Niedrige Valenz und Gemischtvalenz Lanthanoid Komplexe: Reaktivität und Katalyse

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The present proposal aims at the development of benzyllanthanide chemistry. Emphasis is on the syntheses and structural characterization of neutral homoleptic bis-benzyl-Ln(II) and trisbenzyl-Ln(III) complexes. In our preliminary investigations we isolated and structurally characterized the first homoleptic Ln(II)-benzyls and successfully found simple synthetic routes to (o-Me2N-C6H4CH2)3Y(III) and (o-Me2N-C6H4CH2)3La(III) which were shown to be isostructural. Since these highly reactive benzyllanthanides are potential precursors in the syntheses of lanthanide catalysts, we would like to expand our efforts in this area. We are especially interested in the syntheses of homoleptic benzyllanthanide complexes, that are not stabilized by electron-withdrawing groups at the benzylic carbon and also do not contain an intramolecular Lewis-base. Part of our research includes studies on the decomposition reactions of benzylic lanthanide complexes and the challenge to isolate soluble well-defined lanthanide-benzylidenes that could be structurally investigated. This group of compounds is still unknown, but could show interesting reactivity and catalytical activity. The third part of these studies encompass styrene polymerization with Ln(II)-benzyls that are partly available from our preliminary research and partly will be prepared within this project. The unexpected high syndiotacticity (r = 95 %) of the polystyrene obtained with these systems calls for further research activity in this area. We especially aim at a living and syndiotactic styrene polymerization, which would give access to thermoplastic materials with enhanced properties.