Bi-Dentate Pyridyl Amine-Derived Complexes of Aluminium: Synthesis, Structure and ROP Capability

The pyridylamines 2,6-Me2C6H3NHCR2-C5H5H-2 (R = H, L1H; Me, L2H) on treatment with Me3Al (one equivalent) afforded the complexes [Al(Me)2(L1)] (1) and [Al(Me)2L2] (2), respectively. Use of excess L1H led to [Al(Me)(L1)2] (3). The molecular structures of 1–3 are reported, and the three complexes, as well as the parent compounds L1H and L2H, have been screened, in the presence of benzyl alcohol (BnOH), as catalysts for the ring opening polymerization (ROP) of ε-caprolactone and δ-valerolactone. Results revealed that these ROPs proceed in a controlled nature (Đ ≤ 1.33 for ε-CL and ≤1.48 for δ-VL) in the process without catalyst deactivation, whilst the products formed were predominantly linear with OBn/OH end groups; L1H and L2H exhibited little or no activity.