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Title: Multimetallic lithium complexes derived from the acids Ph 2 C(X)CO 2 H (X=OH, NH 2 ): Synthesis, structure and ring opening polymerization of lactides and lactones
Authors: Al-Khafaji, Yahya
Prior, Timothy J.
Horsburgh, Lynne
Elsegood, Mark R.J.
Redshaw, Carl
Keywords: Benzilic acid
Diphenylglycine
Lithium
Ring opening polymerization
Structures
Issue Date: 2017
Publisher: © Wiley
Citation: AL-KHAFAJI, Y. ...et al., 2017. Multimetallic lithium complexes derived from the acids Ph 2 C(X)CO 2 H (X=OH, NH 2 ): Synthesis, structure and ring opening polymerization of lactides and lactones. ChemistrySelect, 2(2), pp. 759-768.
Abstract: Reaction of LiOR (R = t-Bu, Ph) with the acids 2,2/-Ph2C(X)(CO2H), X = OH (benzH), NH2 (pdgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)(THF)]2·2THF (1·2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another solvate of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li7(benz)7(MeCN)] (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 Li2O2 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 oC with good control. For rac-LA and δ-VL, temperatures of at least 110 oC over 12h were necessary for activity (conversions > 60%). Systems employing 2 were inactive.
Description: This paper is in closed access until 13th Jan 2018.
Sponsor: The higher committee for education development in Iraq is thanked for financial support.
Version: Accepted for publication
DOI: 10.1002/slct.201602029
URI: https://dspace.lboro.ac.uk/2134/25906
Publisher Link: http://dx.doi.org/10.1002/slct.201602029
ISSN: 2365-6549
Appears in Collections:Closed Access (Chemistry)

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