Cationic alkyl aluminium ethylene polymerization catalysts based on monoanionic N,N,N-pyridyliminoamide ligands

Abstract

Treatment of the 2,6-bis(imino)pyridines {[2,6-(ArNCR)₂C₅H₃N]} [R = H, Ar = 2,6-i-Pr₂C₆H₃ or 2,4,6-Me₃C₆H₂; R = Me, Ar = 2,6-i-Pr₂C₆H₃] with AlMe₃ at elevated temperature gives, via migration of a methyl group to the ligand backbone, the pseudo-five coordinate dimethylaluminium species {2-[ArNCR(Me)],6-(ArNCR)C₅H₃N}- AlMe₂ (1a–c); upon treatment with B(C₆F₅)₃, 1a–c cleanly afford the cationic methyl complexes [{2-[ArNCR(Me)],6-(ArNCR)C₅H₃N}AlMe]⁺[MeB(C₆F₅)₃]^– (2a–c) which are active for ethylene polymerization.