Polymerization of α-Olefins Using a Camphyl α-Diimine Nickel Catalyst at Elevated Temperature

Abstract

Chiral (1S)- and (1R)-camphyl α-diimine nickel complexes were synthesized respectively with (1S)-(+) camphorquinone and (1R)-(−) camphorquinone as raw reagents and used as catalyst precursors for olefin polymerizations. It is found that the ligand chirality has no influence on catalytic activity and regioselectivity for olefin polymerizations. Ethylene, propylene, 1-hexene, and 4-methyl-1-pentene polymerizations with the camphyl α-diimine nickel activated by AlEt2Cl can exhibit some living characteristics under the optimized conditions. The resultant polypropylenes and poly(1-hexene)s have significantly narrow molecular weight distributions (PDI < 1.2) in a wide temperature range, even at an elevated temperature of 70 °C. Sustainable period of the linear relationship of M n vs polymerization time depends on temperature for propylene and 1-hexene polymerizations. Additionally, high 1,3-enchainment fraction of 45% is observed even at −60 °C for propylene polymerization using the camphyl α-diimine catalyst due to 2,1-insertion of propylene and chain walking.

Simple Preparation of Halogen-Substituted &lt;i&gt;α&lt;/i&gt;-Diimine Nickel Complexes Immobilized into Clay Interlayer as Catalysts for Ethylene Oligo-/Polymerization

“…For example, the oligomer share obtained by the L4/Ni 2+ -mica with TIBA increased from 27.6 to 41.7 wt% as the reaction temperature increased from 50˚C to 70˚C. The higher reaction temperature was considered to enhance the rotation of the aryl group in the complex, and thus, the chain transfer rate increased [21] [43]. Also, the branch rates (represents by the share of the branched α-olefins in the oligomer products determined by GC) tended to slightly increase with the increasing reaction temperature.…”

A highly active and thermally stable 6,13-dihydro-6,13-ethanopentacene-15,16-diimine nickel(ii) complex as catalyst for norbornene polymerization

“…Wu have synthesized a-diimine nickel catalyst with a bulky camphyl backbone, which show good thermal stability toward olen polymerizations and obtain special branched polyolen. 30,31 A series of Ni(II) dihalide complexes bearing unsymmetrical a-diimine ligands were synthesized and exhibited high activity and thermal stability in olen polymerization.…”

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

“…The complex A presents a turnover frequency (TOF) of 1.0 × 10 6 h −1 at 90 • C and complex B shows a TOF of 1.7 × 10 4 h −1 at 70 • C [24][25][26]. Subsequently, the camphyl-based nickel catalysts (Scheme 1, C) exhibited good thermal stability; meanwhile, the obtained polymer had a significant narrow molecular weight distribution (polydispersity index: PDI < 1.2) [27,28]. The Long group also reported a robust nickel α-diimine catalyst (Scheme 1, D) for ethylene polymerization at a high temperature.…”

“…Catalysts 2017, 7, 120 2 of 15 distribution (polydispersity index: PDI < 1.2) [27,28]. The Long group also reported a robust nickel α-diimine catalyst (Scheme 1, D) for ethylene polymerization at a high temperature.…”