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Young MS, LaPointe AM, MacMillan SN, Coates GW. Highly Enantioselective Polymerization of β-Butyrolactone by a Bimetallic Magnesium Catalyst: An Interdependent Relationship Between Favored and Unfavored Enantiomers. J Am Chem Soc 2024. [PMID: 38874569 DOI: 10.1021/jacs.4c04716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Herein, we report that (S,S)-prophenolMg2(μ-OnBu)(THF)2 ((S,S)-1, prophenol = (S,S)-2,6-bis[2-(hydroxydiphenylmethyl)pyrrolidin-1-ylmethyl]-4-methylphenol) is a highly enantioselective (kR/kS = 140) precatalyst for ring-opening polymerization of rac-β-butyrolactone (β-BL) to isotactic poly(3-hydroxybutyrate) (i-PHB), a high performance, biodegradable polyester. Precatalyst (S,S)-1 polymerizes (R)-β-BL with an inversion of stereochemistry to (S)-PHB with a m% (percentage of adjacent linkages with a meso configuration) of 98% at 41% conversion and Tm of 165 °C under a variety of conditions. Complex (S,S)-1 demonstrates unique polymerization kinetics, as it does not polymerize the preferred enantiomer, (R)-β-BL, alone. Mechanistic studies revealed that (S)-β-BL is needed to convert (S,S)-1 into the active enantioselective polymerization catalyst. To the best of our knowledge, (S,S)-1 produces i-PHB with the highest degree of isotacticity observed from a polymerization of rac-β-BL. This study informs the design and understanding of future enantioselective and earth-abundant metal catalysts for ring-opening polymerization of β-lactones.
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Affiliation(s)
- Morgan S Young
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Anne M LaPointe
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Geoffrey W Coates
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
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2
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Abdul Rahman M, Neal TJ, Garden JA. Cooperative heterometallic catalysts: balancing activity and control in PCL- block-PLA copolymer synthesis. Chem Commun (Camb) 2024; 60:5530-5533. [PMID: 38695674 DOI: 10.1039/d4cc01664e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Heterometallic cooperativity is gaining momentum in cyclic ester ring-opening polymerisation, yet remains surprisingly underexplored in their block copolymerisations. Here, we report the first homogeneous heterometallic "ate" catalysts for poly(ε-caprolactone)-poly(lactic acid) block copolymers, showcasing the substantial differences in the polymer structures observed upon exchanging Zn for Mg or Ca.
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Affiliation(s)
| | - Thomas J Neal
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Jennifer A Garden
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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3
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Yolsal U, Shaw PJ, Lowy PA, Chambenahalli R, Garden JA. Exploiting Multimetallic Cooperativity in the Ring-Opening Polymerization of Cyclic Esters and Ethers. ACS Catal 2024; 14:1050-1074. [PMID: 38269042 PMCID: PMC10804381 DOI: 10.1021/acscatal.3c05103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/17/2023] [Accepted: 12/19/2023] [Indexed: 01/26/2024]
Abstract
The use of multimetallic complexes is a rapidly advancing route to enhance catalyst performance in the ring-opening polymerization of cyclic esters and ethers. Multimetallic catalysts often outperform their monometallic analogues in terms of reactivity and/or polymerization control, and these improvements are typically attributed to "multimetallic cooperativity". Yet the origins of multimetallic cooperativity often remain unclear. This review explores the key factors underpinning multimetallic cooperativity, including metal-metal distances, the flexibility, electronics and conformation of the ligand framework, and the coordination environment of the metal centers. Emerging trends are discussed to provide insights into why cooperativity occurs and how to harness cooperativity for the development of highly efficient multimetallic catalysts.
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Affiliation(s)
- Utku Yolsal
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Peter J. Shaw
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Phoebe A. Lowy
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Raju Chambenahalli
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Jennifer A. Garden
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
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4
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Hughes JWJ, Babula DJ, Stowers-Veitch F, Yuan K, Uzelac M, Nichol GS, Ingleson MJ, Garden JA. NacNac-zinc-pyridonate mediated ε-caprolactone ROP. Dalton Trans 2023; 52:17767-17775. [PMID: 37981810 PMCID: PMC10696559 DOI: 10.1039/d3dt03344a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 11/10/2023] [Indexed: 11/21/2023]
Abstract
Herein we report the synthesis, isolation and polymerisation activity of two new zinc compounds based on a 2,6-diisopropylphenyl (Dipp) β-diiminate (NacNac) ligand framework with zinc also ligated by an amidate (2-pyridonate or 6-methyl-2-pyridonate) unit. The compounds crystallised as either monomeric (6-Me-2-pyridonate derivative) or dimeric (2-pyridonate) species, although both were found to be monomeric in solution via1H DOSY NMR spectroscopy, which was supported by DFT calculations. These observations suggest that both complexes initiate ring-opening polymerisation (ROP) through a single-site monometallic mechanism. High molecular weight poly ε-caprolactone (PCL) was achieved via exogenous initiator-free ROP conditions with both catalysts. An increase in the 2-pyridonate initiator steric bulk (6-Me- vs. 6-H-) resulted in an improved catalytic activity, facilitating complete monomer conversion within 1 h at 60 °C. Pyridonate end-groups were observed by MALDI-ToF mass spectrometry, contrasting with previous observations for DippNacNac-Zn acetate complexes (where no acetate end groups are observed), instead this more closely resembles the reactivity of DippNacNac-Zn alkoxide complexes in ROP (where RO end groups are observed). Additional major signals in the MALDI-ToF spectra were consistent with cyclic PCL species, which are attributed to back-biting ring-closing termination steps occuring in a process facilitated by the pyridonate unit being an effective leaving group. To the best of our knowledge, these complexes represent the first examples of pyridonate, and indeed amidate, initated ROP.
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Affiliation(s)
- Jack W J Hughes
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Dawid J Babula
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | | | - Kang Yuan
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Marina Uzelac
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Gary S Nichol
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Michael J Ingleson
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Jennifer A Garden
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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5
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Fiorentini F, Diment WT, Deacy AC, Kerr RWF, Faulkner S, Williams CK. Understanding catalytic synergy in dinuclear polymerization catalysts for sustainable polymers. Nat Commun 2023; 14:4783. [PMID: 37553344 PMCID: PMC10409799 DOI: 10.1038/s41467-023-40284-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/20/2023] [Indexed: 08/10/2023] Open
Abstract
Understanding the chemistry underpinning intermetallic synergy and the discovery of generally applicable structure-performances relationships are major challenges in catalysis. Additionally, high-performance catalysts using earth-abundant, non-toxic and inexpensive elements must be prioritised. Here, a series of heterodinuclear catalysts of the form Co(III)M(I/II), where M(I/II) = Na(I), K(I), Ca(II), Sr(II), Ba(II) are evaluated for three different polymerizations, by assessment of rate constants, turn over frequencies, polymer selectivity and control. This allows for comparisons of performances both within and between catalysts containing Group I and II metals for CO2/propene oxide ring-opening copolymerization (ROCOP), propene oxide/phthalic anhydride ROCOP and lactide ring-opening polymerization (ROP). The data reveal new structure-performance correlations that apply across all the different polymerizations: catalysts featuring s-block metals of lower Lewis acidity show higher rates and selectivity. The epoxide/heterocumulene ROCOPs both show exponential activity increases (vs. Lewis acidity, measured by the pKa of [M(OH2)m]n+), whilst the lactide ROP activity and CO2/epoxide selectivity show linear increases. Such clear structure-activity/selectivity correlations are very unusual, yet are fully rationalised by the polymerization mechanisms and the chemistry of the catalytic intermediates. The general applicability across three different polymerizations is significant for future exploitation of catalytic synergy and provides a framework to improve other catalysts.
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Affiliation(s)
| | - Wilfred T Diment
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Arron C Deacy
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Ryan W F Kerr
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Stephen Faulkner
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
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Wu LJ, Lee W, Kumar Ganta P, Chang YL, Chang YC, Chen HY. Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.214847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Fazekas E, Lowy PA, Abdul Rahman M, Lykkeberg A, Zhou Y, Chambenahalli R, Garden JA. Main group metal polymerisation catalysts. Chem Soc Rev 2022; 51:8793-8814. [PMID: 36214205 DOI: 10.1039/d2cs00048b] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
With sustainability at the forefront of current polymerisation research, the typically earth-abundant, inexpensive and low-toxicity main group metals are attractive candidates for catalysis. Main group metals have been exploited in a broad range of polymerisations, ranging from classical alkene polymerisation to the synthesis of new bio-derived and degradable polyesters and polycarbonates via ring-opening polymerisation and ring-opening copolymerisation. This tutorial review highlights efficient polymerisation catalysts based on Group 1, Group 2, Zn and Group 13 metals. Key mechanistic pathways and catalyst developments are discussed, including tailored ligand design, heterometallic cooperativity, bicomponent systems and careful selection of the polymerisation conditions, all of which can be used to fine-tune the metal Lewis acidity and the metal-alkyl bond polarity.
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Affiliation(s)
- Eszter Fazekas
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Phoebe A Lowy
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | | | - Anna Lykkeberg
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Yali Zhou
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Raju Chambenahalli
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Jennifer A Garden
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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Abstract
ConspectusThis Account discusses the evolution of our strategy to conduct environmentally responsible research in the field of polymer chemistry. To contextualize our work, we begin with a broad historical overview of the modern environmental movement, the rise of sustainability as a concept, and how chemistry has responded to these forces, which were often sharply critical of our field. We then trace our own responses, from graduate school onward, chronicling a series of experiences and research projects that molded, challenged, and reshaped how we think about sustainability in polymer science.Since beginning our independent careers in 2004, we have recognized and worked to resolve the tension between designing synthetic polymers for specific desired thermomechanical properties and minimizing environmental impact. In our early years, we were most strongly guided by the 12 Principles of Green Chemistry (12PGC), which had only recently been proposed. The authors' early research agendas had a rather narrow focus on two areas, specifically catalysis and biobased monomers, which we saw as strongly linked to sustainability. Over time, we found these areas to be too narrow in their focus, ignoring important considerations such as the capacity of monomer supply to support scale-up and the impact polymers have at the end of their usage lifetimes. With respect to monomers and catalysts, we consider descriptive metrics that quantify waste production and the toxicity of compounds used during synthesis. In terms of polymer end-of-life, we discuss hydrophobicity as a tool to help understand susceptibility to degradation in the environment as well as some of the concerns with design for degradation, a critical component of 12PGC.Now, after nearly two decades of investigation, we believe that achieving sustainability in polymer science will require us to move beyond the qualitative use of the 12PGC to a portfolio of metrics. We note a heartening increase in the availability and use of such metrics and tools across the field. These include items that provide limited insight but are relatively trivial to integrate into existing workflows such as E factor or the Toxicity Estimation Software Tool. We also appreciate the increased use of Life Cycle Assessment (LCA), which is both dramatically more thorough and difficult to deploy. Finally, we propose the creation of a national LCA center, similar to instrumental core facilities. Such a resource would enable the use of this tool across multiple phases of research and we hope would more effectively guide us to a sustainable future.
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Affiliation(s)
| | - Robert T Mathers
- Department of Chemistry, Pennsylvania State University, New Kensington, Pennsylvania 15068, United States
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9
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Incorporating Sodium to Boost the Activity of Aluminium TrenSal Complexes towards
rac
‐Lactide Polymerisation. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202200134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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10
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Gruszka W, Garden JA. Salt additives as activity boosters: a simple strategy to access heterometallic cooperativity in lactide polymerisation. Chem Commun (Camb) 2022; 58:1609-1612. [PMID: 35018909 DOI: 10.1039/d1cc06594g] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Inorganic salt additives can activate carbonyl groups towards organic addition reactions. Here, we translate this concept to ring-opening polymerisation for the first time, generating heterometallic ProPhenol catalysts in situ, which show similar activity enhancements to pre-formed heterometallic complexes. Extremely high activities are observed, with K/Mg and K/Ca combinations converting >85 eq. lactide in 5 s at room temperature.
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Affiliation(s)
- Weronika Gruszka
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - Jennifer A Garden
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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Petrus R, Utko J, Petrus JK, Awashra M, Lis T. Use of group 13 aryloxides for the synthesis of green chemicals and oxide materials. Dalton Trans 2022; 51:4135-4152. [DOI: 10.1039/d1dt03777c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, group 13 metal aryloxides [Al(MesalO)3] (1), [Me2Ga(MesalO)]2 (2), [AlLi3(MesalO)6] (3) and [Me2GaLi(MesalO)2(THF)] (4), were obtained by reaction of methyl salicylate (MesalOH) with group-13 alkyls MMe3 (for M...
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