Walton Mark J, Lancaster Simon J, Wright Joseph A, Elsegood Mark R J, Redshaw Carl
Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK.
Dalton Trans. 2014 Dec 28;43(48):18001-9. doi: 10.1039/c4dt02226b. Epub 2014 Oct 29.
Reaction of Zn(C6F5)2·toluene (two equivalents) with 1,3-dipropoxy-p-tert-butyl-calix[4]arene (L(1)H2) led to the isolation of the complex [{Zn(C6F5)}2L(1)] (1), whilst similar use of Zn(Me)2 resulted in the known complex [{Zn(Me)}2L(1)] (2). Treatment of L(1)H2 with in situ prepared Zn{N(SiMe3)2}2 in refluxing toluene led to the isolation of the compound [(Na)ZnN(SiMe3)2L(1)] (3). The stepwise reaction of L(1)H2 and sodium hydride, followed by ZnCl2 and finally NaN(SiMe3)2 yielded the compound [Zn{N(SiMe3)2}2L(1)] (4). The reaction between three equivalents of Zn(C6F5)2·toluene and oxacalix[3]arene (L(2)H3) at room temperature formed the compound {[Zn(C6F5)]3L(2)} (5); heating of 5 in acetonitrile caused the ring opening of the parent oxacalix[3]arene and rearrangement to afford the complex [(L(2))Zn6(C6F5)(R)(RH)OH]·5MeCN R = C6F5CH2-(p-(t)BuPhenolate-CH2OCH2-)2-p-(t)BuPhenolate-CH2O(-))(3-) (6). The molecular structures of the new complexes 1, 3 and 6, together with that of the known complex 2, whose solid state structure has not previously been reported, have been determined. Compounds 1, 3-5 have been screened for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and rac-lactide. Compounds featuring a Zn-C6F5 fragment were found to be poor ROP pre-catalysts as they did not react with benzyl alcohol to form an alkoxide. By contrast, compound 4, which contains a zinc silylamide linkage, was the most active of the zinc-based calix[4]arene compounds screened and was capable of ROP at ambient temperature with 65% conversion over 4 h.
二苯基锌·甲苯（两当量）与1,3 - 二丙氧基 - 对叔丁基杯[4]芳烃（L(1)H₂）反应，得到配合物[{Zn(C₆F₅)}₂L(1)]（1），而类似地使用二甲基锌则得到已知配合物[{Zn(Me)}₂L(1)]（2）。在回流甲苯中，用原位制备的二（三甲基硅基）氨基锌处理L(1)H₂，得到化合物[(Na)ZnN(SiMe₃)₂L(1)]（3）。L(1)H₂与氢化钠分步反应，接着与氯化锌反应，最后与二（三甲基硅基）氨基钠反应，得到化合物[Zn{N(SiMe₃)₂}₂L(1)]（4）。三当量的二苯基锌·甲苯与氧杂杯[3]芳烃（L(2)H₃）在室温下反应，形成化合物{[Zn(C₆F₅)]₃L(2)}（5）；在乙腈中加热5会导致母体氧杂杯[3]芳烃开环并重排，得到配合物[(L(2))Zn₆(C₆F₅)(R)(RH)OH]·5MeCN ，R = C₆F₅CH₂-(对叔丁基酚盐 - CH₂OCH₂-)₂ - 对叔丁基酚盐 - CH₂O(-))(3 -)（6）。已测定了新配合物1、3和6以及已知配合物2的分子结构，2的固态结构此前尚未报道。已对化合物1、3 - 5进行了ε - 己内酯（ε - CL）和外消旋丙交酯的开环聚合（ROP）筛选。发现具有Zn - C₆F₅片段的化合物是较差的ROP预催化剂，因为它们不与苄醇反应形成醇盐。相比之下，含有锌硅烷基酰胺键的化合物4是所筛选的锌基杯[4]芳烃化合物中活性最高的，能够在室温下进行ROP，4小时内转化率达65%。
