Synthesis, characterization and crystal structure of four new asymmetric triazene ligands: An example of linear HgII complex with Hg... π secondary bonding interactions

Abstract

In this work, the asymmetric ligands [1-(phenyl)-3-(2-nitro-4-methylphenyl)]triazene (1), [1-(4- methylphenyl)-3-(2-nitro-4-methylphenyl)]triazene (2), [1-(4-ethylphenyl)-3-(2-nitro-4-methylphenyl)]triazene (3) and [1-(4-ethoxyphenyl)-3-(2-nitro-4-methylphenyl)]triazene (4), were synthesized. The reaction of the ligand (3) with HgCl 2 in methanol resulted in the formation of the [HgL 2] complex, (5). All compounds were characterized by means of CHN analysis, FT-IR, 1H NMR, 13C NMR spectroscopy. In addition, the crystal structures of the ligands (2) to (4) were investigated by single crystal X-ray analysis. In the solid state, all ligands exhibited trans conformation about the –N =N– double bond. The Hg II complex (5) crystallized in monoclinic system with C2/c space group. The triazene ligand was found to be deprotonated prior to coordination and acts as monodentate ligand. The Hg II which lies on inversion center (site symmetry ı̄), is surrounded by two N atoms from L ligands forming a linear geometry. The other two Hg–N bonds are relatively longer and can only be regarded as weak secondary bonds. Also, Hg- η 3-arene π-interactions are present in this compound. Hydrogen bonds, π⋯π and C–H ⋯π stacking interactions help in the stabilization of the resulted frameworks. These C–H ⋯π edge-to-face interactions are present with H ⋯π distance of 3.00 Å. Synthesis, characterization and X-Ray crystal structures of a few asymmetric triazenes with (–NH–N=N–) moieties and a linear HgII complex (HgL 2) with Hg...π secondary bonding interactions are described.