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Lead calix[n]arenes (n = 4, 6, 8): Structures and ring opening homo-/co-polymerization capability for cyclic esters

Xing, Tian; Prior, Timothy J.; Redshaw, Carl


Tian Xing

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Dr Tim Prior
Senior Lecturer in Inorganic Chemistry

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Professor Carl Redshaw
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry


Reaction of [LiPb(OiPr)3]2 (generated in situ) with either p-tert-butylcalix[4]areneH4 (L4H4) or p-tert-butylcalix[6]areneH6 (L6H6) resulted in the heterometallic lithium/lead complexes [Pb4Li2(L4)4H6(MeCN)3]·4.5MeCN (1·4.5MeCN) and [Pb8Li10Cl2(L6H2)3(L6)(OH)2(O)2(H2O)2(MeCN)4]·14MeCN (2·14MeCN), respectively. Use of the dimethyleneoxa-bridged p-tert-butyltetrahomodioxacalix[6]areneH6 (L6′H6) with five equivalents of [Pb(OiPr)2] afforded [Pb13(L6′)3O4(iPrOH)]·11MeCN (3·11MeCN). Use of the larger p-tert-butylcalix[8]areneH8 (L8H8) with [Pb(OtBu)2] or {Pb[N(TMS)2]} (TMS = SiMe3) afforded the products [Pb12(L8)2O4]·8.7C7H8 (4·8.7C7H8) or [Pb6(SiMe3)2(L8)O2Cl2] (5), respectively. Reaction of {Pb[N(TMS)2]} (generated in situ from (Me3Si)2NH, nBuLi and PbCl2) with L6H6 afforded, after work-up (MeCN), the mixed-metal complex [Pb10Li2(L6)2(OH)Cl(O)4]·9.5MeCN (6·9.5MeCN). Reaction of distilled {Pb[N(TMS)2]} (six equivalents) with L8H8 resulted in the complex [Pb12(L8)2O4]·12MeCN (7·12MeCN). Complexes 1-7, Pb(OiPr)2 and [Pb(N(TMS)2)2] have been screened for their potential to act as pre-catalysts in the ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL) and δ-valerolactone (δ-VL) and the copolymerization thereof. Generally, the lithiated complexes 1 and 2 exhibited better activities than the other pre-catalysts screened herein. For ϵ-CL and δ-VL, moderate activity at 130 °C over 24 h was observed for 1-7. In the case of the co-polymerization of ϵ-CL with δ-VL, 1-7, Pb(OiPr)2 and [Pb(N(TMS)2)2] afforded reasonable conversions and high molecular weight polymers. The systems 1-7, Pb(OiPr)2 and [Pb(N(TMS)2)2] also proved to be active in the ROP of the rac-lactide (r-LA); the activity trend was found to be 1 > 2 ≈ Pb(OiPr)2 ≈ [Pb(N(TMS)2)2] > 4 > 5 ≈ 6 ≈ 7 > 3.


Xing, T., Prior, T. J., & Redshaw, C. (2021). Lead calix[n]arenes (n = 4, 6, 8): Structures and ring opening homo-/co-polymerization capability for cyclic esters. Dalton Transactions : an international journal of inorganic chemistry, 50(42), 15140-15152.

Journal Article Type Article
Acceptance Date Sep 30, 2021
Online Publication Date Sep 30, 2021
Publication Date Nov 14, 2021
Deposit Date Sep 30, 2021
Publicly Available Date Nov 26, 2021
Journal Dalton Transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 50
Issue 42
Pages 15140-15152
Keywords Inorganic Chemistry
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