Aluminum Complexes Stabilized by Piperazidine-Bridged Bis(phenolate) Ligands: Syntheses, Structures, and Application in the Ring-Opening Polymerization of epsilon-Caprolactone

作者：Li Wenyi; Yao Yingming^*; Zhang Yong; Shen Qi

来源：Chinese Journal of Chemistry, 2012, 30(3): 609-615.

DOI：10.1002/cjoc.201100438

• piperazine-bridged bis(phenolate) ligand
• synthesis
• crystal structure
• polymerization
• e-caprolactone

The synthesis and characterization of aluminum alkoxide and alkyl complexes stabilized by piperazidine-bridged bis(phenolate) ligands are described. Treatment of ligand precursors H2[ONNO]1 {H2[ONNO]1=1,4-bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)piperazidine} and H2[ONNO]2 {H2[ONNO]2=1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazidine} with AlEt2(OCH2Ph) and AlEt2(OPr-i), which were generated in situ by the reactions of AlEt3 with equivalent of the corresponding alcohols, in a 1:1 molar ratio in THF gave the corresponding aluminum alkoxide complexes [ONNO]1Al(OCH2Ph) (1) and [ONNO]2Al(OPr-i) (2), respectively. The reaction of H2[ONNO]1 with AlEt2(OCH2Ph) in a 1:2 molar ratio in THF afforded a mixture of monometallic aluminum ethyl complex [ONNO]1AlEt (3) and complex 1, which can be isolated by stepwise crystallization. Similarly, H2[ONNO]2 reacted with AlEt2(OPr-i) in a 1:2 molar ratio in THF to give a mixture of aluminum ethyl complex [ONNO]2AlEt (4) and complex 2. Complexes 1 and 2 were also available via treatment of complexes 3 and 4 with 1 equiv. of benzyl alcohol and isopropyl alcohol, respectively. All of these complexes were fully characterized including X-ray structural determination. It was found that complexes 1 to 4 can initiate the ring-opening polymerization of e-caprolactone, and complexes 1 and 2 showed higher catalytic activity in comparison with complexes 3 and 4.

• 出版日期2012-3
• 单位苏州大学