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<p>A series of bis(amidinate) amide complexes [C<sub>6</sub>H<sub>4</sub>-1,2-{NC(Bu<sup>t</sup>)N(2,6-R<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)}<sub>2</sub>]-LnN(SiMe<sub>3</sub>)<sub>2</sub>(L) (Ln = Nd, R = Me, L = DME (<b>1</b>); Ln = Y, R = Me, L = THF (<b>2</b>); Ln = Nd, R = Pr<sup>i</sup>, L = THF (<b>3</b>); Ln = Y, R = Pr<sup>i</sup>, L = THF (<b>4</b>)) were synthesized by the reaction of <i>ansa</i>-bis(amidines) C<sub>6</sub>H<sub>4</sub>-1,2-{NC(Bu<sup>t</sup>)N(2,6-R<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)H}<sub>2</sub> (R = Me (L<sup>1</sup>H), Pr<sup>i</sup> (L<sup>2</sup>H)) with Ln[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> (Ln = Nd, Y). The X-ray diffraction analysis demonstrated that the bis(amidinate) ligand bearing 2,6-dimethylphenyl substituents at the nitrogen atoms (L<sup>1</sup>) in complexes <b>1</b> and <b>2</b> is coordinated to the metal atoms in a <i>ϰ</i><sup>4</sup>-N,N-chelating fashion, whereas the ligand bearing 2,6-diisopropylphenyl substituents (L<sup>2</sup>) in complexes <b>3</b> and <b>4</b> is coordinated to the metal centers in a <i>ϰ</i><sup>3</sup>-N,N-fashion. Complexes <b>1–4</b> initiate ring-opening polymerization of <i>rac</i>-lactide and provide the quantitative monomer-to-polymer conversion ([Monomer]/[Ln] = 100–500) at room temperature within 10 min, giving polylactides characterized by an atactic microstructure, high molecular weights (<i>M</i><sub>n</sub> = 16100–80700), and a narrow molecular weight distribution (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> = 1.34–1.63). In the case of <i>ε</i>-caprolactone, the quantitative monomer-to-polymer conversion is achieved within 1 min, and the synthesized poly-<i>ε</i>-caprolactones have high <i>M</i><sub>n</sub> (25400–135000) and a relatively broad molecular weight distribution (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> = 1.60–4.79). Complexes <b>1–4</b> can initiate immortal polymerization of <i>rac</i>-lactide and ε-caprolactone in the presence of 1–5 equiv. of isopropyl alcohol as a chain transfer agent.</p>

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Neodymium and yttrium amide complexes supported by ansa-bis(amidinate) ligands: synthesis, structure, and catalytic activity in rac-lactide and ε-caprolactone polymerization

  • 期刊论文

  • 发表日期：

    2025年3月1日

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  • A. O. Tolpygin,
  • A. V. Cherkasov,
  • G. K. Fukin,
  • A. A. Trifonov

摘要

A series of bis(amidinate) amide complexes [C6H4-1,2-{NC(But)N(2,6-R2C6H3)}2]-LnN(SiMe3)2(L) (Ln = Nd, R = Me, L = DME (1); Ln = Y, R = Me, L = THF (2); Ln = Nd, R = Pri, L = THF (3); Ln = Y, R = Pri, L = THF (4)) were synthesized by the reaction of ansa-bis(amidines) C6H4-1,2-{NC(But)N(2,6-R2C6H3)H}2 (R = Me (L1H), Pri (L2H)) with Ln[N(SiMe3)2]3 (Ln = Nd, Y). The X-ray diffraction analysis demonstrated that the bis(amidinate) ligand bearing 2,6-dimethylphenyl substituents at the nitrogen atoms (L1) in complexes 1 and 2 is coordinated to the metal atoms in a ϰ4-N,N-chelating fashion, whereas the ligand bearing 2,6-diisopropylphenyl substituents (L2) in complexes 3 and 4 is coordinated to the metal centers in a ϰ3-N,N-fashion. Complexes 1–4 initiate ring-opening polymerization of rac-lactide and provide the quantitative monomer-to-polymer conversion ([Monomer]/[Ln] = 100–500) at room temperature within 10 min, giving polylactides characterized by an atactic microstructure, high molecular weights (Mn = 16100–80700), and a narrow molecular weight distribution (Mw/Mn = 1.34–1.63). In the case of ε-caprolactone, the quantitative monomer-to-polymer conversion is achieved within 1 min, and the synthesized poly-ε-caprolactones have high Mn (25400–135000) and a relatively broad molecular weight distribution (Mw/Mn = 1.60–4.79). Complexes 1–4 can initiate immortal polymerization of rac-lactide and ε-caprolactone in the presence of 1–5 equiv. of isopropyl alcohol as a chain transfer agent.