Lewis pair polymerization by classical and frustrated Lewis pairs: Acid, base and monomer scope and polymerization mechanism

Handle URI:
http://hdl.handle.net/10754/562005
Title:
Lewis pair polymerization by classical and frustrated Lewis pairs: Acid, base and monomer scope and polymerization mechanism
Authors:
Zhang, Yuetao; Miyake, Garret; John, Mallory G.; Falivene, Laura; Caporaso, Lucia; Cavallo, Luigi ( 0000-0002-1398-338X ) ; Chen, Eugene You Xian
Abstract:
Classical and frustrated Lewis pairs (LPs) of the strong Lewis acid (LA) Al(C 6F 5) 3 with several Lewis base (LB) classes have been found to exhibit exceptional activity in the Lewis pair polymerization (LPP) of conjugated polar alkenes such as methyl methacrylate (MMA) as well as renewable α-methylene-γ-butyrolactone (MBL) and γ-methyl- α-methylene-γ-butyrolactone (γ-MMBL), leading to high molecular weight polymers, often with narrow molecular weight distributions. This study has investigated a large number of LPs, consisting of 11 LAs as well as 10 achiral and 4 chiral LBs, for LPP of 12 monomers of several different types. Although some more common LAs can also be utilized for LPP, Al(C 6F 5) 3-based LPs are far more active and effective than other LA-based LPs. On the other hand, several classes of LBs, when paired with Al(C 6F 5) 3, can render highly active and effective LPP of MMA and γ-MMBL; such LBs include phosphines (e.g., P tBu 3), chiral chelating diphosphines, N-heterocyclic carbenes (NHCs), and phosphazene superbases (e.g., P 4- tBu). The P 4- tBu/Al(C 6F 5) 3 pair exhibits the highest activity of the LP series, with a remarkably high turn-over frequency of 9.6 × 10 4 h -1 (0.125 mol% catalyst, 100% MMA conversion in 30 s, M n = 2.12 × 10 5 g mol -1, PDI = 1.34). The polymers produced by LPs at RT are typically atactic (P γMMBL with ∼47% mr) or syndio-rich (PMMA with ∼70-75% rr), but highly syndiotactic PMMA with rr ∼91% can be produced by chiral or achiral LPs at -78 °C. Mechanistic studies have identified and structurally characterized zwitterionic phosphonium and imidazolium enolaluminates as the active species of the current LPP system, which are formed by the reaction of the monomer·Al(C 6F 5) 3 adduct with P tBu 3 and NHC bases, respectively. Kinetic studies have revealed that the MMA polymerization by the tBu 3P/ Al(C 6F 5) 3 pair is zero-order in monomer concentration after an initial induction period, and the polymerization is significantly catalyzed by the LA, thus pointing to a bimetallic, activated monomer propagation mechanism. Computational study on the active species formation as well as the chain initiation and propagation events involved in the LPP of MMA with some of the most representative LPs has added our understanding of fundamental steps of LPP. The main difference between NHC and PR 3 bases is in the energetics of zwitterion formation, with the NHC-based zwitterions being remarkably more stable than the PR 3-based zwitterions. Comparison of the monometallic and bimetallic mechanisms for MMA addition shows a clear preference for the bimetallic mechanism. This journal is © 2012 The Royal Society of Chemistry.
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division; KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division; Chemical Science Program
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Dalton Transactions
Issue Date:
2012
DOI:
10.1039/c2dt30427a
Type:
Article
ISSN:
14779226
Sponsors:
This work was supported by the National Science Foundation (CHE 1150792) for the study carried out at Colorado State University. MGJ thanks NSF-REU (CHE 1004924) for support of summer research. LC thanks the HPC team of Enea (www.enea.it) for using the ENEA-GRID and the HPC facilities CRESCO (www.cresco.enea.it) in Portici, Italy. We thank Boulder Scientific Co. for the research gifts of B(C<INF>6</INF>F<INF>5</INF>)<INF>3</INF> and [Ph<INF>3</INF>C][B(C<INF>6</INF>F<INF>5</INF>)<INF>4</INF>], and Dr. Brian Newell for the help on the X-ray structural analysis.
Is Supplemented By:
Zhang, Y., Miyake, G. M., John, M. G., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2013). CCDC 865899: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccy2178; DOI:10.5517/ccy2178; HANDLE:http://hdl.handle.net/10754/624675; Zhang, Y., Miyake, G. M., John, M. G., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2013). CCDC 865898: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccy2167; DOI:10.5517/ccy2167; HANDLE:http://hdl.handle.net/10754/624674
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Chemical Science Program; KAUST Catalysis Center (KCC); Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorZhang, Yuetaoen
dc.contributor.authorMiyake, Garreten
dc.contributor.authorJohn, Mallory G.en
dc.contributor.authorFalivene, Lauraen
dc.contributor.authorCaporaso, Luciaen
dc.contributor.authorCavallo, Luigien
dc.contributor.authorChen, Eugene You Xianen
dc.date.accessioned2015-08-03T09:36:04Zen
dc.date.available2015-08-03T09:36:04Zen
dc.date.issued2012en
dc.identifier.issn14779226en
dc.identifier.doi10.1039/c2dt30427aen
dc.identifier.urihttp://hdl.handle.net/10754/562005en
dc.description.abstractClassical and frustrated Lewis pairs (LPs) of the strong Lewis acid (LA) Al(C 6F 5) 3 with several Lewis base (LB) classes have been found to exhibit exceptional activity in the Lewis pair polymerization (LPP) of conjugated polar alkenes such as methyl methacrylate (MMA) as well as renewable α-methylene-γ-butyrolactone (MBL) and γ-methyl- α-methylene-γ-butyrolactone (γ-MMBL), leading to high molecular weight polymers, often with narrow molecular weight distributions. This study has investigated a large number of LPs, consisting of 11 LAs as well as 10 achiral and 4 chiral LBs, for LPP of 12 monomers of several different types. Although some more common LAs can also be utilized for LPP, Al(C 6F 5) 3-based LPs are far more active and effective than other LA-based LPs. On the other hand, several classes of LBs, when paired with Al(C 6F 5) 3, can render highly active and effective LPP of MMA and γ-MMBL; such LBs include phosphines (e.g., P tBu 3), chiral chelating diphosphines, N-heterocyclic carbenes (NHCs), and phosphazene superbases (e.g., P 4- tBu). The P 4- tBu/Al(C 6F 5) 3 pair exhibits the highest activity of the LP series, with a remarkably high turn-over frequency of 9.6 × 10 4 h -1 (0.125 mol% catalyst, 100% MMA conversion in 30 s, M n = 2.12 × 10 5 g mol -1, PDI = 1.34). The polymers produced by LPs at RT are typically atactic (P γMMBL with ∼47% mr) or syndio-rich (PMMA with ∼70-75% rr), but highly syndiotactic PMMA with rr ∼91% can be produced by chiral or achiral LPs at -78 °C. Mechanistic studies have identified and structurally characterized zwitterionic phosphonium and imidazolium enolaluminates as the active species of the current LPP system, which are formed by the reaction of the monomer·Al(C 6F 5) 3 adduct with P tBu 3 and NHC bases, respectively. Kinetic studies have revealed that the MMA polymerization by the tBu 3P/ Al(C 6F 5) 3 pair is zero-order in monomer concentration after an initial induction period, and the polymerization is significantly catalyzed by the LA, thus pointing to a bimetallic, activated monomer propagation mechanism. Computational study on the active species formation as well as the chain initiation and propagation events involved in the LPP of MMA with some of the most representative LPs has added our understanding of fundamental steps of LPP. The main difference between NHC and PR 3 bases is in the energetics of zwitterion formation, with the NHC-based zwitterions being remarkably more stable than the PR 3-based zwitterions. Comparison of the monometallic and bimetallic mechanisms for MMA addition shows a clear preference for the bimetallic mechanism. This journal is © 2012 The Royal Society of Chemistry.en
dc.description.sponsorshipThis work was supported by the National Science Foundation (CHE 1150792) for the study carried out at Colorado State University. MGJ thanks NSF-REU (CHE 1004924) for support of summer research. LC thanks the HPC team of Enea (www.enea.it) for using the ENEA-GRID and the HPC facilities CRESCO (www.cresco.enea.it) in Portici, Italy. We thank Boulder Scientific Co. for the research gifts of B(C<INF>6</INF>F<INF>5</INF>)<INF>3</INF> and [Ph<INF>3</INF>C][B(C<INF>6</INF>F<INF>5</INF>)<INF>4</INF>], and Dr. Brian Newell for the help on the X-ray structural analysis.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.titleLewis pair polymerization by classical and frustrated Lewis pairs: Acid, base and monomer scope and polymerization mechanismen
dc.typeArticleen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentChemical Science Programen
dc.identifier.journalDalton Transactionsen
dc.contributor.institutionDepartment of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, United Statesen
dc.contributor.institutionDipartimento di Chimica, Università di Salerno, Via Ponte don Melillo, I-84084 Fisciano, Italyen
kaust.authorCavallo, Luigien
dc.relation.isSupplementedByZhang, Y., Miyake, G. M., John, M. G., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2013). CCDC 865899: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccy2178en
dc.relation.isSupplementedByDOI:10.5517/ccy2178en
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624675en
dc.relation.isSupplementedByZhang, Y., Miyake, G. M., John, M. G., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2013). CCDC 865898: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccy2167en
dc.relation.isSupplementedByDOI:10.5517/ccy2167en
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624674en
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