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.