Live hard die young: Insight into the short life time of highly active vanadium(III) catalysts. The James Dean of alpha-olefin polymerization catalysts

The effects of different donor atoms of the supporting ligands (i.e. oxygen and nitrogen donor ligands) are at the root of this study as well as an attempt to improve our understanding of the catalyst/co-catalyst interaction.; Simply based on the lack of knowledge in the area of vanadium polymerization mechanism our group has set out to investigate possible activation pathways through a series of alkylation reactions to assess the vanadium-carbon bond stability by using a variety of oxygen and nitrogen donor-based supporting ligands. Upon using alkylating agents such as the alkylaluminium co-catalysts, attempts to trap and crystallize the active intermediate were attempted only to elucidate the deactivation process.; Insight into the activation and deactivation pathways of vanadium-based catalysts and a few other metal congeners such as zirconium, chromium, and manganese will be investigated in the following thesis.; The second chapter will cover insight into the activation and deactivation pathways of the industrially used tris(acetylacetonato) vanadium complex in the copolymerization of ethylene and propylene forming a polymer used in the production of synthetic rubber.; In attempt to combine the migratory properties of the oxygen donor based ligands and the stabilization properties nitrogen donor based ligands, the reactivity of the acetylpyrrolide ligand system was investigated with V(III). Two novel organometallic complexes were synthesized where, in one case, vanadium(III) mediated an aldolic condensation of the acetylpyrrolide ligand and in a second case a vanadium(II) metal centre promoted a pinacolic coupling of the ligand (Chapter 5).; Chapter 6 in mainly focused on the vanadium/aluminium interaction and the role of the co-catalyst in the activation and deactivation of the vanadium metal centre. In this case the vanadium centre is supported by the bulky N,N,N, tris-trimethylsilyl diethylenediamidoamino ligand. Formation of novel vanadium/aluminium clusters were synthesized and have given great insight into the vanadium/aluminium interaction and have demonstrated involvement of the ligand as seen previously in the case of the bis(imino)pyridyl ligand system.; Preliminary reactivity of the meso-diphenyldipyrrolemethane ligand was investigated with Zr(IV), V(III), Cr(III), Cr(II) in Chapter 7. These reactions revealed the possible bonding modes of the pyrrolide moiety with the metal centre. Treatment of the V(III) meso-diphenyldipyrrolidemethane complex with a sterically demanding aryloxide led to an interesting deoxygenation reaction of the aryloxide to form an oxygen bridged vanadium dimer which exerted high polymerization activities upon activation with dimethylaluminiumchloride. (Abstract shortened by UMI.)...