The control of the stereochemistry of macromolecules is a very important goal, and coordination-insertion polymerization is superior with respect to the other polymerization methods for its achievement. In this contribution, we focus on Pd(II) homogeneous catalysts for the stereocontrolled synthesis of CO/vinyl arene polyketones. We developed a library of aldo- and keto-iminopyridine ligands N-N′ that feature an α- or β-naphthyl or anthracenyl moiety on the imino nitrogen atom (N_imm). With such ligands, the Pd(II) monocationic complexes [Pd(CH₃)(CH₃CN)(N-N′)][PF₆] were synthesized. NMR spectroscopy shows that in solution, each complex exists as an equilibrium mixture of cis and trans stereoisomers, the latter having the CH₃ ligand opposite to the Pd–N_imm bond. The isomeric population depends on the N-N′ ligand: an almost 1:1 ratio is found for the ketimine complexes, whereas those with the aldimines show a preference for the trans geometry. These complexes generate very efficient catalysts for the CO/vinyl arene copolymerization. Catalyst performances depend both on the nature of N-N′ and of the vinyl arene comonomer. The ketimine-based catalysts are more stable and more productive than the aldimine counterpart, leading to prevailingly syndiotactic macromolecules of high M_w (up to 280 kDa). The aldimine derivatives produce copolymers with isotactic and syndiotactic stereoblocks of different lengths depending on the vinyl arene. The effect of the prochiral monomer on the copolymer tacticity is steric in nature as demonstrated by the stereochemistry of the obtained CO/4-fluorostyrene polyketone, whose synthesis is reported here for the first time. As a conclusion, we have now demonstrated that when catalysts with nonsymmetric ancillary ligands are used, and stereoisomers are present, the stereochemistry of the copolymerization is driven by both the catalyst isomeric distribution and the prochiral comonomer.

中文翻译：

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Pd催化的CO /乙烯基芳烃共聚：当立体化学受共聚单体控制时

控制大分子的立体化学是一个非常重要的目标，而配位插入聚合在实现该目标方面优于其他聚合方法。在这项贡献中，我们集中于Pd（II）均相催化剂，用于立体控制合成CO /乙烯基芳烃聚酮。我们开发了一个亚氨基和酮亚氨基吡啶配体NN'库，其特征是亚氨基氮原子（N _imm）上的α-或β-萘基或蒽基部分。利用这种配体，合成了Pd（II）单阳离子络合物[Pd（CH ₃）（CH ₃ CN）（NN'）] [PF ₆ ]。NMR光谱表明，溶液中每种络合物均以顺式和反式立体异构体的平衡混合物形式存在，后者具有CH与Pd–N _imm键相反的_3个配体。异构体的数量取决于NN'配体：酮亚胺配合物的比例几乎为1：1，而带有醛亚胺的配合物显示出对反式几何结构的偏爱。这些配合物为CO /乙烯基芳烃共聚生成非常有效的催化剂。催化剂的性能取决于NN'和乙烯基芳烃共聚单体的性质。基于酮亚胺的催化剂更稳定，比醛亚胺对口更有效率，导致高的prevailingly间同大分子中号_{w ^}（最高280 kDa）。醛亚胺衍生物产生的共聚物具有等长和间同的立体嵌段，其长短取决于乙烯基芳烃。如所获得的CO / 4-氟苯乙烯聚酮的立体化学所证实，前手性单体对共聚物立构规整度的影响本质上是空间性的，其合成是首次在此报道。作为结论，我们现在证明，当使用具有非对称辅助配体的催化剂并且存在立体异构体时，共聚的立体化学既受催化剂异构体分布又受前手性共聚单体的驱动。