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Synthesis, structure and ROP capability of a tetra(amidine)bis(zirconium) calix[8]arene complex

Lookup NU author(s): Professor William Clegg, Dr Mark Elsegood

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique, 2026. The solvate {Zr[NHC(Me)NMe2]2}2L·7.25MeCN (1·7.25MeCN) has been obtained on interaction of [Zr(NMe2)4] with p-tert-butylcalix[8]areneH8 (LH8) and subsequent work-up in acetonitrile. The X-ray crystal structure of the solvate reveals a tetra(amidine) complex with two distorted octahedral zirconium centres, each of which is bound by two cis amidine ligands, which result from acetonitrile insertion into the amide bonds; the coordination sphere at each metal is completed by the fully deprotonated calix[8]arene. Preliminary screening of tetra(amidine) complex 1, LH8 and [Zr(NMe2)4], in the presence of benzyl alcohol (BnOH) for 1 and [Zr(NMe2)4], for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) reveals the formation of low molecular weight polycaprolactone (PCL) (Mn ≤ 2280 Da) and high molecular weight polyvalerolactone (PVL) (Mn ≤ 23430 Da), respectively. In both cases, kinetics revealed superior activity for 1versus [Zr(NMe2)4] and LH8. Both cyclic and linear (H/OBn end groups) polymers were formed.

Publication metadata

Author(s): Clegg W, Elsegood MRJ, Redshaw C

Publication type: Article

Publication status: Published

Journal: New Journal of Chemistry

Year: 2026

Volume: 50

Issue: 3

Pages: 1663-1669

Print publication date: 19/01/2026

Online publication date: 22/12/2025

Acceptance date: 21/12/2025

Date deposited: 19/01/2026

ISSN (print): 1144-0546

ISSN (electronic): 1369-9261

Publisher: Royal Society of Chemistry

URL: https://doi.org/10.1039/d5nj04144a

DOI: 10.1039/d5nj04144a

ePrints DOI: 10.57711/1bt7-h484

Data Access Statement: All data generated and analyzed during this study have been included in the main manuscript and SI. Supplementary information: selected 1H NMR spectroscopic data for 1; individual kinetic curves and 1H NMR spectra for PCL and PVL conversions using 1; representative GPC traces of PCL and PVL. Graphs and tables. See DOI: https://doi.org/10.1039/d5nj04144a. CCDC 2495319 contains the supplementary crystallographic data for this paper.23

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