Structure and characterization of novel zinc(II) and cadmium(II) complexes with 2-(benzoylamino)benzenethiolate and 1-methylimidazole. NH· · ·S Hydrogen bonding in metal complexes with a S2N2 binding site

Abstract

Neutral four-co-ordinate zinc(II) and cadmium(II) complexes [M(S-2-PhCONHC₆H₄)₂(1-MeIm)₂]·0.5H₂O (M = Zn 1 or Cd 2, 1-MeIm = 1-methylimidazole), were synthesized and their structures determined by X-ray crystallography. In both complexes the metal atoms have distorted tetrahedral configurations with S₂N₂ binding sets. The formation of a NH· · ·S hydrogen bond in 1 and 2 was confirmed by IR spectroscopic measurements in the solid state. The solution properties of the complexes were investigated by NMR spectroscopy. In ¹H NMR spectra downfield shifted signals were observed for amide NH protons of complexes 1 and 2 in acetonitrile-d₃ solution. The results indicate that there are also interactions between the NH and sulfur atom in solution. Such non-covalent NH· · ·S interactions are considered to be important in controlling the conformation and properties of complexes with S₂N₂ binding sites.