School of Materials Science and Chemical Engineering, Key Laboratory of Advanced Mass Spectrometry and Molecular Analysis of Zhejiang Province, Ningbo University, Ningbo 315211, P. R. China.
Ningbo Polytechnic, Ningbo 315800, P. R. China.
Inorg Chem. 2023 Mar 13;62(10):4322-4329. doi: 10.1021/acs.inorgchem.3c00004. Epub 2023 Feb 28.
The development of efficient catalysts for the copolymerization of nonpolar monomers with polar monomers remains a great challenging task in polymer synthesis. A one-pot reaction of anhydrous LnCl with pyridyl-methylene-functionalized octamethylfluorenyl lithium OctFlu-CHPyLi in a 1:1 molar ratio, followed by alkylation with 2 equiv of LiCHSiMe in THF afforded the fluorenyl-ligated rare-earth metal bis(alkyl) complexes (OctFlu-CHPy)Ln(CHSiMe)(THF) [Ln = Sc (1), Y (2)]. Both complexes were isolated as neutral species and were characterized by NMR spectrum and elemental analysis. Complex 2 was subjected to single-crystal X-ray diffraction, which showed that the whole modified fluorenyl ligand was coordinated to Y in the η/κ mode to form a constrained geometry configuration. In the presence of excess AlBu, and on activation with 1 equiv of [PhC][B(CF)] in toluene, complexes 1 and 2 became active for both styrene (St) and -methoxystyrene (MOS) polymerization, giving polymers with high syndiotacticity (rrrr > 99%) without solvent extraction. Moreover, the ternary catalyst system composed of complex 2/AlBu/[PhC][B(CF)] was highly effective for the syndiospecific copolymerization of styrene with MOS, producing random copolymers with high molecular weights and narrow molecular weight distributions. The contents of MOS in the copolymers could be easily tuned in a wide range (11-93 mol %) by simply changing the MOS-to-St feed ratios.
高效催化剂的开发对于非极性单体与极性单体的共聚反应仍然是聚合合成领域的一项巨大挑战。无水 LnCl 与吡啶亚甲基功能化的八甲基芴基锂 OctFlu-CHPyLi 以 1:1 的摩尔比进行一锅反应，然后用 2 当量的 LiCHSiMe 在 THF 中进行烷基化，得到芴基配位的稀土金属双（烷基）配合物（OctFlu-CHPy）Ln（CHSiMe）（THF）[Ln = Sc（1），Y（2）]。这两种配合物均以中性物种分离，并通过 NMR 光谱和元素分析进行了表征。配合物 2 进行了单晶 X 射线衍射，结果表明整个修饰的芴基配体以 η/κ 模式与 Y 配位，形成约束几何构型。在过量 AlBu 的存在下，并在甲苯中用 1 当量的[PhC][B(CF)]活化后，配合物 1 和 2 对苯乙烯（St）和甲氧基苯乙烯（MOS）聚合均具有活性，无需溶剂萃取即可得到高间规立构规整度（rrrr > 99%）的聚合物。此外，由配合物 2/AlBu/[PhC][B(CF)]组成的三元催化剂体系对 St 与 MOS 的间规共聚具有高活性，可制备出具有高分子量和较窄分子量分布的随机共聚物。通过简单改变 MOS 与 St 的进料比，共聚物中 MOS 的含量可在很宽的范围内（11-93 mol%）进行调节。
