Aluminium complexes containing bidentate and symmetrical tridentate pincer type pyrrolyl ligands: Synthesis, reactions and ring opening polymerization

Wen Yen Huang, Sheng Jie Chuang, Nien Tsu Chunag, Ching Sheng Hsiao, Amitabha Datta, Shau Jiun Chen, Ching Han Hu, Jui Hsien Huang, Ting Yu Lee, Chia Her Lin

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Abstract

A series of aluminium derivatives containing substituted bidentate and symmetrical tridentate pyrrolyl ligands, [C4H3NH(2-CH 2NHtBu)] and [C4H2NH(2,5-CH 2NHtBu)2], in toluene or diethyl ether were synthesized. Their reactivity and application for the ring opening polymerization of ε-caprolactone have been investigated. The reaction of AlMe3 with one equiv. of [C4H3NH(2-CH 2NHtBu)] in toluene at room temperature affords [C 4H3N(2-CH2NHtBu)]AlMe2 (1) in 70% yield by elimination of one equiv. of methane. Interestingly, while reacting AlMe3 with one equiv. of [C4H3NH(2- CH2NHtBu)] in toluene at 0°C followed by refluxing at 100°C, [{C4H3N(2-CH2NtBu)}AlMe] 2 (2) has been isolated via fractional recrystalliztion in 30% yield. Similarly, reacting AlMe3 with two equiv. of C4H 3NH(2-CH2NHtBu) generates [C4H 3N(2-CH2NHtBu)]2AlMe (3) in a moderate yield. Furthermore, complex 1 can be transformed to an aluminium alkoxide derivative, [C4H3N(2-CH2NH tBu)][OC6H2(-2,6-tBu 2-4-Me)]AlMe (4) by reacting 1 with one equiv. of HOC 6H2(-2,6-tBu2-4-Me) in toluene via the elimination of one equiv. of methane. The reaction of AlR3 with one equiv. of [C4H2NH(2,5-CH2NH tBu)2] in toluene at room temperature affords [C 4H2N(2,5-CH2NHtBu) 2]AlR2 (5, R = Me; 6, R = Et) in moderate yield. Surprisingly, from the reaction of two equiv. of [C4H 2NH(2,5-CH2NHtBu)2] with LiAlH 4 in diethyl ether at 0°C, a novel complex, [C4H 2N(2-CH2NtBu)(5-CH2NH tBu)]2AlLi (7) has been isolated after repeating re-crystallization. Furthermore, reacting one equiv. of C4H 2NH(2,5-CH2NHtBu)2 with AlH 3·NMe3 in diethyl ether generates an aluminium dihydride complex, [C4H2N(2,5-CH2NH tBu)2]AlH2 (8), in high yield. Additionally, treating 8 with one equiv. of HOC6H2(-2,6- tBu2-4-Me) in methylene chloride produces [C 4H2N(2,5-CH2NHtBu) 2][OC6H2(-2,6-tBu 2-4-Me)]AlH (9) with the elimination of one equiv. of H2. The aluminium alkoxide complex 4 shows moderate reactivity toward the ring opening polymerization of ε-caprolatone in toluene.

Original languageEnglish
Pages (from-to)7423-7433
Number of pages11
JournalDalton Transactions
Volume40
Issue number28
DOIs
Publication statusPublished - 2011 Jul 28

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All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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