Ring-opening polymerization of l-lactide by organotin(IV)alkoxides,R2Sn(OPr)2: Estimation of the activation parameters |
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Authors: | Malcolm H. Chisholm Judith C. GallucciClemens Krempner |
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Affiliation: | Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210-1185, USA |
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Abstract: | The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R2Sn(OPri)2 compounds, where R = Bun and p-XC6H4 (X = CF3, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol−1. The entropy of activation, ΔS≠, is consistently large and negative, −50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph2Sn(OPri)2, (p-FC6H4)2Sn(OPri)2 and (p-Me2NC6H4)3SnOPri are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPri ligands. |
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Keywords: | Tin Alkoxides Catalysis Lactide polymerization |
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