D.Phil. / Porphyrazines like porphyrins and phthalocyanines have unique physical, chemical and spectral properties. This allows them to have many impressive applications. They are less studied than phthalocyanines because of the absence of convenient methods for their synthesis. However, recent studies, including this one, have made these compounds more accessible. The palladium-imidazolium salt systems have proved to be one of the most successful catalysts for the Heck and Suzuki coupling reactions. Substituents on nitrogen atoms of imidazolium significantly influence the catalytic activities of the corresponding palladiumimidazolium salt systems in the Heck and Suzuki coupling. The synthesis of the imidazolium salts is discussed in this study. The synthesis of the imidazoles started from diamines. A new route for the synthesis of 4,5-diaminophthalonitrile is discussed here and so far it is the most convenient and less tedious route with higher yields. The catalytic activities on different substrates have also been extensively investigated and gave impressive results, on the Heck and Suzuki reaction. The catalysis study was first performed using the dicyanoimidazolium salts and then with the imidazolium salts of the porphyrazines. The results indicate that both these systems are active ligands for Suzuki and Heck reactions. Two complexes, [1’,1’’-dibutyl-3’,3’’-(4,5-(1,2-dicyanobenzene))diimidazolium dibromide] and [2,3-benzo(2’,3’-(3’’,3’’’-dibutyldiimidazolium-2’,2’’-diylidene)palladium(II)- dibromide)-7,8,12,13,17,18-hexapropyl,porphyrazine] were synthesised successfully in good yields and used for Suzuki and Heck catalysis reactions. Catalyst recovery in homogeneous catalysis is always a major problem; this led this study to make use of porphyrazines in biphasic catalysis because of their high extinction coefficient which comes from their very intense colour. The reactions were performed in a combination of water with toluene and also water with ionic liquid. Both this systems gave results which proved that it is possible to separate the catalyst and the products once the reaction is complete. Two aminoporphyrazines and phthalonitriles were also synthesised in multistep synthesis. The synthesis involved a lot of protection and deprotection steps. These compounds are starting materials to aminophosphine ligands which have a wide variety of catalysis applications.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:2573 |
| Date | 16 August 2012 |
| Creators | Tshivhase, Mmboneni Gifty |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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