Synthesis and Crystal Structure of Two New Quaternary Thallium(I) Copper(I) Lutetium(III) Selenides: TlCu3Lu2Se5 and Tl2Cu5Lu3Se8

Abstract

AbstractTlCu3Lu2Se5 and Tl2Cu5Lu3Se8 were prepared by the reaction of copper and lutetium metal with elemental selenium in an excess of TlCl as flux at 850 °C. Orange TlCu3Lu2Se5 or deep orange Tl2Cu5Lu3Se8 lath‐shaped crystals emerged from these reactions. TlCu3Lu2Se5 crystallizes in the orthorhombic space group Cmcm [a = 404.83(2), b = 1432.56(8), c = 1670.81(9) pm, Z = 4], whereas Tl2Cu5Lu3Se8 crystallizes in the monoclinic space group Cm [a = 1427.23(8), b = 404.59(2), c = 1464.37(8) pm, β = 110.52(1), Z = 2]. In both structures the Tl+ cations are eightfold coordinated with Se2– anions in the shape of a bicapped trigonal prism and the Cu+ cations are fourfold coordinated with Se2– anions in both single [CuSe4]7– and double tetrahedral [Cu2Se6]10– units. The latter copper‐selenium units are connected to each other through edges to build corrugated $\rm^{2}_{\infty}${[Cu3Se5]7–} layers in TlCu3Lu2Se5 and a three‐dimensional $\rm^{3}_{\infty}${[Cu5Se8]11–} framework in Tl2Cu5Lu3Se8. The lutetium Lu3+ cations are sixfold coordinated with Se2– anions in an octahedral environment. The [LuSe6]9– polyhedra form only double octahedral chains in the first compound, while both single and double chains are found in the second. The double chains are joined to each other through vertices to form markedly corrugated $\rm^{2}_{\infty}${[Lu2Se5]4–} layers in TlCu3Lu2Se5. In Tl2Cu5Lu3Se8 both single and double chains are connected to build less corrugated $\rm^{2}_{\infty}${[Lu3Se8]7–} layers. The two compounds are three‐dimensional anionic frameworks $\rm^{3}_{\infty}${[Cu3Lu2Se5]}– and $\rm^{3}_{\infty}${[Cu5Lu3Se8]}2–, respectively, in which the Tl+ cations occupy channels.