Comprehensive studies of the ligand electronic effect on unsymmetrical α-diimine nickel(ii) promoted ethylene (co)polymerizations

The ligand electronic effect plays a significant role in tuning the catalytic activity, molecular weight and topology of polymers, and comonomer incorporation in ethylene (co)polymerization; however, studies are rather limited in the milestone α-diimine late transition metal catalysts. In this contribution, by tailoring a sterically encumbered pentiptycenyl/dibenzhydryl substituted framework, the ligand electronic effects derived from both the para-position of the N-aryl group (horizontal axis: Me, MeO, and Cl) and the para-position of the dibenzhydryl moiety (vertical axis: Me, H, and F) are comprehensively investigated in unsymmetrical α-diimine Ni(II) promoted ethylene (co)polymerizations for the first time. In the ethylene polymerization, the electron-withdrawing Cl group (horizontal axis) prefers to give a higher branching density (145/1000 C) with higher catalytic activity (29 200 kg mol−1 h−1), while the electron-donating Me group affords a higher molecular weight (2573 kDa). Moreover, the electron-withdrawing F group (vertical axis) again generates a higher branching density, but a lower molecular weight with reduced catalytic activity. In contrast, in the ethylene copolymerization with methyl 10-undecenoate, the electron-donating Me group derived from both the horizontal axis and vertical axis is concurrently beneficial, giving an increased polymer molecular weight (374 kDa) and comonomer incorporation with higher catalytic activity. However, all of the electron-withdrawing groups coming from either the horizontal axis (Cl) or vertical axis (F) is not good for copolymerization. This work sheds light on the different effects of electronic substituents on ethylene polymerization and ethylene-polar monomer copolymerization.

[1]  Yixin Zhang,et al.  Unsymmetrical Strategy Makes Significant Differences in α‐Diimine Nickel and Palladium Catalyzed Ethylene (Co)Polymerizations , 2020 .

[2]  Shuaikang Li,et al.  A remote nonconjugated electron effect in insertion polymerization with α-diimine nickel and palladium species , 2020 .

[3]  Zhongbao Jian,et al.  A comprehensive study on highly active pentiptycenyl-substituted bis(imino)pyridyl iron(II) mediated ethylene polymerization , 2020 .

[4]  Hongliang Mu,et al.  Systematic studies on dibenzhydryl and pentiptycenyl substituted pyridine-imine nickel(ii) mediated ethylene polymerization. , 2020, Dalton transactions.

[5]  Changle Chen,et al.  Concerted steric and electronic effects on α-diimine nickel- and palladium-catalyzed ethylene polymerization and copolymerization. , 2020, Science bulletin.

[6]  Binyuan Liu,et al.  π–π interaction effect in insertion polymerization with α-Diimine palladium systems , 2019, Journal of Catalysis.

[7]  Qing Wu,et al.  Effects of backbone substituent and intra-ligand hydrogen bonding interaction on ethylene polymerizations with α-diimine nickel catalysts , 2019, Journal of Catalysis.

[8]  Lei Cui,et al.  Preparation and in situ chain-end-functionalization of branched ethylene oligomers by monosubstituted α-diimine nickel catalysts , 2019, Polymer Chemistry.

[9]  Changle Chen,et al.  A continuing legend: the Brookhart-type α-diimine nickel and palladium catalysts , 2019, Polymer Chemistry.

[10]  Lei Cui,et al.  Pentiptycenyl Substituents in Insertion Polymerization with α-Diimine Nickel and Palladium Species , 2019, Organometallics.

[11]  H. Plenio,et al.  Bispentiptycenyl–Diimine–Nickel Complexes for Ethene Polymerization and Copolymerization with Polar Monomers , 2019, Organometallics.

[12]  Changle Chen,et al.  Synthesis of polyolefin elastomers from unsymmetrical α-diimine nickel catalyzed olefin polymerization , 2018 .

[13]  M. Brookhart,et al.  Exploring Ethylene/Polar Vinyl Monomer Copolymerizations Using Ni and Pd α-Diimine Catalysts. , 2018, Accounts of chemical research.

[14]  Changle Chen.  Designing catalysts for olefin polymerization and copolymerization: beyond electronic and steric tuning , 2018, Nature Reviews Chemistry.

[15]  G. Coates,et al.  Synthesis of Semicrystalline Polyolefin Materials: Precision Methyl Branching via Stereoretentive Chain Walking. , 2018, Journal of the American Chemical Society.

[16]  P. Fornasiero,et al.  The contradictory effect of the methoxy-substituent in palladium-catalyzed ethylene/methyl acrylate cooligomerization. , 2018, Dalton transactions.

[17]  Wen‐Hua Sun,et al.  Recent advances in Ni-mediated ethylene chain growth: N imine -donor ligand effects on catalytic activity, thermal stability and oligo-/polymer structure , 2017 .

[18]  Yi Luo,et al.  A Second-Coordination-Sphere Strategy to Modulate Nickel- and Palladium-Catalyzed Olefin Polymerization and Copolymerization. , 2017, Angewandte Chemie.

[19]  P. Fornasiero,et al.  Palladium‐Catalyzed Ethylene/Methyl Acrylate Co‐Oligomerization: The Effect of a New Nonsymmetrical α‐Diimine with the 1,4‐Diazabutadiene Skeleton , 2017 .

[20]  Yun-peng Zhu,et al.  Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization , 2017 .

[21]  Qing Wu,et al.  Precision Synthesis of Ethylene and Polar Monomer Copolymers by Palladium-Catalyzed Living Coordination Copolymerization , 2017 .

[22]  Wen‐Hua Sun,et al.  Elastomeric polyethylenes accessible via ethylene homo-polymerization using an unsymmetrical α-diimino-nickel catalyst , 2017 .

[23]  Changle Chen,et al.  Unsymmetrical α-diimine palladium catalysts and their properties in olefin (co)polymerization , 2017 .

[24]  Guodong Liang,et al.  Enhancing Thermal Stability and Living Fashion in α-Diimine–Nickel-Catalyzed (Co)polymerization of Ethylene and Polar Monomer by Increasing the Steric Bulk of Ligand Backbone , 2017 .

[25]  W. Zhang,et al.  Systematic Investigations of Ligand Steric Effects on α-Diimine Palladium Catalyzed Olefin Polymerization and Copolymerization , 2016 .

[26]  Changle Chen,et al.  Direct Synthesis of Functionalized High-Molecular-Weight Polyethylene by Copolymerization of Ethylene with Polar Monomers. , 2016, Angewandte Chemie.

[27]  G. Coates,et al.  Semi-Crystalline Polar Polyethylene: Ester-Functionalized Linear Polyolefins Enabled by a Functional-Group-Tolerant, Cationic Nickel Catalyst. , 2016, Angewandte Chemie.

[28]  Changle Chen,et al.  Influence of ligand second coordination sphere effects on the olefin (co)polymerization properties of α-diimine Pd(II) catalysts , 2016 .

[29]  Lihua Guo,et al.  Investigations of the Ligand Electronic Effects on α-Diimine Nickel(II) Catalyzed Ethylene Polymerization , 2016, Polymers.

[30]  Lihua Guo,et al.  Palladium and Nickel Catalyzed Chain Walking Olefin Polymerization and Copolymerization , 2016 .

[31]  Changle Chen,et al.  Highly Robust Palladium(II) α-Diimine Catalysts for Slow-Chain-Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate. , 2015, Angewandte Chemie.

[32]  F. Bertini,et al.  Ni(II) α-Diimine-Catalyzed α-Olefins Polymerization: Thermoplastic Elastomers of Block Copolymers , 2015 .

[33]  O. Daugulis,et al.  Living Polymerization of Ethylene and Copolymerization of Ethylene/Methyl Acrylate Using “Sandwich” Diimine Palladium Catalysts , 2015 .

[34]  B. Long,et al.  Enhancing α-Diimine Catalysts for High-Temperature Ethylene Polymerization , 2014 .

[35]  B. Long,et al.  A robust Ni(II) α-diimine catalyst for high temperature ethylene polymerization. , 2013, Journal of the American Chemical Society.

[36]  E. T. Nadres,et al.  Synthesis of Highly Branched Polyethylene Using “Sandwich” (8-p-Tolyl naphthyl α-diimine)nickel(II) Catalysts , 2013 .

[37]  P. Fornasiero,et al.  Palladium‐Catalyzed Ethylene/Methyl Acrylate Cooligomerization: Effect of a New Nonsymmetric α‐Diimine , 2013 .

[38]  Z. Guan,et al.  Systematic Investigation of Ligand Substitution Effects in Cyclophane-Based Nickel(II) and Palladium(II) Olefin Polymerization Catalysts(1) , 2011 .

[39]  Z. Guan,et al.  Effect of Ligand Electronics on the Stability and Chain Transfer Rates of Substituted Pd(II) α-Diimine Catalysts(1) , 2010 .

[40]  Z. Guan,et al.  Efficient incorporation of polar comonomers in copolymerizations with ethylene using a cyclophane-based Pd(II) alpha-diimine catalyst. , 2007, Journal of the American Chemical Society.

[41]  Othmar Marti,et al.  New nickel(II) diimine complexes and the control of polyethylene microstructure by catalyst design. , 2007, Journal of the American Chemical Society.

[42]  Z. Guan,et al.  Ligand Electronic Effects on Late Transition Metal Polymerization Catalysts , 2005 .

[43]  J. Ziller,et al.  Cyclophane-based highly active late-transition-metal catalysts for ethylene polymerization. , 2004, Angewandte Chemie.

[44]  M. Brookhart,et al.  Mechanistic studies of nickel(II) alkyl agostic cations and alkyl ethylene complexes: investigations of chain propagation and isomerization in (alpha-diimine)Ni(II)-catalyzed ethylene polymerization. , 2003, Journal of the American Chemical Society.

[45]  E. Oñate,et al.  Synthesis of branched polyethylene using (α-diimine)nickel(II) catalysts : influence of temperature, ethylene pressure, and ligand structure on polymer properties , 2000 .

[46]  McLain,et al.  Chain walking: A new strategy to control polymer topology , 1999, Science.

[47]  S. Mecking,et al.  Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and α-Olefins with Methyl Acrylate , 1998 .

[48]  S. Mecking,et al.  Copolymerization of Ethylene and Propylene with Functionalized Vinyl Monomers by Palladium(II) Catalysts , 1996 .

[49]  Maurice Brookhart,et al.  New Pd(II)- and Ni(II)-Based Catalysts for Polymerization of Ethylene and .alpha.-Olefins , 1995 .