The first rare-earth metal telluride chlorides, RTeCl (R = La, Ce, Pr, Nd)

The first rare-earth metal telluride chlorides, RTeCl with R = La, Ce, Pr, Nd, were obtained as single crystals and/or powder samples by the reaction of anhydrous rare-earth trichlorides, RCl₃, with the respective rare-earth metals R and elemental tellurium (Te) in sealed tantalum containers at temperatures as high as 1050 C. All four telluride-chlorides crystallize with the so-called tetragonal PbFCl type of structure but according to RTeCl = PbClF, with, for the example of LaTeCl-I, a = 451.7(1), c = 827.4(2) pm, V_E/Z = 84.5(1) Aa³, tetragonal, P4/nnm (No. 129). LaTeCl and CeTeCl are dimorphic, the second modification crystallizes with the PbCl₂ type of structure with, for LaTeCl-II, a = 795.2(1), b = 450.8(1), c = 940.4(1) pm, V_E/Z = 84.3(1) Aa³, orthorhombic, Pnma (No. 62). In both structures, La³⁺ is nine-coordinate, [LaTe₅Cl₄], with similar mean La-Te and La-Cl distances in both modifications, 333.2 vs. 333.1 pm and 302.9 vs. 301.8 pm, respectively. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)