Rare-earth diiodides and derivatives

The rare-earth diiodides, MI2, may be synthesized from the corresponding triiodides, MI3, by reduction with their metals at elevated temperatures or, alternatively, through so-called metallothermic reduction reactions with alkaline or alkaline-earth metals. In these cases, ternary iodides may be obtained that may be derived from the binary diiodides by either formal addition or substitution. Prominent formula types that are thus obtained are A(1)MI(3), or the mixed-valent A(5)(I)M(2)(II)M(III)I(12) and A(II)MI(4) with A(I) and A(II) representing alkaline or alkaline-earth elements (and their analogues), respectively. Further iodides that are relevant in these systems are, for example, Pr2I5, Ba6Pr3I19 and interstitially stabilized phases such as {Er-14(N-2)(C-2)(2)}I-24, La9O4I16 and Ba{Ce4N2}I-8. (C) 2004 Elsevier B.V. All rights reserved.