Shapeshifting Ligands Mask Lewis Acidity of Dicationic Palladium(II)

Supporting ligands limit the degree of electrophilic ac-tivation for any substrate because they also reduce the Lewis acidity of the transition metal ion. Here, we tem-porarily mask the Lewis acidity of dicationic Pd(II) by using “shapeshifting” bidentate pyrimidine/olefin lig-ands L1 and L2. These ligands delocalize/relocalize charge via reversible C–N bond formation. So, although ligated dicationic Pd compounds [1]2+ and [2]2+ appear charge separated (distributed across Pd and ligand), they react comparably to a solvated Pd(II) dication. We also observe properties that are atypical of electrophilic cata-lysts (e.g. broader functional group tolerance). We pro-pose these properties originate from the more nucleo-philic (charge separated) state. More broadly, catalysts featuring reversible dynamics may be advantaged rela-tive to structurally static counterparts.