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, VE/Z = 84.5(1) A3, 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, VE/Z = 84.3(1) A3, 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.