Chiral Naphthyl-α-diimine Nickel(II) Catalysts Bearing sec-Phenethyl Groups: Chain-Walking Polymerization of Ethylene at High Temperature and Stereoselective Polymerization of Methyl Methacrylate at Low Temperature

Abstract

A series of new naphthyl-α-diimine nickel(II) complexes, {bis[N,N′-(1-naphthyl)imino]-1,2-dimethylethane}dibromonickel (2a), {bis[N,N′-(2-methyl-1-naphthyl)imino]-1,2-dimethylethane}dibromonickel (2b), {bis[N,N′-(2-sec-phenethyl-1-naphthyl)imino]-1,2-dimethylethane}dibromonickel (rac-(RR/SS)-2c), {bis[N,N′-(2-methyl-1-naphthyl)imino]acenaphthene}dibromonickel (2d), and {bis[N,N′-(2-naphthyl)imino]-1,2-dimethylethane}dibromonickel (2e), were synthesized and characterized. The crystal structures of ligands 1b, rac-(RR/SS)-1c, 1d, 1e and their representative complexes rac-(RR/SS)-2c and 2d were determined by X-ray crystallography. These complexes, activated by diethylaluminum chloride (DEAC), were tested in the polymerization of ethylene and methyl methacrylate under mild conditions. Complex rac-(RR/SS)-2c, bearing chiral bulky sec-phenethyl groups in the o-naphthyl position, activated by diethylaluminum chloride (DEAC) shows highly catalytic activity for the polymerization of ethylene (2.81 × 106 g PE/((mol of Ni) h bar)) and produced branched polyethylene (75 methyl, 9 ethyl, 5 propyl, and 19 butyl or longer branches/1000 C at 40 °C). Interestingly, rac-(RR/SS)-2c could produce syndiotactic PMMA at low temperature (−30 °C: rr 88.75%, mr 7.26%, mm 3.99%).

Analogies and Differences in Palladium‐Catalyzed CO/Styrene and Ethylene/Methyl Acrylate Copolymerization Reactions

“…The studied ligands were synthesized by following the literature procedures, which are based on condensation reactions between the desired naphthylamine and either the acenaphthenequinone [24,39] for 1 BIAN [34] and 2 BIAN, or the 2,3-butanedione [40] for 1 DAB and 2 DAB. [35] The only difference with respect to the literature procedures concerns the DAB ligands, which were obtained with yields of 50 % by simply leaving the reaction mixture for 1 d at room temperature, and not under heating to reflux for the same time as recently reported. [35] 1 BIAN and 2 BIAN are obtained as red solids, and 1 DAB and 2 DAB are yellow solids.…”

“…A paper firstly anticipated ligand 2 DAB during the preparation of this manuscript. [35] The 1 DAB and 2 DAB nickel(II) complexes were applied as precatalysts for both ethylene and methyl methacrylate homopolymerizations. [35] During 2013, the 8-p-tolyl naphthyl-BIAN and -DAB ligands were also synthesized for the first time.…”

“…[35] The 1 DAB and 2 DAB nickel(II) complexes were applied as precatalysts for both ethylene and methyl methacrylate homopolymerizations. [35] During 2013, the 8-p-tolyl naphthyl-BIAN and -DAB ligands were also synthesized for the first time. The related nickel(II) complexes were found to be catalysts for ethylene homopolymerization yielding the most highly branched polyethylene produced till now by Ni II catalysts.…”

Precision Chain‐Walking Polymerization of trans‐4‐Octene Catalyzed by α‐Diimine Nickel(II) Catalysts Bearing ortho‐sec‐Phenethyl Groups

“…We have previously reported that bulky ortho‐sec‐ phenethyl ‐ substituted and ortho‐ phenyl substituted α‐ diimine nickel and palladium complexes exhibited high activities toward ethylene polymerization and produced highly branched polyethylene upon activation with Et 2 AlCl or MMAO, and also produced branched poly(1‐alkene)s with high molecular weight. We anticipated that bulky α‐ diimine ligands might control chain walking and produce regioregular polymers.…”

Room‐temperature Suzuki–Miyauracross‐coupling reaction with α‐diimine Pd(II) catalysts

“…Recently, we reported bulky chiral ortho‐sec ‐diphenethyl substituted (Figs. (a) and (c)) and ortho ‐phenyl substituted (Figs. (b) and (d)) α‐diimine Ni(II) complexes that exhibited high activities towards ethylene polymerization to produce highly branched polyethylene.…”