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Monocationic Bis-Alkyl and Bis-Allyl Yttrium Complexes: Synthesis, 89Y NMR Characterization, Ethylene or Isoprene Polymerization, and Modeling

Abstract : Monocationic complexes of yttrium with various bis-alkyl and bis-allyl ligands Y(CH2SiMe2Ph)2(THF)4][B(C6F5)4], [Y(CH2C6H4NMe2)2(THF)2][B(C6F5)4], and [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4] have been prepared by protonolysis of the corresponding homoleptic tris-alkyl or -allyl complexes using the anilinium borate salt [PhNMe2H][B(C6F5)4]. The resulting ion-pair complexes have been isolated and characterized by different techniques such as elemental analysis, 1H, 13C, and 89Y NMR, and EXAFS for the allyl cationic complex [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4]. More specifically, a 1H-coupled 89Y INEPT sequence has been developed in order to quantify the metal/alkyl ligand stoichiometry of both synthesized neutral tris-alkyl and cationic bis-alkyl yttrium complexes. The activity of the cationic complexes toward ethylene and isoprene homopolymerization has been assessed. In presence of TiBA, polyethylene was produced with activities ranging from 6 to 26 kgPE molY–1 h–1 bar–1. The molar mass of the yielded polymers shows a bimodal distribution. Under similar conditions, polyisoprene was produced up to full conversion of the monomer. The microstructure of the yielded polyisoprene displayed mainly cis-1,4-units (ca. 60–70%) and 3,4-units (ca. 20–30%). Only a few percent of trans-1,4 units was revealed.
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Submitted on : Wednesday, March 24, 2021 - 2:02:20 PM
Last modification on : Thursday, October 14, 2021 - 3:06:17 AM

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Alexis Oswald, Aymane El Bouhali, Emmanuel Chefdeville, Pierre-Alain Breuil, Hélène Olivier-Bourbigou, et al.. Monocationic Bis-Alkyl and Bis-Allyl Yttrium Complexes: Synthesis, 89Y NMR Characterization, Ethylene or Isoprene Polymerization, and Modeling. Organometallics, American Chemical Society, 2021, 40 (2), pp.218-230. ⟨10.1021/acs.organomet.0c00709⟩. ⟨hal-03179735⟩

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