Bivalent metal complexes of 1,11-diamino-3,6,9-trithiaundecane and the crystal structures of adducts with nickel(II) and copper(II) bromides

Abstract

The hydrobromide salt of the quinquedentate ligand 1,11-diamino-3,6,9-trithiaundecane (L¹) reacts with copper(II) and nickel(II) acetates to form [MBrL¹] Br (M = Cu or Ni). By anion-exchange reactions a whole series of compounds of general formula [MXL¹]X′, X = CI, Br, I, or NCS, X′= Cl, Br, I, NCS, PF₆, or ClO₄, were prepared. Results of conductivity and spectroscopic measurements indicate that these species all contain six-co-ordinate metal ions. For two compounds the geometry was confirmed by X-ray crystallography. Crystals of [CuBrL¹] Br· H₂O are monoclinic, space group P2₁/m, Z= 2, a= 5.559(7), b= 10.009(11), c= 14.720(13)Å, and β= 90.0(1)°. Crystals of [NiBrL¹] Br are orthorhombic, space group Pmnb, Z= 4, a= 10.185(12), b= 16.963(12), and c= 9.028(7)Å. 843 and 968 Independent reflections above background have been collected on a diffractometer and refined to R 0.102, 0.067 respectively for M = Cu, Ni. Both structures contain discrete cations of formula [MBrL¹]⁺ which have crystallographically imposed C_s symmetry. The metal atoms are in distorted octahedral environments with bond lengths [M = Cu: M–N 2.03(2), M–S 2.340(6), 2.576(9), M–Br 3.310(5)] and [M = Ni : M–N 2.074(17), M–S 2.393(6), 2.437(8), M–Br 2.578(5)]. The Cu–Br and the longer of the Cu–S bonds are mutually trans and are particularly long due to the Jahn–Teller effect.