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Pure Appl. Chem., 2001, Vol. 73, No. 2, pp. 279-282

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.