Accessing osmium(vi) nitrido complexes with N-heterocyclic carbene ligands

The synthesis of the first osmium(vi) nitrido complexes bearing NHC ligands is described. Herein, NBu4OsNCl4 is reacted with two equivalents of Cl-IMes NHC to afford the neutral complex OsN(Cl)3(Cl-IMes)2. Subsequent ligand substitution reactions selectively replace the chloride ligands while preserving the OsN–NHC core, providing access to a series of stable complexes of the general formula OsN(X)3(Cl-IMes)2. These compounds represent the first examples of osmium–NHC complexes in an oxidation state higher than +IV. The ligand exchange reactions enable systematic tuning of the coordination environment and the associated electronic properties.