This work set out to develop synthetic routes to transition metal complexes containing the ligands of general type [PPh₂(X)][PPh₂(Y)][PPh₂(Z)]CH and [PPh₂(X)][PPh₂(Y)][PPh₂(Z)]C⁻, where X, Y, Z = various combinations of O, S, Se and electron pairs. The aim would then be to fully characterise the complexes by various spectroscopic methods to determine the modes of coordination of the ligands and rationalise any dynamic processes which may be occurring in solution. Finally the complexes would be investigated in terms of chemical reactivity, especially with regards to potential catalytic activity. The synthesis and characterisation of a series of rhodium, iridium, platinum, and palladium complexes containing the phosphine chalcogenide ligands, [CH(P(S)Ph₂)₃]/[C(P(S)Ph₂)₃]⁻ and [CH (PPh₂)(P(S)Ph₂)₂]/[C(PPh₂)(P(S)Ph₂)₂]⁻, are described.The crystal structures of seven of these complexes plus that of the ligand, [CH(PPh₂)(P(S)Ph₂)₂], have been determined. These structures include [Pd(n³-C₄H₇){CH(PPh₂)(P(S)Ph₂)₂-P,S}]BF₄ 2H₂O, [Pd(n³-QH₇){CH(P(S)Ph₂)₃-S,S,S]BF4, [Rh(cod){C(P(S)Ph₂)₃-S,S}], [Ir(CO)3 {C(P(S)Ph₂)3 -S,S}], [Rh(cod){C(PPh₂(P(S)Ph₂)₂-P,S}] CH₂Cl₂. [Rhl₂CBuNC)₂ {C(PPh₂)(P(S)Ph₂)₂-P,S}], and [Ir(cod){CH(PPh₂)(P(S)Ph₂)₂-P,S}]BF₄ CH₂Cl₂, which are all discussed in detail. The [CH(P(S)Ph₂)₃] ligand coordinates in an n³ mode to metal centres. The anionic ligand [C(P(S)Ph₂)₃]⁻ coordinates to metals in an n² mode using two of its sulphur atoms, leaving a -P(S)Ph₂ group dangling. The ligand, [CH(PPh₂)(P(S)Ph₂)₂], can either coordinate in an n² P,S mode, using a phosphorus and a sulphur atom, or in an n³ P.S.S mode using a phosphorus and two sulphur atoms. The anionic ligand, [C(PPh₂)(P(S)Ph₂)₂], acts as a four electron donor, using one phosphorus and one sulphur atom, to metal centres. The reaction of [Ir(cod){C(P(S)Ph₂)₃-S,S}] with CO to give [Ir(CO)₂{C(P(S)Ph₂)₃-S,S}] is described. The reaction of [Rh(cod){C(PPh₂)(P(S)Ph₂)₂-P,S}] with tBuNC to give [Rh(tBuNC)₂{C(PPh₂)(P(S)Ph₂)₂-P,S}] is discussed. The subsequent oxidative additions of I₂ and benzyl bromide, to give isomeric mixtures of [RhI₂(tBuNC)₂{C(PPh₂)(P(S)Ph₂-P,S}] and [RhBr)(Bz)(tBuNC)₂ {C(PPh₂)(P(S)Ph₂)₂-P,S}] respectively, are also presented. The fluxional behaviours of [Pd(n³-C₄H₇){CH(PPh₂(P(S)Ph₂)₂-P,S}]BF₄, [Pd(n³-₄H₇){C(P(S)Ph₂)3-S,S}, [Pt(MeOcod){C(P(S)Ph₂)₃-S,S}], and [Rh(cod){C(P(S)Ph₂)₃}] are discussed in detail.The two -Ph₂P=S groups in the above complexes undergo a rapid intramolecular site exchange at ambient temperature in solution. Line shape analysis of variable temperature ³¹P{¹H} NMR data gives the following ΔG° for this dynamic exchange of coordinated and noncoordinated sulphur at 298 K. [Pd(n³-C₄H₇){CH(PPh₂)(P(S)Ph₂)₂-P,S)}]BF₄ 48 kJ/mol [Pd(n³-C₄H₇ ){C(P(S)Ph₂)₃-S,S}] 38 kJ/mol [Pt(MeOcod){C(P(S)Ph₂)₃-S,S}] 48 kJ/mol [Rh(cod){C(P(S)Ph₂)₃-S,S}] 46 kJ/mol / Graduate

Prof. A. Roodt

Eight rare earth complexes with bis(2-pyridylmethyl)amine (DPA) were synthesised and recrystallised, under air-sensitive or low moisture conditions. The crystal structures were successfully determined, via SC-XRD, and the asymmetric units of five complexes (1, 3, 5, 6 and 7) were submitted for DFT molecular modelling calculations, which involved geometry optimisation and frequency calculations. The neutral complexes obtained were bis(bis(2-pyridylmethyl)amine)-trichloro-lanthanum(III) [LaCl3(DPA)2] (1), bis(bis(2-pyridylmethyl)amine)-trichloro-cerium(III)) [CeCl3(DPA)2] (2), bis(μ2-chloro)-diaqua-tetrachloro-bis(bis(2-pyridylmethyl)amine)-di-praseodymium(III) [PrCl2(μ-Cl)(DPA)(OH2)]2 (3) and bis(μ2-methoxo)-bis(bis(2-pyridylmethyl)amine)- tetrachloro-di-dysprosium(III) [DyCl2(μ-OCH3)(DPA)]2 (4). The cationic complexes obtained in this study were dichloro-bis(bis(2-pyridylmethyl)amine)- neodymium(III) chloride methanol solvate [NdCl2(DPA)2]Cl·CH3OH (5), dichloro-bis(bis(2- pyridylmethyl)amine)-dysprosium(III) chloride methanol solvate [DyCl2(DPA)2]Cl·CH3OH (6), dichloro-bis(bis(2-pyridylmethyl)amine)-yttrium(III) chloride methanol solvate [YCl2(DPA)2]Cl·CH3OH (7) and dichloro-bis(bis(2-pyridylmethyl)amine)-lutetium(III) chloride methanol solvate [LuCl2(DPA)2]Cl·CH3OH (8). The ‘Quantum theory of atoms in molecules’ approach was used to investigate the electron density topology, primarily in order to investigate the hydrogen and coordination bonds for three of the eight complexes. Two of the neutral complexes contain the ‘early’ rare earth elements lanthanum and praseodymium and one cationic complex contains the ‘late’ lanthanide element dysprosium. Noncovalent interaction analysis was also performed on the aforementioned complexes in order to gain a deeper understanding of the intra-molecular stereo-electronic interactions. Spin density analysis was used to investigate the distribution of unpaired electron density at and around the metal centres of the aforementioned paramagnetic Pr- and Dy-complexes. A ligand conformation search for DPA was undertaken and 32 low energy conformers were identified and their relative energies were determined using two DFT functionals, namely M06 and M06-2X.

The role of metal ions as catalysts for numerous biochemical reactions has been the subject of many investigations. One of the most important classes of ligands are phosphate esters. In this thesis I describe the investigation of some phosphate ester-metal ion equilibria. Formation constants for the complexation of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate, methyl phosphate, 8-quinolyl phosphate, 8-quinolyl methyl phosphate, triphosphate and fluorotriphosphate with protons, copper, zinc and calcium ions were determined by potentiometry. In addition, the complexation of 1-naphthyl phosphate, 8-quinolyl phosphate and 8-quinolyl methyl phosphate with nickel and cobalt ions was also studied. Protonation enthalpies and copper complexation enthalpies of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate and methyl phosphate were determined by calorimetry. A correlation between the nucleophilicity of the ester group and the magnitude of the stability constants of the proton, copper and zinc complexes of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate and methyl phosphate is found and explained in terms of electronic induction effects, i.e. by polarisation of the phosphate oxygens by the ester group. The calorimetric results show that the desolvation of ligand and metal ion during the complexation plays an important role. The possibility of similar correlations for complexes of triphosphates is also discussed.

No description available.

The electrochemistry of solid electrodes of charge transfer complexes of tetracyanoquinodimethane (TCNQ) and copper complexes with nitrogen containing chelates, such and dipyridylamine (dpaH), bipyridyl (bpy) and 1,10-dimethyl-2,9-phenanthroline (dmp), has been investigated with cyclic voltammetry. Pressed pellet electrodes of these complexes exhibit a broad electrochemically stable region. The oxidative and reductive breakdown reactions involve solid state reactions into the bulk electrode. These materials also act as electron mediators for glucose oxidation in glucose oxidase modified electrodes. The structure of the model compound, copper(I)(dpaH)₂Cl has been determined to have a distorted tetrahedral coordination sphere. The electrochemistry of solid electrodes of charge transfer complexes of tetrathiafulvalene (TTF) with copper chloride and copper bromide has been investigated with cyclic voltammetry. Pressed pellet electrodes do not exhibit a broad stable region, as do the TCNQ complexes. A preliminary structure of the organic part of tetramethyltetraselenafulvalene copper chloride has been determined from the solution of the Patterson function and exhibits a displacive modulation with a repeat unit of seven TMTSF molecules. (TTF)(SCN)₀ͺ₆₆ and (TTF)Cu(SCN)₂ have been investigated by infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. (TTF)(SCN)₀ͺ₆₆ crystallized in a tetragonal space group with a disordered column of thiocyanate anions. (TTF)Cu(SCN)₂ is an insulator with a two-dimensional network of Cu(SCN)₂⁻ ions. X-ray crystal structures of four compounds prepared in association with copper complex chemistry have been determined; (1) 5,5'-dibromo-2,2'-bithiophene, (2) 3,5,5'-tribromo-2,2'-bithiophene, (3) Cu(dmp)(CN)₂ ⁻ · Bu₄N⁺ and (4) the 1:2 adduct of dimercaptosuccinic acid and dimethylformamide.

Call number: LD2668 .T4 1978 J34 / Master of Science

Call number: LD2668 .T4 1979 G44 / Master of Science

Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Ruthenium, as one of the platinum group metals, was investigated to determine the aquation rate constant of [RuCl6]3- and the anation rate constant of [RuCl5(H2O)]2-. This two reactions represent the equilibrium reaction [RuCl6]3- + H2O ⇄ [RuCl5(H2O)]2- + Cl-. The reactions were followed, using stopped-flow injection and UV/Visible spectroscopy, at different temperatures. The aquation and anation rate constants were determined with good precision and thermodynamic values for the reactions were calculated. The pseudo first order aquation rate constant, k65, was determined by calculation from the regression line as k65 = 52.1 (±3.7) x10-3 s-1 at 25°C. The activation energy, Ea, is 90.1 (±1.2) kJ.mol-1 and the enthalpy and entropy of activation is 87.7 (±1.2) kJ.mol-1 and 24.7 (±4.3) J.K-1.mol-1, respectively. The aquation rate constant was found to be dependent on the hydrochloric acid concentration, decreasing with increasing hydrochloric acid concentration. From the regression line at 25°C the second order anation rate constant, k56, was calculated as 1.62 (±0.11) x10-3 M-1s-1. The activation energy is 88.0 (±1.4) kJ.mol-1, with the enthalpy and entropy of activation 85.6 (±1.4) kJ.mol-1 and –11.2 (±4.7) J.K-1.mol-1, respectively. The influence of the hydrochloric acid concentration of the solution on the anation rate constant was not investigated. The equilibrium constant for the reaction studied was calculated from the rate constants for the aquation and anation reactions. The equilibrium constant, K6, was calculated as 0.0311 M-1 at 25°C. The equilibrium constant, when compared to literature, was found to be dependent on the hydrochloric acid concentration. It was then used, in conjunction with data from the literature, to construct two distribution diagrams. Distribution diagrams for the Ru(III) aquachloro species show between 79.9% to 72.3% [RuCl6]3- present in 12M HCl. The two distribution diagrams were very similar and it is not possible to resolve the issue of a final distribution diagram for the aqua-chloro Ru(III) system without further investigation into the all the other rate constants of the Ru(III) aqua-chloro species. The rate constants and thermodynamic values for the Ru(III) reaction were compared to corresponding data (from literature) for Rh(III) and Ir(III) because several comparisons between these platinum group metals have been noted. It was found that for both the aquation and anation rate constants, the following trend was observed: Ru(III) > Rh(III) > Ir(III). These differences are in certain cases exploited in the refining of these platinum group metals. Crystals of diethylenetriamine hexachlororuthenate(III) was prepared and characterised by x-ray crystallography and CHN analysis. The average Cl-Ru bond length for the crystal was 2.371 Å. The crystal structure was compared to hexaaquaaluminium hexachlororuthenate(III) tetrahydrate and diethylenetriamine hexachlororhodate(III). The metal-chloride bond lengths of all the crystals were found to be similar (2.350 Å – 2.375 Å). The diethylenetriamine crystal structures compared well. The conclusion was that the crystals prepared were diethylenetriamine hexachlororuthenate(III). / AFRIKAANSE OPSOMMING: Ruthenium(III), een van die platinum groep metaal-ione, is in hierdie studie ondersoek om die akwasie tempo konstante van [RuCl6]3- en die anasie tempo konstante van [RuCl5(H2O)]2- te bepaal. Dié twee reaksies verteenwoordig die ewewigsreaksie [RuCl6]3- + H2O ⇄ [RuCl5(H2O)]2- + Cl-. Die verloop van die reaksies is met behulp van UV/Sigbare spektroskopie by verskillende temperature gevolg. Die akwasie en anasie tempo konstantes is bepaal met goeie presisie en die termodinamiese konstantes van die reaksies is bereken. Die pseudo-eerste orde akwasie tempo konstante, k65, is bepaal deur middel van regressie, as 52.1 (±3.7) x10-3 s-1 by 25°C. Die aktiverings energie, Ea, is bereken as 90.1 (±1.2) kJ.mol-1 en die entalpie en entropie van aktivering is onderskeidelik 87.7 (±1.2) kJ.mol-1 en 24.7 (±4.3) J.K-1.mol-1. Daar is gevind dat die akwasie reaksie konstante afhanklik was van die soutsuur konsentrasie: dit neem af soos die soutsuur konsentrasie toeneem. Met behulp van die regressie lyn is die anasie tempo konstante bepaal by 25°C as 1.62 (±0.11) x10-3 M-1s-1. Die aktiveringsenergie is bepaal as 88.0 (±1.4) kJ.mol-1 en die entalpie en entropie van aktivering, onderskeidelik as 85.6 (±1.4) kJ.mol-1 en –11.2 (±4.7) J.K-1.mol-1. Die invloed van die soutsuur konsentrasie op die anasie tempo konstante is nie bepaal nie. Die ewewigskonstante vir die reaksie wat ondersoek is, is bereken met die tempo konstantes vir die akwasie en anasie reaksies. Die ewewigskonstante, K6, is bereken as 0.0311 M-1 by 25°C. Toe die ewewigskonstante vergelyk is met die literatuur waardes, is gevind dat die ewewigskonstante afhanklik is van die soutsuur konsentrasie. Saam met die waardes wat in die literatuur gevind is, is die ewewigskonstante gebruik om twee distribusie diagramme te bereken. Die distribusie diagramme vir die Ru(III) spesies toon onderskeidelik 79.9% en 72.3% [RuCl6]3- in 12M HCl. Die twee distribusie diagramme is baie eenders en dit is nie moontlik om ‘n finale distribusie diagram op te trek totdat die uitstaande tempo konstantes tussen die akwachloro Ru(III) spesies bepaal word nie. Die tempo konstantes en termodinamiese waardes wat bepaal is vir die Ru(III) reaksie is vergelyk met gelyksoortige waardes in die literatuur van Rh(III) en Ir(III) omdat daar ooreenkomste tussen die platinum groep metale opgemerk is. Daar is bevind dat die akwasie én anasie reaksies die volgende patroon volg: Ru(III) > Rh(III) > Ir(III). Die verskille word in sekere gevalle benut in die raffinering van hierdie metale. Kristalle van dietileentriamien heksachlororuthenaat(III) is berei en gekarakteriseer met behulp van CHN analise en x-straal kristallografie. Die gemiddelde Cl-Ru bindingsafstand vir die kristal was 2.371 Å. Die kristalstruktuur is vergelyk met dié van heksaäkwaäluminium hexachlororuthenaat(III) tetrahidraat en diëtileentriamien heksachlororhodaat(III). Die chloried-metaal bindingsafstand vir die kristalle was soortgelyk (2.350 Å – 2.375 Å). Die diëtileentriamien kristalstrukture stem goed ooreen. Die gevolgtrekking was dat die kristalle wat voorberei is wel diëtileentriamien heksachlororuthenaat(III) was.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Please refer to full text for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming