Xing Tian, Jiang Chengying, Elsegood Mark R J, Redshaw Carl
Plastics Collaboratory, Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
Chemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.
Inorg Chem. 2021 Oct 18;60(20):15543-15556. doi: 10.1021/acs.inorgchem.1c02192. Epub 2021 Oct 1.
A variety of lithiated calix[]arenes, for which = 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 -lactide (-LA). In particular, interaction of --butylcalix[6]areneH (LH) with LiOBu in THF led to the isolation of [Li(LH)(CO)(THF)(OH)]·14THF (·14THF), the core of which has a chain of five LiO diamonds. Similar use of --butylcalix[8]areneH (LH) afforded [Li(L)(OH)(THF)]·7THF (·7THF), where the core is composed of a six-rung Li-O ladder. Use of debutylated calix[8]areneH (deBuLH) led to an elongated dimer [Li(deBuL)(OBu)(THF)]·4THF (·4THF) in which the calix[8]arenes possess a wavelike conformation forming bridges to link three separate LiO clusters (where and = 6, ignoring the THF donor oxygens). Interaction of LH with LiOH·HO afforded [Li(LH)(OH)(THF)]·5.5THF (·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 MeAl to the solution generated from LH and LiOBu led to the isolation of [(AlMe)Li(LH)(OH)(O)(OH)(NCMe)]·10MeCN (·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 -LA. For the ROP of ε-CL, δ-VL, and -LA, systems - exhibited moderate activity at 130 °C over 8 h. In the case of ROP using the mixed-metal (Li/Al) system , 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.
已经分离、表征了多种杯芳烃（其中 = 6 或 8）的锂化物，并评估了它们作为环状酯 ε-己内酯（ε-CL）、δ-戊内酯（δ-VL）和丙交酯（-LA）的开环聚合（ROP）催化剂的性能。特别地，在四氢呋喃（THF）中，叔丁基杯[6]芳烃-H（LH）与丁基锂（LiOBu）相互作用，得到了[Li(LH)(CO)(THF)(OH)]·14THF（·14THF），其核心有一个由五个锂氧金刚石组成的链。类似地，使用叔丁基杯[8]芳烃-H（LH）得到了[Li(L)(OH)(THF)]·7THF（·7THF），其核心由一个六梯级的锂氧梯子组成。使用脱丁基杯[8]芳烃-H（deBuLH）得到了一个拉长的二聚体[Li(deBuL)(OBu)(THF)]·4THF（·4THF），其中杯[8]芳烃具有波浪状构象，形成桥连接三个独立的锂氧簇（其中 和 = 6，忽略THF供体氧）。LH与氢氧化锂·水合物相互作用得到了[Li(LH)(OH)(THF)]·5.5THF（·5.5THF），其中涉及锂、氧和氢的分子内氢键相互作用在结构核心构建了一个有六元环和八元环的笼。最后，向由LH和LiOBu生成的溶液中加入甲基铝，得到了[(AlMe)Li(LH)(OH)(O)(OH)(NCMe)]·10MeCN（·10MeCN），其中锂、氧、铝和氮中心构建了一个多面体核心。已经筛选了这些配合物作为ε-CL、δ-VL和-LA开环聚合（ROP）预催化剂的潜力。对于ε-CL、δ-VL和-LA的ROP，体系 - 在130℃下8小时表现出中等活性。在使用混合金属（Li/Al）体系 的ROP情况下，实现了更好的转化率和高分子量聚合物。在ω-十五内酯（ω-PDL）的ROP情况下，这些体系在本文采用的条件下被证明是无活性的。
