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Abstract
Homobimetallic zinc complexes have shown extremely high activity in lactide (LA) ring-opening polymerisation (ROP). In contrast, heterobimetallic ROP catalysts combining zinc with other divalent heterometals such as Mg and Ca are unknown, despite heterometallic cooperativity leading to improved catalyst performance with other heterocombinations. Here, we report the first heterobimetallic LA ROP catalysts featuring only divalent metals, by systematically replacing one Zn centre in a bis-Zn ProPhenol complex with Mg or Ca. The Mg/Zn and Ca/Zn complexes are highly active and outperform their homobimetallic counterparts in rac-LA and ε-caprolactone (ε-CL) ROP. The Ca/Zn complex exhibits the highest activity, converting 48 eq. rac-LA in 5 s and 380 eq. ε-CL in 30 s at room temperature. The activity enhancements are credited to Lewis acidic Mg and Ca enhancing monomer coordination as well as altering the catalyst electronics by increasing the polarity of the Zn-Et initiating group. The heterobimetallic catalysts also display unusual two-step kinetic plots in rac-LA ROP, which is attributed to the initial catalyst preference for the coordination and insertion of one of the rac-LA stereoisomers.
Original language | English |
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Pages (from-to) | 1070-1079 |
Number of pages | 10 |
Journal | Catalysis Science and Technology |
Volume | 12 |
Issue number | 4 |
Early online date | 16 Nov 2021 |
DOIs | |
Publication status | Published - 21 Feb 2022 |
Bibliographical note
Funding Information:We would like to thank the CRITICAT Centre for Doctoral Training and EPSRC (W.G., EP\L016419\1), Royal Society (J.A.G., RSG\R1\180101; A.B., UF\160021 fellowship), British Ramsay Memorial Trust (J.A.G.), L'Or?al-UNESCO For Women in Science (J.A.G.) and UKRI Future Leaders Fellowship (Grant MR/T042710/1) for funding. We would also like to thank Dr Faye Cruickshank at the Scottish Instrumentation and Resource Centre for Advanced Mass Spectrometry (The University of Edinburgh) for performing the APPI-MS analysis.
Funding Information:
We would like to thank the CRITICAT Centre for Doctoral Training and EPSRC (W.G., EP\L016419\1), Royal Society (J.A. G., RSG\R1\180101; A.B., UF\160021 fellowship), British Ramsay Memorial Trust (J.A.G.), L'Oréal-UNESCO For Women in Science (J.A.G.) and UKRI Future Leaders Fellowship (Grant MR/T042710/1) for funding. We would also like to thank Dr Faye Cruickshank at the Scottish Instrumentation and Resource Centre for Advanced Mass Spectrometry (The University of Edinburgh) for performing the APPI-MS analysis.
Publisher Copyright:
© 2022 The Royal Society of Chemistry
ASJC Scopus subject areas
- Catalysis
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- 1 Finished
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UR Fellowship - Sugar-based Polymers for a New Generation of Sustainable Materials
Buchard, A. (PI)
1/10/17 → 30/09/22
Project: Research council