| dc.description.abstract | metal-containing complexes, that exhibit enhanced chemical and physical properties. This thesis describes the synthesis of new metal-containing linear polymers and dendritic molecules.
Chapter 1 presents an overview of the field of metal-containing polymers, with particular attention to the synthesis of polymers via condensation polymerisation. This review
includes the various types of metal-containing condensation polymers and the applications of these materials, where available. This discussion is followed by a brief summary of
metal-containing dendrimers, which includes a concise description of their structure and applications in general.
There are two routes to preparing metal-containing polymers. Chapter 2 describes the synthesis of three bifunctional organometallic monomers, of the general type [M]-O-{2,6-(CH2OH)2-4-CH3-C6H2}, where [M] represents the various metal-containing moieties, (η5-C5H5)(CO)2 Fe(CH2)3 (25), (η5-C5H4-CH2CH2CH2-)Re(CO)3 (26) and Fpdendr
(27). These monomers were prepared using 2,6-bis(hydroxymethyl)-p-cresol as the key reagent. The monomers were used in classical polycondensation reactions with
terephthaloyl chloride using ambient temperature solution techniques. This yielded new low molecular weight oligomeric polyesters, that were characterised using FTIR and 1HNMR
spectroscopy, differential scanning calorimetry, thermogravimetric analysis and sizeexclusion
chromatography. In Chapter 3, an alternate route to metal-containing polymers is described. In this case, bifunctional organic monomers were polymerised to give preformed organic polymers. Two types of organic polymers were prepared, viz. polyesters (with pendant vinyl moieties) and polyimines (with α-diimine units along the polymer backbone).
Functionalisation of these preformed organic polymers with various metal sources was attempted. Hydrozirconation reactions of the vinyl polyesters with Schwartz’s reagent,
Cp2Zr(H)Cl, were attempted and were largely unsuccessful. Competing reactions with the ester functionality prevailed, preventing the desired reaction. Reaction of the polyimines
with PdCl2(COD) yielded insoluble, intractable metal-containing oligomers. Partial characterisation of the complexes is described. The synthesis of new poly(propylene imine) iminopyridyl metallodendrimers is described
in Chapter 4. Schiff-base condensation reaction of the commercially available DAB dendrimers with 2-pyridinecarboxaldehyde, gave the dendrimers 51, 52, and 53, with four, eight and sixteen pyridylimine functionalities respectively on the periphery. Successful complexation reactions with PdCl2(COD), PtCl2(COD) and CuCl2 produced the corresponding metal-containing dendrimers, with either PdCl2 (54, 55, 56), PtCl2 (57) or CuCl2 (58) moieties bound on the periphery. The metallodendrimers were insoluble in the
more common organic solvents, and were characterised by IR and 1H-NMR spectroscopy and microanalysis where possible. Dendrimers with salicylaldiminato ligands on the periphery were prepared by reacting the DAB dendrimers with salicylaldehyde. These ligands were reacted with various metal acetates in an attempt to prepare new metalcontaining
salicylaldimine dendrimers. This work yielded either paramagnetic metal complexes or insoluble, intractable compounds. Chapter 5 describes the applications of the catalyst precursors (54, 55, 56, 57, 58), discussed in Chapter 4, in the polymerisation of ethylene and the use of complexes 54 and 55 as Heck cross-coupling catalyst precursors. The complexes all showed catalytic activity toward ethylene polymerisation. A discussion of their activity, the polyethylene molecular weight and microstructure is presented in this chapter. The precursors 54 and 55 are also effective catalysts in the Heck reactions, coupling iodobenzene with methyl acrylate, styrene and 1-octene in high conversions. | en_US |
