The use of a new asymmetric -diketiminate ligand, N-{4- [(2,6-diisopropyl-phenyl)imino]pent-2-en-2-yl}pyridin-2amine (HL), in the organometallic chemistry of aluminium is reported. Reactions of HL with AlMe 3 , Et 2 AlCl, and AlEtCl 2 , respectively, afforded [Al(L)Me 2 ] (1), [Al(L)EtCl] (2), and [Al(L)Cl 2 ] (3) in high yields. The structures of 1-3 were established by singlecrystal X-ray diffraction. They were tested as precursors in the ring-opening polymerization (ROP) of ε-caprolactone in the absence and presence of benzyl alcohol. Complexes 1 and 2 were found to catalyze the ROP of ε-caprolactone with moderate activities in the absence of benzyl alcohol, and complex 3 showed low [a] College