Publication: Syntheses of bis(pyrrolylaldiminato)aluminum complexes for the polymerisation of lactide
Issued Date
2013-11-14
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ISSN
14779234
14779226
14779226
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2-s2.0-84885391409
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Mahidol University
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SCOPUS
Bibliographic Citation
Dalton Transactions. Vol.42, No.42 (2013), 15191-15198
Suggested Citation
Supathana Pracha, Siriwan Praban, Amornrat Niewpung, Gulthawach Kotpisan, Palangpon Kongsaeree, Saowanit Saithong, Tossapol Khamnaen, Phairat Phiriyawirut, Sumate Charoenchaidet, Khamphee Phomphrai Syntheses of bis(pyrrolylaldiminato)aluminum complexes for the polymerisation of lactide. Dalton Transactions. Vol.42, No.42 (2013), 15191-15198. doi:10.1039/c3dt51377g Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/31504
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Title
Syntheses of bis(pyrrolylaldiminato)aluminum complexes for the polymerisation of lactide
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Abstract
Seven bis(pyrrolylaldiminato)aluminum methyl complexes were synthesized from the reactions of AlMe3and two equiv. of the corresponding pyrrolylaldimine ligands. The ligands were modified to have different steric hindrances (C6H5(1), 2,6-Me2C6H3(2), 2,4,6-Me3C6H2(3), 2,6-Et2C6H3(4) and 2,6-iPr2C6H3(5)) and electronic contributions (4-CF3C6H4(6) and 4-OMeC6H4(7)). Crystal structures of complexes 3-7 were determined and shown to have distorted trigonal bipyramidal geometry (4, 6, 7) and intermediates between trigonal bipyramidal and square pyramidal geometries (3 and 5). The rotation around the N-Carylbond was fast for ligands having small ortho substituents and became slower as the size of the substituents increased. Polymerisations of l-lactide using complexes 1-7 and benzyl alcohol as an initiator were carried out giving the rate dependence on steric hindrance (5 < 4 < 3 < 2 < 1) and electronic contribution (6 < 7 < 1). Larger substituents and electron withdrawing groups were found to suppress the polymerisation rates. Despite having C2symmetry in the crystal structures of compounds 3-7, only slight enhancement for isotactic enchainment was found in the polymerisation of rac-lactide. © 2013 The Royal Society of Chemistry.