A series of eight scorpionate ligands (Ar)₂CHR (1–4) were synthesized and coordinated to aluminum to produce Al(CH₂CH₃)((Ar)₂CHR) (5–8), where R = CH₂OCH₃ (1 or 5), CH₂N(CH₃)₂ (2 or 6), imidazole (3 or 7), or N-methylimidazole (4 or 8), and Ar = 2,4-dimethylphenol (a) or 2-tert-butyl-4-methylphenol (b). The bisphenol compounds were generated using a Friedel–Crafts alkylation reaction starting with commercially available reagents. The scorpionate species were subsequently combined with triethylaluminum in order to probe the coordination geometries of 1–4. The resulting complexes 5–8 displayed distorted tetrahedral structures with the bisphenolate ligands acting as tridentate donors. The only exception was 5a, which formed phenolate bridged dimers in the solid state. Additionally, complexes 5–8 were found to be active catalysts for the ring-opening polymerization of ε-caprolactone. The aluminum alkyl species affected this transformation both with and without the use of an alcohol co-catalyst, but higher activities and cleaner activations were seen when 1 equiv of iPrOH was employed. The less sterically hindered complexes with more weakly bound hemilabile “tails” showed the highest activities, with nearly 100% conversion after 1 h at 50 °C, and a catalyst loading of 1 mol %.

中文翻译：

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带有双阴离子蝎形配体的烷基铝配合物开环聚合ε-己内酯

合成了一系列八个蝎形配体 (Ar) ₂ CHR ( 1 – 4 ) 并与铝配位以产生 Al(CH ₂ CH ₃ )((Ar) ₂ CHR) ( 5 – 8 )，其中 R = CH ₂ OCH ₃ ( 1或5 )、CH ₂ N(CH ₃ ) ₂ ( 2或6 )、咪唑( 3或7 )或N-甲基咪唑( 4或8 )，Ar＝2,4-二甲基苯酚(a ) 或 2-叔丁基-4-甲基苯酚 ( b )。双酚化合物是使用市售试剂开始的 Friedel-Crafts 烷基化反应生成的。所述蝎物种以探针的几何形状协调与三乙基铝随后被组合1 - 4。将得到的复合物5 - 8显示的扭曲的四面体结构与配体双酚作为三齿供体。唯一的例外是5a，它在固态下形成酚盐桥接二聚体。此外，复合体5 – 8被发现是ε-己内酯开环聚合的活性催化剂。烷基物种铝影响该转化具有和不使用醇助催化剂，但是，当1个当量的被视为更高的活性和清洁器激活我被采用异丙醇。具有更弱结合的半稳定性“尾部”的空间位阻较小的配合物显示出最高的活性，在 50°C 下 1 小时后转化率接近 100%，催化剂负载量为 1 mol%。