The first N,Nʹ-diamidocarbene (DAC) with a seven-membered ring has been synthesized by chemists at the University of Texas, Austin (Organometallics, DOI: 10.1021/om1007665). A variation of popular N-heterocyclic carbenes (NHCs), which serve as ligands for transition-metal homogeneous catalysts, six-membered-ring DACs have broadened the reactivities of NHCs to include intramolecular C–H insertion, ketenimine formation, reversible carbonylation, and NH3 activation. Todd W. Hudnall, Andrew G. Tennyson, and Christopher W. Bielawski reasoned that they could increase the nucleophilicity of DACs by expanding the ring size and increasing the N–C–N angle. They treated the condensation product of N,N´-dimesitylformamidine and phthaloyl chloride with base to produce the seven-membered-ring DAC shown. Reactivity and spectroscopic studies of rhodium, iridium, and gold complexes of the ligand indicate that it’s a stronger electron donor than its six-membered-ring counterparts. Modulating the ring size of DACs to alter orbital hybridization at the carbene nucleus “is an important variable to consider in determining carbene character and reactivity,” the researchers write.