Neutral and Cationic Tetracoordinated Aluminum Complexes Featuring Tridentate Nitrogen Donors: Synthesis, Structure, and Catalytic Activity for the Ring-Opening Polymerization of Propylene Oxide and (<scp>d</scp>,<scp>l</scp>)-Lactide
tetracoordinated aluminum cations 12 (94% yield), 13 (93% yield), and 14 (90% yield), respectively. Single-crystal X-ray diffraction studies of derivatives 4, 5, 8, 10, 11, 12, and 15 have been carried out. They revealed that the tridentate nitrogen donors enforce an approximately trigonal-monopyramidal coordination geometry for neutral and cationic four-coordinate aluminumcomplexes. All cationic aluminum derivatives