title: Zirconium complexes of phenylene-bridged {ONSO} ligands: coordination chemistry and stereoselective polymerization of rac-lactide.
abstract: Sequential tetradentate dianionic thio-imine diphenolate ligands featuring an ortho-phenylene core and their zirconium complexes are described for the first time. Ligands that include different combinations of bulky-alkyl groups and halo groups on the two phenol arms were prepared by a substitution/condensation reaction sequence. An unexpected fac-fac wrapping mode was found in the solid state for the ligands in the octahedral [{ONSO}Zr(O(t)Bu)2] complexes. The complexes were all fluxional, and the barrier for enantiomer interconversion was found to depend on the phenolate substituents. The complexes were found to catalyze the polymerization of rac-lactide to poly(lactic acid) in solution with polymer tacticities varying from heterotactic to atactic which showed correlation to the nature of phenolate substituents but not to the degree of complex fluxionality.
authors.affiliation: School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University , Ramat Aviv, Tel Aviv 69978, Israel.
authors.forename: Ayellet
authors.initials: A
authors.lastname: Stopper
authors.forename: Konstantin
authors.initials: K
authors.lastname: Press
authors.forename: Jun
authors.initials: J
authors.lastname: Okuda
authors.forename: Israel
authors.initials: I
authors.lastname: Goldberg
authors.forename: Moshe
authors.initials: M
authors.lastname: Kol
mesh_terms: D018360:Crystallography, X-Ray; D004146:Dioxanes / Q000737:chemistry*; D008024:Ligands; D010636:Phenols / Q000737:chemistry*; D058105:Polymerization; D066244:Proton Magnetic Resonance Spectroscopy; D021241:Spectrometry, Mass, Electrospray Ionization; D015040:Zirconium / Q000737:chemistry*
chemical_list: D004146:Dioxanes; D008024:Ligands; D010636:Phenols; C091880:dilactide; D015040:Zirconium