New aluminium complexes containing bis-BTP ligands (BTP = N,O-bidentate benzotriazole phenoxide) were synthesized and structurally characterized. Amine elimination of Al(NMe₂)₃ with ^RBTP-H ligands (^CMe2PhBTP-H = 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, ^t-BuBTP-H = 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol and ^TMClBTP-H = 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol) (2.0 mol equiv.) in toluene or hexane afforded the penta-coordinated single-site amidoaluminium complexes [(^RBTP)₂Al(NMe₂)] (R = CMe2Ph for 1; R = t-Bu for 2; R = TMCl for 3) in satisfactory yields. With the addition of H₂O (0.5 molar equiv.), the hydrolysis of Al amides 2 and 3 in a mixed solvent of THF/toluene at 25 °C produced oxo-bridged bimetallic aluminium complexes [{(^RBTP)₂Al}₂(μ-O)] (R = t-Bu for 4 and R = TMCl for 5) in ≥70% yield. According to single crystal X-ray diffraction studies, complex 2 shows a monomeric Al(III) amide with bis(^t-BuBTP) ligands and one –NMe₂ group, whereas alumoxane 4 is a dinuclear species, in which the bonding mode of the Al–O–Al moiety from μ₂-oxo assumes a linear type. Catalysis for ring-opening polymerization of lactide (LA) and CO₂/propylene oxide (PO) coupling was systematically studied. Single-site Al amide 3 is an efficient initiator for LA polymerizations with a living character; the polymerization displays a first-order dependence on the concentration of L-LA. Bimetallic BTP-ligated alumoxane 5 is an active catalyst (TOF: 120 h⁻¹) for the coupling of CO₂ with PO in the presence of n-Bu₄NBr to give propylene carbonate under mild conditions.