Jump to main content
Jump to site search

Issue 32, 2013
Previous Article Next Article

Synthesis, characterization and reactivity of single-site aluminium amides bearing benzotriazole phenoxide ligands: catalysis for ring-opening polymerization of lactide and carbon dioxide/propylene oxide coupling

Author affiliations

Abstract

New aluminium complexes containing bis-BTP ligands (BTP = N,O-bidentate benzotriazole phenoxide) were synthesized and structurally characterized. Amine elimination of Al(NMe2)3 with RBTP-H ligands (CMe2PhBTP-H = 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, t-BuBTP-H = 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol and TMClBTP-H = 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol) (2.0 mol equiv.) in toluene or hexane afforded the penta-coordinated single-site amidoaluminium complexes [(RBTP)2Al(NMe2)] (R = CMe2Ph for 1; R = t-Bu for 2; R = TMCl for 3) in satisfactory yields. With the addition of H2O (0.5 molar equiv.), the hydrolysis of Al amides 2 and 3 in a mixed solvent of THF/toluene at 25 °C produced oxo-bridged bimetallic aluminium complexes [{(RBTP)2Al}2(μ-O)] (R = t-Bu for 4 and R = TMCl for 5) in ≥70% yield. According to single crystal X-ray diffraction studies, complex 2 shows a monomeric Al(III) amide with bis(t-BuBTP) ligands and one –NMe2 group, whereas alumoxane 4 is a dinuclear species, in which the bonding mode of the Al–O–Al moiety from μ2-oxo assumes a linear type. Catalysis for ring-opening polymerization of lactide (LA) and CO2/propylene oxide (PO) coupling was systematically studied. Single-site Al amide 3 is an efficient initiator for LA polymerizations with a living character; the polymerization displays a first-order dependence on the concentration of L-LA. Bimetallic BTP-ligated alumoxane 5 is an active catalyst (TOF: 120 h−1) for the coupling of CO2 with PO in the presence of n-Bu4NBr to give propylene carbonate under mild conditions.

Graphical abstract: Synthesis, characterization and reactivity of single-site aluminium amides bearing benzotriazole phenoxide ligands: catalysis for ring-opening polymerization of lactide and carbon dioxide/propylene oxide coupling

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 16 Apr 2013, accepted on 06 Jun 2013 and first published on 06 Jun 2013


Article type: Paper
DOI: 10.1039/C3DT51003D
Citation: Dalton Trans., 2013,42, 11488-11496
  •   Request permissions

    Synthesis, characterization and reactivity of single-site aluminium amides bearing benzotriazole phenoxide ligands: catalysis for ring-opening polymerization of lactide and carbon dioxide/propylene oxide coupling

    C. Li, D. Liu and B. Ko, Dalton Trans., 2013, 42, 11488
    DOI: 10.1039/C3DT51003D

Search articles by author