Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters

Santoro, Orlando; Elsegood, Mark R. J.; Teat, Simon J.; Yamato, Takehiko; Redshaw, Carl

doi:10.1039/d1ra00175b

Cited by 10 publications

(10 citation statements)

References 51 publications

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“…37 The screening of 1−5 (Table 1; for M n,cal , PDIs, and TONs, see Table S1) revealed that under these conditions the lithium/ Chart 3. Literature Complexes I−III 9,35 aluminum-based complex, namely 5, could achieve higher activities when compared with the other complexes herein.…”

Section: Resultsmentioning

confidence: 80%

“…With the track record of lithium-based systems for the ring-opening polymerization (ROP) of cyclic esters in mind, ,,, the ability of the complexes herein to perform as catalysts in the ROP of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), and rac -lactide ( r -LA), in the presence of 1 equiv of benzyl alcohol (BnOH) per lithium, has been studied. Results are discussed versus reported calixarene complexes I – III (Chart ).…”

Section: Resultsmentioning

confidence: 99%

“…Results are discussed versus reported calixarene complexes I−III (Chart 3). 9,10,35 ROP of ε-Caprolactone (ε-CL). The complexes 1−5 were accessed for their potential to polymerize ε-caprolactone, and the results are collected in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…The versatility of calixarenes is now well documented with applications ranging from their use in nuclear waste to use in hair dyes. − These uses stem from the facile functionalization of either the lower or upper rims and the conformational flexibility displayed by such calixarenes which often results in the beneficial presence of π-rich cavities. Our interest stems from their ability to act as useful ancillary ligands in catalysis. , In recent work, we have reported that a family of lithiated calix[4]arenes are capable of acting as efficient catalysts in the ring-opening polymerization (ROP) of a number of cyclic esters, albeit with a lack of control . This area is topical given the current issues with petroleum-based plastics and the need to develop new polymeric materials with more environmentally friendly properties .…”

Section: Introductionmentioning

confidence: 99%

“…Our interest stems from their ability to act as useful ancillary ligands in catalysis. 8,9 In recent work, we have reported that a family of lithiated calix [4]arenes are capable of acting as efficient catalysts in the ring-opening polymerization (ROP) of a number of cyclic esters, albeit with a lack of control. 10 This area is topical given the current issues with petroleum-based plastics and the need to develop new polymeric materials with more environmentally friendly properties.…”

Section: Introductionmentioning

confidence: 99%

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Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

et al. 2021

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A variety of lithiated calix[n]arenes, for which n = 6 or 8, have been isolated, structurally characterized, and evaluated as catalysts for the ring-opening polymerization (ROP) of the cyclic esters ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), and rac-lactide (r-LA). In particular, interaction of p-tert-butylcalix[6]areneH6 (L6H6) with LiOtBu in THF led to the isolation of [Li14(L6H)2(CO3)2(THF)6(OH2)6]·14THF (1·14THF), the core of which has a chain of five Li2O2 diamonds. Similar use of p-tert-butylcalix[8]areneH8 (L8H8) afforded [Li10(L8)(OH)2(THF)8]·7THF (2·7THF), where the core is composed of a six-rung Li–O ladder. Use of debutylated calix[8]areneH8 (deBuL8H8) led to an elongated dimer [Li18(deBuL8)2(OtBu)2(THF)14]·4THF (3·4THF) in which the calix[8]arenes possess a wavelike conformation forming bridges to link three separate Li x O y clusters (where x and y = 6, ignoring the THF donor oxygens). Interaction of L8H8 with LiOH·H2O afforded [Li4(L8H4)(OH2)4(THF)6]·5.5THF (4·5.5THF), where intramolecular H-bond interactions involving Li, O, and H construct a cage in the core of the structure with six- and eight-membered rings. Lastly, addition of Me3Al to the solution generated from L8H8 and LiOtBu led to the isolation of [(AlMe2)2Li20(L8H2)2(OH2)4(O2–)4(OH)2(NCMe)12]·10MeCN (5·10MeCN) in which Li, O, Al, and N centers build a polyhedral core. These complexes have been screened for their potential to act as precatalysts in the ring-opening polymerization (ROP) of ε-CL, δ-VL, and r-LA. For the ROP of ε-CL, δ-VL, and r-LA, systems 1–4 exhibited moderate activity at 130 °C over 8 h. In the case of ROP using the mixed-metal (Li/Al) system 5, better conversions and high molecular weight polymers were achieved. In the case of the ROP of ω-pentadecalactone (ω-PDL), the systems proved to be inactive under the conditions employed herein.

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

et al. 2021

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Metallocalix[n]arenes in catalysis: A 13-year update

Santoro

Redshaw

2021

Coordination Chemistry Reviews

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A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal–Thioether, −Selenoether, and −Telluroether Interactions

Gray,

Vargas-Baca,

Emslie

2023

Inorg. Chem.

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The rigid thioether-and selenoether-containing pro-ligands, 4,5-bis(phenylsulfido)-2,7,9,9-tetramethylacridan (H[AS 2 Ph2 ] (1)) and 4,5-bis(phenylselenido)-2,7,9,9-tetramethylacridan (H[ASe 2 Ph2 ] (2)), were deprotonated with one equiv of n BuLi to afford dimeric lithium complexes [Li(AE 2 Ph2 )] 2 (E = S (3), Se (4)) or with one equiv of KCH 2 Ph to afford the previously reported potassium complexes [K(AS 2 Ph2 )(dme)] x (5) and [K(ASe 2 Ph2 )(dme) 2 ] (6). Attempts to prepare a direct telluroether analogue of compounds 1−2 were unsuccessful. However, the bulky selenoether-and telluroether-containing pro-ligands 4,5bis(2,4,6-triisopropylphenylselenido)-2,7,9,9-tetramethylacridan (H[ASe 2 Tripp2 ] (7)) and 4,5-bis(2,4,6-triisopropylphenyltellurido)-2,7,9,9-tetramethylacridan (H[ATe 2 Tripp2] (8)) were accessed via the reaction of 4,5-dibromo-2,7,9,9-tetramethylacridan with three equiv of n BuLi, followed by the addition of two equiv of the corresponding diaryl dichalcogenide and quenching with dilute HCl (aq) . The new selenoether-and telluroether-containing pro-ligands were subsequently deprotonated using KCH 2 Ph to afford [K(AE 2 Tripp2 )(dme) 2 ] (E = Se (9), Te (10)). Compounds 1−10 were characterized by 1 H, 13 C{ 1 H}, 77 Se{ 1 H}, 125 Te{ 1 H}, and 7 Li NMR spectroscopy, where applicable, and single-crystal X-ray structures were obtained for all lithium and potassium complexes (3− 6 and 9−10). DFT calculations were also performed to assess the nature of bonding between the hard group 1 cations and the soft chalcogenoethers.

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Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters

Abstract: Novel Li-calix[n]arene complexes (n = 3, 4) having (–S–), (–SO–), (–SO2–), (–CH2OCH2–) or (–CH2–) bridges have been synthesized and fully characterized. Their catalytic activity in the ring opening polymerization of lactones has been studied.

Cited by 10 publications

References 51 publications

Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

Metallocalix[n]arenes in catalysis: A 13-year update

A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal–Thioether, −Selenoether, and −Telluroether Interactions

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