Unexpected Periodicity in Cationic Group 5 Initiators for the Ring-Opening Polymerization of Lactones.
Unexpected Periodicity in Cationic Group 5 Initiators for the Ring-Opening Polymerization of Lactones.
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DOI：
10.1021/acs.inorgchem.3c03854
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发表时间：
2024-01-08
影响因子：
4.6
通讯作者：
McKeown P
中科院分区：
文献类型：
--
作者：
Buchard A;Davidson MG;Gobius du Sart G;Jones MD;Kociok-Köhn G;McCormick SN;McKeown P
ε-己内酯(ε-CL)是阳离子、胺三酚负载的Nb(V)和Ta(V)乙氧化物的加合物，引发内酯的开环聚合。本文制备和应用的Ta(V)物种在ε-己内酯的开环聚合反应中表现出比以前报道的Nb(V)等结构络合物更高的活性，这与文献中基于Nb(V)和Ta(V)的协议的比较相矛盾。这两个系统还启动了δ-valerolacone和rac-β-丁内酯的ROP，动力学研究证实了Ta同系物保留了更高的活性。Rac-β-丁内酯和δ-戊内酯的聚合以前分别在V族或Ta族条件下没有实现，尽管前者只能得到低相对分子质量的环状聚3-羟基丁酸酯。本文还报道了阳离子乙氧基-Nb(V)和−-Ta(V)δ-戊内酯加合物，证明了δ-戊内酯作为配体的可行性和合成方法的通用性。这两种δ-戊内酯复合体都能启动ε-己内酯、δ-戊内酯和β-丁内酯的ROP。因此，我们阐明了反应活性的趋势并研究了这类体系的引发机理，插入事件是基于相邻烷氧基团对配位内酯的分子内亲核攻击而预测的。该机制能够定量地、化学计量地安装不同于聚合物链主体的单个单体残基，并允许通过操纵分子结构和调节聚合动力学来改变聚合物的性质，从而允许通过迄今无法获得的对引发事件的独立控制来实现分散性。将配位ε-己内酯和δ-戊内酯分子的Nb(V)和Ta(V)醇盐配合物用于催化ε-己内酯、δ-戊内酯和RAc-β-丁内酯的开环聚合。每个络合物在常温下都是稳定的，加热时通过配位单体的开环进行引发。与文献先例相反，所有基于Ta的体系表现出明显高于其Nb类似物的活性。通过化学计量开环开启不同的(金属配位的)内酯引发内酯聚合，为操纵聚合物的结构和性质提供了机会。
ε-Caprolactone (ε-CL) adducts of cationic, amine tris(phenolate)-supported niobium(V) and tantalum(V) ethoxides initiate the ring-opening polymerization of lactones. The Ta(V) species prepared and applied catalytically herein exhibits higher activity in the ring-opening polymerization (ROP) of ε-caprolactone than the previously reported, isostructural Nb(V) complex, contradicting literature comparisons of Nb(V)- and Ta(V)-based protocols. Both systems also initiate the ROP of δ-valerolactone and rac-β-butyrolactone, kinetic studies confirming retention of higher activity by the Ta congener. Polymerizations of rac-β-butyrolactone and δ-valerolactone were previously unrealized under Group V- or Ta-mediated conditions, respectively, although the former has afforded only low molecular weight, cyclic poly-3-hydroxybutyrate. Cationic ethoxo–Nb(V) and −Ta(V) δ-valerolactone adducts are also reported, demonstrating the facility of δ-valerolactone as a ligand and the generality of the synthetic method. Both δ-valerolactone-bearing complexes initiate the ROP of ε-caprolactone, δ-valerolactone, and rac-β-butyrolactone. Accordingly, we have elucidated trends in reactivity and investigated the initiation mechanism for such systems, the insertion event being predicated upon intramolecular nucleophilic attack on the coordinated lactone by the adjacent alkoxide moiety. This mechanism enables quantitative, stoichiometric installation of a single monomer residue distinct from the bulk of the polymer chain, and permits modification of polymer properties via both manipulation of the molecular architecture and tuning of the polymerization kinetics, and thus dispersity, through hitherto inaccessible independent control of the initiation event. Niobium(V) and tantalum(V) alkoxide complexes bearing coordinated ε-caprolactone and δ-valerolactone molecules were applied to the catalytic ring-opening polymerization of ε-caprolactone, δ-valerolactone, and rac-β-butyrolactone. Each complex is stable at ambient temperature, initiation proceeding via ring opening of the coordinated monomer on heating. Contrary to literature precedent, all Ta-based systems exhibited markedly higher activity than their Nb analogues. Initiation of lactone polymerization by stoichiometrically ring opening a different (metal-coordinated) lactone provides opportunities for manipulation of the polymer architecture and properties.
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影响因子：
2.3
作者：
Alonso-Moreno, Carlos;Antinolo, Antonio;Tercero-Morales, Maria T.
通讯作者：
Tercero-Morales, Maria T.
影响因子：
4.6
作者：
Buchard, Antoine;Davidson, Matthew G.;du Sart, Gerrit Gobius;Jones, Matthew D.;Kociok-Kohn, Gabriele;Mccormick, Strachan N.;Mckeown, Paul
通讯作者：
Mckeown, Paul
DOI：
10.1016/0030-4220(71)90044-2
发表时间：
1971-01-01
影响因子：
--
作者：
CUTRIGHT, DE;HUNSUCK, EE
通讯作者：
HUNSUCK, EE
影响因子：
4.6
作者：
Azor, Laurine;Bailly, Corinne;Dagorne, Samuel
通讯作者：
Dagorne, Samuel
影响因子：
2.8
作者：
Gallegos, Carlos;Tabernero, Vanessa;Cano, Jesus
通讯作者：
Cano, Jesus