Wang Xiaohua, Dong Bo, Yang Qi, Liu Heng, Hu Yanming, Zhang Xuequan
CAS Key Laboratory of High-Performance Synthetic Rubber and its Composite Materials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022, Jilin China.
School of Applied Chemistry and Engineering, University of Science and Technology of China Hefei 230026, Anhui, China.
Inorg Chem. 2021 Feb 15;60(4):2347-2361. doi: 10.1021/acs.inorgchem.0c03185. Epub 2021 Jan 27.
Increasing the thermostability of α-diimine late-transition-metal complexes and therefore rendering them more active at higher temperatures is of great importance, yet challenging for the olefin polymerization field. In the present research, a new family of α-diimine palladium complexes that can promote norbornene polymerization at high temperatures (up to 140 °C) is disclosed. Because of the conformational restriction caused by increasing the axial and equatorial bulkiness as well as the presence of intraligand H···F hydrogen bonds, -aryl rotations can be efficiently restricted, therefore circumventing the deactivation of the active species at high temperatures. At 80-140 °C, these complexes can efficiently catalyze norbornene homopolymerizations, giving high catalytic activities up to 5.65 × 10 g of PNB per mole Ni per hour and polymers with high molecular weights up to 37.2 × 10 g/mol, which are highly superior to catalytic systems mediated by CF-free complexes. Moreover, these complexes could also afford medium catalytic activities in the presence of polar 5-norbornene-2-carboxylic acid methyl ester (NB-COOCH).
提高α-二亚胺后过渡金属配合物的热稳定性，从而使其在更高温度下更具活性，这一点非常重要，但对烯烃聚合领域来说具有挑战性。在本研究中，公开了一类新型的α-二亚胺钯配合物，它们能够在高温（高达140°C）下促进降冰片烯聚合。由于轴向和赤道方向上体积增大以及配体内H···F氢键的存在所导致的构象限制，芳基旋转能够被有效限制，从而避免了活性物种在高温下失活。在80 - 140°C下，这些配合物能够有效催化降冰片烯均聚反应，每摩尔镍每小时的催化活性高达5.65×10克聚降冰片烯，并且能够得到分子量高达37.2×10克/摩尔的聚合物，这远远优于无CF配合物介导的催化体系。此外，在极性的5-降冰片烯-2-羧酸甲酯（NB-COOCH）存在的情况下，这些配合物也能提供中等的催化活性。
