Synthesis of aluminium complexes bearing a piperazine-based ligand system

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• 作者：Nick C. Johnstone ; Elham S. Aazam ; Peter B. Hitchcock ; J. Robin Fulton
• 关键词：Aluminium ; N ; O-ligands ; Piperazine-ligands ; Polymerisation ; Caprolactone
• 刊名：Journal of Organometallic Chemistry
• 出版年：2010
• 出版时间：15 January 2010
• 年：2010
• 卷：695
• 期：2
• 页码：170-176
• 全文大小：692 K

文摘

Aluminium complexes bearing the N,N-chelating ligand 1,4-bis(2-hydroxy-3,5-di-tert-butyl)piperazine (1) have been synthesised. Both monometallic and bimetallic aluminium methyl complexes (2 and 3, respectively) were prepared by treatment of 1 with the appropriate amount of AlMe<sub>3sub>. Complex 2 can be converted to 3 by addition of excess AlMe<sub>3sub>. Bimetallic aluminium-ethyl complex 4 was also prepared. Treatment of 1 with AlEt<sub>2sub>Cl afforded the monometallic chloride complex 5. Treatment of this latter complex with potassium alkoxides (KOR, R = Me, Et, <sup>isup>Pr, <sup>tsup>Bu) or AgOTf afforded the corresponding aluminium alkoxide complexes (6, R = Et; 7, R = Me; 8, R = <sup>isup>Pr; 9, R = <sup>tsup>Bu; 10, R = OTf) in good yields. Aluminium ethoxide complex 6 was also synthesised by treatment of 1 with AlEt<sub>2sub>OEt. All of these complexes were tested as potential catalysts in the ring-opening polymerisation of rac-lactide and caprolactone with limited success.