N-heterocyclic carbenes are well known, but their analogs where the carbon is swapped for nitrogen to form a nitrenium ligand were unknown. Researchers have now filled the gap among main-group analogs of N-heterocyclic carbenes (NHCs) by replacing the carbon with an isoelectronic nitrogen cation to form a nitrenium.

This novel entity acts as a ligand for transition metals forming strong bonds with the metal as confirmed by unambiguous X-ray crystallography and solution studies with selective nitrogen-15-labeling. Additional experiments and computational analysis demonstrates that these novel ligands are poor sigma-donor but a good π-donor.

The team is now making more examples and investigating the ligand complexes as catalysts.

• Nitrenium ions as ligands for transition metals
  Y. Tulchinsky, M. A. Iron, M. Botoshansky, M. Gandelman,
  Nature Chem. 2011.
  DOI: 10.1038/nchem.1068