The long-term goal of the project is to systematically study the reaction pathways and activation sequences in empirically designed multicomponent Ziegler-Natta catalysts and, based on fundamental insights, to develop more efficient polymerization catalys ts. The focus of the predominantly synthetic work lies on the utilization of tailor-made rare-earth metal components (keywords: alkylaluminates, half-metallocenes, alkoxides, and carboxylates) for examining the alkyl, hydride, and chloride transfer capab ility of tailor-made organoaluminum (cocatalyst) components. Rare-earth metal centers are known not only to display highly active polymerization initiators but also to provide a favorable stereoelectronic environment for the isolation and spectroscopic/s tructural characterization of Ln-Al heterobimetallic complexes which can be seen as activation intermediates. Correspondingly, the current project will also focus on the elucidation of supported rare-earth metal-based Ziegler-Natta catalysts according to a surface organolanthanide chemistry (SOLnC). Such unprecedented SOLnC involves periodic mesoporous semicrystalline silica of different topology (2D/3D hexagonal versus cubic) and pore configuration (channel- versus cage-like) as well as non-porous amor phous silica (aerosil) as support materials. Homoleptic Ln(II) and Ln(III) alkylaluminate and heteroleptic half-metallocene complexes will be employed as discrete molecularly defined organolanthanide components. Contemporary molecular oxo surfaces such as functionalized (silylated/alkylated) silsesquioxanes and calix[n]arenes are used for SOLnC modeling. The initiator activity of all Ziegler systems, half-metallocene and model complexes as well as grafted rare-earth surface species will be examined for the homo- and copolymerization of ethylene, propylene, 1-hexene, butadiene, styrene, acrylonitrile, acetylene, methyl methacrylate, and oxiranes.