Aluminium complexes supported by a thioether-bridged salen ligand: synthesis, characterization and application in ε-caprolactone homopolymerization and copolymerization with L-lactide

• Published in: Journal of organometallic chemistry Vol. 951; pp. 122007 - 122015
• Main Authors: Qian, Chenyun, Yuan, Dan, Wang, Yaorong, Yao, Yingming
• Format: Journal Article
• Language: English
• Published: LAUSANNE Elsevier B.V 15.10.2021; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Copolymerizaton; Organoaluminium complex; Physical Sciences; Ring-opening polymerization; Salen; Science & Technology; ε-Caprolactone; Salen; Ring-opening polymerization; ε-Caprolactone; Copolymerizaton; Organoaluminium complex; COORDINATION CHEMISTRY; CYCLIC ESTERS; ZINC-COMPLEXES; METHYL; RAC-LACTIDE; TITANIUM COMPLEXES; epsilon-Caprolactone; PENTADENTATE SCHIFF-BASE; EARTH-METAL COMPLEXES; CATALYTIC-ACTIVITY
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2021.122007

•Two aluminium methyl complexes and three aluminium alkyloxide complexes stabilized by a new thioether-bridged salen ligand were synthesized.•Aluminium alkoxide complexes exhibited higher activity and better controllability for the homopolymerization of ε-caprolactone than aluminium methyl complexes.•Aluminium alkoxide complexes could serve as efficient initiators for the copolymerization of ε-caprolactone and L-lactide to give practically random copolymers. Several aluminium alkyl and alkyloxide complexes supported by a thioether-bridged salen ligand were synthesized by the protonolysis reaction. Reactions of N,N’-bis(3,5-di-tert-butylsalicylidene)-2,2’-diaminophenylsulfide (H2L) with one or two equivalents of AlMe3 in toluene at 100 °C afforded the corresponding mono- and binuclear aluminium methyl complexes LAlMe (1) and L(AlMe2)2 (2). Treatment of the in situ generated complex 1 with one equivalent of ROH (R = PhCH2, iPr, CH3OCH2CH2) produced the desired aluminium alkyloxide complexes LAlOCH2Ph (3), LAl(OiPr) (4) and LAlO(CH2)2OCH3 (5). All the molecular structures were established by single crystal X-ray diffraction studies. It was found that aluminium alkyloxide complexes 3-5 showed higher catalytic activity for the homopolymerization of ε-caprolactone (ε-CL) than corresponding aluminium methyl complexes 1 and 2. Furthermore, these alkyloxide complexes were also efficient initiators for the copolymerization of L-lactide and ε-CL to give practically random copolymers. Several aluminium alkyl and alkyloxide complexes supported by a thioether-bridged salen ligand were synthesized and characterized. The aluminium alkoxide complexes could serve as efficient initiators for the ε-caprolactone homopolymerization and copolymerization wth L-lactide. [Display omitted]