Mechanism of Initiation Stereocontrol in Polymerization of rac-Lactide by Aluminum Complexes Supported by Indolide-Imine Ligands

Anna M. Luke, Appie Peterson, Sina Chiniforoush, Mukunda Mandal, Yanay Popowski, Hussnain Sajjad, Caitlin J. Bouchey, Dimitar Y. Shopov, Brendan J. Graziano, Letitia J. Yao, Christopher J. Cramer, Theresa M. Reineke, William B. Tolman

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Abstract

The solid state and fluxional behaviors in solution of complexes L2AlOBn and L7AlOBn (Bn = benzyl) supported by an analog of salen incorporating indolide arms connected via their 2- and 7-positions were defined by experiment and theory. The complexes catalyze the stereoselective conversion of rac-lactide (rac-LA) to isotactically enriched polylactide. A key aspect of the stereocontrol was examined through study of the initiation reactions via NMR spectroscopy, X-ray crystal structures of the ring-opened products, and theory. The results include the first unambiguous structural definition of stereocontrol in ring-opening of LA by a metal-alkoxide complex and the finding that definition of the stereochemistry of initiation by the studied system is governed thermodynamically rather than kinetically.

Original languageEnglish (US)
Pages (from-to)1809-1818
Number of pages10
JournalMacromolecules
Volume53
Issue number5
DOIs
StatePublished - Mar 10 2020

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Luke, A. M., Peterson, A., Chiniforoush, S., Mandal, M., Popowski, Y., Sajjad, H., Bouchey, C. J., Shopov, D. Y., Graziano, B. J., Yao, L. J., Cramer, C. J., Reineke, T. M., & Tolman, W. B. (2020). Mechanism of Initiation Stereocontrol in Polymerization of rac-Lactide by Aluminum Complexes Supported by Indolide-Imine Ligands. Macromolecules, 53(5), 1809-1818. https://doi.org/10.1021/acs.macromol.0c00092