Quantitative Investigation of the Electronic and Steric Influences on Ethylene Oligo/Polymerization by 2‐Azacyclyl‐6‐aryliminopyridylmetal (Fe, Co, and Cr) Complexes

Abstract

The multiple linear regression analysis is performed to investigate both electronic and steric effects of ligands on the catalytic activities of the transition metal complexes in ethylene oligo/polymerization. The Hammett constants (F) and effective net charge (Q) are used to describe the electronic effect, meanwhile the steric effect is illustrated by open cone angle (θ) and bite angle (β). Four series of 2‐azacyclyl‐6‐aryliminopyridylmetal (Fe, Co, and Cr) analog complexes are calculated and the catalytic activity can be efficiently analyzed through taking both the electronic and steric effects into account. All of the obtained correlation coefficient R 2 values are over 0.93. The electronic effect is dominant in determining the catalytic activities for Fe and Co complexes; however, the steric effect plays a major role in controlling activities of Cr complexes.

The Catalytic Activities of Carbocyclic Fused Pyridineimine Nickel Complexes Analogues in Ethylene Polymerization by Modeling Study

“…The values of the open cone angle (θ) gradually reduced from 253 • to 244 • , corresponding to the change of the R 2 substituents regarding complexes 6-8, and showing the same trend for complexes 9 to 10. Therefore, the catalytic activity presented an increasing correlation with the open cone angle (θ), which is in agreement with the previous study [20]. The variation of the bite angle (β) was very small, with the values of β keeping almost constant and independent on the substituents.…”

“…The bite angle (β) was measured as the angle of N1-Ni-N2 in complex. The open cone angle (θ) was obtained according to [20], accounting for the space to accommodate the incoming monomer.…”

“…Besides the electronic effect, the impact of the steric effect on the catalytic activity is also investigated in terms of the open cone angle (θ) and bite angle (β). The former describes the space around the central metal in the complex to accommodate the approaching ethylene monomer [20], and the latter is the coordination angle of the metal with bonded nitrogens [21,22]. By using the multiple linear regression analysis (MLRA) method, the catalytic activities of azacyclyl-6aryliminopyridylmetal (Fe, Co, and Cr) complexes are predicted by considering both the electronic (Qeff and Hammett constant F) and steric effects (θ and β) [20].…”

“…The former describes the space around the central metal in the complex to accommodate the approaching ethylene monomer [20], and the latter is the coordination angle of the metal with bonded nitrogens [21,22]. By using the multiple linear regression analysis (MLRA) method, the catalytic activities of azacyclyl-6aryliminopyridylmetal (Fe, Co, and Cr) complexes are predicted by considering both the electronic (Qeff and Hammett constant F) and steric effects (θ and β) [20]. Furthermore, modified MLRA is carried out to investigate the variation of activities between 2-imino-1,10-phenanthrolinylmetal analogues, by using the variation of descriptors as independent variables and variation of the activity as a dependent variable.…”

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

“…As a result, the quantitative structure-property relationship (QSPR) approach has proven to be useful. In our previous studies, the relationship between the structure of a catalyst and its catalytic activity was investigated by molecular modeling, which successfully predicted the catalytic activities of late transition metal complex precatalysts toward ethylene oligo/polymerization, through electronic effects [38][39][40][41] or both from electronic and steric effects [42,43]. Regarding the influence of the catalyst structure on its thermal stability, several possible factors were proposed by previous experimental research [19,[24][25][26][29][30][31][32][33][34][35][36].…”