Crystals of the adduct Hg(SCN)2 · 2HgCl2·2C6H12N4 were obtained from an aqueous solution containing 0.1 mol/l hexamethylenetetramine and 0.05 mol/l potassium thiocyanate and mercury(II) chloride. The compound crystallizes monoclinically; space group P21/n, a = 767.3(4), b = 1854.7(7), c = 872.5(7) pm, and β = 101.48(5)°. The structure consists of a net work of chains -Cl-Hg-Cl-Hg- and -(Cl-Hg-)2NCS-Hg-SCN-(Hg-Cl)2-which share common Hg atoms and form distorted hexagonal and trigonal channels. The hexamethylenetetramine molecules lie in the hexagonal channels. They act as μ3 bridging ligands, forming bonds to two Hg atoms in a given layer, and an additional bond to a Hg atom a neighbouring layer.
Einkristalle einer neuen Verbindung im System Cd(CN)2‐Hexamethylentetramin (HMTA) der Zusammensetzung [Cd(CN)2 · 2/3 C6H12N4] wurden durch Kristallisation aus einer wäßrigen Lösung von Cd(CN)2 und HMTA erhalten. Die Verbindung besitzt eine „supramolekulare”︁ Struktur von vernetzten CdCNCd‐ und CdHMTACd‐Ketten. Die Struktur wird mit der einer bereits bekannten Verbindung [Cd(CN)2 · 1/3 C6H12N4] verglichen.
Crystals of the adduct Cd(SCN )2 ·C6H12N4 · 2H2O were obtained by diffusion of an aqueous solution of hexamethylenetetramine into an aqueous solution of cadmium thiocyanate. The crystals are triclinic, space group P 1̄, Z = 2, a = 600.4(2), b = 1005.1(3), c = 1283.9(4) pm , α= 105.79(9), β = 102.63(7), γ = 103.65(3)°. Each cadmium atom is bonded to one hexamethylenetetramine ligand, one water molecule, and, via the N atoms, to two NCS groups, which act as bridging ligands and form bonds, via the S atoms, to adjacent cadmium atoms. Thus a polymeric chain structure is formed. There is an other water molecule present per formula unit, which is not coordinated to cadmium but is located in channels between the chains. Between the oxygen atoms of this water molecule and the oxygen atom of the coordination water molecule, as well as the nitrogen atom of the hexamethylenentetramine ligand, a system of hydrogen bonds is formed. The coordination of the cadmium atoms is approximately octahedral.
Reactions of 1,4-diazabicyclo[2.2.2]octane (“dabco”) with K2[HgI4] or Hg(SCN)2 yield crystals of [Hg(dabco)I2] (1) and [Hg(dabco)(SCN)2] (2). 1 crystallizes monoclinically, space group P21/a. Z = 4, a = 1211.6(5), b = 682.3(6), c = 1430.4(3) pm, β = 98.90(5)°; 2 is orthorhombic, space group Pmmn, Z = 2, a - 740.5(3), b = 609.1(4), c = 1220.0(8) pm. In 1 HgI2 groups are connected by bridging dabco molecules to give a chain structure. The Hg atoms are tetrahedrally coordinated. In 2 the Hg atoms are bridged by two SCN ligands and the chains thus formed are again interconnected by bridging dabco molecules, whereby layers are formed. The coordination polyhedron for the Hg atoms is a distorted octahedron.
Crystals of the adducts Zn(SCN)2 · (C6H12N4)2 (1), and {Zn(SCN)2 · C6H12N4 · 2H2O}n (2) were obtained by crystallization from aqueous solutions containing hexamethylenetetramine, potassium thiocyanate and zinc nitrate or zinc sulfate, resp., under identical conditions, as two totally different products. 1 crystallizes orthorhombically, space group P nmm, Z = 2, a = 622.4(5), b = 1152.3(7), c = 1394.0(9) pm; 2 is monoclinic, space group C2/c, a = 984.4(3), b = 1217.0(5), c = 1257.4(6) pm, and β = 111.69(5)°. The crystal structure of 1 contains discrete molecules of the complex, in which the zinc ion is tetrahedrally coordinated by two NCS ligands, and two hexamethylenetetramine molecules, which act as monodentate ligands. In 2 however, the zinc ions are octahedrally coordinated. A “supramolecular” structure is formed: The hexamethylenetetramine molecules act as bridging bidentate ligands and connect [Zn(H2O)2(NCS)2] units forming zig-zag chains. Adjacent chains are interconnected via hydrogen bonds. The formation of the two compounds with different coordination may be due to the fact, that the educts Zn(NO3)2 · 4H2O and ZnSO4 · 7H2O contain Zn(H2O)4 and Zn(H2O)6 moieties, resp., and that these species are retained in solution.
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