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Phosphine-Phenoxide Nickel Catalysts for Ethylene/Acrylate Copolymerization: Olefin Coordination and Complex Isomerization Studies Relevant to the Mechanism of Catalysis

Shoshani, Manar M. and Xiong, Shuoyan and Lawniczak, James J. and Zhang, Xinglong and Miller, Thomas F., III and Agapie, Theodor (2022) Phosphine-Phenoxide Nickel Catalysts for Ethylene/Acrylate Copolymerization: Olefin Coordination and Complex Isomerization Studies Relevant to the Mechanism of Catalysis. Organometallics, 41 (15). pp. 2119-2131. ISSN 0276-7333. doi:10.1021/acs.organomet.2c00241.

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The insertion copolymerization of ethylene and acrylate remains a challenge in polymer synthesis due to decreased activities upon incorporation of the polar monomer. Toward gaining mechanistic insight, two elusive four-membered chelated intermediates generated after acrylate insertion were prepared (1-CCO and 2-CCO), and their ligand coordination and substitution behavior were studied. Specifically, an ethylene-coordinated species was characterized by NMR spectroscopy upon exposing 2-CCO to ethylene at low temperatures, a rare observation for neutral late-transition metal polymerization catalysts. Thermodynamics of chelate-opening and monomer coordination from 2-CCO were determined at −90 °C (ΔG of 0.4 kcal/mol for ethylene and 1.9 kcal/mol for 1-hexene). The Gibbs energy barrier of ligand exchange from pyridine to ethylene, a prerequisite for ethylene insertion in catalysis, was determined to be 3.3 kcal/mol. Ligand-binding studies reveal that compared to NiMe and Ni(CH₂SiMe₃) complexes, acrylate inserted species 1L-CCO and 2L-CCO produce compressed thermodynamic binding scales for both electronically and sterically differentiating ligands, potentially related to their more electron-deficient nickel centers as suggested by computational studies. Triethylphosphine complexes 1P, 2P, and 2P–Me were observed as both cis and trans isomers in solution. ³¹P{¹H} EXSY NMR studies of 2P reveal conversion between a cis and trans isomers that does not involve exchange with free PEt₃, supporting the mechanism of intramolecular isomerization. 2-CCO, a neutral Ni(II) precatalyst that does not display an auxiliary ligand, serves as a highly active catalyst for copolymerization.

Item Type:Article
Related URLs:
URLURL TypeDescription
Shoshani, Manar M.0000-0002-4051-3367
Xiong, Shuoyan0000-0002-2579-4260
Lawniczak, James J.0000-0003-1898-9809
Zhang, Xinglong0000-0003-1698-692X
Miller, Thomas F., III0000-0002-1882-5380
Agapie, Theodor0000-0002-9692-7614
Additional Information:© 2022 American Chemical Society. Published online 14 July 2022. We are grateful to Dow (T.A.) and the Natural Sciences and Engineering Research Counsel of Canada (M.M.S.) for funding. X.Z. acknowledges the Agency for Science, Technology and Research (A*STAR), Singapore, for a National Science Scholarship. We thank Brad Bailey and Heather Spinney (Dow) for insightful discussions. We thank Michael Takase and Lawrence Henling for assistance with X-ray crystallography and David VanderVelde for assistance with NMR spectroscopy. We thank Alex Nett, Briana Henderson, and Hannah Bailey (Dow) for assistance in collecting polymer characterization data (GPC, DSC, and FT-IR). Support has been provided for the X-ray diffraction and NMR instrumentation via the Dow Next Generation Educator Fund. This work used the Bridges-2 system at the Pittsburgh Supercomputing Center (PSC). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE--1144469. Author Contributions. M.M.S and S.X contributed equally. The authors declare no competing financial interest. Accession Codes. CCDC 2173352–2173356 and 2173358 contain the supplementary crystallographic data for this paper.
Funding AgencyGrant Number
Dow Next Generation Educator FundUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Agency for Science, Technology and Research (A*STAR)UNSPECIFIED
NSF Graduate Research FellowshipDGE-1144469
Subject Keywords:Catalysts, Hydrocarbons, Ligands, Molecular structure, Organic compounds
Issue or Number:15
Record Number:CaltechAUTHORS:20220720-918328000
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Official Citation:Phosphine-Phenoxide Nickel Catalysts for Ethylene/Acrylate Copolymerization: Olefin Coordination and Complex Isomerization Studies Relevant to the Mechanism of Catalysis. Manar M. Shoshani, Shuoyan Xiong, James J. Lawniczak, Xinglong Zhang, Thomas F. Miller III, and Theodor Agapie. Organometallics 2022 41 (15), 2119-2131; DOI: 10.1021/acs.organomet.2c00241
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115705
Deposited By: George Porter
Deposited On:22 Jul 2022 21:25
Last Modified:24 Aug 2022 21:53

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