Preparation and structures of enantiomeric dinuclear zirconium and hafnium complexes containing two homochiral N atoms, and their catalytic property for polymerization of rac-lactide
2010 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 18, 4440-4446 p.Article in journal (Refereed) Published
The hydroxy-and phenoxy-bridged dinuclear zirconium and hafnium complexes 2 and 3 of an amine-pyridine-bis(phenolate) ligand (H2L) were prepared from the reaction of Na2L and ZrCl4 in the presence of 0.5 equiv of water in THF, while the reaction of H2L with NaH and then with ZrCl4 in the freshly distilled THF gave an eight-coordinate bis(homoleptic) mononuclear complex L2Zr (1). Two homochiral N atoms were created in each complex upon coordination of the unsymmetric tertiary amine ligands to the metal centers. Enantiomeric dinuclear complexes 2 and 3 both undergo spontaneous resolution during crystallization. The molecular structure of each enantiomer of 2 and 3, as well as the structure of 1, was determined by X-ray analysis and the circular dichroism spectra of N(R)N(R)-2 and N(S)N(S)-2 were studied. The racemates of 2 and 3 catalyzed controlled polymerization of rac-lactide in terms of the linearity of molecular weight versus conversion, forming isotactic-rich polylactide in high yields with a narrow polydispersity.
Place, publisher, year, edition, pages
2010. Vol. 39, no 18, 4440-4446 p.
RING-OPENING POLYMERIZATION, AQUEOUS HYDROGEN-PEROXIDE, OLEFIN POLYMERIZATION, ASYMMETRIC EPOXIDATION, GROUP-4 COMPLEXES, CYCLIC ESTERS, TITANIUM, LIGANDS, AMINE, INITIATOR
IdentifiersURN: urn:nbn:se:kth:diva-28258DOI: 10.1039/c001148gISI: 000277031800024ScopusID: 2-s2.0-77951575533OAI: oai:DiVA.org:kth-28258DiVA: diva2:387610
FunderKnut and Alice Wallenberg Foundation
QC 201101142011-01-142011-01-122011-01-14Bibliographically approved