Reactions of dimeric aluminium hydride compounds containing bidentate dianionic pyrrolyl ligands and their applications in ring-opening polymerization of ε-caprolactone

Ya Chi Chen, Che Yu Lin, Wen Yen Huang, Amitabha Datta, Jui-Hsien Huang, Meng Shiue Tsai, Ting Yu Lee, Cheng Yi Tu, Ching-Han Hu

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A series of dimeric aluminium compounds containing substituted bidentate dianionic pyrrolyl ligands have been synthesized and their reactivity and application in the ring-opening polymerization of ε-caprolactone have been studied. The reactions of [{C4H3N(2-CH2NtBu)} AlH]2 (1) with 2 equiv. of 1-indanone and 9-fluorenone in dichloromethane generated [{C4H3N(2-CH2NtBu)} Al(μ-OC9H9)]2 (2) and [{C4H 3N(2-CH2NtBu)}Al{μ-OCH(C12H 8)}]2 (3), respectively, by hydroalumination. Similarly, the reactions of 1 with 2 equiv. of 2-cyclohexen-1-one, 1-(2,4,6- trimethylphenyl)-1-ethanone, benzophenone, and 1,1-diphenylacetone in dichloromethane afforded NtBu-bridged dialuminium compounds 4-7, [{C 4H3N(2-CH2NtBu)}Al(OR)]2 [4, R = C6H9; 5, R = CH(Me)(C6H2-2,4,6- Me3); 6, R = CHPh2; 7, R = CH(Me)(CHPh2)] by insertion. A similar insertion occurred when 1 was treated with 2 equiv. of 2,4-pentandione and dibenzoylmethane in dichloromethane to yield NtBu-bridged dioxylate aluminium dimeric compounds 8 and 9, respectively. The Al atoms in compounds 2 and 4-7 possess a distorted tetrahedral geometry whereas the Al atoms in 8 and 9 have a square-pyramidal environment. All the compounds have been well characterized by NMR spectroscopy and compounds 2 and 4-9 in the solid state were subjected to X-ray diffraction analysis. A study of the polymerization of ε-caprolactone revealed that the activity of the Al complexes is largely reliant on the steric nature of the substituents of their alkoxide groups.

Original languageEnglish
Pages (from-to)2459-2469
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Issue number15
Publication statusPublished - 2011 May 1


All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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