title: Aluminium alkyl complexes supported by [OSSO] type bisphenolato ligands: synthesis, characterization and living polymerization of rac-lactide.
abstract: Aluminium alkyl complexes [(OSSO)AlR](1-3: R = Me, Et) were isolated in good yields from the protonolysis reaction of AlR3 with the corresponding tetradentate 1,omega-dithiaalkanediyl-bridged bisphenols (1,4-dithiabutanediyl-bis(6-tert-butyl-4-methylphenol), etbmpH2; ortho-xylylenedithio-bis(6-tert-butyl-4-methylphenol), xytbmpH2). The monomeric structures of all three complexes were confirmed by X-ray diffraction studies. Complexes 1 and 2 have an isotypic packing arrangement. The aluminium center is coordinated by the etbmp ligand and one alkyl group with distorted trigonal bipyramidal geometry. Complex 3 shows Cs symmetry with square pyramidal geometry around the metal center. Substitution reaction of complex 1 with trityl alcohol gave the monomeric alkoxide complex [(etbmp)Al(OCPh3)] 4, which has a similar trigonal bipyramidal geometry around the aluminium atom as complex 1. In the presence of isopropanol, complexes 1-3 initiated the living ring-opening polymerization of rac-lactide (PDI = 1.03-1.06, Mw/Mn). The ligand structure influenced the tacticity of the obtained polymer, with complex 3 giving heterotactic-enriched polylactides.
authors.affiliation: Institute of Inorganic Chemistry, Aachen University of Technology (RWTH), Professor-Pirlet-Strasse 1, D-52056 Aachen, Germany.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Ma
authors.forename: Gianluca
authors.initials: G
authors.lastname: Melillo
authors.forename: Leone
authors.initials: L
authors.lastname: Oliva
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Spaniol
authors.forename: Ulli
authors.initials: U
authors.lastname: Englert
authors.forename: Jun
authors.initials: J
authors.lastname: Okuda
mesh_terms: D017607:Aluminum Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D010636:Phenols / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D017607:Aluminum Compounds; D008024:Ligands; D010636:Phenols; D011091:Polyesters; D011108:Polymers; C033616:poly(lactide)