1
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Rosetto G, Vidal F, McGuire TM, Kerr RWF, Williams CK. High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics. J Am Chem Soc 2024; 146:8381-8393. [PMID: 38484170 PMCID: PMC10979403 DOI: 10.1021/jacs.3c14170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/19/2024] [Accepted: 02/22/2024] [Indexed: 03/28/2024]
Abstract
Using carbon dioxide (CO2) to make recyclable thermoplastics could reduce greenhouse gas emissions associated with polymer manufacturing. CO2/cyclic epoxide ring-opening copolymerization (ROCOP) allows for >30 wt % of the polycarbonate to derive from CO2; so far, the field has largely focused on oligocarbonates. In contrast, efficient catalysts for high molar mass polycarbonates are underinvestigated, and the resulting thermoplastic structure-property relationships, processing, and recycling need to be elucidated. This work describes a new organometallic Mg(II)Co(II) catalyst that combines high productivity, low loading tolerance, and the highest polymerization control to yield polycarbonates with number average molecular weight (Mn) values from 4 to 130 kg mol-1, with narrow, monomodal distributions. It is used in the ROCOP of CO2 with bicyclic epoxides to produce a series of samples, each with Mn > 100 kg mol-1, of poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC, by hydrogenation of PvCHC), and poly(cyclopentene carbonate) (PCPC). All these materials are amorphous thermoplastics, with high glass transition temperatures (85 < Tg < 126 °C, by differential scanning calorimetry) and high thermal stability (Td > 260 °C). The cyclic ring substituents mediate the materials' chain entanglements, viscosity, and glass transition temperatures. Specifically, PCPC was found to have 10× lower entanglement molecular weight (Me)n and 100× lower zero-shear viscosity compared to those of PCHC, showing potential as a future thermoplastic. All these high molecular weight polymers are fully recyclable, either by reprocessing or by using the Mg(II)Co(II) catalyst for highly selective depolymerizations to epoxides and CO2. PCPC shows the fastest depolymerization rates, achieving an activity of 2500 h-1 and >99% selectivity for cyclopentene oxide and CO2.
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Affiliation(s)
| | | | - Thomas M. McGuire
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Rd, Oxford OX1 3TA, U.K.
| | - Ryan W. F. Kerr
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Rd, Oxford OX1 3TA, U.K.
| | - Charlotte K. Williams
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Rd, Oxford OX1 3TA, U.K.
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2
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Vidal F, van der Marel ER, Kerr RWF, McElroy C, Schroeder N, Mitchell C, Rosetto G, Chen TTD, Bailey RM, Hepburn C, Redgwell C, Williams CK. Designing a circular carbon and plastics economy for a sustainable future. Nature 2024; 626:45-57. [PMID: 38297170 DOI: 10.1038/s41586-023-06939-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 12/05/2023] [Indexed: 02/02/2024]
Abstract
The linear production and consumption of plastics today is unsustainable. It creates large amounts of unnecessary and mismanaged waste, pollution and carbon dioxide emissions, undermining global climate targets and the Sustainable Development Goals. This Perspective provides an integrated technological, economic and legal view on how to deliver a circular carbon and plastics economy that minimizes carbon dioxide emissions. Different pathways that maximize recirculation of carbon (dioxide) between plastics waste and feedstocks are outlined, including mechanical, chemical and biological recycling, and those involving the use of biomass and carbon dioxide. Four future scenarios are described, only one of which achieves sufficient greenhouse gas savings in line with global climate targets. Such a bold system change requires 50% reduction in future plastic demand, complete phase-out of fossil-derived plastics, 95% recycling rates of retrievable plastics and use of renewable energy. It is hard to overstate the challenge of achieving this goal. We therefore present a roadmap outlining the scale and timing of the economic and legal interventions that could possibly support this. Assessing the service lifespan and recoverability of plastic products, along with considerations of sufficiency and smart design, can moreover provide design principles to guide future manufacturing, use and disposal of plastics.
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Affiliation(s)
- Fernando Vidal
- Department of Chemistry, University of Oxford, Oxford, UK
- POLYMAT, University of the Basque Country (UPV/EHU), Donostia-San Sebastian, Spain
| | - Eva R van der Marel
- Faculty of Law, University of Oxford, Oxford, UK
- Faculty of Law, UiT The Arctic University of Norway, Tromsø, Norway
| | - Ryan W F Kerr
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Caitlin McElroy
- Smith School of Enterprise and the Environment, University of Oxford, Oxford, UK
| | - Nadia Schroeder
- Smith School of Enterprise and the Environment, University of Oxford, Oxford, UK
| | - Celia Mitchell
- Smith School of Enterprise and the Environment, University of Oxford, Oxford, UK
| | - Gloria Rosetto
- Department of Chemistry, University of Oxford, Oxford, UK
| | | | - Richard M Bailey
- School of Geography and the Environment, University of Oxford, Oxford, UK
| | - Cameron Hepburn
- Smith School of Enterprise and the Environment, University of Oxford, Oxford, UK.
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3
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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4
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Kerr RWF, Williams CK. Zr(IV) Catalyst for the Ring-Opening Copolymerization of Anhydrides (A) with Epoxides (B), Oxetane (B), and Tetrahydrofurans (C) to Make ABB- and/or ABC-Poly(ester- alt-ethers). J Am Chem Soc 2022; 144:6882-6893. [PMID: 35388696 PMCID: PMC9084548 DOI: 10.1021/jacs.2c01225] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Poly(ester-alt-ethers) can combine beneficial ether linkage flexibility and polarity with ester linkage hydrolysability, furnishing fully degradable polymers. Despite their promising properties, this class of polymers remains underexplored, in part due to difficulties in polymer synthesis. Here, a catalyzed copolymerization using commercially available monomers, butylene oxide (BO)/oxetane (OX), tetrahydrofuran (THF), and phthalic anhydride (PA), accesses a series of well-defined poly(ester-alt-ethers). A Zr(IV) catalyst is reported that yields polymer repeat units comprising a ring-opened PA (A), followed by two ring-opened cyclic ethers (B/C) (-ABB- or -ABC-). It operates with high polymerization control, good rate, and successfully enchains epoxides, oxetane, and/or tetrahydrofurans, providing a straightforward means to moderate the distance between ester linkages. Kinetic analysis of PA/BO copolymerization, with/without THF, reveals an overall second-order rate law: first order in both catalyst and butylene oxide concentrations but zero order in phthalic anhydride and, where it is present, zero order in THF. Poly(ester-alt-ethers) have lower glass-transition temperatures (-16 °C < Tg < 12 °C) than the analogous alternating polyesters, consistent with the greater backbone flexibility. They also show faster ester hydrolysis rates compared with the analogous AB polymers. The Zr(IV) catalyst furnishes poly(ester-alt-ethers) from a range of commercially available epoxides and anhydride; it presents a straightforward method to moderate degradable polymers' properties.
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Affiliation(s)
- Ryan W F Kerr
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K
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5
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Diment WT, Gregory GL, Kerr RWF, Phanopoulos A, Buchard A, Williams CK. Catalytic Synergy Using Al(III) and Group 1 Metals to Accelerate Epoxide and Anhydride Ring-Opening Copolymerizations. ACS Catal 2021. [DOI: 10.1021/acscatal.1c04020] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Wilfred T. Diment
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Georgina L. Gregory
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Ryan W. F. Kerr
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Andreas Phanopoulos
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Antoine Buchard
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K
| | - Charlotte K. Williams
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
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6
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DeJesus JF, Kerr RWF, Penchoff DA, Carroll XB, Peterson CC, Arnold PL, Jenkins DM. Actinide tetra-N-heterocyclic carbene 'sandwiches'. Chem Sci 2021; 12:7882-7887. [PMID: 34168841 PMCID: PMC8188502 DOI: 10.1039/d1sc01007g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/15/2021] [Indexed: 11/21/2022] Open
Abstract
Highly-symmetrical, thorium and uranium octakis-carbene 'sandwich' complexes have been prepared by 'sandwiching' the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms. The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.
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Affiliation(s)
- Joseph F DeJesus
- Department of Chemistry, The University of Tennessee Knoxville Tennessee 37996 USA
| | - Ryan W F Kerr
- School of Chemistry, University of Edinburgh West Mains Road Edinburgh EH9 3JJ UK
| | - Deborah A Penchoff
- Howard H. Baker Jr. Center for Public Policy, The University of Tennessee Knoxville Tennessee 37996 USA
| | - Xian B Carroll
- Department of Chemistry, The University of Tennessee Knoxville Tennessee 37996 USA
| | - Charles C Peterson
- Howard H. Baker Jr. Center for Public Policy, The University of Tennessee Knoxville Tennessee 37996 USA
- Research IT Services, University of North Texas Denton Texas 76201 USA
| | - Polly L Arnold
- School of Chemistry, University of Edinburgh West Mains Road Edinburgh EH9 3JJ UK
| | - David M Jenkins
- Department of Chemistry, The University of Tennessee Knoxville Tennessee 37996 USA
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7
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Affiliation(s)
- Ryan W. F. Kerr
- EaStCHEM School of Chemistry, University of Edinburgh, The King’s Buildings, Edinburgh EH9 3FJ, U.K
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, U.K
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Paul M. D. A. Ewing
- EaStCHEM School of Chemistry, University of Edinburgh, The King’s Buildings, Edinburgh EH9 3FJ, U.K
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, U.K
| | - Sumesh K. Raman
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Andrew D. Smith
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, U.K
| | - Charlotte K. Williams
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Polly L. Arnold
- EaStCHEM School of Chemistry, University of Edinburgh, The King’s Buildings, Edinburgh EH9 3FJ, U.K
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8
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Deacy AC, Durr CB, Kerr RWF, Williams CK. Heterodinuclear catalysts Zn(ii)/M and Mg(ii)/M, where M = Na(i), Ca(ii) or Cd(ii), for phthalic anhydride/cyclohexene oxide ring opening copolymerisation. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00238d] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A series of heterodinuclear catalysts, coordinated by a Schiff base ligand, for ring opening copolymerisation of phthalic anhydride/cyclohexene oxide, highlight the best metal combinations for fast and selective catalysis.
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Affiliation(s)
- Arron C. Deacy
- Chemistry Research Laboratory
- Department of Chemistry
- Oxford OX1 3TA
- UK
| | | | - Ryan W. F. Kerr
- Chemistry Research Laboratory
- Department of Chemistry
- Oxford OX1 3TA
- UK
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9
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Diment WT, Stößer T, Kerr RWF, Phanopoulos A, Durr CB, Williams CK. Ortho-vanillin derived Al(iii) and Co(iii) catalyst systems for switchable catalysis using ε-decalactone, phthalic anhydride and cyclohexene oxide. Catal Sci Technol 2021. [DOI: 10.1039/d0cy02164d] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Switchable catalysis is a useful one-pot method to prepare block polyesters utilising a single catalyst exposed to a mixture of monomers.
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Affiliation(s)
| | - Tim Stößer
- Oxford Chemistry
- Chemical Research Laboratory
- Oxford
- UK
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10
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Raman SK, Deacy AC, Pena Carrodeguas L, Reis NV, Kerr RWF, Phanopoulos A, Morton S, Davidson MG, Williams CK. Ti(IV)-Tris(phenolate) Catalyst Systems for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide. Organometallics 2020; 39:1619-1627. [PMID: 32421072 PMCID: PMC7218927 DOI: 10.1021/acs.organomet.9b00845] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Indexed: 01/05/2023]
Abstract
![]()
Titanium(IV)
complexes of amino-tris(phenolate) ligands (LTiX,
X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium
chloride (PPNCl) are active catalyst systems for the ring-opening
copolymerization of carbon dioxide and cyclohexene oxide. They show
moderate activity, with turnover frequency values of ∼60 h–1 (0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their
absolute performances are lower than those of the most active Ti(IV)
catalyst systems. The reactions proceed with linear evolution of polycarbonate
(PCHC) molar mass with epoxide conversion, consistent with controlled
polymerizations, and evolve bimodal molar mass distributions of PCHC
(up to Mn = 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl,
allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized
using single-crystal X-ray diffraction techniques. The anionic titanium
complex [LTi(OR)Cl]− is proposed as a model for
the propagating alkoxide intermediates in the catalytic cycle.
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Affiliation(s)
- Sumesh K Raman
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Arron C Deacy
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Leticia Pena Carrodeguas
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Natalia V Reis
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Ryan W F Kerr
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Andreas Phanopoulos
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Sebastian Morton
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Matthew G Davidson
- Centre for Sustainable Chemical Technologies, Department of Chemistry, University of Bath, Bath BA2 7AY, U.K
| | - Charlotte K Williams
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
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11
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Arnold PL, Kerr RWF, Weetman C, Docherty SR, Rieb J, Cruickshank FL, Wang K, Jandl C, McMullon MW, Pöthig A, Kühn FE, Smith AD. Selective and catalytic carbon dioxide and heteroallene activation mediated by cerium N-heterocyclic carbene complexes. Chem Sci 2018; 9:8035-8045. [PMID: 30568765 PMCID: PMC6262539 DOI: 10.1039/c8sc03312a] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/05/2018] [Indexed: 11/21/2022] Open
Abstract
A series of rare earth complexes of the form Ln(LR)3 supported by bidentate ortho-aryloxide-NHC ligands are reported (LR = 2-O-3,5-tBu2-C6H2(1-C{N(CH)2N(R)})); R = iPr, tBu, Mes; Ln = Ce, Sm, Eu). The cerium complexes cleanly and quantitatively insert carbon dioxide exclusively into all three cerium carbene bonds, forming Ce(LR·CO2)3. The insertion is reversible only for the mesityl-substituted complex Ce(LMes)3. Analysis of the capacity of Ce(LR)3 to insert a range of heteroallenes that are isoelectronic with CO2 reveals the solvent and ligand size dependence of the selectivity. This is important because only the complexes capable of reversible CO2-insertion are competent catalysts for catalytic conversions of CO2. Preliminary studies show that only Ce(LMes·CO2)3 catalyses the formation of propylene carbonate from propylene oxide under 1 atm of CO2 pressure. The mono-ligand complexes can be isolated from reactions using LiCe(NiPr2)4 as a starting material; LiBr adducts [Ce(LR)(NiPr2)Br·LiBr(THF)]2 (R = Me, iPr) are reported, along with a hexanuclear N-heterocyclic dicarbene [Li2Ce3(OArCMe-H)3(NiPr2)5(THF)2]2 by-product. The analogous para-aryloxide-NHC proligand (p-LMes = 4-O-2,6-tBu2-C6H2(1-C{N(CH)2NMes}))) has been made for comparison, but the rare earth tris-ligand complexes Ln(p-LMes)3(THF)2 (Ln = Y, Ce) are too reactive for straightforward Lewis pair separated chemistry to be usefully carried out.
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Affiliation(s)
- Polly L Arnold
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK .
| | - Ryan W F Kerr
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK . .,EaStCHEM School of Chemistry , University of St. Andrews , North Haugh, St. Andrews , KY16 9ST , UK, E-mail:
| | - Catherine Weetman
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK .
| | - Scott R Docherty
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK .
| | - Julia Rieb
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK . .,Molecular Catalysis, Faculty of Chemistry and Catalysis Research Center , Technical University Munich , Lichtenbergstr. 4 , 85748 Garching bei München , Germany
| | - Faye L Cruickshank
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK .
| | - Kai Wang
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK .
| | - Christian Jandl
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK . .,Molecular Catalysis, Faculty of Chemistry and Catalysis Research Center , Technical University Munich , Lichtenbergstr. 4 , 85748 Garching bei München , Germany
| | - Max W McMullon
- EaStCHEM School of Chemistry , University of Edinburgh , The King's Buildings , Edinburgh , EH9 3FJ , UK . .,Molecular Catalysis, Faculty of Chemistry and Catalysis Research Center , Technical University Munich , Lichtenbergstr. 4 , 85748 Garching bei München , Germany
| | - Alexander Pöthig
- Molecular Catalysis, Faculty of Chemistry and Catalysis Research Center , Technical University Munich , Lichtenbergstr. 4 , 85748 Garching bei München , Germany
| | - Fritz E Kühn
- Molecular Catalysis, Faculty of Chemistry and Catalysis Research Center , Technical University Munich , Lichtenbergstr. 4 , 85748 Garching bei München , Germany
| | - Andrew D Smith
- EaStCHEM School of Chemistry , University of St. Andrews , North Haugh, St. Andrews , KY16 9ST , UK, E-mail:
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12
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Stark DG, Williamson P, Gayner ER, Musolino SF, Kerr RWF, Taylor JE, Slawin AMZ, O'Riordan TJC, Macgregor SA, Smith AD. Isothiourea-catalysed enantioselective pyrrolizine synthesis: synthetic and computational studies. Org Biomol Chem 2016; 14:8957-65. [PMID: 27489030 PMCID: PMC5314687 DOI: 10.1039/c6ob01557c] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 07/21/2016] [Indexed: 11/21/2022]
Abstract
The catalytic enantioselective synthesis of a range of cis-pyrrolizine carboxylate derivatives with outstanding stereocontrol (14 examples, >95 : 5 dr, >98 : 2 er) through an isothiourea-catalyzed intramolecular Michael addition-lactonisation and ring-opening approach from the corresponding enone acid is reported. An optimised and straightforward three-step synthetic route to the enone acid starting materials from readily available pyrrole-2-carboxaldehydes is delineated, with benzotetramisole (5 mol%) proving the optimal catalyst for the enantioselective process. Ring-opening of the pyrrolizine dihydropyranone products with either MeOH or a range of amines leads to the desired products in excellent yield and enantioselectivity. Computation has been used to probe the factors leading to high stereocontrol, with the formation of the observed cis-steroisomer predicted to be kinetically and thermodynamically favoured.
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Affiliation(s)
- Daniel G. Stark
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | - Patrick Williamson
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | - Emma R. Gayner
- Institute of Chemical Sciences , Heriot-Watt University , Edinburgh , EH14 4AS , UK .
| | - Stefania F. Musolino
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | - Ryan W. F. Kerr
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | - James E. Taylor
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | - Alexandra M. Z. Slawin
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
| | | | - Stuart A. Macgregor
- Institute of Chemical Sciences , Heriot-Watt University , Edinburgh , EH14 4AS , UK .
| | - Andrew D. Smith
- EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , UK .
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