Synthesis of Al complexes containing phenoxy-imine ligands and their use as the catalyst precursors for efficient living ring-opening polymerisation of ε-caprolactone
作者:Jingyu Liu、Naruhito Iwasa、Kotohiro Nomura
DOI:10.1039/b801561a
日期:——
Al complexes containing phenoxy-imine ligands of type, Me2Al[O-2-R1-6-(R2NCH)C6H3] [R1 = Me, R2 = 2,6-iPr2C6H3 (1a), tBu (1b); R1 = tBu, R2 = 2,6-iPr2C6H3 (2a), tBu (2b), cyclohexyl (2c), adamantyl (2d), C6H5 (2e), 2,6-Me2C6H3 (2f), C6F5 (2g)] have been prepared in high yields from AlMe3 by treating with 1.0 equiv. of 2-R1-6-(R2NCH)C6H3OH in n-hexane. Structures for 1a, 1b, 2aâe and 2g were determined by X-ray crystallography, and these complexes have a distorted tetrahedral geometry around Al; both the AlâO and the AlâN bond distances were influenced by substituents in both the aryloxo and the imino groups. Me2Al[μ2-O-2-(R2NCH)C6H4](AlMe3) [R2 = 2,6-iPr2C6H3 (3a), tBu (3b)] were prepared exclusively by reaction of AlMe3 with 2-(R2NCH)C6H4OH, and these complexes form a distorted tetrahedral geometry around each Al centre with additional AlMe3 coordinating to the oxygen in the phenoxy-imine ligand. Complexes 1a, 1b and 2aâg were tested as catalyst precursors for ring-opening polymerisation (ROP) of ε-caprolactone (CL) in the presence of nBuOH (1.0 equiv. to Al), and their catalytic activities were strongly influenced by the imino substituent (R2). The efficient ROP has been achieved using the C6F5 analogue (2g), with the ROP taking place in a living manner.
含有苯氧亚胺配体类型的 Al 配合物 Me2Al[O-2-R1-6-(R2NCH)C6H3] [R1 = Me, R2 = 2,6-iPr2C6H3 (1a), tBu (1b); R1 = tBu, R2 = 2,6-iPr2C6H3 (2a), tBu (2b), cyclohexyl (2c), adamantyl (2d), C6H5 (2e), 2,6-Me2C6H3 (2f), C6F5 (2g)],通过在 n-己烷中用 1.0 当量的 2-R1-6-(R2NCH)C6H3OH 处理 AlMe3 高产率地制备。通过 X 射线晶体学确定了 1a, 1b, 2a–e 和 2g 的结构, 这些配合物在 Al 周围具有扭曲的四面体几何结构; Al–O 和 Al–N 键距离都受到 aryloxo 和 imino 基团中取代基的影响。 Me2Al[μ2-O-2-(R2NCH)C6H4](AlMe3) [R2 = 2,6-iPr2C6H3 (3a), tBu (3b)], 通过 AlMe3 与 2-(R2NCH)C6H4OH 的反应独有地制备, 这些配合物在每个 Al 中心周围形成扭曲的四面体几何结构, 并额外有 AlMe3 与苯氧亚胺配体中的氧配位。 1a, 1b 和 2a–g 被测试为环开聚合 (ROP) 的催化剂前体, 在 nBuOH (相对于 Al 为 1.0 当量) 存在下进行 ε-己内酯 (CL) 的 ROP, 其催化活性强烈受到 imino 取代基 (R2) 的影响。使用 C6F5 类似物 (2g) 实现了高效的 ROP, 其中 ROP 以活性方式进行。