Abstract
| Original language | Undefined |
|---|---|
| Pages (from-to) | 9836-9845 |
| Journal | Chemistry: a European journal |
| Volume | 15 |
| Issue number | 38 |
| DOIs | |
| Publication status | Published - 2009 |
Keywords
- Chirality
- Aluminum
- Polymerization
- IR-72591
- salan
- METIS-262785
- lactide
Cite this
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Chiral salan aluminium ethyl complexes and their application in lactide polymerization. / Du, H(ongzhi); Velders, Aldrik; Dijkstra, Pieter J.; Sun, Jingru; Zhong, Zhiyuan; Chen, Xuesi; Feijen, Jan.
In: Chemistry: a European journal, Vol. 15, No. 38, 2009, p. 9836-9845.Research output: Contribution to journal › Article › Academic › peer-review
TY - JOUR
T1 - Chiral salan aluminium ethyl complexes and their application in lactide polymerization
AU - Du, H(ongzhi)
AU - Velders, Aldrik
AU - Dijkstra, Pieter J.
AU - Sun, Jingru
AU - Zhong, Zhiyuan
AU - Chen, Xuesi
AU - Feijen, Jan
PY - 2009
Y1 - 2009
N2 - Synthetic routes to aluminium ethyl complexes supported by chiral tetradentate phenoxyamine (salan-type) ligands [Al(OC6H2(R-6-R-4)CH2)2{CH3N(C6H10)NCH3}-C2H5] (4, 7: R=H; 5, 8: R=Cl; 6, 9: R=CH3) are reported. Enantiomerically pure salan ligands 1–3 with (R,R) configurations at their cyclohexane rings afforded the complexes 4, 5, and 6 as mixtures of two diastereoisomers (a and b). Each diastereoisomer a was, as determined by X-ray analysis, monomeric with a five-coordinated aluminium central core in the solid state, adopting a cis-(O,O) and cis-(Me,Me) ligand geometry. From the results of variable-temperature (VT) 1H NMR in the temperature range of 220–335 K, 1H–1H NOESY at 220 K, and diffusion-ordered spectroscopy (DOSY), it is concluded that each diastereoisomer b is also monomeric with a five-coordinated aluminium central core. The geometry is intermediate between square pyramidal with a cis-(O,O), trans-(Me,Me) ligand disposition and trigonal bipyramidal with a trans-(O,O) and trans-(Me,Me) disposition. A slow exchange between these two geometries at 220 K was indicated by 1H–1H NOESY NMR. In the presence of propan-2-ol as an initiator, enantiomerically pure (R,R) complexes 4–6 and their racemic mixtures 7–9 were efficient catalysts in the ring-opening polymerization of lactide (LA). Polylactide materials ranging from isotactically biased (Pm up to 0.66) to medium heterotactic (Pr up to 0.73) were obtained from rac-lactide, and syndiotactically biased polylactide (Pr up to 0.70) from meso-lactide. Kinetic studies revealed that the polymerization of (S,S)-LA in the presence of 4/propan-2-ol had a much higher polymerization rate than (R,R)-LA polymerization (kSS/kRR=10.1).
AB - Synthetic routes to aluminium ethyl complexes supported by chiral tetradentate phenoxyamine (salan-type) ligands [Al(OC6H2(R-6-R-4)CH2)2{CH3N(C6H10)NCH3}-C2H5] (4, 7: R=H; 5, 8: R=Cl; 6, 9: R=CH3) are reported. Enantiomerically pure salan ligands 1–3 with (R,R) configurations at their cyclohexane rings afforded the complexes 4, 5, and 6 as mixtures of two diastereoisomers (a and b). Each diastereoisomer a was, as determined by X-ray analysis, monomeric with a five-coordinated aluminium central core in the solid state, adopting a cis-(O,O) and cis-(Me,Me) ligand geometry. From the results of variable-temperature (VT) 1H NMR in the temperature range of 220–335 K, 1H–1H NOESY at 220 K, and diffusion-ordered spectroscopy (DOSY), it is concluded that each diastereoisomer b is also monomeric with a five-coordinated aluminium central core. The geometry is intermediate between square pyramidal with a cis-(O,O), trans-(Me,Me) ligand disposition and trigonal bipyramidal with a trans-(O,O) and trans-(Me,Me) disposition. A slow exchange between these two geometries at 220 K was indicated by 1H–1H NOESY NMR. In the presence of propan-2-ol as an initiator, enantiomerically pure (R,R) complexes 4–6 and their racemic mixtures 7–9 were efficient catalysts in the ring-opening polymerization of lactide (LA). Polylactide materials ranging from isotactically biased (Pm up to 0.66) to medium heterotactic (Pr up to 0.73) were obtained from rac-lactide, and syndiotactically biased polylactide (Pr up to 0.70) from meso-lactide. Kinetic studies revealed that the polymerization of (S,S)-LA in the presence of 4/propan-2-ol had a much higher polymerization rate than (R,R)-LA polymerization (kSS/kRR=10.1).
KW - Chirality
KW - Aluminum
KW - Polymerization
KW - IR-72591
KW - salan
KW - METIS-262785
KW - lactide
U2 - 10.1002/chem.200900799
DO - 10.1002/chem.200900799
M3 - Article
VL - 15
SP - 9836
EP - 9845
JO - Chemistry: a European journal
JF - Chemistry: a European journal
SN - 0947-6539
IS - 38
ER -