[Me4N] + (1488 cm -1 ), are observable in the spectra of the corresponding products. The spectra of products prepared from py-AlX 3 (X = Me, Et, Cl) (Figure ) are identical and all contain vibration bands at 1455, 1495, and 1622 cm -1 assigned to Lewis acid-bound pyridine (marked L-py in Figures), indicating a single, well-defined mode of ligand coordination and the convergent nature of the synthesis from different precursors. In general, the fingerprint area is nearly identical across all ligands/precursors.