C-3-Symmetric chiral organolanthanide complexes: Synthesis, characterization, and stereospecific polymerization of alpha-olefins.
Fiche publication
Date publication
août 2007
Auteurs
Membres identifiés du Cancéropôle Est :
Dr BELLEMIN-LAPONNAZ Stéphane
Tous les auteurs :
Lukesova L, Ward BD, Bellemin-Laponnaz S, Wadepohl H, Gade LH
Lien Pubmed
Résumé
The trialkyl complexes [M(iPr-trisox)(CH2SiMe2R)(3)] (R = Me, M = Y, (1), R = Ph, M = Lu (2a), R = Me, M = Lu (2b), Tm (3), Er (4), Ho (5), and Dy (6)) were prepared from 1,1,1-tris[(S)-4-isopropyloxazolinyl]ethane (iPr-trisox) and the corresponding trialkyl precursors [M(CH2SiMe2R)(3)(THF)(n)]. Their molecular structures all display a highly distorted octahedral geometry, with the angles subtended at the metal center significantly deviating from the ideal 90 degrees, which is attributed to the steric demands imposed by the large CH2SiMe2R ligands, both with each other and with the isopropyl groups of the iPr-trisox ligand. Active catalysts for the polymerization of alpha-alkenes (n-hexene, n-heptene, and n-octene) were generated in situ by reaction of the trialkyl precatalyst with 2 equiv of trityl tetrakis(pentafluorophenyl)borate. In all cases polyolefins with M-w/M-n values of between 1.58 and 2.08 and isotacticities of 80-95% were obtained. The polymerization activity increases from lutetium to thulium and then subsequently decreases with increasing ionic radius of the metal due to a combination of activation with increasing ionic radius and decreasing catalyst stability.
Référence
Organometallics. 2007 Aug 27;26(18):4652-7.