Nh2H6
  • NhH5
Group 14 hydrides
Hydrocarbons
Silanes
Silenes
Silynes
Germanes
Stannanes
Plumbanes
Flerovanes (predicted)
  • FlH
  • FlH2
  • FlH4
Pnictogen
(Group 15) hydrides
Azanes
Azenes
Phosphanes
Phosphenes
Arsanes
Stibanes
Bismuthanes
Moscovanes
Hydrogen
chalcogenides
(Group 16 hydrides)
Polyoxidanes
  • H2O
  • H2O2
  • H2O3
  • H2O4
  • H2O5
  • more...
  • Polysulfanes
    Selanes
    Tellanes
    Polanes
    Livermoranes
    Hydrogen halides
    (Group 17 hydrides)
  • HF
  • HCl
  • HBr
  • HI
  • HAt
  • HTs (predicted)
  • Transition metal hydrides
    Lanthanide hydrides
    Actinide hydrides
    Exotic matter hydrides
    Categories: