Pb(18-crown-6)Cl2 and Hg(18-crown-6)I2: 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 (3) over bar, 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 MX2 (Hgl(2) or PbCl2) 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 MX2@18-crown-6 units are packed. Whereas the Hg(18-crown-6)l, molecules are arranged in a (distorted) cubic closest packing, the Pb(18-crown-6)Cl-2 molecules adopt a hexagonal closest packing.