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Alkane elimination reactions of amino-amino-bis(phenols) H₂L^1-4, Salan H₂L⁵, and methoxy-β-diimines HL^6,7 with lanthanide tris(alkyl)s, Ln(CH₂SiMe₃)₃(THF)₂ (Ln = Y, Lu), respectively, afforded a series of lanthanide alkyl complexes 1−8 with the release of tetramethylsilane. Complexes 1−6 are THF-solvated mono(alkyl)s stabilized by O,N,N,O-tetradentate ligands. Complexes 1−3 and 5 adopt twisted octahedral geometry, whereas 4 contains a tetragonal bipyramidal core. Bearing a monoanionic moiety L⁶ (L⁷), complex 7 (8) is a THF-free bis(alkyl). In complex 7, the O,N,N-tridentate ligand combined with two alkyl species forms a tetrahedral coordination core. Complexes 1, 2, and 3 displayed modest activity but high stereoselectivity for the polymerization of rac-lactide to give heterotactic polylactide with the racemic enchainment of monomer units P_r ranging from 0.95 to 0.99, the highest value reached to date …