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|Title:||Syntheses of bis(pyrrolylaldiminato)aluminum complexes for the polymerisation of lactide|
Prince of Songkla University
SCG Chemicals Co.
|Citation:||Dalton Transactions. Vol.42, No.42 (2013), 15191-15198|
|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.|
|Appears in Collections:||Scopus 2011-2015|
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