Quantitative Structure-Thermostability Relationship of Late Transition Metal Catalysts in Ethylene Oligo/Polymerization

Wenhong Yang,Zhifeng Ma,Wen-Hua Sun,Jun Yi

doi:10.3390/catal7040120

Abstract

Quantitative structure–thermostability relationship was carried out for four series of bis(imino)pyridine iron (cobalt) complexes and α-diimine nickel complexes systems in ethylene oligo/polymerization. Three structural parameters were correlated with thermal stability, including bond order of metal-nitrogen (B), minimum distance (D) between central metal and ortho-carbon atoms on the aryl moiety and dihedral angle (α) of a central five-membered ring. The variation degree of catalytic activities between optimum and room temperatures (AT) was calculated to describe the thermal stability of the complex. By multiple linear regression analysis (MLRA), the thermal stability presents good correlation with three structural parameters with the correlation coefficients (R2) over 0.95. Furthermore, the contributions of each parameter were evaluated. Through this work, it is expected to help the design of a late transition metal complex with thermal stability at the molecular level.

Highlights

Since the discovery of nickel and palladium catalysts bearing α-diimine ligands, the growth of late transition metal complex catalysts for ethylene reactivity has been promoted due to their particular features, such as stable structure, low cost and high catalytic activities in the polymerization of ethylene [1,2,3,4,5,6]
The property of thermal stability for late transition metal complex precatalysts is very important for ethylene polymerization, which greatly influences their potential applications in the field of industry
Four series of complexes with thermal stability containing typical structures were investigated quantitatively by the multiple linear regression analysis (MLRA) method, which was used in our previous studies on the catalytic activities

Summary

Introduction

Since the discovery of nickel and palladium catalysts bearing α-diimine ligands, the growth of late transition metal complex catalysts for ethylene reactivity has been promoted due to their particular features, such as stable structure, low cost and high catalytic activities in the polymerization of ethylene [1,2,3,4,5,6]. In order to get desirable catalytic performance, extensive achievement and progress have been obtained through modifying substituents of used ligands and designing alternative ligands as well as optimizing reaction conditions [7,8,9,10,11,12,13,14,15,16,17,18]. To improve the thermal stability of a catalyst, tremendous experimental works were conducted and significant progress achieved. Guan et al early reported a series of novel nickel catalysts bearing the cyclophane ligands (Scheme 1, A) and phosphine imine hybrid ligands (Scheme 1, B), which revealed high activities at high temperatures for ethylene polymerization. The camphyl-based nickel catalysts (Scheme 1, C) exhibited good thermal

Methods

Results

Conclusion