Sulphur ligand–metal complexes. Part 16. Copper complexes of thioethers and the single-crystal X-ray structure of the polymeric mixed-valence complex, penta-µ-chloro-tris-µ-tetrahydrothiophene-tetracopper(I,II)

Abstract

The interaction of the cyclic, thioether ligand, L¹(tetrahydrothiophene), with CuCl₂·2H₂O in acetone yields the polymeric, mixed-valence complex [{Cu^I₃Cu^IIL¹₃Cl₅}_n], the crystal and molecular structure of which has been determined by X-ray diffraction techniques. Crystals of the complex are monoclinic, space group P2₁/n, with a= 12.2288(6), b= 13.0277(7), c= 14.0605(7). Å, β= 95.815(4)°, and Z= 4. The structure was solved by direct methods and Fourier-difference techniques, and refined by block-diagonal least squares to R= 0.029 for 2 770 observed intensities. The structure is polymeric with µ-Cl or µ-L¹ linkages between Cu atoms giving rise to three different ring systems, viz.[Cu(µ-Cl)]₂ and [Cu(µ-L¹)]₃ fused to [Cu(µ-L¹){Cu(µ-Cl)}₂]. The copper atoms designated as Cu^II are bound to four chlorine atoms to give a geometry intermediate between tetrahedral and square planar, and those designated as Cu^I have distorted tetrahedral S₂Cl₂ donor sets. This complex, if left in its mother-liquor, forms the oxidised thioether ligand complex [{Cu(L¹O)Cl₂}_n](L¹O = tetrahydrothiophene 1-oxide). Other cyclic thioethers, L²(thiacyclohexane) and L³(1,3-dithiacyclopentane), from either copper(I) or copper(II) complexes: [CuLX](L = L¹ or L³, X = Cl or Br; L = L², X = Cl), [(CuCl)₃L¹₂], [CuL³₂]ClO₄·2H₂O, and [CuL³Cl₂]. The bidentate thioethers L⁴(2,2,7,7-tetramethyl-3,6-dithiaoctane), L⁵(3,8-dithiadecane), L⁶(2,9-dithiadecane), and L⁸[3,4-di(methylthio)toluene] yield the complexes: [CuLX](L = L⁴, X = Cl or Br), [(CuX)₂L](L = L⁴ or L⁵; X = Cl, Br, or I), [CuL₂]BF₄(L = L⁴ or L⁵), [(CuCl₂)₂L⁴], [CuL⁴(NO₃)₂]·H₂O, [(CuX)₃L⁶₂](X = Cl, Br or I), and [CuL⁸Cl₂]. The ligand L⁷(tetradecylthioacetate ion) forms the copper(II) complex [CuL⁷₂]·2H₂O. These complexes have been characterised by a variety of spectroscopic techniques and, where possible, structures are proposed.