Polonium dichloride

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Polonium dichloride
Polonium-dichloride-xtal-2x2x2-1955-3D-balls.png
Properties
Molecular formula PoCl2
Molar mass 279.91 g mol−1
Appearance ruby-red solid[1]
Density 6.50 g cm−3[2]
Melting point 355 °C (671 °F; 628 K) (sublimes at 130 °C)[1]
Structure
Crystal structure orthorhombic, oP3[2]
Space group Pmmm (No 47)
Lattice constant a = 0.367 nm, b = 0.435 nm, c = 0.450 nm
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Polonium dichloride is a chemical compound of the radioactive metalloid polonium and chlorine. Its chemical formula is PoCl2.

Structure[edit]

Polonium dichloride appears to crystallise with an orthorhombic unit cell in either the P222, Pmm2 or Pmmm space group, although this is likely a pseudo-cell. Alternatively, the true space group may be monoclinic or triclinic, with one or more cell angles close to 90°.[2] Assuming the space group is P222, the structure exhibits distorted cubic coordination of Po as {PoCl8} and distorted square planar coordination of Cl as {ClPo4}.

Distorted cubic coordination of polonium by eight chlorines Space-filling model of 2x2x2 unit cells (8 cells in total)

Preparation[edit]

PoCl2 can be obtained either by halogenation of polonium metal or by dehalogenation of polonium tetrachloride, PoCl4.[1] Methods for dehalogenating PoCl4 include thermal decomposition at 300 °C, reduction of cold, slightly moist PoCl4 by sulfur dioxide; and heating PoCl4 in a stream of carbon monoxide or hydrogen sulfide at 150 °C.[2]

Reactions[edit]

PoCl2 dissolves in dilute hydrochloric acid to give a pink solution, which autoxidises to Po(IV). PoCl2 is rapidly oxidised by hydrogen peroxide or chlorine water. Addition of potassium hydroxide to the pink solution results in a dark brown precipitate – possibly hydrated PoO or Po(OH)2 – which is rapidly oxidised to Po(IV). With dilute nitric acid, PoCl2 forms a dark red solution followed by a flaky white precipitate of unknown composition.[2]

References[edit]

  1. ^ a b c Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, p. 594, ISBN 0-12-352651-5 
  2. ^ a b c d e Bagnall, K. W.; d'Eye, R. W. M.; Freeman, J. H. (1955). "The polonium halides. Part I. Polonium chlorides". Journal of the Chemical Society (Resumed): 2320. doi:10.1039/JR9550002320.