A Comparative Study on Dinuclear and Mononuclear Aluminum Methyl Complexes Bearing Piperidyl–Phenolato Ligands in ROP of Epoxides

Dinuclear aluminum
methyl complexes stabilized by piperidyl–phenolato
ligands were prepared and characterized. The ring-opening polymerizations
of cyclohexene oxide (CHO) and propylene oxide (PO) initiated by dinuclear
complexes and mononuclear analogues were investigated and compared.
Enhanced activity of dinuclear complexes compared to that of mononuclear
analogues in both the ring-opening polymerization of CHO and PO proves
the synergistic interaction of two Al centers in the former. End-group
analysis of oligomers by MALDI-TOF mass spectrometry confirms the
role of methyl groups as initiating groups. A bimetallic mechanism
is proposed, in which the cooperation of two Al centers are involved
in polymerization processes.