Expanded polycationic mercury–chalcogen networks in the layered compounds Hg 3E2[ MX6] ( E=S, Se; M=Zr, Hf; X=Cl, Br)

Abstract

The reactions of Hg E ( E=S, Se) with Hg X 2 and MX 4 ( M=Zr, Hf; X=Cl, Br) in evacuated glass ampoules lead to a series of isotypic compounds of the general formula Hg 3 E 2[ MX 6] in the form of colorless ( X=Cl) and light-yellow ( X=Br) air-sensitive crystals. The crystal structures of Hg 3S 2[ZrCl 6] (I), Hg 3S 2[HfCl 6] (II), Hg 3Se 2[ZrCl 6] (III), Hg 3Se 2[HfCl 6] (IV), Hg 3S 2[ZrBr 6] (V), and Hg 3Se 2[ZrBr 6] (VI) were refined based on single-crystal data. All compounds crystallize in the monoclinic space group P2 1/ a with the lattice parameters a=662.18(2) pm, b=734.97(3) pm, c=1290.83(5) pm, β=91.755(2)° for (I) and and a=701.97(3) pm, b=756.79(3) pm, c=1350.99(6) pm, β=92.164(3)° for (VI). The structures are built of (Hg 3 E 2) 2+ layers stacked perpendicular to the c-axis. The polycationic layers consist of two-dimensionally linked 12-membered Hg 6 E 6 rings in the chair conformation with linear coordinated Hg and trigonal pyramidal coordinated chalcogen atoms. Almost regular octahedral [ MX 6] 2− ions are embedded between the layers. This arrangement is closely related to the structure of Hg 3S 2[SiF 6], which represents a higher symmetric congener. The structure relation is discussed using the supergroup–subgroup relation between space groups.