One Ligand, Three Roles: L‐, X‐, and Z‐Type Coordination at Nitrogen

Nitrogen‐based ligands are central to coordination chemistry but are limited to L‐ and X‐type donor behavior. Here we report a fundamentally new class of nitrogen ligands based on N ‐heterocyclic nitrenium (NHN) frameworks that exhibit multimodal L‐, X‐, and Z‐type coordination with reversible switching demonstrated between the L‐ and X‐type states. These ligands represent the first examples of nitrogen‐based Z ‐ligands, with the ability to switch between donor and acceptor modes in response to the coordination environment. As such, the formal oxidation state of a transition metal is reversibly changed simply by adding or removing a coordinating solvent introducing a unique concept of “redox‐by‐coordination”. The coordination mode is confirmed by x‐ray crystallography and comprehensive computational analysis.