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.