Abstract
Six examples of 2-(1-arylimino)ethyl-9-arylimino-5,6,7,8-tetrahydrocycloheptapyridine-cobalt(II) chloride complexes, [2-(1-ArN)C2H3-9-ArN-5,6,7,8-C5H8C5H3N]CoCl2, (Ar = 2-(C5H9)-6-MeC6H3 Co1, 2-(C6H11)-6-MeC6H3 Co2, 2-(C8H15)-6-MeC6H3 Co3, 2-(C5H9)-4,6-Me2C6H2 Co4, 2-(C6H11)-4,6-Me2C6H2 Co5, and 2-(C8H15)-4,6-Me2C6H2 Co6), were synthesized by the direct reaction of the corresponding ortho-cycloalkyl substituted carbocyclic-fused bis(arylimino)pyridines (L1–L6) and cobalt(II) chloride in ethanol with good yields. All the synthesized ligands (L1–L6) and their corresponding cobalt complexes (Co1–Co6) were fully characterized by FT-IR, 1H/13C-NMR spectroscopy and elemental analysis. The crystal structure of Co2 and Co3 revealed that the ring puckering of both the ortho-cyclohexyl/cyclooctyl substituents and the one pyridine-fused seven-membered ring; a square-based pyramidal geometry is conferred around the metal center. On treatment with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the six complexes showed high activities (up to 4.09 × 106 g of PE mol−1 (Co) h−1) toward ethylene polymerization at temperatures between 20 °C and 70 °C with the catalytic activities correlating with the type of ortho-cycloalkyl substituent: Cyclopentyl (Co1 and Co4) > cyclohexyl (Co2 and Co5) > cyclooctyl (Co3 and Co6) for either R = H or Me and afforded strictly linear polyethylene (Tm > 130 °C). The narrow unimodal distributions of the resulting polymers are consistent with single-site active species for the precatalyst. Furthermore, compared to the previously reported cobalt analogues, the titled precatalysts exhibited good thermo-stability (up to 70 °C) and possessed longer lifetime along with a higher molecular weight of PE (Mw: 9.2~25.3 kg mol−1).
Highlights
Were fully characterized by FT-IR, 1 H/13 C-NMR spectroscopy and elemental analysis
Considering the potential positive effect by the cycloalkyl substituent on group and the backbone of monocycloheptyl fused pyridine(imino) on the thermal stability and the ortho position of N-aryl group and the backbone of monocycloheptyl fused pyridine(imino) on the polymerization activity toward ethylene polymerization, in this work we focused on the thermal stability and polymerization activity toward ethylene polymerization, in this work mono cycloheptyl‐fused bis(imino)pyridine cobalt complexes that incorporated the different ring we focused on the mono cycloheptyl-fused bis(imino)pyridine cobalt complexes that incorporated size of cycloalkyl on the ortho position of N‐aryl group and their catalytic behavior toward ethylene the different ring size of cycloalkyl on the ortho position of N-aryl group and their catalytic behavior polymerization in detail
2-cycloalkylaniline hydrochloride derivatives derivatives wereinconducted in n-butanol the refluxing n‐butanol to form the desired
Summary
The crystal structure of Co2 and Co3 revealed that the ring puckering of both the ortho-cyclohexyl/cyclooctyl substituents and the one pyridine-fused seven-membered ring; a square-based pyramidal geometry is conferred around the metal center. Compared to the previously reported cobalt analogues, the titled precatalysts exhibited good thermo-stability (up to 70 ◦ C) and possessed longer lifetime along with a higher molecular weight of PE (Mw : 9.2~25.3 kg mol−1 ). N‐aryl groups and the backbone of pyridine, have been made well-defined bis(imino)pyridine-cobalt and -iron complexes (A) as highly active precatalysts for ethylene to the bis(imino)pyridine To enhance the thermal stability, one efficient method was introduced to thehave bulky reported substituentthat on bis(imino)pyridine iron complexes (A1)
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