Structure D 2000Investigations on Iodomercurates: Crystal Structures of Bis-tetramethylammonium Tetraiodomercurate(II), Tetramethylammonium Pentaiododimercurate(II) and Bis[di(12-crown-4)lithium]decaiodotetramercurate(II). -As revealed by single crystal XRD, compound (II) crystallizes in the orthorhombic space group P212121 with Z = 4, compound (III) in the orthorhombic space group Pcab with Z = 8, and compound (V) in the monoclinic space group P2 1 /c with Z = 2. The [Hg 2 I 5 ]ion in (III) has a polymeric sheet structure, built up from [Hg2I6] units bridged by [HgI4] groups sharing common apices. The [Hg4I10] 2ion in (V) consists of four [HgI4] tetrahedra sharing common edges. -(PICKARDT*, J.; WIESE, S.; BOROWSKI, M.; Z. Naturforsch., B: Chem. Sci. 61 (2006) 8, 935-941; Inst.