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Polyolefins are the most consumed polymeric materials extensively used in our daily life and are usually generated by coordination polymerization in the polyolefin industry. Olefin polymerization catalysts containing transition metal–organic compound combinations are undoubtedly crucial for the development of the polyolefin industry. The nitrogen donor atom has attracted considerable interest and is widely used in combination with the transition metal for the fine-tuning of the chemical environment around the metal center. In addition to widely reported olefin polymerization catalysts with imine and amide donors (sp2 hybrid N), late transition metal catalysts with chelating amine donors (sp3 hybrid N) for olefin polymerization have never been reviewed. In this review paper, we focus on late transition metal (Ni, Pd, Fe, and Co) catalysts with chelating amines for olefin polymerization. A variety of late transition metal catalysts bearing different neutral amine donors are surveyed for olefin polymerization, including amine–imine, amine–pyridine, α-diamine, and [N, N, N] tridentate ligands with amine donors. The relationship between catalyst structure and catalytic performance is also encompassed. This review aims to promote the design of late transition metal catalysts with unique chelating amine donors for the development of high-performance polyolefin materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electron-rich ligand facilitates Ni/Pd complex synthesis and thermal stability. • Electronic effects of amine-imine Ni/Pd catalysts on ethylene (co)polymerization. • The electron-donating group promotes Pd-catalyzed E/MA copolymerization. • Electron-rich Pd catalyst favors producing main-chain MA unit in EMA. A series of bis-(aryl)-amine-imine nickel and palladium complexes with electron-donating (OMe), H, and -withdrawing (F and Br) groups at the para -aryl position were synthesized and characterized to probe the ligand electronic effects on homo- and copolymerization of ethylene. The influences of electronic perturbations on complex synthesis, polymerization property, and polymer microstructure were investigated systematically. The electronic effects of para -substituents were verified by Hammett constants and topographic steric maps of nickel and palladium complexes. Electron-rich ligands had stronger complexation ability to the nickel and palladium metal, thereby facilitating the synthesis of nickel and palladium complexes. Ethylene polymerizations at different temperatures showed that electron-deficient amine-imine nickel and palladium catalysts were more active than electron-rich analogues at low temperatures while the reverse trend was observed at high temperatures. The electronic effects of para -substituents affected polyethylene molecular weight, but had little influence on the branching density of highly branched polyethylenes. Copolymerization of ethylene and methyl acrylate (MA) using palladium catalysts demonstrated that the electron-donating group promoted copolymerization performance, and was favorable for direct insertion of MA to produce main-chain MA unit. Electronic effects of amine-imine nickel and palladium catalysts on ethylene polymerization were comprehensively summarized to electronic perturbations on the metal electrophilicity and the thermal tolerance of catalyst. [ABSTRACT FROM AUTHOR]

Poly(norbornene- co-styrene) copolymers were synthesized by copolymerizations of norbornene (NB) and styrene (St) with bis(β-ketoamino) copper complexes [ArNC(R)CHC(R)O]Cu (1, Ar = 2,6-dimethylphenyl, R = CH; 2, Ar = 2,6-diisopropylphenyl, R = CH; 3, Ar = 2,6-diisopropylphenyl, R = CF) in the presence of methylaluminoxane (MAO). The influences of catalyst structure, comonomer feeding ratio, n(Al)/n(Cu) molar ratio, and copolymerization temperature on catalytic activity and compositions of the copolymers were typically investigated. Determination of the reactivity ratios shows a much high reactivity for norbornene ( r(NB) = 19.52, r(St) = 0.48), which supports a coordination mechanism. The structural characterizations of the obtained poly(NB- co-St) copolymers show that styrene units are successfully incorporated into norbornene sequences, and isolated styrene or very short styrene sequences are randomly distributed on the copolymer chain. A high incorporation of styrene up to 35.6 mol% in the poly(NB- co-St) copolymer can be achieved by bis(β-ketoamino) copper catalyst 1. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A novel fluorinated bis(β-ketoamino) copper complex was synthesized and characterized. Norbornene polymerizations with bis(β-ketoamino) copper complexes activated with methylaluminoxane (MAO) were investigated. The highest catalytic activity up to now reported for copper based systems in norbornene polymerization was achieved using fluorinated bis(β-ketoamino) copper/MAO. The influence of precursor structure including steric and electronic effects on catalytic activity for norbornene polymerization was evaluated in detail. Bulky steric substituents and strong electron-withdrawing groups can enhance catalytic activity of precursor for norbornene polymerization through a dissociative mechanism. The influences of polymerization parameters such as polymerization temperature and Al/Cu ratio on norbornene polymerization with bis(β-ketoamino) copper catalysts were also examined. Norbornene polymerization catalyzed by bis(β-ketoamino) copper complexes/MAO proceeded on Cu(I) species through a coordination/insertion mechanism to produce vinyl-addition polynorbornene. [Copyright &y& Elsevier]

Abstract: Norbornene polymerizations with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane were investigated. The influence of ligand structure such as β-diimine, β-diketiminate, fluorinated β-diketiminate, and anilido-imine ligand on catalytic activities for norbornene polymerization was evaluated in detail. Ligands led to different electrophilicity of the nickel metal center, and a relatively positive nickel metal center would result in high catalytic activities for norbornene polymerization. The influences of polymerization temperature and Al/Ni ratio on norbornene polymerization with nickel catalysts bearing β-diimine, β-diketiminate, and fluorinated β-diketiminate ligands were also examined. All of the obtained polymers catalyzed by these nickel catalysts bearing [N,N] ligand are vinylic addition polynorbornenes with different molecular weights. [Copyright &y& Elsevier]

Abstract: The polymerization of styrene with novel catalytic systems of anilido–imino nickel complexes (Ar1N=CHC6H4NAr2) NiBr (Ar1 =Ar2 =2,6-dimethylphenyl, 1; Ar1 =2,6-dimethylphenyl, Ar2 =2,6-diisopropylphenyl, 2; Ar1 =Ar2 =2,6-diisopropylphenyl, 3; Ar1 =2,6-diisopropylphenyl, Ar2 =2,6-dimethylphenyl, 4) activated by methylaluminoxane was investigated. The influence of reaction parameters (temperature, Al/Ni mole ratio, and polymerization time) on styrene polymerization was evaluated. The influence of the bulkiness of the substituents on polymerization activity and polymer characteristics was also ascertained. The obtained polystyrene was an iso-rich atactic polymer and its weight–average molecular weight reached 70500. NMR analysis of the end groups further confirmed that styrene polymerization catalyzed by anilido–imino nickel complexes/MAO systems proceeded through a coordination mechanism, and the chain was initiated through styrene secondary insertion into the Niminated mainly through β-H elimination of styrene producing the chain-end group (ph name="dbnd" />CHPh). [Copyright &y& Elsevier]