<i>N</i>-Oxides amplify catalyst reactivity and isoselectivity in the ring-opening polymerization of <i>rac</i>-β-butyrolactone

Xiang, Dong; Brown, Alexander M.; Woodside, Audra J.; Robinson, Jerome R.

doi:10.1039/d1cc05127j

Cited by 13 publications

(8 citation statements)

References 58 publications

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“…Changing either the temperature or ionic radii of the initiators did not lead to any improvement, which is different from those observed in rac -lactide polymerization. , The polymerizations initiated by complexes 1 , 2 , 5 , and 6 gave polymers of narrower Đ (1.30–1.40), indicating that these lanthanide complexes have good control on mass distributions of polymers. These results are comparable with those reported initiated by lanthanide complexes . The M n values determined are larger than the theoretical ones ( M c ) suggesting that the average number of propagating chains per dinuclear complex may be between 1 and 2.…”

Section: Resultssupporting

confidence: 88%

Synthesis of N-Methyl-o-phenylenediamine-Bridged Bis(phenolato) Lanthanide Alkoxides and Their Catalytic Performance for the (Co)Polymerization of rac-Butyrolactone and l-Lactide

et al. 2022

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A series of lanthanide alkoxo complexes supported by ONNO salalen ligands were synthesized and characterized. A one-pot reaction of LH)) with LnCp 3 (THF) in a 1:1 molar ratio followed by the addition of 1 equiv of ROH (R = Bn, i Pr, and CF 3 CH 2 ), afforded the dimeric lanthanide alkoxo complexes 5), and [L 2 Yb(μ-OCH 2 CF 3 )] 2 (6) in good isolated yields. All these lanthanide complexes were characterized by elemental analysis and FT-IR spectroscopy. In addition, complex 1 has been characterized by NMR spectroscopy. Singlecrystal X-ray diffraction analysis of complexes 1, 2, 5, and 6 showed that these lanthanide alkoxo complexes are dimeric in the solid state. Complexes 1−6 showed good activity toward the homopolymerization of rac-butyrolactone (rac-BBL) to give atactic PHB, and ionic radii of central metals have profound influence on the polymerization. The polymerization behavior of L-lactide (L-LA) initiated by complex 2 was also explored. The kinetic study revealed that the polymerizations of rac-BBL and L-LA initiated by salalen lanthanide akoxide are first order for both the monomer and the initiator concentrations. Furthermore, it was found that complexes 1 and 2 showed good activity in the copolymerization of L-LA and rac-BBL, affording gradient copolymers.

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Section: Resultssupporting

confidence: 88%

Synthesis of N-Methyl-o-phenylenediamine-Bridged Bis(phenolato) Lanthanide Alkoxides and Their Catalytic Performance for the (Co)Polymerization of rac-Butyrolactone and l-Lactide

et al. 2022

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“…The development of volcano plots provides a straightforward method to map catalyst structural attributes with their performance and can provide rational approaches for further catalyst design. The observation of volcano plots and Sabatier relationships have been limited in homogeneous catalysis, but the utility of such relationships in heterogeneous (electro)catalysis suggests a rich opportunity for both experimental and in silico catalyst optimization. This should also include the optimization of catalysts capable of accessing different copolymer architectures, where the selection of catalysts with appropriate relative rates of monomer homopolymerization might generate block, gradient, or random copolymers .…”

Section: Discussionmentioning

confidence: 99%

Zinc Aryl/Alkyl β-diketiminates: Balancing Accessibility and Stability for High-Activity Ring-Opening Polymerization ofrac-Lactide

2022

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The development of nontoxic initiators which display both high activity and stability at low catalyst concentrations can be challenging, as these desired attributes often involve antagonistic design elements. In this study, we report a family of N-aryl/N′-alkyl zinc β-diketiminate catalysts, Zn( Ar/Alk L)[N(SiMe 3 ) 2 ] and [Zn( Dipp/Bn L)(O i Pr)] 2 , which can overcome historic challenges encountered with traditional zinc systems in the ring-opening polymerization (ROP) of rac-lactide and l-lactide. The disymmetric 2,6-diisopropylphenyl (Dipp)/benzyl (Bn) derivative, Zn( Dipp/Bn L)[N(SiMe 3 ) 2 ], can access polylactic acid (PLA) with a wide range of molecular weights in the presence of a chain transfer agent (e.g., isopropanol; M n(PLA) = 7–521 kg/mol, D̵ = 1.03–1.07). ROP proceeds rapidly at RT with high turnover frequencies (TOFs = 13,950 h–1 at 0.1 mol % [Zn]; [lactide] = 1.0 M) and low catalyst loadings (down to 0.02 mol %) and enables the synthesis of narrow dispersity ultrahigh molecular weight PLA (UHMW-PLA). Our detailed mechanistic studies identify a unifying and quantitative structure–function relationship for a diverse range of Zn( R1/R2 L)[N(SiMe 3 ) 2 ]. This takes the form of a volcano plot, which links the catalyst’s reaction site steric profile (V b,RS) with catalyst activity in the ROP of rac-lactide [log(k p)]. Our results establish the utility of disymmetric designs in accessing catalysts with high activity and stability at low concentrations and the prevalence of Sabatier’s principle and volcano plots in the design of homogeneous catalysts for ROP.

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“…In contrast to that, examples of discrete, isoselective initiators in the ROP of β-BL remain very scarce. Chromium salen catalysts yielding isotactic-enriched PHB with P m up to 0.67 were reported by our group in 2008. − A heterogenous neodymium-based catalyst achieved high stereocontrol ( P m = 0.85) as well as lanthanum bis(phenolate) systems resembling those of Carpentier and co-workers in combination with neutral donor ligands ( P m up to 0.82). , Very interestingly, Luo and co-workers showed recently that rare-earth metal salan-type catalysts are capable of either producing syndiotactic- or isotactic-enriched PHB ( P r = 0.78, P m = 0.77) depending on the ligand substitution …”

Section: Introductionmentioning

confidence: 97%

“…34−36 A heterogenous neodymium-based catalyst achieved high stereocontrol (P m = 0.85) 37 as well as lanthanum bis(phenolate) systems resembling those of Carpentier and co-workers 22 in combination with neutral donor ligands (P m up to 0.82). 38,39 Very interestingly, Luo and co-workers showed recently that rareearth metal salan-type catalysts are capable of either producing syndiotactic-or isotactic-enriched PHB (P r = 0.78, P m = 0.77) depending on the ligand substitution. 40 It was in this context that we became interested in understanding the factors influencing activity as well as stereocontrol in catalyst design for ROP of β-BL.…”

Section: ■ Introductionmentioning

confidence: 99%

High-Throughput Approach in the Ring-Opening Polymerization of β-Butyrolactone Enables Rapid Evaluation of Yttrium Salan Catalysts

2023

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Poly(3-hydroxybutyrate) (PHB) is a material produced naturally by bacteria but is also chemically accessible via ring-opening polymerization (ROP) of β-butyrolactone (β-BL). In ROP, catalyst design plays a key role in the production of PHB with different stereomicrostructures, i.e., syndiotactic, isotactic, or atactic PHB. In this work, we demonstrate a simple procedure for generating the catalysts in situ by conveniently combining a suitable yttrium precursor with the respective salan pro-ligand. This approach circumvents the elaborate isolation of the catalyst and enables the high-throughput screening of a library of yttrium salan catalysts for the ROP of β-BL. Electronic and steric influences of the ligand framework on stereoselectivity and activity of the catalyst as well as limitations could be determined, and structure–property relationships were established. Depending on the substitution pattern, these in situ-generated catalysts produced syndiotactic-enriched, isotactic-enriched, or atactic PHB with high activity.

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N-Oxides amplify catalyst reactivity and isoselectivity in the ring-opening polymerization of rac-β-butyrolactone

Abstract: N-oxides can amplify the performance of a lanthanum aminobisphenolate catalyst in the ring-opening polymerization (ROP) of rac-β-butyrolactone (rac-BBL) to unprecedented levels (TOF / Pm ; At RT: 1,900 h-1 /...

Cited by 13 publications

References 58 publications

Synthesis of N-Methyl-o-phenylenediamine-Bridged Bis(phenolato) Lanthanide Alkoxides and Their Catalytic Performance for the (Co)Polymerization of rac-Butyrolactone and l-Lactide

Synthesis of N-Methyl-o-phenylenediamine-Bridged Bis(phenolato) Lanthanide Alkoxides and Their Catalytic Performance for the (Co)Polymerization of rac-Butyrolactone and l-Lactide

Zinc Aryl/Alkyl β-diketiminates: Balancing Accessibility and Stability for High-Activity Ring-Opening Polymerization ofrac-Lactide

High-Throughput Approach in the Ring-Opening Polymerization of β-Butyrolactone Enables Rapid Evaluation of Yttrium Salan Catalysts

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