新型碳硼烷配体过渡金属烯烃聚合催化剂及催化性能研究

Polyolefin are widely used polymer material which accounted for one-third of total polymer materials. It plays a very important role on the development of national economy. Design and synthesis of effective catalysts are the key to the development of polyolefin industry. Complexes with three dimensional aromatic carborane ligands usually have good solubility, good thermal stability, and can stabilize the active sites of the catalysts. In this project, a series of transition metal catalysts based on carborane ligands have been designed and synthesized, and then they are applied in ethylene polymerization, ethylene copolymerization with α-olefin, cycloolefin, or polar olefin. In order to investigate the relationship between structures and catalytic properties, and the catalytic mechanism, X-ray absorption spectra will be employed in monitering the whole catalytic process to isolated intermediates within catalytic process. By DFT calculation, investigate activation energies in the processes such as the coordination and insertion of olefins as well as any "chain transfer" (?-hydrogen immigration), and the intermediates within catalytic process would be measured. This research would helpfully improve the performance of polyolefin materials and develop new varieties of polyolefin materials. There are both basic research significance, and the profound application development prospects. This research would provide technological foundation for improving the performance of polyolefin materials and developing new varieties of polyolefin materials, which are both basic research significance and profound development prospects.

聚烯烃占整个高分子材料的1/3，是一种应用数量大且十分广泛的材料，对国民经济的发展有十分重要作用，而催化剂的设计和合成则是聚烯烃工业发展的关键。本项目拟利用三维共轭碳硼烷配合物溶解性好、稳定性强和化学反应性丰富等诸多优点，与过渡钛系金属或镍系金属配位，合成一系列过渡金属烯烃聚合催化剂。研究它们催化乙烯均聚、乙烯与α-烯烃和环状烯烃共聚、乙烯与极性烯烃单体共聚等反应。并采用x-射线吸收谱原位监测整个烯烃聚合过程，捕捉催化过程活性中间体。利用DFT理论计算过渡态、活性中间体的能量，了解烯烃配位、插入成键、"贝塔-H迁移"及链增长等中间步骤的活化能等，从而明晰催化剂结构与性能之间的关系，深入了解含碳硼烷配体过渡金属配合物催化烯烃聚合机理。本项目的研究为改进聚烯烃材料的性能、开发新的聚烯烃材料的品种奠定科学技术基础，既有基础研究意义，又有深刻的应用开发前景。

本项目经过4年的努力，运用烯烃配位聚合催化原理、采用取代碳硼烷的配体与过渡金属、特别是半夹心结构过渡金属结合，形成含有碳硼烷单元的有机金属化合物，利用这类化合物作为催化剂研究了它们在助催化剂存在下催化乙烯聚合、乙烯与丁烯-1的共聚合、乙烯与-烯烃极性单体((CH2)8OH，(CH2)8COOMe和(CH2)3COOMe)共聚合反应以及催化降冰片烯的聚合性能。系统地研究了在不同条件下（不同聚合温度、不同聚合压力、不同聚合介质以及不同催化剂与助催化剂的比例等等）探索性能优异的催化剂和最佳的催化条件。发现半夹心结构锆的碳硼烷化合物在助催化剂（MAO）存在下具有极高的催化性能和温度耐受能力，而且聚合产物分子量可控，是一类有应用前景的新型催化体系。另外我们利用取代碳硼烷配体与半夹心结构的铑、铱化合物作用得到了一类由碳硼烷所稳定的16-电子体系半夹心结构有机金属化合物，发现它们可以与氢气分子作用形成金属氢化物，而这类金属氢化物可以还原二氧化碳成一氧化碳或者甲酸，就是这类含有碳硼烷16-电子体系半夹心结构有机金属化合物可以直接催化氢气还原二氧化碳, 这为在温和条件下氢气的可逆化学转化提供了一种新的途径。还利用半夹心结构化合物作为Building Block制备出一系列有机金属大环和孔道结构化合物，并研究了他们吸附、催化小分子活化反应。这些研究成果发表了六篇JACS、一篇Angew. Chem.和一篇Chem等33篇论文，被Accounts和Coord. Chem. Rev.邀请撰写综述文章6篇。