The coordination chemistry of periodate and tellurate ligands

Oldroyd, Richard Duncan (1994) The coordination chemistry of periodate and tellurate ligands. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Complexes of general formula M'MIO₆ have been synthesised for M = Ni, Mn, Ge, Sn and Pb all in the +4 oxidation state, and M' = Na, K, NH₄, Rb and Cs. X-ray powder diffraction (XPD) determined that a layered structure is adopted by these complexes, with space group P312 for M = Ni, Ge and P6₃22 for M = Sn, Pb. Multi-edge EXAFS was used to help assign lattice positions for the M and I atoms that could not be unambiguously determined by XPD, and to deduce the layered structure for the manganese complexes. The paramagnetism of the nickel complexes has been attributed to the presence of octahedral Ni(II) centres, with Ni(III) being observed in the Na and K salts. Temperature independent paramagnetism may also contribute.

Several periodate and tellurate complexes adopting discrete molecular structures have also been synthesised and their structures determined by the use of IR, UV/Visible ¹²⁵Te NMR and multi-edge EXAFS spectroscopy. The crystal structure of Rb₂Na₄[OsO₂(H₂TeO₆)₂].16H₂O has been determined. EXAFS studies have shown that the Ru(VI) bis-tellurate and the Os(VI) bis-periodate and tellurate complexes are all similar in structure, with two bidentately bound ligands and a trans-oxo group on the metal centre. The silver(III) and gold(III) bis-tellurates contain a square planar metal centre with two bidentate tellurate ligands. The manganese(IV) tris-tellurate complex, Na₇K[Mn(H₂TeO₆)₃].3H₂O, also contains bidentate ligands and is similar in structure to the analogous manganese(IV) tris-periodate. Several other complexes previously reported in the literature have also been examined by these techniques with attempts to synthesise new examples.

The co-ordination chemistry of telluracyclopentane (tcp), Te(CH₂)₄, has been investigated. Pd(II) and Pt(II) halide complexes of general formula MX₂(tcp)₂ (X = halide) were synthesised and characterised by ¹²⁵Te NMR, IR and UV/Visible spectroscopy. All complexes exist as trans isomers in the solid state and solution, with the exception of [Pt(tcp)₂Cl₂] which is cis in the solid state and a mixture of isomers in solution.(DX183,773)

This record has no associated files available for download.