Synthesis, crystal structure and catalytic activity of some new chiral ansa-metallocenes of yttrium, lanthanum, samarium, lutetium and of zirconium

Chiral silicon bridged yttrio- and lanthanidocene chlorides [MeRSi(C5H4)(C5Me4)LnCl]2 (R=Et (a), Ph (b); Ln=Y (4a, b), La (5a, b), Sm (6a, b), Lu (7a, b)) and zirconocene dichlorides [MeRSi(C5H4)(C5Me4)ZrCl2] (R=Et (8a), Ph (8b)) were synthesized. Compounds 4–7 react with sodium acetate yielding the corresponding monomeric acetates [MeRSi(C5H4)(C5Me4)LnO2CMe] (R=Et (a), Ph (b); Ln=Y (9a, b), La (10a, b), Sm (11a, b), Lu (12a, b)). All compounds were characterized by elemental analysis, 1H and 13C{1H}-NMR spectroscopy, and by mass spectrometry. Single crystal X-ray structure determinations show a dimer for 6a and a monomer for 8a. The zirconocenes 8a, b are active catalysts for the polymerization of ethylene and propylene in the presence of methylalumoxane (MAO).