Repositori URV

Identifier: TDX:842

Handle: https://hdl.handle.net/20.500.11797/TDX842

Authors:
Bastero Rezola, Amaya

Abstract:
The development and study of new palladium catalysts for the copolymerization of 4-tert-butylstyrene with carbon monoxide was the main objective in the present thesis. The role played by the chelating ligands and in particular by their donating atoms is known to be fundamental in this catalytic process and therefore sulfur and nitrogen-donating ligands were studied. As a result from this study, the following conclusions can be drawn:The new palladium(II) neutral and cationic complexes containing bis(thio)ethers as chelating ligands, synthesized in Chapter 3, show different behavior in solution depending on the rigidity of the ligand. The cationic complexes are precursors for the copolymerization of CO/4-tertbutylstyrene although they are quite unstable under carbon monoxide pressure and get reduced to inactive palladium metal. By choosing chiral bis-(thio)ethers with the appropriate backbone rigidity, good stereocontrol of the styrene insertion in the polyketone chain may be obtained.In Chapter 4 the coordination of a family of Cs-symmetrical pyrazolcontaining bisnitrogen ligands to palladium-methyl cationic complexes leads to different stereoisomers depending on the steric hindrance of the bisnitrogen ligand. They behave as active precursors for the copolymerization reaction and allow the synthesis of syndiotactic polyketones, irrespectively of the stereochemistry of the precatalyst. Under mild copolymerization conditions the pyrazol-containing catalysts are an example of living copolymerization catalysts.Chapter 5 deals with the synthesis of new chiral N1-substituted imidazolines which allow tuning the electronic properties of the metal to which they are coordinated. The differently substituted C1-symmetrical pyridine-imidazolines may lead to the selective synthesis o