Synthesis and Characterization of Lanthanide(III) Bis(guanidinate) Derivatives and the Catalytic Activity of Methyllanthanide Bis(guanidinate) Complexes for the Polymerization of ϵ‐Caprolactone and Methyl Methacrylate

Abstract

AbstractThe synthesis and structure of new lanthanide complexes with the guanidinate ligand [(Me3Si)2NC(NiPr)2−] are described. Reaction of a THF slurry of LnCl3 with a hexane solution of [(SiMe3)2NC(NiPr)2]Li (1) in a 1:2 molar ratio afforded the new soluble organolanthanide complexes [(SiMe3)2NC(NiPr)2]Ln(μ‐Cl)2Li(THF)2 [Ln = Yb (2), Nd (3)]. Alkylation of 2 and 3 with 2 equiv. of MeLi in hexane gave [(SiMe3)2NC(NiPr)2]Ln(μ‐Me)2Li(TMEDA) [Ln = Yb (4), Nd (5)] in good yield as crystalline solids. The molecular structures of 2 and 5 were determined by single‐crystal X‐ray analysis. The lanthanide ions in these complexes display a distorted pseudo‐octahedral coordination geometry. Complexes 4 and 5 exhibited extremely high activity for the ring‐opening polymerization of ϵ‐caprolactone to give high molecular weight polymers. Complex 5 also showed good catalytic activity for the syndiotactic polymerization of methyl methacrylate. (© Wiley‐VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2002)