Anomalous solution behaviour of isomorphous complexes of zirconium- and hafnium-(IV)

The synthesis of [Zr(IV)(egta)] and [Hf(IV)(egta)] in aqueous solution, where H-4egta = ethylenedioxydiethyl-enedinitrilotetraacetic acid, is reported. The eight-co-ordinate complexes have been characterised by X-ray crystallography, H-1 NMR spectroscopy, mass spectrometry and elemental analysis. The two compounds are isostructural in the solid state. Solution studies by H-1 NMR spectroscopy show that the hafnium analogue has a higher degree of symmetry. In particular, the spectrum of the zirconium complex reveals all of the methylene groups to be inequivalent whereas in the hafnium complex the -N (CH2CO2)2- and the -NCH2CH2O- methylene groups show increased magnetic equivalence.</p

IMMOBILIZATION OF THALLIUM BY TANDEM OXIDATION REDUCTION COMPLEXATION OF THALLIUM(I/III)

Development of management procedures for toxic superconducting thallium-copper-alkaline earth ceramics and their byproducts requires better understanding of the complexometric chemistry of thallium in the presence of copper and alkaline earth cations. This study reveals that thallium can be immobilized as a thallium-rich mixed-valence solid[(Tl18c6)4CuCl4][TlCl4]2.nH2O(1, n = 0; 2, n = 0.25). When either Tl(I) or Tl(III) is treated with 18-crown-6 (18c6) in the presence of copper(II) (or zinc) chloride, tandem oxidation (or reduction) complexation occurs to an extent sufficient to form 1 and/or 2. The divalent transition metal ion (M) plays a beneficial role of concentrating Tl+ as a cation [(Tl18C6)4MCl4]2+, M = Cu or Zn. The template concerted reduction/oxidation-complexation reactions appear to take advantage of the high stability of the TlC14 anions. Similar complexes are obtained if Cl- is replaced by Br-, Tl+ by Rb+, and Cu2+ by Mn2+ and Co2+. The crystal structures of 1, 2, (Rb18c6)2Cu2Cl6 (5), and (Ba18c6)2(CuCl4)2-3H2O(6) along with solid-state thallium-205 NMR spectra of 1,2,[(Tl18c6)4ZnCl4][TlCl4]2 (3), and [(Rb18c6)4CuCl4][TlCl4]2 (4) are reported. The cubic (F23) complexes 1, 2, and 4 feature a room-temperature average T(d) geometry for CuCl42- anions, and the T(d) nature (required by symmetry) of the position it occupies is confirmed by the luminescence of T(d) MnCl42- and the blue color of T(d) CoCl42- ions substituting for CuCl42- species. Crystal data are as follows. 1: cubic, space group F23 with a = 20.728 (2) angstrom, V = 8905.1 (9) angstrom3, and Z = 4; with 661 reflections having I &gt; 1-sigma(I), R = 0.038. 2: cubic, space group F23 with a = 20.748 (5) angstrom, V = 8932 angstrom3, Z = 4; with 549 independent reflections having \F(o)\ &gt; 3-sigma(\F(o)\), R = 0.043. 5: monoclinic, space group P2(1)/c with a = 11.100 (2) angstrom, b = 8.168 (1) angstrom, c = 22.626 (5) angstrom, beta = 97.55 (2)-degrees, V = 2034 angstrom3, and Z = 2; with 2456 reflections (\F(o)\ &gt; 3-sigma(\F(o)\)), R = 0.042. 6: triclinic P1BAR with a = 8.757 (3) angstrom, b = 17.174 (5) angstrom, c = 17.616 (6) angstrom, alpha = 66.23 (3)-degrees, beta = 77.31 (3)-degrees, gamma = 75.71 (2)-degrees, V = 2327.9 (13) angstrom, and Z = 2; using 6214 reflections (I &gt; 3-sigma(I)), R = 0.051.</p