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Multimetallic lithium complexes derived from the acids Ph₂C(X)CO₂H (X = OH, NH₂) : synthesis, structure and ring opening polymerization of lactides and lactones

Al-Khafaji, Yahya F.; Prior, Timothy J.; Horsburgh, Lynne; Elsegood, Mark R. J.; Redshaw, Carl

Authors

Yahya F. Al-Khafaji

Lynne Horsburgh

Mark R. J. Elsegood

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Professor Carl Redshaw C.Redshaw@hull.ac.uk
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry



Abstract

Reaction of LiOR (R=t-Bu, Ph) with the acids 2,2/-Ph₂C(X)(CO₂H), X=OH (benzH), NH₂ (dpgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)]2⋅2THF (1⋅2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another polymorph of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li₇(benz)₇(MeCN)] 2MeCN THF (2⋅2MeCN⋅THF). Use of LiOt-Bu (2 equivalents) led to {Li₈(Ot-Bu)₂[(benz)](OCPh₂CO₂CPh₂CO2t-Bu)₂(THF)₄} (3), the core of which comprises two open cubes linked by benz ligands. For dpgH, two equivalents of LiOt-Bu in THF afforded [Li6(Ot-Bu)₂(dpg)₂(THF)₂] (4), which contains an Li₂Ov 6-step ladder. Similar reaction of LiOPh afforded [Li₈(PhO)₄(dpg)₄(MeCN)₄] (5). Complexes 1–5 were screened for their potential as catalysts for ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL), rac-lactide (rac-LA) and δ-valerolactone (δ-VL). For ROP of ϵ-CL, conversions > 70 % were achievable at 110 °C with good control. For rac-LA and δ-VL, temperatures of at least 110 °C over 12 h were necessary for activity (conversions > 60 %). Systems employing 2 were inactive

Citation

Al-Khafaji, Y. F., Prior, T. J., Horsburgh, L., Elsegood, M. R. J., & Redshaw, C. (2017). Multimetallic lithium complexes derived from the acids Ph₂C(X)CO₂H (X = OH, NH₂) : synthesis, structure and ring opening polymerization of lactides and lactones. ChemistrySelect, 2(2), 759-768. https://doi.org/10.1002/slct.201602029

Acceptance Date Jan 5, 2017
Online Publication Date Jan 18, 2017
Publication Date Jan 13, 2017
Deposit Date Jan 24, 2017
Publicly Available Date Jan 17, 2018
Journal ChemistrySelect
Electronic ISSN 2365-6549
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 2
Issue 2
Pages 759-768
DOI https://doi.org/10.1002/slct.201602029
Keywords Benzilic acid; Diphenylglycine; Lithium; Ring opening polymerization; Structures
Public URL https://hull-repository.worktribe.com/output/447438
Publisher URL http://onlinelibrary.wiley.com/doi/10.1002/slct.201602029/abstract;jsessionid=FB9CF207DF1F0EE00E3B94C8D8792540.f04t04?system
Copyright Statement ©2018 University of Hull
Additional Information Authors' accepted manuscript of article: Y. F. Al-Khafaji, T. J. Prior, L. Horsburgh, M. R. J. Elsegood, C. Redshaw, ChemistrySelect 2017, 2, 759.

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