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Metal‐Size Influence in Iso‐Selective Lactide Polymerization
Author(s) -
Bakewell Clare,
White Andrew J. P.,
Long Nicholas J.,
Williams Charlotte K.
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201403643
Subject(s) - lutetium , polymerization , polymer chemistry , lactide , metal , derivative (finance) , chemistry , monomer , selectivity , materials science , organic chemistry , polymer , catalysis , oxide , economics , financial economics , yttrium
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.