Münzmetall-Lanthanid-Chalkogenide: I. Kupfer(I)-Lanthanid(III)-Sulfide der Zusammensetzung CuMS2 (M = La – Nd, Sm, Gd, Tb) im monoklinen A-Typ / Coinage Metal Lanthanide Chalcogenides: I. Copper(I) Lanthanide(III) Sulfides of the Composition CuMS2 (M = La – Nd, Sm, Gd, Tb) with the Monoclinic A-Type Structure

Abstract

Single crystals of the ternary copper(I) lanthanide(III) sulfides with the composition CuMS2 (M = La - Nd, Sm, Gd, Tb) form within seven days at 800 °C by oxidation of elemental copper and lanthanide metal with sulfur (molar ratio: 1 : 1 : 2) in evacuated silica tubes when equimolar quantitites of CsCl are present as flux. The crystal structures (monoclinic, P21/c, Z = 4; e. g. CuLaS2: a = 662.04(6), b = 730.89(6), c = 692.73(6) pm, β = 98.741(7)° and CuTbS2: a = 639.13(6), b = 700.02(6), c = 670.46(6) pm, β = 98.214(7)°) exhibit corrugated layers 2∞ {[Cu(S1)3/3(S2)1/1]3−} parallel to (100) which consist of vertex-linked pairs of [CuS4]7− tetrahedra sharing a common edge ([Cu2S6]10−). Their three-dimensional cross-linkage is achieved by M3+ cations in monocapped trigonal prismatic coordination of seven S2− anions. The metal sulfur distances in the [CuS4]7− units cover with 230 - 233 (Cu-S2) and 231 - 238 (Cu-S1) as well as 241 - 248 (Cu-S1’) and 245 - 251 pm (Cu-S1”) a rather broad range, whereas those within the [MS7]11− polyhedra lie relatively closer together (M-S: 276 - 307 pm). The present work is the first comprehensive account of the knowledge acquired from X-ray single-crystal diffraction data for the whole isotypic series CuMS2 (M = La - Nd, Sm, Gd, Tb).