Neutral Tridentate α‑Sulfonato-β-diimine Nickel Catalyst for (Co)polymerizations of Ethylene and Acrylates

The development of highly tolerable
metal catalysts to polar monomers
is of fundamental importance for the metal-catalyzed copolymerization
of ethylene and industrial polar vinyl monomers under mild conditions
but still remains a scientific challenge. In this paper, a neutral
tridentate α-sulfonato-β-diimine nickel catalyst with
an apical SO3–Ni coordination was initially designed
and synthesized in three dimensions. Combining advantages of cationic
diimine and neutral phosphine-sulfonato-type catalysts, the α-sulfonato-β-diimine
nickel catalyst showed good thermostability and controllability as
well as high tolerance toward polar alkyl acrylates. Copolymerization
of ethylene and methyl acrylate (MA) produced branched ethylene–methyl
acrylate (EMA) copolymers with both high molecular weight (Mn > 20 × 103) and high MA
incorporation
(up to 10 mol %), whose branching structure was similar to commercial
EMA industrially prepared by radical polymerization under harsh polymerization
conditions. Density functional theory calculations were also performed
to illuminate the formation of the EMA copolymer with terminal MA
units.