10.1021/om401047r.s002
Joice
S. Klitzke
Joice
S.
Klitzke
Thierry Roisnel
Thierry
Roisnel
Evgeny Kirillov
Evgeny
Kirillov
Osvaldo de L. Casagrande
Osvaldo
de L. Casagrande
Jean-François Carpentier
Jean-François
Carpentier
Yttrium– and Aluminum–Bis(phenolate)pyridine
Complexes: Catalysts and Model
Compounds of the Intermediates for the Stereoselective Ring-Opening
Polymerization of Racemic Lactide and β‑Butyrolactone
American Chemical Society
2014
Racemic Lactide
ONOMe
yttrium centers
carbonyl group
PHB
Yttrium compounds 1
ROP
aluminum complexes
parent methyl
BBL
aluminum compounds
heterotactic PLAs
racemic LA
13 C NMR data
Model Compounds
carbonyl groups
Optimal conditions
1 equiv
2014-01-13 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Yttrium_and_Aluminum_Bis_phenolate_pyridine_Complexes_Catalysts_and_Model_Compounds_of_the_Intermediates_for_the_Stereoselective_Ring_Opening_Polymerization_of_Racemic_Lactide_and_Butyrolactone/2333398
Yttrium
and aluminum complexes of an original pyridine-bis(phenolate)
ligand have been prepared. Reactions of {ONO<sup>Me,Cumyl</sup>}Y[N(SiHMe<sub>2</sub>)<sub>2</sub>](THF)(Et<sub>2</sub>O) (<b>1</b>) with 1 equiv of methyl (<i>R</i>)-3-hydroxybutyrate and
methyl (<i>S,S</i>)-lactyllactate afforded respectively
{ONO<sup>Me,Cumyl</sup>}Y((<i>R</i>)-OCH(CH<sub>3</sub>)CH<sub>2</sub>COOMe) (<b>2</b>) and {ONO<sup>Me,Cumyl</sup>}Y((<i>S</i>,<i>S</i>)-OCH(CH<sub>3</sub>)CO<sub>2</sub>CH(CH<sub>3</sub>)CO<sub>2</sub>Me) (<b>3</b>), which are rare
models of the active species in the ring-opening polymerization (ROP)
of β-butyrolactone (BBL) and lactide (LA), respectively. <sup>13</sup>C NMR data for <b>2</b> and <b>3</b> indicate
that, in solution, the carbonyl groups coordinate onto the yttrium
centers, forming mononuclear species with six- and five-membered cycles,
respectively. The aluminum compounds {ONO<sup>Me,Cumyl</sup>}Al(<i>i</i>Pr (<i>S</i>)-lactate) (<b>5</b>), {ONO<sup>Me,Cumyl</sup>}Al((<i>R</i>)-OCH(CH<sub>3</sub>)CH<sub>2</sub>COOCH<sub>3</sub>) (<b>6</b>), and {ONO<sup>Me,Cumyl</sup>}Al((<i>rac</i>)-OCH(CF<sub>3</sub>)CH<sub>2</sub>CO<sub>2</sub>C<sub>2</sub>H<sub>5</sub>) (<b>7</b>) were prepared
analogously from the parent methyl complex {ONO<sup>Me,Cumyl</sup>}AlMe (<b>4</b>). NMR data and the solid-state structure of <b>6</b> confirm the coordination of the carbonyl group. Yttrium
compounds <b>1</b> and <b>2</b> are active initiators
for the ROP of racemic LA and BBL. Their performances (activity, control
of the molecular weights, tacticity) are much affected by the nature
of the solvent or by the addition of just a few equivalents of pyridine.
Optimal conditions are quite contrasted for the ROP of <i>rac</i>-LA and <i>rac</i>-BBL, highlighting fundamental differences
between these two monomers. In the best cases, highly heterotactic
PLAs (<i>P</i><sub>r</sub> up to 0.96) and syndiotactic-enriched
PHB (<i>P</i><sub>r</sub> up to 0.86), with good control
over the molecular weights, were obtained.