Thermostable α-Diimine Nickel Complexes with Substituents on Acenaphthequinone-backbone for Ethylene Polymerization

Trapping the Short-Chain Odd Carbon Number Olefins Using Nickel(II)-catalyzed Tandem Ethylene Oligomerization and Friedel-Crafts Alkylation of Toluene

“…The bis(pyrazolyl)methane ligands in 5a, 5b, 6 and 8 adopt a butterfly conformation with the interplane angle between the pyrazole rings of 60.8(2)/57.3(2), 61.86 (17), 55.64(16)/45.69 (17) and 56.6(2) for 5a, 5b, 6 and 8, respectively. As it can be expected, the endo-cyclic Ni─N─N angles are substantially smaller than the exo-cyclic Ni─N─C angles.…”

“…Recently the area of nickel-catalyzed oligomerization and polymerization of olefins received a new boost. Nickel complexes are being widely employed for processes of chain-walking ethylene polymerization [4,5,[14][15][16][17][18][19][20][21][22][23]6,[24][25][26][27][7][8][9][10][11][12][13] and copolymerization of ethylene with polar monomers [22,24,[35][36][37][38][39][40][41][42][43][44][27][28][29][30][31][32][33][34]. However, the interest in the development of new nickel-based catalytic systems for ethylene oligomerization is still high [4,6,[53][54]…”

Improvement of catalytic activity for α‐diimine nickel complex with active sites stabilized by bulky boron counterions at elevated temperature

“…Yang et al synthesized a series of α ‐diimine nickel catalysts with hydroxyethyl phenoxyl group on acenaphthequinone backbone ( I in Chart 1). [ 24 ] The catalytic activity of I (R 1 = Ph, R 2 = Me) still maintained at 670 kg (PE) [mol (Ni) h] −1 (120°C, 0.5 MPa). Gao et al synthesized bulkier dinaphthyobarrelene backbone‐based α ‐diimine Ni (II) and Pd (II) catalysts with 3D‐constrainedspace ( II in Chart 1), and the 3D‐constrained space around metal center enhanced the thermal stability, living fashion, and tolerance toward polar groups in polymerizations of ethylene and polar monomers.…”

Redox Potential as a Predictor of Polyethylene Branching Using Nickel α-Diimine Catalysts

“…In addition to changes in reaction parameters (e.g., ethylene feed pressure and reaction temperature), changes in α-diimine ligand structure are also known to influence PE branching. Changes in α-diimine ligand design that have been shown to alter PE branching include α-diimine backbone structure, ,, steric parameters, ,,,− and electronic effects. ,,,,− Salient examples include studies by Guan and co-workers, who showed that placement of electron-withdrawing (EW) substituents on the N -aryl moieties of Pd-based α-diimines produced higher degrees of PE branching, whereas catalysts bearing electron-donating (ED) substituents produce more linear PE under identical polymerization conditions . They hypothesized that this change in branching content arises due to changes in the σ-donating ability of the ligand, which, in turn, alters the Lewis acidity of the active metal center and the rate of chain walking relative to that of coordination and insertion. ,,, Chen and co-workers showed that the placement of ED methoxy (−OMe) substituents on the acenaphthene backbone moiety of Pd- and Ni-based α-diimine catalysts may also influence PE branching.…”

“…Second, systematic studies comparing placement of EW and ED substituents on the acenaphthene-based backbone versus placement of those same substituents on the N -aryl moieties of α-diimine ligands are absent from the literature. Lastly, we noted that the trends observed in most prior studies ,,,,,− ,,,, were determined experimentally, requiring the iterative synthesis of multiple discrete catalyst and ligand species, as well as extensive polymerization studies. We envisioned that if PE branching density could be predicted based on catalyst structure or intrinsic catalyst and/or ligand characteristics, without requiring extensive polymerization studies and/or catalyst syntheses, that the selection and design of future catalytic species may be greatly accelerated.…”