Homogene Katalyse der starken und schwachen Wechselwirkungen: der Hafnium-Effekt bei Constrained Geometry Katalysatoren und neuartige Komplexe mit hyperverzweigten Liganden
FacultiesFakultät für Naturwissenschaften
LicenseStandard (Fassung vom 01.10.2008)
Chapter 1: Since 1990, transition metal complexes with bridged cyclopentadienylamido-ligands have aroused great interest in academia and industry. Especially, the so-called "constrained geometry catalysts" of the fourth subgroup are successfully applied in homo- and copolymerization reactions. The corresponding polymers possess uniform microstructures and extraordinary material properties. In this work, a zirconium and a hafnium constrained geometry complex have been synthesized, comprehensively analyzed and applied in numerous polymerization reactions. It has been proven that the so-called "first hafnium effect" is also valid for the class of CGCs. Despite the similar crystal structures both catalysts show dramatically different polymerization behaviors. The discrepancies in metal-C bond length seem to be minor but result in a change of the relationship between chain propagation and chain termination reactions so that the hafnium catalyst is able to produce ultra-high molecular weight polymers whereas the zirconium catalyst only leads to oligomers. Within this work it has been shown that there is no reason why hafnium catalysts should be neglected. Chapter 2: Chiral hyperbranched polyglycidols are highly interesting macromolecules that can be produced in a one-pot synthesis by ring-opening multi-branching polymerization of glycidol (ROMBP). The initiator molecule will be present as functional core within the product, which offers the possibility of further reactions. Aim of this work was the synthesis of newly complexes bearing hyperbranched polyglycerols as ligands.
Subject HeadingsHafnium [GND]
Homogene Katalyse [GND]