Neutral and cationic aluminium methyl complexes of 2-anilinotropone ligands: synthesis, characterization, and reactivity toward ethylene and propylene oxide

Some new aluminium complexes bearing bidentate monoanionic 2-anilinotroponate ligands have been synthesized and characterized. Reaction of 2-(2,6-diisopropylanilino) tropone or 2-(perfluoroanilino)tropone with AlMe3 (1 equiv.) gave, by methane elimination, compounds [2-(2,6-diisopropylanilino) tropone]AlMe2 (1) and [2-(perfluoroanilino)- tropone]AlMe2 (2), respectively, as yellow solids. Reaction of 1 with 1 equiv. of the ligand furnished, by protodealumination of a second Al−CH3 bond, the [2-(2,6-diisopropylanilino) tropone]2AlMe derivative 3. The structure of 3 has been determined by single-crystal X-ray diffraction, showing a five-coordinate aluminium atom with a distorted trigonal-bipyramidal geometry. Compounds 1 and 3 underwent methyl abstraction reactions with B(C6F5)3; the resulting cationic species was trapped in the presence of THF in dichloromethane solution. The reactivity of the synthesized compounds in ethylene polymerisation has also been explored.