We studied the addition polymerization of readily available bifunctional norbornene derivatives, 5-alkylidene-2-norbornenes, in the presence of modified Pd complexes with N-heterocyclic carbene ligands activated by borates. The Pd–N-heterocyclic carbene complex/phosphine/borate systems selectively catalyze the addition polymerization of 5-methylene-2-norbornene and 5-ethylidene-2-norbornene with the participation of the endocyclic norbornene double bond, whereas the exocyclic double bond remained intact. The catalysts exhibited extremely high activity and durability: the activity was higher than 1 × 10⁸ g_polymer/(mol_Pd·h) and some catalysts were active at a very high monomer/Pd molar ratio of 2 × 10⁷ or at a Pd complex concentration of 5 × 10^–6 mol %. The structure–catalytic activity relationships were established for Pd–N-heterocyclic carbene complexes: the Pd complexes bearing five-membered heterocyclic rings and/or less sterically hindered aryl groups at nitrogen atoms in carbene ligands exhibited the highest activity. The polymerization can be performed in an atmosphere of air and in wet solvents. The resulting polymers are amorphous and high-molecular-weight products consisting of rigid saturated main chains and reactive side groups. Thus, they can be considered as promising intermediates in the production of polymeric materials with high glass-transition temperatures and desired properties by targeted modifications.

中文翻译：

---

高活性Pd-N-杂环碳烯络合物催化剂与5-亚烷基-2-降冰片烯的聚合反应：催化剂的结构-活性关系

我们研究了在硼酸活化的N-杂环卡宾配体与修饰的Pd配合物存在下，容易获得的双官能降冰片烯衍生物5-亚烷基-2-降冰片烯的加成聚合反应。Pd–N-杂环卡宾配合物/膦/硼酸酯系统在环降冰片烯双键的参与下选择性催化5-亚甲基-2-降冰片烯和5-亚乙基-2-降冰片烯的加成聚合，而环外双键仍然存在完好无损的。该催化剂具有极高的活性和耐久性：该活性高于1×10 ⁸ g_聚合物/（mol _Pd ·h），一些催化剂在很高的单体/ Pd摩尔比2×10 ⁷下具有活性。或Pd络合物浓度为5×10 ^–6 mol％。建立了Pd-N-杂环卡宾配合物的结构-催化活性关系：在卡宾配体的氮原子上带有五元杂环和/或较少空间位阻的芳基的Pd配合物表现出最高的活性。聚合可以在空气气氛和湿溶剂中进行。所得的聚合物是由刚性饱和主链和反应性侧基组成的无定形和高分子量产物。因此，通过定向改性，它们可以被认为是具有高玻璃化转变温度和所需性能的聚合物材料生产中的有前途的中间体。