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Use of titanocalix[4]arenes in the ring opening polymerization of cyclic esters
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2020/01/27 , DOI: 10.1039/c9cy02571e
Ziyue Sun 1, 2, 3, 4 , Yanxia Zhao 1, 2, 3, 4 , Orlando Santoro 5, 6, 7, 8, 9 , Mark R. J. Elsegood 9, 10, 11, 12 , Elizabeth V. Bedwell 9, 10, 11, 12 , Khadisha Zahra 9, 13, 14, 15 , Alex Walton 9, 13, 14, 15 , Carl Redshaw 1, 2, 3, 4, 5
Affiliation  

The known dichloride complexes [TiCl2L(O)2(OR)2] (type I: R = Me (1), n-Pr (2) and n-pentyl (3); L(OH)2(OR)2 = 1,3-dialkyloxy-p-tert-butylcalix[4]arene), together with the new complexes {[TiL(O)3(OR)]2(μ-Cl)2}·6MeCN (R = n-decyl (4·6MeCN)), and [Ti(NCMe)Cl(L(O)3(OR))]·MeCN (type II: R = Me, 5·MeCN) are reported. Attempts to prepare type II for R = n-Pr and n-pentyl using [TiCl4] resulted in the complexes {[TiL(O)3(On-propyl)]2(μ-Cl)(μ-OH)} 6·7MeCN and {[TiL(O)3(On-pentyl)]2(μ-Cl)(μ-OH)}·7.5MeCN (7·7.5MeCN), respectively; use of [TiCl4(THF)2] resulted in a co-crystallized THF ring-opened product [Ti(NCMe)(μ3-O)L(O)4TiCl(O(CH2)4Cl)]2–2[TiCl(NCMe)(L(O)3(On-Pr))]·11MeCN (8·11MeCN). The molecular structures of 2·2MeCN, 4·6MeCN, and 5·MeCN together with the hydrolysis products {[TiL(O)3(OR)]2(μ-Cl)(μ-OH)} (R = n-Pr 6·7MeCN; n-pentyl, 7·7.5MeCN, 9·9MeCN); R = n-decyl 10·8.5MeCN) and that of the ring opened product 8·11MeCN and the co-crystallized species [Ti2(OH)Cl(L(O)3(OR))][L(OH)2(OR)2]·2.85(C2H3N)·0.43(H2O) (R = n-pentyl, 11·2.85(C2H3N)·0.43(H2O)) are reported. Type I and II complexes have been screened for their ability to act as catalysts in the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), ω-pentadecalactone (ω-PDL) and rac-lactide (r-LA), both with and without benzyl alcohol present and either under N2 or in air. The copolymerization of ε-CL with δ-VL and with r-LA has also been investigated. For the ROP of ε-CL, all performed efficiently (>99% conversion) at 130 °C over 24 h both under N2 and in air, whilst over 1 h, for the type I complexes the trend was 3 > 2 > 1 but all were poor (≤12% conversion). By contrast, 5 over 1 h at 130 °C was highly active (85% conversion). At 80 °C, the activity trend followed the order 54 > 3 > 2 > 1. For δ-VL, at 80 °C the activity trend 54 > 1 > 2 > 3 was observed. ROP of the larger ω-PDL was only possible using 5 at 130 °C over 24 h with moderate activity (48% conversion). For r-LA, only low molecular weight products were obtained, whilst for the co-polymerization of ε-CL with δ-VL using 5, high activity was observed at 80 °C affording a polymer of molecular weight >23 000 Da and with equal incorporation of each monomer. In the case of ε-CL/r-LA co-polymerization using 5 either under N2 or air, the polymerization was more sluggish and only 65% conversion of CL was observed and the resultant co-polymer had 65 : 35 incorporation. Complex 5 could also be supported on silica, however this system was not as active as its homogeneous counterpart. Finally, the activity of these complexes is compared with that of three benchmark species: a di-phenolate Ti compound {TiCl2(2,2′-CH3CH[4,6-(t-Bu)2C6H2O]2)} (12) and a previously reported NO2-containing titanocalix[4]arene catalyst, namely cone-5,17-bis-tert-butyl-11,23-dinitro-25,27-dipropyloxy-26,28-dioxo-calix[4]arene titanium dichloride (13), as well as [Ti(Oi-Pr)4]; the parent calixarenes were also screened.

中文翻译:

钛氧杯[4]芳烃在环酯的开环聚合中的应用

已知的二氯化物络合物[TiCl 2 L(O)2(OR)2 ](类型I:R = Me(1),n -Pr(2)和n-戊基(3); L(OH)2(OR)2 = 1,3- dialkyloxy-对叔-butylcalix [4]芳烃),与新的复合物一起{[TIL(O)3(OR)] 2(μ-Cl)的2 }·6MeCN(R = ñ -报道了癸基(4 ·6MeCN)和[Ti(NCMe)Cl(L(O)3(OR))]·MeCN(II型:R = Me,5 ·MeCN)。尝试为R = n准备II型[TiCl 4 ]合成-Pr和戊基生成络合物{[TiL(O)3(O n -propyl)] 2(μ-Cl)(μ-OH)} 6 ·7MeCN和{[TiL(O )3(O n-戊基)] 2(μ-Cl)(μ-OH)}·7.5MeCN(7 ·7.5MeCN);使用的[的TiCl 4(THF)2 ]导致的共结晶的THF开环产物钛[Ti(NCMe)(μ 3 -O)L(O)4的TiCl(O(CH 24 Cl)的] 2 - 2 [TiCl(NCMe)(L(O)3(O n -Pr)))·11MeCN(8·11MeCN)。2 ·2MeCN,4 ·6MeCN和5 ·MeCN的分子结构以及水解产物{[TiL(O)3(OR)] 2(μ-Cl)(μ-OH)}(R = n -Pr 6 ·7MeCN;戊基,7 ·7.5MeCN,9 ·9MeCN); R =癸基10 ·8.5MeCN)和开环产物8 ·11MeCN和共结晶物[Ti 2(OH)Cl(L(O)3(OR))] [L(OH)2(OR)2 ]·2.85(C 2 H 3 N)·0.43(H 2O)(R =戊基,11 ·2.85(C 2 H 3 N)·0.43(H 2 O))。已筛选I型和II型配合物在ε-己内酯(ε-CL),δ-戊内酯(δ-VL),ω-十五内酯(ω-PDL)的开环聚合(ROP)中起催化剂作用的能力在存在和不存在苯甲醇的情况下以及在N 2下或在空气中都存在外消旋和外消旋丙交酯(r -LA)。还研究了ε-CL与δ-VL和r -LA的共聚。对于ε-CL的ROP,在N 2下均在130°C下经过24小时有效地执行了转化(> 99%转化)。在空气中,超过1小时,对于I型配合物,趋势为3 > 2 > 1,但均较差(转化率≤12%)。相比之下,在130°C下历时1小时有5次是高度活跃的(转化率为85%)。在80℃下,活动趋势依次为54 > 3 > 2 > 1。对于δ-VL,在80℃下的活性趋势54 > 1 > 2 > 3中观察到。较大的ω-PDL的ROP仅可在130°C下使用5在24 h内具有中等活性(转化率为48%)。对于r-LA,仅获得低分子量产物,而对于使用5的ε-CL与δ-VL进行共聚,则在80°C时观察到高活性,提供分子量> 23000 Da且均等掺入的聚合物每个单体的数量 在N 2或空气中使用5的ε-CL/ r -LA共聚的情况下,聚合反应更加缓慢,仅观察到CL的65%转化,所得共聚物的掺入量为65:35。配合物5也可以负载在二氧化硅上,但是该系统的活性不如同类均质体系。最后,将这些配合物的活性与三种基准物质进行比较:二酚盐Ti化合物{TiCl 2(2,2'-CH 3 CH [4,6-(t -Bu)2 C 6 H 2 O] 2)}(12)和先前报道的含NO 2的钛杯[4]芳烃催化剂,即5,17-二叔丁基-11,23-二硝基-25,27-二丙氧基-26,28-二氧杂杯[4]芳烃二氯化钛(13)以及[Ti(O i -Pr)4 ]; 还筛选了父母杯芳烃。
更新日期:2020-03-26
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