Synthese und Kristallstrukturen von PrSe 2 und NdSe 2

Synthesis and Crystal Structures of PrSe 2 and NdSe 2 Crystals of PrSe 2 and NdSe 2 can be made by chemical transport reactions starting from pre‐annealed powders (800 – 600 °C, 2 weeks, I 2 as transport agent). Both compounds adopt the CeSe 2 ‐type structure. They crystallize in the monoclinic space group P 2 1 / a with four formula units and lattice parameters of a = 8.396(2) Å, b = 4.184(1) Å, c = 8.431(2) Å, and β = 90.08(4)° (PrSe 2 ) and a = 8.352(2) Å, b = 4.164(1) Å, c = 8.412(2) Å, and β = 90.00(3)° (NdSe 2 ), respectively. The crystal structures consist of puckered double layers of Ln and Se atoms and planar Se layers stacked in an alternating way along the crystallographic c axis. The Se atoms of the planar layers form diselenide dumb‐bells   2 2− , which are arranged in a herringbone‐like pattern. The Se–Se distances in the Se‐dimers are 2.467(1) Å in PrSe 2 and 2.476(1) Å in NdSe 2 .