Zur Katalyse der stereospezifischen Butadienpolymerisation mit den Katalysatorsystemen aus Nd(η3‐C3H5)3 · dioxan und methylaluminoxan (MAO) sowie Hexaisobutylaluminoxan (HIBAO)

The activation of the tris(allyl)neodymium complex Nd(eta(3)-C3H5)(3) . dioxane with alkylaluminoxanes (MAO or HIBAO) results in highly selective catalysts for the 1,4-cis-polymerization of butadiene (cis-selectivity up to 80%). Under standard conditions (50 degrees C, toluene), the turnover frequency (TOF) of the catalyst/MAO system amounts to 10-15000 mol butadiene/(mol Nd . h). Molecular weight determinations indicate the formation of only one polymer chain per neodymium center as in a living polymerization reaction, and for the catalyst/HIBAO system the rate law r(p) = k(p)[Nd][C4H6] with k(p) = 8,7.10(-2) mol/(L . s) (at 25 degrees C) has been derived. As the catalytically active species, a cationic monobutenyl neodymium(III) complex is discussed, which is stabilized through coordinative interaction with the counter anion as well as the growing polybutadiene chain. This cationic complex reacts under insertion with butadiene in a bimolecular fashion.