Synthesis, structural studies and ligand influence on the stability of aryl-NHC stabilised trimethylaluminium complexes

Treatment of a series of aromatic NHCs (IMes, SIMes, IPr and SIPr) with trimethylaluminium produced their corresponding Lewis acid-base adducts: IMes·AlMe₃ (1), SIMes·AlMe₃ (2), IPr·AlMe₃ (3), and SIPr·AlMe₃ (4). These complexes expand the few known examples of saturated NHC stabilised Group 13 complexes. Furthermore, compounds 1-4 show differential stability depending on the nature of the NHC ligand. Analyses of topographic steric maps and NHC %V_Bur were used to explain these differences. All the compounds have been fully characterised by multinuclear NMR spectroscopy, IR and single crystal X-ray analysis together with computational studies.