Praseodymium diiodide

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Praseodymium diiodide
Identifiers
Properties
I2Pr
Molar mass 394.71660 g·mol−1
Appearance bronze solid[1][2]
Melting point 758 °C[1][2]
Related compounds
Other cations
Cerium(II) iodide
Neodymium(II) iodide
Related compounds
 Praseodymium(III) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Praseodymium diiodide is a chemical compound with the empirical formula of PrI2, consisting of praseodymium and iodine. It is an electride, with the ionic formula of Pr3+(I−)2e−,[2] and therefore not a true praseodymium(II) compound.

Preparation

Praseodymium diiodide can be obtained by reacting praseodymium(III) iodide with metallic praseodymium at 800 °C to 900 °C in an inert atmosphere:[3]

Pr + 2 PrI3 → 3 PrI2

It can also be obtained by reacting praseodymium with mercury(II) iodide where praseodymium displaces mercury:[3]

Pr + HgI2 → PrI2 + Hg

Praseodymium diiodide was first obtained by John D. Corbett in 1961.[4]

Properties

Praseodymium diiodide is an opaque, bronze-coloured solid with a metallic lustre that is

soluble in water.[3] The lustre and very high conductivity can be explained by the formulation {PrIII,2I−,e−}, with one electron per metal centre delocalised in a conduction band.[2]

The compound is extremely

hygroscopic, and can only be stored and handled under carefully dried inert gas or under a high vacuum.[citation needed] In air it converts into hydrates by absorbing moisture, but these are unstable and more or less rapidly transform into oxide iodides with the evolution of hydrogen:[citation needed
]

2PrI2 + 2H2O → 2PrOI + H2↑ + 2HI

With water, these processes take place much faster.[3]

Praseodymium diiodide has five

lattice parameters a = 426.5 pm and c = 2247,1 pm; however, the spinel structure of praseodymium diiodide is cubic,[6] with space group F43 (No. 216), and lattice parameter a = 1239.9 pm.[7]

References

  1. ^
    OCLC 793213751
    .
  2. ^
    ISBN 978-0-08-037941-8
    .
  3. ^
    OCLC 310719485
    .
  4. OCLC 86225074
    .
  5. OCLC 237200027
    .
  6. doi:10.1002/zaac.19794590120
    .
  7. ISSN 0925-8388
    .
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