Pb(18‐crown‐6)Cl 2 and Hg(18‐crown‐6)I 2 : Molecular Dihalides Trapped in a Crown Ether

Pb(18‐crown‐6)Cl 2 and Hg(18‐crown‐6)I 2 are obtained as transparent colourless crystals of needle and hexagonal shape, respectively, by isothermal evaporation of their dichloromethane solutions. Pb(18‐crown‐6)Cl 2 crystallizes with the trigonal crystal system [ $R{\bar 3}$ , no. 148, a = b = 1176.3(2), c = 1191.8(3) pm, V = 1428.2(5) 10 6 ·pm 3 , Z = 3] whereas Hg(18‐crown‐6)I 2 crystallizes with the orthorhombic crystal system ( Pnma , no. 62, a = 1613.9(2) pm, b = 2822.2(5) pm, c = 841.3(1) pm, V = 3832(1)10 6 ·pm 3 , Z = 8). Both compounds are characterized by linear MX 2 (HgI 2 or PbCl 2 ) molecular units which are encrypted by the crown ether. In both cases, the divalent metal ion resides in the middle of the crown ether resulting in a hexagonal bipyramidal coordination environment for the metal cations. The molecular symmetry comes close to D 3d . Hg(18‐crown‐6)I 2 and Pb(18‐crown‐6)Cl 2 differ in the way the single MX 2 @18‐crown‐6 units are packed. Whereas the Hg(18‐crown‐6)I 2 molecules are arranged in a (distorted) cubic closest packing, the Pb(18‐crown‐6)Cl 2 molecules adopt a hexagonal closest packing.