Ethylene polymerization by the thermally unique 1-[2-(bis(4-fluoro phenyl)methyl)-4,6-dimethylphenylimino]-2-aryliminoacenaphthylnickel precursors

Abstract

A series of 1-[2-(bis(4-fluorophenyl)methyl)-4,6-dimethylphenylimino]-2-aryliminoacenaphthylene derivatives together with the corresponding nickel bromide complexes was synthesized and characterized. Representative complexes C2 and C5 were characterized by the single-crystal X-ray diffraction, revealing a distorted tetrahedral geometry. Upon activation with either methylaluminoxane (MAO) or ethylaluminum sesquichloride (EASC), all nickel complexes exhibited high activities towards ethylene polymerization, producing polyethylene with a relatively low degree of branching and narrow polydispersity. Complex C1 maintained good activity at elevated reaction temperatures, which indicates significant thermal stability of the active species.

Ultra-high molecular weight elastomeric polyethylene using an electronically and sterically enhanced nickel catalyst

“…As with the Ni1-Ni10/Et2AlCl-promoted systems, the ones involving MMAO as co-catalyst reveal similar effects on activity and molecular weight. By comparison with previously reported unsymmetrical bis(arylimino)acenaphthene-nickel catalysts, 12,18 it is clear once again that the incorporation of a para t-butyl group to the N-2,6-benzydrylphenyl unit has a key influence on the productivities as well as the molecular weight of the resultant polyethylene ( Figure 6). Indeed, the more sterically hindered Ni3 pre-catalyst in combination with MMAO gives the highest molecular weight of all the polymers generated in this work [30.8 × 10 5 g mol −1 ] (entry 3, Table 6), which is higher than seen when Et2AlCl as the co-catalyst [9.0 x 10 5 g mol −1 ] (entry 3, Table 5).…”

Branched polyethylenes attainable using thermally enhanced bis(imino)acenaphthene-nickel catalysts: Exploring the effects of temperature and pressure

“…The catalytic activities are generally high peaking at 12.7 × 10 6 g PE mol -1 (Ni) h -1 using EASC and then decrease in the order: EASC > MAO > Et2AlCl > MMAO [41][42][43][44]. In common to all four types of co-catalyst, good activities of more than 8.59 × 10 6 g PE mol -1 (Ni) h -1 are achieved with molecular weights for the polyethylenes in the 10 5 g mol -1 range [56]. However, based on the numerical values of the catalytic activities, MAO and EASC were chosen for the subsequent more in-depth catalytic evaluations.…”

A continuing legend: the Brookhart-type α-diimine nickel and palladium catalysts

“…[57][58][59] These complexes displayed remarkable thermal stability, maintaining high activity of up to 2.85 × 10 6 g PE (mol Ni h) −1 (100°C, 10 min). 57 In addition, moderately branched polyethylenes (63-75 branches/1000 C) with high M n [68][69][70][71][72][73][74][75] values (>6 × 10 5 g mol −1 ) and narrow polydispersities (M w /M n ≤ 1.31) were generated. This type of catalyst showed the characteristics of living polymerization even at 75°C.…”

“…5) bearing different substituents for ethylene polymerization. [68][69][70][71][72] Electron-withdrawing groups (F, Cl, NO 2 ) led to great thermal stability and high activities of up to 10 7 g PE (mol Ni h) −1 . They also synthesized a class of 2,6dibenzhydryl-based unsymmetrical nickel catalysts C11 (Fig.…”