Lewis Acid Effects on Calculated Ligand Electronic Parameters

Adding Lewis acids to coordinated ligands can impart systematic changes to their properties. We computationally explored the effects of acid-induced changes to the donor strength (Tolman electronic parameter) of 17 ligands, in addition to changes to the charge distribution and binding energies for a representative set of ligands. These results were compared using a combined experimental/computational study with cyanide. The combined results demonstrate: (1) large effects for the initial binding of even weak Lewis acids, with smaller changes as Lewis acidity is increased, (2) Lewis acid modifications afford smaller tunability than covalent substitution (Hammett parameters), and (3) binding energy provides a reasonable guide that can be used for designing cooperative interactions.