Copper-63 nuclear quadrupole resonance frequencies and molecular geometries of three-co-ordinate complexes of copper(I) halides with N-alkylimidazolidinethione and thiazolidinethione ligands

The crystal structures of seven three-co-ordinated complexes of copper(I) halides with thione ligands, [CuXL2], where L = 1,3-thiazolidine-2-thione and X = Cl or Br, L =N-ethylimidazolidine-2-thione and X = Br, L =N-isopropylimidazolidine-2-thione and X = Cl or Br, and L =N-propylimidazolidine-2-thione and X = Cl or I have been determined. In all complexes, the copper lies in a trigonal-planar environment and the thiazolidine or imidazolidine rings show no major distortion from planarity. Owing to the presence of hydrogen bonding involving H[N(2)], or H[N(02)], and the halogen atom all complexes adopt a W-shaped conformation. The 63Cu NQR frequencies of these complexes, together with those of two other similar complexes whose structures were already available, depend, for a given halide, on the S–Cu–S bond angle, a decrease in angle producing an increase in resonance frequency: νCl= 28.7 – 0.544Δθ and νBr= 26.9 – 0.229Δθ MHz, where Δθ is the difference between the S–Cu–S bond angle and 120°. This behaviour has been rationalized in terms of a partial field-gradient model of the resonance frequencies.