CuPrOS: No impressive acronym, rather a real quaternary chalcogenide with stuffed PbFCl-type crystal structure [German]

摘要

During attempts to synthesize copper(I) praseodymium(III) disulfide (CuPrS2) from 1:1:2-molar mixtures of the elements (Cu, Pr and S) after seven days at 850 degreesC in sealed evacuated silica tubes the almost quantitative formation of the quaternary chalcogenide CuPrOS indicated that some massive oxygen-contaminant (most probably surface-oxidized praseodymium metal) must have been present. The unexpected product becomes even single-crystalline and emerges as yellowish green transparent platelets with square cross-section when equimolar amounts of CsCl; work as fluxing agent. The crystal structure of CuPrOS (tetragonal, P4mm; a = 394.19(4), c = 843.98(9) pm; c/a = 2.141, Z = 2) can be described as an anionic PbFCl-type arrangement according to (2)(infinity){[(Pr3+)(O2-)(4/4)(S2-)(4/4)](-)} with Pr3+ in square-antiprismatic coordination of four F- and four S2- anions which is "stuffed" by Cu+ cations within tetrahedral interstices between the S2- double layers for charge balance. Another description emphasizes two kinds of layers (anionic (2)(infinity){[(Cu+)(S2-)(4/4)](-)} and cationic (2)(infinity){[O2-)(Pr3+)(4/4)](+)} ones) consisting of condensed [(Cu+)(S2-)(4)](7-) and [(O2-)(Pr3+)(4)](10+) tetrahedra, respectively, each of which share four of their six edges. Both types of square layers exhibit the same topology and are alternatingly sheethed parallel (001). The most important internuclear distances range from 233 (d(O-Pr), 4x) via 243 (d(Cu-S), 4x) up to 320 pm (d(Pr-S), 4x). [References: 18]