Synthesis and spectroscopic and structural properties of mercury(II) tetramethylthiourea complexes. Crystal structure of di-µ-bromo-bis-[bis(tetramethylthiourea-S)mercury(II)] tetrafluoroborate

Abstract

The structure of the title complex has been determined by X-ray diffraction methods. Crystals are triclinic, space group P, with unit-cell dimensions a= 12.554(6), b= 10.737(6), c= 8.362(4)Å, α= 111.93(2), β= 90.63(5), γ= 105.88(6)°, Z= 1 : R= 0.046. The structure comprises discrete [{Hg(tmtu)₂Br}₂]²⁺ binuclear cations and [BF₄]^– anions (tmtu = tetramethylthiourea). Each mercury(II) atom is four-co-ordinated by two sulphur and two bromine atoms, the bromines bridging two mercury(II) atoms to give a dimer. Also prepared and investigated are complexes of the type [{Hg(tmtu)₂X}₂]Y₂(X ≠ Y, X = Cl or Br, Y = BF₄ or ClO₄; X = Y = BF₄ or ClO₄) and Hg(tmtu)₄Y₂. The i.r. spectra (60–4 000 cm^–1) of all the complexes show shifts of the characteristic tetramethylthiourea bands suggesting co-ordination of the ligand through the sulphur atom. In the far-i.r. spectra of the complexes, metal–sulphur and halide bands have been assigned on the basis of C_i and T_d symmetry for the [{Hg(tmtu)₂X}₂]Y₂ and Hg(tmtu)₄Y₂ complexes, respectively.