Lewis-acidic organometallic compounds of the lanthanides and the
alkaline earth metals as catalysts for the activation of carbonyl groups*
Herbert Schumann**, Mario Glanz, Jochen Gottfriedsen, Sebastian Dechert,
and Dietmar Wolff
Technische Universität Berlin, Institut für
Anorganische und Analytische Chemie, Sekr. C2, Straße des 17.
Juni 135, D-10623 Berlin, Germany
Abstract: 1,3-dialkyl-4,5-dimethylimidazol-2-ylidenes form adducts
with various bis (alkylcyclopentadienyl) complexes of magnesium, calcium,
strontium, barium, samarium, and ytterbium. The X-ray structures of
selected metallocenes and carbene adducts are discussed. Liquid-crystalline
homo- and block copolymers with a narrow molecular mass distribution
index were obtained in high yields by living polymerization of mesogenic
methacrylates with organosamarium complexes. Depending on the structure
of the catalyst and the polarity of the solvent used, different, partially
competitive reaction mechanisms are observed.
* Lecture presented at the XIXth International Conference
on Organometallic Chemistry (XIX ICOMC) , Shanghai, China, 23-28 July
2000. Other presentations are published in this issue, pp. 205-376.
** Corresponding author
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