中文摘要：

1-己烯和1-辛烯是制备高性能聚烯烃产品的重要共聚单体，近年来，PNP型铬系乙烯选择性三聚／四聚催化体系成为本领域研究热点。针对实验研究报道的系列氮上取代PNP型铬系催化剂，采用二维定量构效关系（QSPR）方法结合密度泛函理论（DFT）建立了该催化体系1-己烯、1-辛烯选择性的线性回归模型。研究中同时采用了启发式方法和最佳多元线性回归方法，考察了自定义描述符和铬金属活性中心价态（包括一价和二价）对线性回归模型的影响。通过分析发现：基于DFT的自定义描述符的引入能够明显提高模型的相关性和稳定性；基于一价Cr的活性中心模型更适合关联乙烯三聚选择性，二价Cr的活性中心模型更适合关联乙烯四聚选择性；PNP。Cr骨架几何结构尤其是较小的PNP角度是获得较高1-己烯和1-辛烯选择性的关键。最后，根据最佳线性回归模型对新型PNP配体进行了预测，发现了9种新的PNP配体结构可能具有更高的1-辛烯或1-己烯／1-辛烯共选择性，为进一步的实验开发奠定了良好的理论基础。

英文摘要：

1-Hexene and 1-octene are important comonomers for the synthesis of high performance polyolefins. Recently, Cr-bis（diphenylphosphino）amine （PNP-Cr） catalysts show the potential as excellent candidates for highly selective ethylene trimerization/tetramerization. In this work, a series of substituting PNP-Cr catalysts were studied by two-dimensional quantitative structure-property relationship （QSPR） method based on density functional theory （DFT） calculations. The heuristic method （HM） and best multi-linear regression （BMLR） were used for establishing the best linear regression models to describe the relationship between catalyst selectivity and its structure. Both Cr（ I ） and Cr（ II ） active site models for ethylene trimerization/tetramerization were considered. It was found that using self-defined descriptors from DFT calculations could increase the relativity and stability of the models. Monovalent Cr（ I ） center was the most plausible active site for ethylene trimerization, while ethylene tetramerization was most possibly proceeded over divalent Cr（II） active site. The skeleton structures of the PNP-Cr system especially a small PNP angle were crucial for achieving excellent catalytic selectivity. Nine new PNP ligands with high selectivity towards ethylene trimerization/tetramerization were predicted based on the best linear regression models providing a good basis for further development of novel catalyst systems with better performance.