Suppression of chain transfer via a restricted rotation effect of dibenzosuberyl substituents in polymerization catalysis

Abstract

The introduction of bulky ortho-steric substituents into α-diimine Ni(II) and Pd(II) species has been often used as an effective strategy to retard the chain transfer in olefin polymerization. In this...

Direct synthesis of hyperbranched ethene oligomers and ethene‐MA co‐oligomers using iminopyridyl systems with weak neighboring group interactions

“…Similar to the α‐diimine Pd(II) system, 39–44 iminopyridine Pd(II) catalysts can also be used for the copolymerization of ethene and polar monomers. In this contribution, the newly synthesized iminopyridine Pd(II) catalysts were also tested for the copolymerization of ethene with MA.…”

“…This further indicates that the Pd(II) species can carry out more in-depth chain isomerization and give a more topological molecular structure than the corresponding Ni(II) species. Similar to the α-diimine Pd(II) system, [39][40][41][42][43][44] iminopyridine Pd(II) catalysts can also be used for the copolymerization of ethene and polar monomers. In this contribution, the newly synthesized iminopyridine Pd(II) catalysts were also tested for the copolymerization of ethene with MA.…”

“…11 These results definitely verified the hyperbranched microstructure of the obtained ethene-MA co-oligomers and the ester group is located at the end of the oligomer branches consistent with previous α-diimine Pd(II) catalysts and iminopyridine Pd(II) catalysts. [39][40][41][42][43][44]…”

Synthesis of Branched Polyethylene and Ethylene-MA Copolymers Using Unsymmetrical Iminopyridyl Nickel and Palladium Complexes

“…Our previous studies have shown that the remote nonconjugated electron effect significantly affects the polymerization activity, molecular weight, and branching density of the polyolefins in the α-diimine system. , However, in the iminopyridine Ni­(II) system, the remote nonconjugated electronic substituents (H, Me, F, Cl) exhibited no significant effect on the polymerization parameters (Figure ). Our recent work has revealed a rotation-restricted dibenzosuberyl substituent can effectively retard the chain transfer during ethylene polymerization, thus, leading to a high molecular weight. ,,, The dibenzosuberyl substituent in the iminopyridine Ni­(II) system demonstrated a significant impact on the molecular weight of the generated polyethylene. Compared with the diarylmethyl catalysts Ni1 – Ni4 , the one with the dibenzosuberyl substituent ( Ni5 ) generated an order of magnitude higher molecular weight (Figure b), thus, transforming the system from ethylene oligomerization to ethylene polymerization.…”

“…Our recent work has revealed a rotation-restricted dibenzosuberyl substituent can effectively retard the chain transfer during ethylene polymerization, thus, leading to a high molecular weight. 46,47,53,54 The dibenzosuberyl substituent in the iminopyridine Ni(II) system demonstrated a significant impact on the molecular weight of the generated polyethylene.…”