Thiophenophanes and their coordination chemistry

Liu, Shuang (1990) Thiophenophanes and their coordination chemistry. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis describes studies of thiophenophane ligands and their coordination chemistry. In Chapter 1, aspects of macrocyclic thioether chemistry have been briefly reviewed. In Chapter 2, synthesis and characterization of eight thiophenophane ligands are described. The molecular structures of 2,5,8-trithia[9](2,5)thiophenophane, 2,5,8,1 l-tetrathia[12](2,5)thiophenophane and 2,5,9,13-tetrathia[ 13](2,5)thiophenophane have been determined by X-ray methods. The effect of the rigid thiophene subunit with its two attached methylenes on the solid state conformations of the three macrocycles is discussed. In chapter 3, synthesis and properties of 15 copper(I) and (II) complexes of thiophenophane ligands and the open-chain ligand, 2,5-bis(2-hydroxyethylthiomethyl)thiophene, are described. The molecular structures of seven of these compounds are presented and spectral details are interpreted in the light of these structures. The redox properties of the complexes have been examined by cyclic voltammetry and the effect of solvent on their electrochemistry is discussed. In the first part of Chapter 4, synthesis and properties of palladium(II) and platinum(II) complexes of open-chain and macrocyclic thioether ligands are presented. The molecular structure of [PdBr₂L1] (L1=2,5,8-trithia[9](2,5)thiophenophane) has been determined. Variable temperature ¹H nmr spectra show that the open-chain dithioether complexes undergo rapid conformational exchange at room temperature but are configurationally rigid while the macrocyclic thioether complexes, [MX₂L1] (M=Pt, X=C1; M=Pd, X=C1, Br, I, SCN), undergo very limited conformational and no configurational exchange up to their decomposition temperatures. Chemical exchange of acidic ligand hydrogens and a metal-ligand dissociative equilibrium were detected when M=Pd and X=SCN. In the second part of Chapter 4, preparations of seven π-allylpalladium complexes of open-chain dithioether and macrocyclic thiophenophane Iigands are described. The molecular structure of [Pd(C₃H₅)L1]⁺ reveals an asymmetric π-allyl group and a rare, unusually short apical Pd-S(thiophene) bond (2.786(4)A). Variable temperature ¹H nmr spectra of these complexes show that open-chain dithioether complexes undergo rapid inversion at coordinated sulfurs while the complex, [Pd(C₃H₅)L1]CF₃SO₃ undergoes a 14-metallotropic shift on the heteroatoms of the macrocycle at room temperature and a dissociative inversion at thioether sulfurs at elevated temperatures. In Chapter 5, synthesis and properties of thirteen silver(I) complexes are presented. The molecular structure of [Ag₂(L2)₂](ClO₄) ₂’ which contains a centrosymmetric dinuclear cation with a slightly distorted trigonal bypyramidal coordination geometry about each silver atom has been determined. The chemical and photochemical stabilities of these complexes are discussed with respect to the structure of [Ag₂(L2)₂](ClO₄) ₂²⁺.

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