A series of yttrium amido complexes bearing quadridentate binaphthyl-bridged Schiff-base salen-like and diamine bisphenolate salan-like ligands are synthesized and characterized. The complexes act as active initiators in the polymn. of rac-β-butyrolactone (rac-BBL) under mild conditions. The obtained poly(3-hydroxybutyrate) (PHBs) are syndiotactic enriched. 13C NMR spectroscopy microstructure anal. shows the probability of racemic linkages Pr to be up to 0.81. Statistical Bernoullian anal. evidences that a chain-end mechanism of steric control operates for the salan-like compd. bearing cumyl substituents in the ortho position of the phenolate rings. The melting temps. of the syndiotactic enriched PHBs are in the range 120-157 °C, depending on the degree of stereoregularity of the polymers.
Ring-Opening Polymerization of Racemic β-Butyrolactone Promoted by Salan- and Salen-Type Yttrium Amido Complexes
LAMBERTI, Marina;PELLECCHIA, Claudio
2013-01-01
Abstract
A series of yttrium amido complexes bearing quadridentate binaphthyl-bridged Schiff-base salen-like and diamine bisphenolate salan-like ligands are synthesized and characterized. The complexes act as active initiators in the polymn. of rac-β-butyrolactone (rac-BBL) under mild conditions. The obtained poly(3-hydroxybutyrate) (PHBs) are syndiotactic enriched. 13C NMR spectroscopy microstructure anal. shows the probability of racemic linkages Pr to be up to 0.81. Statistical Bernoullian anal. evidences that a chain-end mechanism of steric control operates for the salan-like compd. bearing cumyl substituents in the ortho position of the phenolate rings. The melting temps. of the syndiotactic enriched PHBs are in the range 120-157 °C, depending on the degree of stereoregularity of the polymers.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
