Rare-earth metal-based Ziegler catalysts: structure-reactivity relationships in anionic coordination polymerization

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Ziegler-Mischkatalysatoren represent one of the most important and impactful discoveries in metalorganic catalysis displaying unique application potential for the fabrication of synthetic polymers. The long-term scientific goal of the project is to gain a profound knowledge of such empirically designed multicomponent Ziegler catalysts by considering the rare-earth metal-based stereospecific coordination polymerization, in particular 1,3-diene polymerization, as an example. The focus of the predominantly experimental work lies on the utilization of tailor-made rare-earth metal components (keywords: alkylaluminates, amides, carboxylates, half-sandwich complexes) for examining the alkyl, hydrido, and chloro transfer capability of tailor-made organoaluminum (cocatalyst) components. The systematic study will not only provide fundamental insights into the reaction pathways and activation sequences involved but also assist in developing more efficient polymerization catalysts and ultimately in paving the way for the synthesis of single-component catalysts. Crucially, rare-earth metal centers display highly active polymerization initiators and at the same time facilitate the isolation and spectroscopic/structural characterization of Ln-Al heterobimetallic complexes which can be seen as activation intermediates. Subprojects will deal with the reduction capability of organoaluminum hydrides toward rare-earth metal carboxylates or the elucidation of factors such as cocatalyst metal, cocatalyst ligand, and weakly coordinating anions (including the investigation of pseudo halides). The obtained data will allow conclusions to structure-reactivity relationships in related polymerization catalysts involving early d-transition metals, in particluar group 4 metals.