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

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
• 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.