Copper(I) and Copper(II) Complexes of a New Tetradentate Chelating Ligand Containing Imidazole and Thioether Groups. The X-ray Structure of Trigonal-Bipyramidal bromocopper(II) Bromide

Article abstract of DOI:10.1021/ja00390a027

The synthesis and characterization of a new potentially tetradentate chelating imidazole-thioether ligand 1,6-bis(N-benzylimidazol-2-yl)-2,5-dithiahexane, <CH2SCH2>2, BBIDH, and some of its Cu^I, Cu^II, and Zn^II complexes are described.X-ray crystal structure determination showed that the Cu^II atom in Br*xsolvent is in a trigonal-bipyramidal coordination geometry with two axial imidazole N donor atoms (Cu-N = 1.93(2) and 1.94(2) Angstroem) and two thioether S atoms and a Br^- ion in equatorial plane (Cu-S = 2.565(6) and 2.470(6) Angstroem, Cu-Br = 2.417(3) Angstroem).The compounds crystallizes in space group P1/ with a = 8.397(2), b = 11.415(2), and c = 18.016(2) Angstroem, α = 103.74(1), β = 94.49(2), and δ = 100.48(2) deg, and Z = 2.Intensities of 3982 unique reflections (θ < 22 deg) were measured on an automatic diffractometer (Mo Kα radiation).The structure was solved by use of direct methods and refined with full-matrix least-squares techniques using the 1793 reflections with I > 2?(I) to a final R value of 0.071.From ESR and visible spectra, it was inferred that other solid Cu^II compounds also have a trigonal-bipyramidal coordination geometry, with H2O as the fifth ligand if no halogenide ions are available.The spectra of solutions of the Cu^II compounds indicate a change in coordination geometry.In I(BBIDH)>⁺, the Cu atom is probably linearly coordinated by two N atoms.The ZnCl2 adduct is a nonelectrolyte.The coordination chemistry of this imidazole-thioether ligand is in this respect not different from its earlier reported benzimidazole-containing analogon, (C7H5N2CH2SCH2)2, justifying the use of benzimidazole derivatives in model systems for the coordination of Cu in copper proteins.