Metal-rich chalcogenides. Synthesis, structure, and bonding of the layered Lu11Te4. Comparison with the similar Sc8Te3 and Ti11Se4.

The high-yield synthesis of Lu11Te4 by reaction of the components and annealing at 1200 degrees C is described. The structure determined by single-crystal diffraction means is monoclinic C2/m, Z = 6, a = 30.412(3) A, b = 3.9504(4) A, c = 21.073(2) A, beta = 102.96 degrees and consists of two independent condensed puckered sheets of Lu separated by individual Te atoms. Notwithstanding, the geometric structure is closely related to but distinctly different from those of both Sc8Te3 and Ti11Se4 (also C2/m), principally through displacements of pairs of atoms (the structure of the last was determined by electron diffraction). Further, close electronic similarities among the three structures are demonstrated by EHTB results in terms of both effective atom charge and bond overlap population trends between equivalent positions or functions.