Trinuclear zinc calix[4]arenes: synthesis, structure, and ring opening polymerization studies

Xing, Tian; Frese, Josef; Derbyshire, Max; Glenister, Mollie A; Elsegood, Mark Robert James; Redshaw, Carl

Abstract

The trinuclear zinc calix[4]arene complexes [Zn3(O2CCH3)2(L(O)2(OMe)2)2·xMeCN (x = 7.5, 1; x = 6, 1′), [Zn3(O2CCH3)2(L(O)2(OnPr)2)2·5MeCN (2·5MeCN), [Zn3(OEt)2(L(O)2(OMe)2)2]·4MeCN (3·4MeCN), [Zn3(OEt)2(L(Opentyl)2)2]·4.5MeCN (4·4.5MeCN) and [Zn3(OH)2(L(O)2(On-pentyl)2]·8MeCN (5·8MeCN) have been isolated from reaction of [(ZnEt)2(L(O)2(OR)2)2] (L(OH)2(OR)2 = 1,3-dialkoxy-4-tert-butylcalix[4]arene; R = methyl, n-propyl or pentyl) and the reagents acetic acid, ethanol, and presumed adventitious water, respectively. Attempts to make 5via a controlled hydrolysis led only to the isolation of polymorphs of (L(OH)2(Opentyl)2·MeCN. Reaction of [Zn(C6F5)2] with L(OH)2(Opentyl)2, in the presence of K2CO3, led to the isolation of the complex [Zn6(L(On-pentyl))2(OH)3(C6F5)3(NCMe)3]·3MeCN (6·3MeCN). The molecular structures of 1-6 reveal they all contain a near linear (163 to 179°) Zn3 motif. In 1-5, a central tetrahedral Zn centre is flanked by trigonal bipyramidal Zn centres, whilst in 6, for the linear Zn3 unit, a central distorted octahedral zinc centre is flanked by trigonal planar and a tetrahedral zinc centres. Screening for the ring opening polymerization (ROP) of ϵ-caprolactone at 90 °C revealed that they are active with moderate to good conversion affording low to medium molecular weight products with at least two series of ions. For comparative studies, the trinuclear aminebis(phenolate) complex [Zn3(Oi-Pr)2L/] (L/ = n-propylamine-N,N-bis(2-methylene-4,6-di-tert-butylphenolate) I was prepared. Kinetics revealed the rate order I > 4 > 6 ≈ 2 ≈ 1 > 3.

Citation

Xing, T., Frese, J., Derbyshire, M., Glenister, M. A., Elsegood, M. R. J., & Redshaw, C. (2022). Trinuclear zinc calix[4]arenes: synthesis, structure, and ring opening polymerization studies. Dalton Transactions : an international journal of inorganic chemistry, https://doi.org/10.1039/d2dt01496c

• Journal Article Type: Article
• Acceptance Date: Jul 11, 2022
• Online Publication Date: Jul 11, 2022
• Publication Date: Jul 11, 2022
• Deposit Date: Jul 21, 2022
• Publicly Available Date: Jul 25, 2022
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1039/d2dt01496c
• Keywords: Inorganic Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4032917