title: Bimetallic salen aluminum complexes: cooperation between reactive centers in the ring-opening polymerization of lactides and epoxides.
abstract: Three dinuclear aluminum alkyl complexes of the general formula LAl2Me4, where L are salen ligands with an alkyl backbone of different lengths between the nitrogen atoms (1,3-propylene (1), 1,5-pentylene (2) and 1,12-dodecaylene (3)), have been prepared through alkane elimination reactions between each ligand and two equivalents of AlMe3. The related hemi-salen aluminum complex 4 was prepared by an analogous reaction between a phenoxy-imine ligand and a single equivalent of AlMe3. The activities of these aluminum complexes in the ring-opening polymerization (ROP) of rac-lactide and of several epoxides have been investigated and compared. The dinuclear complex 1, bearing the salen ligand with the shortest alkyl bridge, was the most active in the ROP of LA producing isotactic enriched PLA. Otherwise, the other complexes (2 and 3), in which the metal centers are remote, produced atactic PLA with inferior activity. Analogous differences in terms of activity emerged in the ROP of epoxides. The comparison of the catalytic behavior of the dinuclear complexes as well as their mononuclear counterparts suggests the cooperation between the two aluminum metal centers of the dinuclear species in which these are close enough.
authors: Department of Chemistry and Biology "A. Zambelli" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy. mmazzeo@unisa.it.
authors: Florence
authors: F
authors: Isnard
authors: Department of Physics "E. Caianiello" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy.
authors: Marina
authors: M
authors: Lamberti
authors: Department of Chemistry and Biology "A. Zambelli" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy. mmazzeo@unisa.it.
authors: Luana
authors: L
authors: Lettieri
authors: Department of Chemistry and Biology "A. Zambelli" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy. mmazzeo@unisa.it.
authors: Ilaria
authors: I
authors: D'auria
authors: School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
authors: Konstantin
authors: K
authors: Press
authors: Department of Chemistry and Biology "A. Zambelli" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy. mmazzeo@unisa.it.
authors: Rubina
authors: R
authors: Troiano
authors: Department of Chemistry and Biology "A. Zambelli" University of Salerno, I-84084, Giovanni Paolo II, 132 Fisciano, Salerno, Italy. mmazzeo@unisa.it.
authors: Mina
authors: M
authors: Mazzeo
mesh_terms: D002384:Catalysis; D053138:Cyclohexenes / Q000737:chemistry; D004146:Dioxanes / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D005029:Ethylenediamines / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D058105:Polymerization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013237:Stereoisomerism
chemical_list: D053138:Cyclohexenes; D004146:Dioxanes; D004852:Epoxy Compounds; D005029:Ethylenediamines; D009942:Organometallic Compounds; C524024:salen-aluminum complex; C007193:cyclohexene oxide; C091880:dilactide