Homoleptic aminophenolates of Zn, Mg and Ca. Synthesis, structure, DFT studies and polymerization activity in ROP of lactides
作者:Jakub Wojtaszak、Krzysztof Mierzwicki、Sławomir Szafert、Nurbey Gulia、Jolanta Ejfler
DOI:10.1039/c3dt52868e
日期:——
The reaction of MgBu2, ZnEt2 or Ca(OiPr)2 with 2 eq. of three-coordinating N-[methyl(2-hydroxy-3,5-dimethylphenyl)]-N-methyl-N-methyl-1,3-oxolaneamine (mpoa-H) or N-[methyl(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-methyl-1,3-oxolaneamine (tbpoa-H) gave neutral, monomeric [Mg(mpoa)2], [Zn(mpoa)2], [Zn(tbpoa)2], and [Ca(tbpoa)2] as white powders in 58–90% yields. The resulting aminophenolates were characterized in solution by NMR showing, in the case of [Zn(tbpoa)2], interesting dynamics. [Zn(tbpoa)2] and [Ca(tbpoa)2] were characterized by X-ray crystallography to show the Zn atom to be pseudo-octahedrally coordinated and the Ca atom in six-coordination mode. The new homoleptic complexes were tested in the polymerization of lactide with an external alcohol to reveal stable behaviour (during the polymerization process) only in the case of [Zn(tbpoa)2]. The high activity of the catalyst was correlated with a ligand flexibility that was further supported by theoretical studies.
MgBu2、ZnEt2 或 Ca(OiPr)2 与 2 eq.的三配位 N-[甲基(2-羟基-3,5-二甲基苯基)]-N-甲基-N-甲基-1,3-氧杂戊环胺(mpoa-H)或 N-[甲基(2-羟基-3,5-二叔丁基苯基)]-N-甲基-N-甲基-1、3-oxolaneamine (tbpoa-H)得到中性单体[Mg(mpoa)2]、[Zn(mpoa)2]、[Zn(tbpoa)2]和[Ca(tbpoa)2]白色粉末,产率为 58-90%。通过核磁共振分析,[Zn(tbpoa)2]在溶液中显示出有趣的动态变化。X 射线晶体学对[Zn(tbpoa)2]和[Ca(tbpoa)2]进行了表征,显示 Zn 原子为假八面体配位,Ca 原子为六配位模式。新的同色复合物在与外部醇聚合乳酸时进行了测试,结果显示只有[Zn(tbpoa)2]具有稳定的行为(在聚合过程中)。催化剂的高活性与配体的灵活性有关,理论研究进一步证实了这一点。