A series of tridentate imine bis(phenolate) ligands have been synthesised and complexed to aluminium. Solid-state analysis identified two structural motifs of an aluminium dimer [Al2(Me)2(X)2]; one consisting of two five-coordinate aluminium centres and a second containing aluminium centres in both a six- and four-coordinate geometry. Pairing with solution-state NMR spectroscopic analysis suggested that the geometry isolated was influenced by the ligands' steric bulk. Trialling of Al2(Me)2(1-5)2 as initiators for the ring-opening polymerisation (ROP) of rac-lactide found them all to be active, producing atactic polymeric material. Al2(Me)2(1)2 was found to have good molecular weight control and activity an order of magnitude higher than analogous aluminium dimers.