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Metal-size influence in iso-selective lactide polymerization.

ABSTRACT: Iso-selective initiators for the ring-opening polymerization (ROP) of rac-lactide are rare outside of Group?13. We describe the first examples of highly iso-selective lutetium initiators. The phosphasalen lutetium ethoxide complex shows excellent iso-selectivity, with a P(i) value of 0.81-0.84 at 298?K, excellent rates, and high degrees of polymerization control. Conversely, the corresponding La derivative exhibits moderate heteroselectivity (P(s)=0.74, 298?K). Thus, the choice of metal center is shown to be crucial in determining the level and mode of stereocontrol. The relative order of rates for the series of complexes is inversely related to metallic covalent radius: that is, La>Y>Lu.

SUBMITTER: Bakewell C

PROVIDER: S-EPMC4499264 | biostudies-other | 2014 Aug

REPOSITORIES: biostudies-other

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Metal-size influence in iso-selective lactide polymerization.

Bakewell Clare C White Andrew J P AJ Long Nicholas J NJ Williams Charlotte K CK

Angewandte Chemie (International ed. in English) 20140707 35

Iso-selective initiators for the ring-opening polymerization (ROP) of rac-lactide are rare outside of Group 13. We describe the first examples of highly iso-selective lutetium initiators. The phosphasalen lutetium ethoxide complex shows excellent iso-selectivity, with a P(i) value of 0.81-0.84 at 298 K, excellent rates, and high degrees of polymerization control. Conversely, the corresponding La derivative exhibits moderate heteroselectivity (P(s)=0.74, 298 K). Thus, the choice of metal center i ...[more]

PMID: 25044165

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