Physical Characterization of the Metallic LaI₂ and CeI₂ and of the Phase LaI_2.42

Praseodymium diiodide, PrI2, revisited by synthesis, structure determination and theory

“…Diiodides, MI 2 , were first discovered through phase diagram determinations of the systems M/MI 3 [1,2]. They are formed with most but not all of the rare-earth elements [3], those with terbium, holmium, erbium, and lutetium and yttrium as well are missing.…”

Rare-earth diiodides and derivatives

“…Group II rare-earth diiodides, MI 2 , were first uncovered through phase diagram determinations for the elements lanthanum, cerium and praseodymium [12,13]. They were, ther- modynamically speaking, assumed to be quite stable as their melting points are high (around 800 • C) and are sometimes even higher than those of the respective triiodides, MI 3 .…”

New materials from high temperature synthesis

“…This turns out to be a rather common structure now known not only for chlorides and/or bromides of zirconium and hafnium, where the formal electron count binding the double-metallayers is d3, but also in a dozen rare-earth metal monohalides where the configuration is d2. This decrease in electron count results in weaker bonding between metals in different layers, e.g., 3.09 A in ZrCl increasing to 3.51 A in YC1, together with a somewhat smaller increase within the layers as well. Such phases appear to be metallic, Pauli paramagnetic (except for lanthanide fn cores) and graphitic, with a decomposition point for ZrCl above 1100°C.…”

“…3) and classical halide clusters (which we here restrict to those of four or more atoms) such as (Nb,Ta)6X1211 (X = Cl,Br,I), CsNbX11 and (Mo,W)6X8m+ (Ref. 4).…”