A U(V) Chalcogenide: Synthesis, Structure, and Characterization of K₂Cu₃US₅

The compound K2Cu3US5 was obtained by the reaction of K2S, UCl4, CuCl, and S at 973 K. K2Cu3US5 crystallizes in a new structure type in space group Cmcm of the orthorhombic system in a cell of dimensions a = 3.9374(6) Å, b = 13.813(2) Å, c = 17.500(3) Å, and V = 951.8(2) Å3 at 153 K. The structure comprises [UCu3S52-] slabs separated by K+ cations. The slabs are built from CuS4 tetrahedra and US6 octahedra. Their connectivity differs from other known octahedral/tetrahedral packing patterns. In the temperature range 130−300 K the compound exhibits Curie−Weiss magnetic behavior with μeff = 2.45(8) μB. This result together with both the bond distances and bond valence calculations and the absence of a Cu2+ ESR signal support the formulation of the above compound as K+2Cu+3U5+S2-5.