Tunable Hemilabile Ligands for Adaptive Transition Metal Complexes

A new family of monoanionic hemilabile ligands L1H−L3H with a PNN donor set has been developed, based on Pd-catalyzed C−N bond formation and straightforward phosphorylation. For these structurally related compounds with a hybrid set of donor atoms, the coordination chemistry with both Rh and Ir has been studied. The anticipated hemilabile character of the dimethylamino group was assessed by NMR and IR competition experiments, using isopropyl isocyanide as exogenous substrate. Supporting DFT calculations were used to quantify the electronic differences between the various members of the ligand family. In effect, we have constructed a modular ligand class that exhibits tunable hemilability.