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Issue 24, 2014
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Aluminum complexes with bidentate amido ligands: synthesis, structure and performance on ligand-initiated ring-opening polymerization of rac-lactide

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Abstract

A series of mononuclear aluminum dimethyl complexes bearing bidentate N-[2-(1-piperidinyl)benzyl]anilino or N-(2-morpholinobenzyl)anilino ligands were synthesized via reactions of the corresponding proligands with trimethylaluminum upon heating, while at ambient temperature two trimethylaluminum adducts with neutral N-[2-(1-piperidinyl)benzyl]aniline proligands were obtained. These complexes were well characterized by NMR spectroscopy, elemental analysis and occasionally by EI-HRMS. The molecular structures of the typical trimethylaluminum adduct 2b and aluminum dimethyl complex 3b were further confirmed by X-ray diffraction studies. All the aluminum dimethyl complexes could effectively initiate the ring-opening polymerization (ROP) of rac-lactide in a well-controlled manner to afford PLAs with narrow molecular weight distributions (PDI = 1.06–1.18). The polymer samples obtained are systematically end-capped with the bidentate ancillary ligands as characterized by 1H NMR and ESI-TOF mass spectroscopy. Moreover, the introduction of substituent(s) at the ortho-position(s) of the anilino moiety in the ligand results in an obvious decrease in the catalytic activity of the corresponding aluminum complex, and complexes with meta-chloro substituted anilino units show higher activities likely due to the enhanced electrophilicity of the metal centers induced by the anilino groups.

Graphical abstract: Aluminum complexes with bidentate amido ligands: synthesis, structure and performance on ligand-initiated ring-opening polymerization of rac-lactide

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Publication details

The article was received on 03 Feb 2014, accepted on 10 Mar 2014 and first published on 12 Mar 2014


Article type: Paper
DOI: 10.1039/C4DT00353E
Citation: Dalton Trans., 2014,43, 9098-9110
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    Aluminum complexes with bidentate amido ligands: synthesis, structure and performance on ligand-initiated ring-opening polymerization of rac-lactide

    J. Liu and H. Ma, Dalton Trans., 2014, 43, 9098
    DOI: 10.1039/C4DT00353E

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