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
|
Lanthanum(II) iodide 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.
Praseodymium diiodide can be obtained by reacting praseodymium(III) iodide with metallic praseodymium at 800 °C to 900 °C in an inert atmosphere: [3]
It can also be obtained by reacting praseodymium with mercury(II) iodide where praseodymium displaces mercury: [3]
Praseodymium diiodide was first obtained by John D. Corbett in 1961. [4]
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]
With water, these processes take place much faster. [3]
Praseodymium diiodide has five crystal structures, namely the MoSi2 structure, the hexagonal MoS2 structure, the trigonal MoS2 structure, the cadmium chloride structure and the spinel structure. [5] Praseodymium diiodide with the cadmium chloride structure belongs to the trigonal crystal system, with the space group R3m (No. 166), 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]